Starts on Petrol. Won't start on LPG.

[dom14]

Hi Guys,
My GQ RB30, just had a carby rebuild job done by me.
It was cutting off on both gas & petrol.
So, I decided to do the carby to rule out any issues with that.

Now it's starting ok on petrol, but won't start on LPG. On odd occasion, I was able to get it to start on LPG for couple of times, but it's no good.

To rule out LPG safety switch issues, I bypassed the switch and directly(from the 12V line that goes to the safety switch) connected the power to the LPG solenoid(just before the converter).
I did manage to get the car started once and idle when I did that, but it's still no good.

So, I don't think LPG safety switch is faulty.

I would really like to ascertain whether gas is getting into the mixer, so I can rule out any converter problems.

How do I find out whether gas is coming out of the converter and goes to the mixer??!!

Any help and tips will be much appreciated.

BTW, I put brand new spark plugs as well.

I''ll post some pictures shortly.

[threedogs]

you should be able to hear the solenoid switching,
turn key on and off three or four times , this should give a small burst of gas to start it

[dom14]

you should be able to hear the solenoid switching,
turn key on and off three or four times , this should give a small burst of gas to start it

Yeah, but the solenoid switching noise get 'overcrowded' by the tank solenoid noises mate.
But, yeah, when I give the 12V directly to the solenoid near the converter, it switches, but I have no idea whether any gas comes out of the converter.
How do I find that?
For example, a faulty converter can stop gas getting into the mixer, can it??!!!
If that's the case, it would be helpful for me to find out.

Anyway, I found out by some reading, the PEEL brand safety switch switches the power on to the solenoid once I start cranking.
PEEL CP30 safety switch gets activated by high voltage coil inductance. I couldn't confirm the whether the safety switch is ok or not, 'cos I couldn't find anybody to crank
the motor. If the safety switch is gone cactus, that's fine, I can replace it. But, I don't think it's blown. I reckon, something else is going on with the fuel supply system, ignition system or the carby. I just got a secondhand carby. I'm about to clean it up and hook it up and see whether that makes any difference.
I gota find out whether the converter is good or not though. Not sure how to do that yet. I need some gas techie advice on that.
Thanks

P.S. Tank solenoids are also get activated via the LPG safety switch. So, I gave a direct supply to that line as well. So, I don't think I missed anything vital(Of course I have, that's why I can't have the car running on LPG. :icon_bonk:)

[dom14]

These are the pictures of what I've done with the bypassing the LPG switch.

[threedogs]

where are you ???

[mudnut]

Has your system got and mesh filters in the system? I've had problems with foreign material from the service station tank getting stuck in the piping.

[dom14]

where are you ???

Melbourne, mate.

But, I got some new news about this.

Here it is. And please pardon my French and grammar. :wink:

I just went to wreckers and picked up a secondhand carby and finished cleaning it with petrol and blowing off all the crxp.

Then I went back to the car and hooked up the solenoid 12v Connection(for one last time, before I hook up the 'new' carby for another carby test) and direct from battery temp connection to the tank solenoid as well(exactly as yesterday).

Then I cranked and it started nicely on LPG.
I thought the since the same thing happened yesterday arvo, I should leave it for 15 minutes to heat up and try again. So, I did. It started on LPG without any dramas.

I tried to fault it by leaving it off for few minutes and tried again. Still it startes without any issues on LPG(and idles fine).

Then I attached the PEEL CP30 safety switch and tried cranking. NO GO. It won't budge.

So, I decided the PEEL switch gota be faulty and I ordered a one.

But, here's the thing guys.

WHAT ON EARTH IS GOING ON GUYS????!!!!

I did the same damn thing the same way yesterday about million times(ok, I'm tad exaggerating), it wasn't starting(or idling). Now it does without any issues.

I need some serious input here.

Should I consult the local guy with the rabbit foot and the crystal ball??!!
Or should I get my head checked by the nearest head doctor???!!
I wasn't drunk yesterday(just pepsi max for a caffeine boost). :wink:

Not sure what to make out this!!!??!!!

