Dual fuel - not running on petrol

[macavity]

Hi !

My GQ wagon stopped working on petrol a few weeks back now. Been going through old threads and guess it's something related to running it for far too long on gas alone, or after recent soaking electrical.
So far I have:

- taken off fuel filter by battery, crank, no fuel coming through
- running on the road on gas, switch to petrol. Nothing doing
- back home, unscrew petrol line on engine side of filter - fuel coming out at high pressure
- spark test OK

Gas/petrol swith looks OK, but the gas meter circuit board was very corroded (still works though). Guess I've had a lot of moisture getting in the back there.

Injectors? Is there a petrol cuut off switch somewhere?

What next?

Thanks, Tim.

[taslucas]

Is this an efi engine (hence the injectors)?
With a carby running on gas alone for too long dries out the rubbers in the carby.
I'm not sure about efi hopefully someone will come along with more knowledge

[macavity]

Is this an efi engine (hence the injectors)?
With a carby running on gas alone for too long dries out the rubbers in the carby.
I'm not sure about efi hopefully someone will come along with more knowledge


Hi taslucas,

Bit of a mechanical idiot over here, but getting better! There's no carby - injectors under a big block with ECCS written on it.

All the best, Tim.

[taslucas]

No worries, I'm no genius myself lol. I don't know anything about the efi models, but I'm guessing it might be a similar problem: long term gas use drying out some rubber components? Or perhaps fuel pump?. Hopefully you will get some better help soon!

[YNOT]

Hi !

My GQ wagon stopped working on petrol a few weeks back now. Been going through old threads and guess it's something related to running it for far too long on gas alone, or after recent soaking electrical.
So far I have:

- taken off fuel filter by battery, crank, no fuel coming through
- running on the road on gas, switch to petrol. Nothing doing
- back home, unscrew petrol line on engine side of filter - fuel coming out at high pressure
- spark test OK

Gas/petrol swith looks OK, but the gas meter circuit board was very corroded (still works though). Guess I've had a lot of moisture getting in the back there.

Injectors? Is there a petrol cuut off switch somewhere?

What next?

Thanks, Tim.

I'm confused as these statements seem to contradict each other?

Generally on EFI vehicles power to the injectors is cut (could be anywhere between the ECU and the injectors) when you switch to gas, the fuel pump is left untouched.
As a general rule if the injectors are gummed/carboned up the engine will still run, just not very well, same if the filter is partly blocked or the fuel stale. If the fuel pump fails it will usually fail totally so the engine won't run at all on petrol.
Other possibillities to look for are air leaks between the air flow meter (on the side air filter housing) and the engine.

Tony

[macavity]

I'm confused as these statements seem to contradict each other?
Tony

Hi Tony,

Working nights so should have a chance to have a good look tomorrow.
Yes, seems odd!

I completely removed the fuel filter, switched to petrol and cranked with my finger over the hose - nothing.
Put it all back together and took it for a spin (first one since running on gas). Tried flicking to petrol a few time on the move - nothing.
Came back and undid the hose on engine side of filter, started pulling it off and petrol started spraying out.

Come to think of it, one of the times when I tried cranking on petrol (I think before I took it for a spin) it fired for maybe a second or so, whereas the norm is for almost immediately cutting off.

Will hunt for air leaks tomorrow.

Thanks, Tim

[Yendor]

If you do have spark and fuel pressure, you will need to check that the injectors have power.

Disconnected one of the injector plugs, you should have power in one of the wires in the connector, possible a white wire with a green trace.

You may need to get someone to keep turning the ignition on and off, depending on what year model yours is.

If you don't have power then have another look at the green relays and fusible link.

The green relay beside the battery will more then likely be the ECU power relay and the other one possible is the fuel pump relay (they should be labeled).

Did you check the connectors for the fuses near the battery?

[macavity]

G'day everybody,

Following on from Tony and Yendor's suggestions....