[threedogs]

could it be that the inside of your gas hose is U/S and breaking down and clogging all the filters.
Im at a loss without seeing it,
Just remember 99% of gas problems are electrical

[dom14]

could it be that the inside of your gas hose is U/S and breaking down and clogging all the filters.
Im at a loss without seeing it,
Just remember 99% of gas problems are electrical

Sorry mate, pardon my ignorance, what is "U/S"?

What are the filters that you're referring to?

I'm still suspecting the converter, it may be temperamental??!!

I took on board your advice about 99%. It's great to know that, so I can do better next time something like this happens.

So, spare with me mate. I don't think this problem is anywhere near over yet.

Can you give me some idea about how to confirm uninterrupted good gas flow between the converter and the mixer??!!
I still have no idea how to go about it.
I got no LPG specialist tools. But, I bet there's a safe backyard method to find it.

I'm thinking about ordering a converter rebuild kit off ebay and to go for it.

What do you reckon?!!! Is it an overkill?? Should I confirm whether the converter is faulty or not first??!!

Thanks mate

[4bye4]

Dom, re PEEL safety switch.
The pin marked NEG COIL should go to either the neg side of your coil or can be wrapped around a spark plug lead. It is to pick up the distributor pulses.
The pin marked GAS LOCK OFF should connect to the input of the gas solenoid. This is to operate the solenoid.
The pin marked GAS 12V is your +batt input and should go to the gas/petrol switch. When there is +ve on this pin the relay operate and operate the solenoid if there are pulses on the first NEG COIL pin
The pin marked GND goes to ground or earth.
To check the relay is operating if you remove the wire from the GAS 12V pin and touch that pin with +ve from the battery, the green light should come on and the relay and solenoid should "click". When you remove the +ve battery, the light should remain on for 8 to 12 seconds. This is whith the engine off.

What happens is this. When you operate the switch to go from petrol to gas, = ve battery is fed to the GAS 12V pin via the gas/petrol select switch. the solenoid will then operate for 8 to 12 seconds to allow gas to flow into the system. By the end of that time your motor should be feeding pulses from the distributor to the spark plugs which should keep the switch operating.
The idea is this;
Gas should only flow when the motor is cranking or running. Initailly you get the 8 to 12 seconds to allow the motor to start turning. As soon as it is turning there is interupted pulses on the NEG COIL pin and the relay will remain operated until the motor stops and the pulses cease.
When you change your switch to petrol, the 12V input to pin GAS 12V is removed and switched to your petrol pump/solenoid.
Tony

[dom14]

What is the reason for the PEEL switch to die like this??!!
It's the second time it happened(or the third time rather).
Last time I had it installed by an auto electrician who advised me that it was wired incorrectly, and hence the reason for dying.
But, this time it lasted just under two years or so. Still not long enough, I reckon.

[threedogs]

US = unserviceable or stuffed
Grab some Carbie cleaner and put a kit through the converter.
Pretty sure those solenoids have a small filter on them ,plus they can only be mounted in one way .
You really need a second pair of hands eh

[mudnut]

Unlikely, but if it is not on full voltage, it will draw more current than normal and may overheat.

[dom14]

US = unserviceable or stuffed
Grab some Carbie cleaner and put a kit through the converter.
Pretty sure those solenoids have a small filter on them ,plus they can only be mounted in one way .
You really need a second pair of hands eh

Ok, cool mate. I'll do the converter rebuild. There's a first time for every new thing. :)

I might also have to either clean the solenoid or source a replacement, if I understood you correctly.(I'll try blowing some pressurized air into it?!)