- I can't find anything obviously amiss on the air leak side of things apart from the housing covering the air filter. This is held down by springs on one side but is missing clips to hold it down on the other. These have not fallen off recently and I guess have been missing for the 3 years I've had the vehicle... Not a perfect seal but it has been running OK like this.

- Injectors. Did I tell you I'm a complete newbie to all this?!! Spent 5 minutes trying to unplug the 1 injector I could get at without success... Gave up as I've convinced myself that this isn't the problem. Wil re-visit later maybe!

- Fuel Pump. I could not replicate the symptoms I described yesterday. No matter what I've tried so far has got any fuel past the filter whatsoever. So, I guess at some point yesterday the pump must have kicked in for a second or so and not done so since.

- This has led me to follow Yendor's suggestions more closely.

A brief bit of history. GQ was off the road for 4 months last year coz I didn't have enough cash to replace the clutch. Fixed eventually, but rego run out; then it wouldn't start at all. Local guy got it running on petrol. Took it to gas guy for tank inspection - an hour job turned into a whole day's work - got it working both ways but said the local guy had completely bodged the job - "illegal" were their words about what he'd don with the wiring...

- Can't find any obvious problems around the green relays (no labels as such on these). Connections from these lead to a harness beneath - there is an obvious 'new' thin red wire that goes back from this to the interior somewhere.
The housing for these relays looks as if it's been tinkered with recently as it's anchored by just one screw.

- Dug up my meter. Checked across obvious fusable links. No resistance.

- When I switch off from petol (not cranking) I hear a click from a small black relay which is rearmost from the green ones (not under the cover). It doesn't click when you you switch 'on' to petrol but guess it must have re-set or something. Anyway, there's a blue lead that goes from this and disappears toward the back of the vehicle, I'm guessing to the fuel pump?

- This relay has a shiny new screw holding it down. I took it off yesterday and I'm pretty sure that is when the engine tried to fire briefly on petrol. No joy today doing the same thing though.

- took the ECU out today as well to check for moisture and obvious stuff. All looks good.
Plus side to all this is at least it's running A1 on gas and I've got a the gas guage working again.

Soz for the long post but hope it might narrow things down. Then again I might be completely barking up the wrong tree...

Thanks, Tim.

[YNOT]

I'd be trying to get the fuel pump working reliably before you do anything else. If you have a good power feed and earth to the pump then I would suspect the pump.

Tony

[macavity]

Hi Tony,

What's the way to go about testing this - like I say, I'm new to mechanics and don't even know where the bugger is located!

Thanks, Tim.

[Yendor]

Hey Tim,

What year model is it?

The reason why I asked you to check if there was power at the injectors is, when running on gas, power should be switched off to the injectors and fuel pump "completely bodged the job - "illegal" then again maybe not the fuel pump on your vehicle???

So it's possible you have an electrical problem when you switch back to petrol, that power is not supplied to the injectors or fuel pump.

The black relay I would say is not genuine but does it plug into a genuine base?, is the blue wire part of the genuine harness? does it have a white stripe on it? are there any numbers on the relay, such as 85,86,30 & 87?

[macavity]

Hey Tim,

What year model is it?

The reason why I asked you to check if there was power at the injectors is, when running on gas, power should be switched off to the injectors and fuel pump "completely bodged the job - "illegal" then again maybe not the fuel pump on your vehicle???

So it's possible you have an electrical problem when you switch back to petrol, that power is not supplied to the injectors or fuel pump.

The black relay I would say is not genuine but does it plug into a genuine base?, is the blue wire part of the genuine harness? does it have a white stripe on it? are there any numbers on the relay, such as 85,86,30 & 87?

Hi Yendor,

Many thanks for the reply. I'll have to check on the finer details in the morning. It's a 92' GQ wagon 4.2 Petrol Injection. Has had many extras fitted over the years.

The black relay: from memorory looking at it today - blue lead (can't remember seeing a white strip) doesn't go to a harness. Single wire straight from the relay that goes down then somewhere towards the rear of the vehicle. Black lead goes to proper harness by the look of things, that goes to the bunch by the injectors. One more - can't remember where that one goes right now.
Need to look and see about numbers on the relay tomorrow. I do remember it had a little circuit diagram on top of it that mentined the coil.
Will re-visit the injectors!

All the best, Tim.

[Yendor]

It could be for the fuel pump, you may need to follow the blue wire and see where it goes.

If it is for the fuel pump we can then test the relay and it's switching and see if we can get fuel pressure.

If you can post some pictures up it may help.

Where on the Sunny Coast are you from?

Cheers Rodney

[macavity]

Hi Rodney,

Thanks. Probably best ingoring my last post. Memory was poor and I guess I also need and eye test!

A couple of photos attached...

The first photo shows the relays by the battery. Found the labels, and as you said, the leftmost green relay is for the fuel pump. 15amp fuse next to it OK. You can see in both photos the new red lead I mentioned. This goes from the switch in the cab to the harnesse under the relays. It looks a bit of a mess down there...

The second photo shows the black relay I mentioned. I was poking around with the multimeter and touched the relay onto something and it sparked. Since then, this relay now clicks both on and off when I switch petrol on/off. Could only detect a click when switching 'off' yesterday. Makes no diference to running though...
4 leads go off this. Red & a black to harness that goes towards injectors. Black to earth. Other one not sure (to switch I guess). All original harnesses I think. The blue lead I was on about yesterday has nothing to do with it. Can be seen in top of photo.

Working the next 3 nights now (bah!) so don't know when I'll get a chance to look again.

All the best, Tim.

PS I'm in Glenview - out behind the Etamogah Pub.

[Yendor]

Hi Tim,

It sounds like that black relay is used to turn off power to the injectors when running on gas. One of these wires "Red & a black to harness that goes towards injectors" should have power in it all the time and the other one should have power when petrol is selected and (just to confuse you a little bit more) the second wire should also have power in it for a short period of time when engine is started on gas. Don't worry to much about this, just for your info.

When you turn on the ignition you should be able to hear the slight buzzing sound of the fuel pump running for about 2-4 seconds, coming from the rear of the vehicle, then it should stop. If you turn the ignition off and on again, you should hear it again for another 2-4 seconds. If you can't hear this and/or you still don't have fuel pressure you will need to check the fuel pump circuit.

It's a bit hard to tell what that red wire does but if it goes to the fuel pump relay and joins to a white with a green trace wire there's a good chance this turns the fuel pump off.

At the fuel pump relay, 2 of the 4 wires should have power in them (both white wires with green traces). The blue wire with a white trace is the wire that goes to the fuel pump. With the relay still in (so you will need to back probe the connect from underneath) This wire should have power in it for the 2-4 seconds when ignition is turned on, it should also have power in it when the engine is cranking and when the engine is running on petrol. If it does and you still don't have fuel pressure you will then need to check that there is power and earth at the fuel pump.

The fuel pump is located at the rear of the vehicle, there is an access cover in the floor on the driver side, just lift up the carpet/vinyl and remove cover.

If it's any help you can call me when you are carrying out the test and I can help you through it.

Good luck with it.

Cheers Rodney

ps Just for my info, the brown relay that is just out of shot in your first photo, what is that relay for? electric window?

[macavity]

Hi Rodney,

Thank loads for the info. Unfortunately not had a moment to look today and won't get a chance till Monday now.

I did have a quick look for the fuel pump the other day but gave up quickly after crawling around getting covered in mud...
I guessed there was an inspection plate and took up the carpet in the back right. The one with 4 screws nearest to where you'd fill it up, right? Anyway, all that was right underneath it was the gas tank...

I'll get back soon with my findings, and ta for the offer to talk me through it.

All the best, Tim.

Tim.

[autotrans]

HI Tim
Just an Idea If all seems OK on the petrol system Have you tryed running on petrol with the gas completely turned of ie gas soleniod disconected it may be duel fueling and this would stop it running quite quickly.I have seen this problem when the emulator fails.
Good Luck Brian

[macavity]

Hi again,

Finally got round to another look today. My wife nicked the car to run up and down to Brisbane a couple of times - a bit cheaper than her old V8 Petrol Landrover...