I did have a second pair of hands while ago, but she wasn't much use with car stuff.:wink:
No mates nearby either. :icon_bonk:
Yeah, I'm pretty much on solo atm. :icon_bonk:

[threedogs]

go easy when blowing stuff clean please

[4bye4]

I'm thinking about ordering a converter rebuild kit off ebay and to go for it.
Hey Dom, I don't know how strict the authorities are in Melbourne, but if you rebuilt a converter over here in WA I wouuldn't tell anybody about it and wouldn't put it on the forum.
Tony. Licensec Gas Fitter

[dom14]

Dom, re PEEL safety switch.
The pin marked NEG COIL should go to either the neg side of your coil or can be wrapped around a spark plug lead. It is to pick up the distributor pulses.
The pin marked GAS LOCK OFF should connect to the input of the gas solenoid. This is to operate the solenoid.
The pin marked GAS 12V is your +batt input and should go to the gas/petrol switch. When there is +ve on this pin the relay operate and operate the solenoid if there are pulses on the first NEG COIL pin
The pin marked GND goes to ground or earth.
To check the relay is operating if you remove the wire from the GAS 12V pin and touch that pin with +ve from the battery, the green light should come on and the relay and solenoid should "click". When you remove the +ve battery, the light should remain on for 8 to 12 seconds. This is whith the engine off.

What happens is this. When you operate the switch to go from petrol to gas, = ve battery is fed to the GAS 12V pin via the gas/petrol select switch. the solenoid will then operate for 8 to 12 seconds to allow gas to flow into the system. By the end of that time your motor should be feeding pulses from the distributor to the spark plugs which should keep the switch operating.
The idea is this;
Gas should only flow when the motor is cranking or running. Initailly you get the 8 to 12 seconds to allow the motor to start turning. As soon as it is turning there is interupted pulses on the NEG COIL pin and the relay will remain operated until the motor stops and the pulses cease.
When you change your switch to petrol, the 12V input to pin GAS 12V is removed and switched to your petrol pump/solenoid.
Tony

Thanks Tony.
Before that I thought the safety switch is solely activate by the inductance of the coil(via the negative coil connection of the safety switch) when I crank the motor.
I didn't know the switch activates for 8-12 seconds, regardless of the pulse coming through or not.

If I understood you correctly, my test so far is not conclusive of the faultiness of the switch. So, I'll have to do the test you mentioned above.
I will do that, but I've already ordered a replacement switch, which I think is a good move anyway. The switch has been blowing itself every two years or so for some unknown reason.

[dom14]

Hey Dom, I don't know how strict the authorities are in Melbourne, but if you rebuilt a converter over here in WA I wouuldn't tell anybody about it and wouldn't put it on the forum.
Tony. Licensec Gas Fitter

Hi Tony,
No I won't put it on the forum. It's a hazardous job, which I'm happy to take the risk. But, I don't think it's a good idea to post pictures and details of my possibly amateur job on the forum, which can mislead any other newbees. I may consider posting stuff like that, once(or if) I'm truly competent on doing such jobs with no margin for mistakes.
Having said that, I reckon in Victoria, the regulations are slightly less strict than WA. Most of the installation and regulation blue prints were developed in WA, I think(somebody told me that ages ago)

BTW, I'm not a total noob to LPG stuff. I've done an auxiliary tank installation with the help of forum guys.:beer::biggrin:

[dom14]

go easy when blowing stuff clean please

Sure, mate. You have my word.:D

BTW, I did blow all of the x'mas globes on the top of the page decorations(That's the forum admin's idea :animierte-smilies-t) Nice flash insert, who ever did that.
I would like to find out how to do that for my web building experiments. I reckon the forum engine does that?!!

[4bye4]

Hi Dom. One thing that can kill these things is water. I had some fail over the years when people had pressure washed them when pressure washing the motor. Don't know how they perform with splashing but assume they would be ok. By the way, I use the AEB 552 switch, made in Italy and have had a good run from them. Available from Sprintgas. I know you have already ordered one but may be worth considering if you get another failure in the future.
Tony

[dom14]

Has your system got and mesh filters in the system? I've had problems with foreign material from the service station tank getting stuck in the piping.

I've completely forgotten about this possibility. I've known junk can get into the LPG tanks via the service stations, but forgotten about it.
Last time I lowered the tank to have it retested, I cleaned the inside of the tank by hosing it off. But, never though about the LPG fuel lines needing a good blow clean.
I reckon it's about time I do it.

[dom14]

Hi Dom. One thing that can kill these things is water. I had some fail over the years when people had pressure washed them when pressure washing the motor. Don't know how they perform with splashing but assume they would be ok. By the way, I use the AEB 552 switch, made in Italy and have had a good run from them. Available from Sprintgas. I know you have already ordered one but may be worth considering if you get another failure in the future.
Tony

Hey Tony,
Yeah, I've already ordered it online, 'cos it's only $30, but around $50 in shop. So, I reckon I can wait few days for a $20 saving(put it away for beer in the piggy cache:D)

BTW, PEEL says it's watertight, but I have to agree with you. It doesn't look that water tight and I did pressure washed the engine combined with degreaser about a month ago or so. Come to think of it, this mystery problem kinda started after that.
It may be that the safety switch and other LPG electrics may have suffered as a result of my super wash attempt. :rolleyes:
It may not be the carby after all. But the carby job had to be redone anyway, 'cos last job was done half cocked.
Adding to my existing neverending projects, I gota secondhand carby that probably need a pretty good rebuild.(It looks pretty bad cosmetically)
I reckon I can do it faster this time since I've done it like million times already! :rolleyes::D

[mudnut]

If I undid any LPG fitting, I used to test each join with a liberal spray of soapy water after re-installation.

[dom14]

If I undid any LPG fitting, I used to test each join with a liberal spray of soapy water after re-installation.

Cool mate. I'll make sure I do that. BTW, mine are not flexy pipes. I"m in the process of converting old copper pipes to flexi ones, just didn't have enough time to do that.

The wiring is kinda dodgy too(not enough insulation by using wire harnesses). I might have to fix that as well.

[mudnut]

One more thing, but it is costly, so you don't distort the fitting, you need to use the quality flange spanners or split ring spanners (like a ring spanner, but beefier and have a gap in them so you can slip them off and on).

[dom14]

One more thing, but it is costly, so you don't distort the fitting, you need to use the quality flange spanners or split ring spanners (like a ring spanner, but beefier and have a gap in them so you can slip them off and on).

Cool. I've got couple of them somewhere. Never had to use them up until now.

BTW, I went back to the car after communicating here and tried starting on LPG again. This time it won't.
No matter what I tried, it won't start on LPG.

Just to make sure it's not the carby, I put the secondhand carby and started on petrol. It's ok.
Now I'm just about to put the LPG mixer on and try it.
It may start, but won't mean a thing unless it can start all the time.

[dom14]

Just as I expected, the second carby didn't make any difference.
Starts and idles nice on petrol, but no go on LPG.

I tapped on the LPG solenoid near the converter with a 12V attached croc clip few times, then tried cranking.
I was able to start it for a fraction of a second.
This solenoid may be the culprit. I'm planning to pull it out tomorrow morning and inspect it.

[dom14]

Unlikely, but if it is not on full voltage, it will draw more current than normal and may overheat.

I'm not sure what was this about mate! Are you referring to the safety switch? What is the full voltage and overheating you're referring to?
Thanx

[threedogs]

sounds like you get a squirt to start and thats it, so you may be right about that solenoid not opening allowing for a full flow of gas;
The system has been bled, as no air pockets

[mudnut]

I'm not sure what was this about mate! Are you referring to the safety switch? What is the full voltage and overheating you're referring to?
Thanx

It was just a passing thought, as you wrote that the auto elec said it wasn't wired correctly. If a solenoid (which is basically a heap of coiled wire ) doesn't have its full voltage supply, they tend to draw more current and run hotter. Maybe also the high voltage spike of the ignition used as a signal is somehow feeding back into the low voltage side of things. Sounds silly but it use to happen on locomotives which used low voltage coils which were operated by high voltage signals.

[dom14]

It was just a passing thought, as you wrote that the auto elec said it wasn't wired correctly. If a solenoid (which is basically a heap of coiled wire ) doesn't have its full voltage supply, they tend to draw more current and run hotter. Maybe also the high voltage spike of the ignition used as a signal is somehow feeding back into the low voltage side of things. Sounds silly but it use to happen on locomotives which used low voltage coils which were operated by high voltage signals.