Fuel pump relay. I've unscrewed the block containing the relay but can get enough slack to either see or get test meter to the underside. Taped up so can't see which wires lead into a block below that I can't get at either. With relay out, there is power always on to 2 connectors and with ignition on, power to another one (same one when switched to gas or petrol). Didn't test while cranking.

Fuel pump. Don't know if mine is a regular set op or what. The gas tank is at the rear lying across the vehicle. Inspection hatch reveals just the top of the tank. Petrol tank is rectangular and runs lengthways beneath the right passenger door. I can't see or trace wires (yet). I guess I'd need to take all the carpets up (and seats??) to see if there is an inspection plate..
I cannot hear any buzzing noise when I turn the ignition on.

I've tried Brian's suggestion - thought it was going to fire, as it seemed to be trying to do something for a while - like a few almost splutters, rather than the one fire (remaining gas in cylinders?).
Undid the fuel line - petrol came out under pressure. So at some point the pump has kicked in I guess.
I could't replicate this when I tried again and again.

Hope things are slowly getting narrowed down!

Thanks & all the best, Tim.

PS Brian: used to climb quite regularly near where you live when I lived in the UK- Bridestones in particular. Lovely spot!

[Bigrig]

Hi again,

Finally got round to another look today. My wife nicked the car to run up and down to Brisbane a couple of times - a bit cheaper than her old V8 Petrol Landrover...

Fuel pump relay. I've unscrewed the block containing the relay but can get enough slack to either see or get test meter to the underside. Taped up so can't see which wires lead into a block below that I can't get at either. With relay out, there is power always on to 2 connectors and with ignition on, power to another one (same one when switched to gas or petrol). Didn't test while cranking.

Fuel pump. Don't know if mine is a regular set op or what. The gas tank is at the rear lying across the vehicle. Inspection hatch reveals just the top of the tank. Petrol tank is rectangular and runs lengthways beneath the right passenger door. I can't see or trace wires (yet). I guess I'd need to take all the carpets up (and seats??) to see if there is an inspection plate..
I cannot hear any buzzing noise when I turn the ignition on.

I've tried Brian's suggestion - thought it was going to fire, as it seemed to be trying to do something for a while - like a few almost splutters, rather than the one fire (remaining gas in cylinders?).
Undid the fuel line - petrol came out under pressure. So at some point the pump has kicked in I guess.
I could't replicate this when I tried again and again.

Hope things are slowly getting narrowed down!

Thanks & all the best, Tim.

PS Brian: used to climb quite regularly near where you live when I lived in the UK- Bridestones in particular. Lovely spot!

Did you test continuity on the relay itself also? Long shot, but worth a go.

P.s. any chance you'll be able to make the forum meet up in October??

[macavity]

Hi bigrig,

How do I test for continuity? I've tried swapping relays...

When and where is the meet? Don't see why I can't make it if I'm not working.

All the best,

Tim.

[Bigrig]

Hi bigrig,

How do I test for continuity? I've tried swapping relays...

When and where is the meet? Don't see why I can't make it if I'm not working.

All the best,

Tim.

Take the relay out and set your multimeter to ohms (20k) and positive and negative connectors on the multimeter to the two other spade connectors (not power or earth) on the relay - should read 1 ohm I believe, but Rod or one of the more electrically minded can let you know that one. I have done it on mine, so have a go at it and you'll more than likely figure it out anyway - only one way will show continuity I believe so swap them around till you get the reading - if you don't then the relay could be receiving power, but still failing you.

Top stuff on the trip mate, jump on the thread and throw up a definite maybe on the poll if you get a chance. Also, PM me your mobile (I won't spam you! lol) as I use SMS to keep in touch with most the qld'ers as its sometimes more convenient than checking on the forum (with the updates changing etc). My email is on the thread also, so shoot one through to that, and that way everyone is assured of having the latest information.