Yeah but he said he wired it correct and the previous bad wiring was the reason for it blowing itself every year or so, and that was over two years ago(or more). Solenoid appear to be faulty. I haven't pulled it out yet, I'm having some trouble undoing it.
I need to shut the gas from the tank by turning the tap(for extra safety), but can't reach it without lowering the tank. I prefer not to rely on the unpowered tank solenoid to shut the gas for me.
It's an old tank, better not to rely on electrical bits alone for the safety.

[threedogs]

sometimes they use 5 min Araldite on the connections to further prevent any sparks, and sparks are danger

[dom14]

It appears that I may be wrong and forgotten about it from the last time. LPG tanks manual tap is apparently for the filling side of it. The output side apparently solely rely on the electric solenoid to shut/open it. When it's unpowered, it's shut and it sounds like I'm gona have to rely on it for the safety. But, there's enough gas stuck between the tank and the solenoid piping.
Enough to give me cold burn from head to toe.
No quiet way to get rid of that, I reckon neighbors gona have to put up with the hissing for few minutes.

[mudnut]

Another reason I won't have lpg anymore. The conversion done to my Fairmont was bloody woeful, the workmanship downright dangerous. And running duel fuel you aren't getting the best performance from either fuel.

[dom14]

Another reason I won't have lpg anymore. The conversion done to my Fairmont was bloody woeful, the workmanship downright dangerous. And running duel fuel you aren't getting the best performance from either fuel.

True. Since, I do long distance cruising, having LPG saves a fair bit of fuel cash. But, if it stuffs up the carby and motor, then it's probably not worth it.
I have a second carby now, but carrying a second motor is a bit heavy exercise. :))

I always focus the tuning on LPG. In central red desert, due to lack of LPG, petrol tuning is preferred.
I would like to solve the issue by manually tuning the carby and dizzy on the fly, as well as changing the spark plugs, leads when running on either fuel.

There's another solution is to install one of these.

http://www.aeb.it/Products/Products/CatID/8/Timing_advance_processors


Cost around $140 when I checked with the supplier in Campbellfield last year.

[mudnut]

I can see that running duel fuel in your case is beneficial for remote touring. A young bloke I spoke to, has a twin turbo ready for his RB30. He was talking of fitting EFI as well. As it is a weekend warrior my mate (mechanic) and I tried to convince him to go a dedicated gas system. Although a big problem with that is if you run out of gas you are stuffed.

I used to have a flash lube drip system to combat valve recession fitted to our engine and had no trouble with that side of things. The unleaded engines handle gas better than those that were designed to run on super any way.

[dom14]

I can see that running duel fuel in your case is beneficial for remote touring. A young bloke I spoke to, has a twin turbo ready for his RB30. He was talking of fitting EFI as well. As it is a weekend warrior my mate (mechanic) and I tried to convince him to go a dedicated gas system. Although a big problem with that is if you run out of gas you are stuffed.

I used to have a flash lube drip system to combat valve recession fitted to our engine and had no trouble with that side of things. The unleaded engines handle gas better than those that were designed to run on super any way.

From what I've heard, EFI is a very good idea for turbo conversion(while turboing or before). Apparently, carby turbo, even with custom air boxes are pain in the ass to tune properly.
That's what I've heard about carby+turbo combination(for RB30 specifically).

I would definitely go for an EFI conversion before going for turbo, or make both into a single project.


What I'm wondering and have no idea about is that whether it's possible and practical to have a duel fuel system with RB30 turbo conversion.(EFI definitely)
I haven't been able to find lot of material about the practicality of that scenario, on the internet, yet.

I see quite a few GQW RB30 turbo conversions on one of the either fuel, but not both.

But, correct me if I'm wrong about that.

[dom14]

Another thing I've read from Altis007(George's) post was that VL computer is more useful for GQ RB30 turbo conversion than R31 EFI computer(something to do with flexibility of the ability to program the computer, I reckon)

In other words R31 non turbo EFI computer and the VL turbo EFI computer aren't the same. And the prospective turbo converter benefit from sourcing the VL turbo EFI computer(or rather VL EFI computer, whether it's turbo or not, I reckon).
I have no experience on this subject. I'm only relaying what I've read earlier.

[mudnut]

Me either, but George (Alitis) would know that and very much more.

[dom14]

Me either, but George (Alitis) would know that and very much more.

Yep, he's done it himself. It would've been great if George documented the whole process.:biggrin:

It's becoming harder to find a VL turbo commodore though. Plenty of non turbo ones around.

[dom14]

Dom, re PEEL safety switch.
The pin marked NEG COIL should go to either the neg side of your coil or can be wrapped around a spark plug lead. It is to pick up the distributor pulses.
The pin marked GAS LOCK OFF should connect to the input of the gas solenoid. This is to operate the solenoid.
The pin marked GAS 12V is your +batt input and should go to the gas/petrol switch. When there is +ve on this pin the relay operate and operate the solenoid if there are pulses on the first NEG COIL pin
The pin marked GND goes to ground or earth.
To check the relay is operating if you remove the wire from the GAS 12V pin and touch that pin with +ve from the battery, the green light should come on and the relay and solenoid should "click". When you remove the +ve battery, the light should remain on for 8 to 12 seconds. This is whith the engine off.

What happens is this. When you operate the switch to go from petrol to gas, = ve battery is fed to the GAS 12V pin via the gas/petrol select switch. the solenoid will then operate for 8 to 12 seconds to allow gas to flow into the system. By the end of that time your motor should be feeding pulses from the distributor to the spark plugs which should keep the switch operating.
The idea is this;
Gas should only flow when the motor is cranking or running. Initailly you get the 8 to 12 seconds to allow the motor to start turning. As soon as it is turning there is interupted pulses on the NEG COIL pin and the relay will remain operated until the motor stops and the pulses cease.
When you change your switch to petrol, the 12V input to pin GAS 12V is removed and switched to your petrol pump/solenoid.
Tony

Hi Tony,
As you advised me, the LPG safety switch needed a proper test, and it turns out that it's not faulty.
I've already ordered a replacement, but it's no waste, because I can use it for a different application.
They are pretty handy to use for anything that need spark coil pulse activation.

I'm suspecting a gas leak as well(from the lines that goes to the tank or the tank itself.)

At the moment the diagnosis has taken towards a bizarre direction with that leakage possibility.

Thank you heaps for giving me some damn good directions.

I'm still at it and bit by bit heading towards cleaning the interior of the LPG system.

I just opened a new thread to understand the wiring that goes in and out of the LPG safety switch.

Can you please have a look at it and post me some advice when you get a chance?

Thanks
Dom

[dom14]

Latest NEWS!!!

I must have fixed the issue, at least temporarily without even realizing it!

I 'fiddled' with electrical connections of the LPG system(s) under the bonnet, including the dodgy looking connections that goes along the gas pipes towards the tank.

Now its starting on LPG like never and the engine is purring!!!

There's more power on LPG like never.

I have few theories about how it may have fixed itself or by me.

1)shutting the auxiliary tank(tank may have been leaking gas)

2)Electrical connection cleaning and fiddling

3)Putting more gas(gas may have leaked completely due to the fact most of it in the auxiliary tank & caused the sludge to block the filters, solenoid etc?!

4)Supernatural intervention(not likely, 'cos I don't watch TV anymore)

5)Somebody's been playing a joke on me behind my back(not likely)


I'm yet to clean the converter, solenoid and LPG pipes. But the sheer performance on LPG is amazing.

I reckon there's high probability the engine was running pretty lean for a quite a while due to an electrical connection issue(solenoid not opening properly, either from tank end or near the converter), or LPG leaking and sludge blocking the filters inside the pipes, solenoid, etc.
I reckon the burning of oil & the bad oil were consistent with that.

[mudnut]

It'll be number 2. My fault, Sorry, I assumed that you had read the post in RB30 thread that I gave the link for in the carby thread today. Electrical connectors can come loose. Even though they may look alright, spade lugs can get a film of carbon under them too. Go back over your wiring. Check that the wires aren't stretched or broken internally or earthing out. Get rid of any scotch locks and solder any joints. Seal them with brush on electrical tape. Re-crimp any lugs and use pliers to tighten any spade lugs.

[dom14]

It'll be number 2. My fault, Sorry, I assumed that you had read the post in RB30 thread that I gave the link for in the carby thread today. Electrical connectors can come loose. Even though they may look alright, spade lugs can get a film of carbon under them too. Go back over your wiring. Check that the wires aren't stretched or broken internally or earthing out. Get rid of any scotch locks and solder any joints. Seal them with brush on electrical tape. Re-crimp any lugs and use pliers to tighten any spade lugs.

Yep, I'll have to do all that.
BTW, I should've mentioned the wiring was pretty substandard even from amateur backyard standards. The wire for the gauge and the tank solenoid was simply wound around the copper gas pipe between the tank and the converter solenoid.
I would have to replace all those wiring with proper ones as you advised above.

I'll do a thorough cleaning of the internals of the LPG pipes, solenoids, converter, etc regardless of what's the real culprit.
I think it will save me lot of trouble in the future and perhaps my life as well.:1087: :biggrin:

thanks mate.

[4bye4]

Hi Dom, glad that you are finally getting somewhere. As mudnut said, often loose connectors can cause issues that are real hard to find. Sometimes just undoing and re tightening a wire can make the problem disappear. I have also had issues (not on the patrol) of crimped wires coming loose in the connector. In the more modern vehicles, the voltages used in engine management systems are much smaller than the old cars where a full earth or full voltage (12V) was used. Some sensors like throttle position and airflow sensors may use say 3.5 to 3.9 volts as a signal to the engine management system. If you have a bad wire or bad connection or even some corrosion in the system you can loose .5 or more of a volt. This may cause the engine management to assume that there is a problem and go to limp mode or even shutdown when it is not needed. With the use of these engine management systems and sensors becoming more prevalent, it is more important to make sure that wiring, connections and earthing is good over the entire vehicle. Sometimes it good to remember when you could chuck a can of petrol on the roof rack and siphon it into the carbi to get home.

[dom14]

Hi Dom, glad that you are finally getting somewhere. As mudnut said, often loose connectors can cause issues that are real hard to find. Sometimes just undoing and re tightening a wire can make the problem disappear. I have also had issues (not on the patrol) of crimped wires coming loose in the connector. In the more modern vehicles, the voltages used in engine management systems are much smaller than the old cars where a full earth or full voltage (12V) was used. Some sensors like throttle position and airflow sensors may use say 3.5 to 3.9 volts as a signal to the engine management system. If you have a bad wire or bad connection or even some corrosion in the system you can loose .5 or more of a volt. This may cause the engine management to assume that there is a problem and go to limp mode or even shutdown when it is not needed. With the use of these engine management systems and sensors becoming more prevalent, it is more important to make sure that wiring, connections and earthing is good over the entire vehicle. Sometimes it good to remember when you could chuck a can of petrol on the roof rack and siphon it into the carbi to get home.

:biggrin:
Yeah Tony, I reckon that makes a huge difference when the engine management system kills the fuel pump and refuses to start the car or the fuel pump decides to die at the worst possible time.. :biggrin:
New technology works pretty well when the minor things like wiring is of good quality workmanship.
High quality wiring is becoming more important than ever.
That explains the reason when some modern cars develop an electrical fault that's not easy to find, they become insurance write-offs fairly quickly.
Even pretty much all the new motorbikes are becoming EFI. So, diagnosing modern automobiles is becoming more and more of an auto electrical job.
Modern mechanics are becoming more and more auto electricians as well as computer techies.
That probably end up closing the gap between two trades. I hope not. Auto electricians haven't been doing that well for a quite a while now.

Cheers mate.
Dom