Vacuum tester test results

[dom14]

Hey guys,

These are the videos of vacuum test results of my GQ RB30 carby model.
These are very short videos, Only half a minute or so each.
The tests were done once the engine is warmed up.
The idling RPM was around 1000rpm.
I did the plain vaccum test on different ports on vaccum lines first.
Then I did the sudden revving thing to see any faulty behaviour.

Test-1(LPG primer vaccum line)
https://www.youtube.com/watch?v=ZqmUswVLiaA&feature=youtu.be
I disconnected the vaccum line where it connects to the LPG converter.
Reading is around 22 In-Hg
The test shows slight constant moving of the vacuum tester dial.
Not sure what to make of it.
I need some expert assistance to interpret the result.


Test-2(Distributor vacuum diaphragm)
https://www.youtube.com/watch?v=xN_WsSxFr9E&feature=youtu.be
I disconnected the vacuum line from the distributor diaphragm.
No vaccum is showing on the tester. Engine is warm. idling was around 1000rpm.
I'm not sure what to make of it.

Test-3(Brake booster vacuum line)
https://www.youtube.com/watch?v=nbKuhIQvlMc&feature=youtu.be
I disconnected the vacuum line from the brake booster & pluged into the tester.
Vacuum line was pulled out of brake booster as in the video.
There's minor movement of the vacuum dial on tester, just like at LPG primer
vacuum line.
Reading is around 22 In-Hg.

Test-4(Thermal vacuum switch-top vacuum line)
https://www.youtube.com/watch?v=6Tj9xb_-IA0&feature=youtu.be
No vacuum shows(virtually zero)

Test-5(Thermal vacuum switch-bottom line)
https://www.youtube.com/watch?v=Ucrf-zWHIcw&feature=youtu.be
Vaccum shows around 11 In-Hg.
As you see in the video I had the top vacuum line open during this test.

Test-6(Thermal vaccum switch-bottom vacuum line-quick revving test)
https://www.youtube.com/watch?v=BeAU38UxfOI&feature=youtu.be
Vacuum shows around 11 In-Hg.
When sudden revving is applies, vacuum drops closer to zero & then go slightly above
11 In-Hg & then settles in 11.

Test-7(Brake booster vacuum line - quick revving test
https://www.youtube.com/watch?v=MxWDzzx_47k&feature=youtu.be
Vaccum shows around 22 In-Hg.
Quick revving doesn't cause the dial to go to zero first.
Vacuum quickly jumps to about 28 In-Hg and then slowly drops back to 22 In-Hg.

Test-8(LPG primer vacuum line-disconnected from LPG converter end- quick revving test)
https://www.youtube.com/watch?v=t4tmZ0Z9kU8&feature=youtu.be
On quick revving vacuum goes from 22 to 0, and then goes to around 27 In-Hg,and
then slowly goes back to 22 In-Hg.

I'm also adding a rough sketch of the vacuum lines, as they are laid out in my RB30.
The vacuum line that comes from the thermal vacuum switch(near radiator & cylinder head connection)
which goes to the carby and then to EGR is blocked from carby onwards.
EGR pipes and valve has been removed a while ago.
Removal of the EGR system did not affect smooth running of the engine.

I would appreciate bit of help with interpreting the test results.
Also wondering the purpose of the vacuum line between inlet manifold and throttle shaft "return
control" thing. It's activated via a some sort of electrical solenoid/valve.
But, it's not getting activated atm 'cos no power gets to it.
I'll post the photos of it shortly.

Thanks guys

[garett]

try this
59128

[dom14]

Thanks Garett. Studying it now.
I'm just preparing the photos.

[mudnut]

The system you have
described could be the FICD.
Its operation is
explained in this thread
http://www.nissanpatrol.com.au/forums/showthread.php?28517-RB30-Facts-Figures-and-Helpful-Hints.
Basically adds revs to
compensate for the
airconditioner.

[garett]

might be worth undoing the manifold side of your cat and retest .... wear some earmuffs if you do. but if it solves your problem you need a new exhaust/part exhaust.

[dom14]

These are the photos of the inlet manifold to throttle vacuum control diaphragm thing.

[dom14]

The system you have
described could be the FICD.
Its operation is
explained in this thread
http://www.nissanpatrol.com.au/forums/showthread.php?28517-RB30-Facts-Figures-and-Helpful-Hints.
Basically adds revs to
compensate for the
airconditioner.

Thanks mate. Lifesaving thread. :smiley_thumbs_up:
Good on you for creating such a great thread.

[dom14]

might be worth undoing the manifold side of your cat and retest .... wear some earmuffs if you do. but if it solves your problem you need a new exhaust/part exhaust.

Hi Garett,
I'm guessing you meant the catalytic converter, right?
I would have to wait until tomorrow then. Not a good idea to do it tonite! :D
I did this to muffler couple of times.
Muffler developed a small leak from a hole on the edge.
I 'fixed' the hole by mig welding them, which fixed up the leaks and noise.
Welding part was easy since I had access to a mig welder.
But, I wasn't sure whether it's the right thing to do.
I was just saving couple of hundred bucks(or more) at that time.
Exhaust is apparently not leaking at the moment(Need to double check though)
But, there's a leak from the gasket between the catalytic converter pipe
and exhaust pipe.(Very small).
I put a new gasket there at the same time I was cleaning and welding the muffler.
I also applied compressed gas to the muffler with the idea of cleaning any junk inside it,
which didn't produce any junks from the other side anyway.
I didn't go ahead with using water or any chemical flushes to clean the exhaust, which I
thought could be bad without knowing what it can do to insides of the muffler.
So, I'm guessing, the leak is due to weak contact(I tried to tighten the nuts, but that didn't help)
From outside, muffler looks almost brand new, from the work(mig welding the holes & spraying)
I did on it. But, I'm not too sure about the inside. Same goes for the catalytic converter(assuming
I have a one on my RB30)

Is there a way to test the catalytic converter(other than vacuum test)?
Other thing is that I hear somewhere the catalytic converter is not required for LPG(straight LPG)
vehicles.
Is there any truth in it?

[dom14]

The system you have
described could be the FICD.
Its operation is
explained in this thread
http://www.nissanpatrol.com.au/forums/showthread.php?28517-RB30-Facts-Figures-and-Helpful-Hints.
Basically adds revs to
compensate for the
airconditioner.

I can't find anything referring to FICD on that thread, but found out what FICD stand for.
FICD = Fast Idle Control Device.
You explained it above anyway.
In my case AC has leaked most of the gas in it.
I need to fix up the leak first before regassing it.
A/C won't affect the idling atm 'cos with low pressure gas, AC clutch won't kick in.
If you're right, this electrically activated vacuum solenoid I was talking about would
only get powered when the A/C is working.
And in my case, it won't get powered 'cos the A/C isn't working atm?!!

I think I can test it easily tomorrow by engaging the A/C clutch by directly powering it up.
That would in turn activate the FICD.
Thanks for the tip mate.

[dom14]

The system you have
described could be the FICD.
Basically adds revs to
compensate for the
airconditioner.

Yes, just found out it's FICD, after activating the A/C clutch directly.
But, it's not working.
It's either the electric solenoid valve is faulty or the vacuum diaphragm is not good.
I'm yet to test them.
But, it's not a concern at this stage, as the A/C need fixing anyway.
I'll test it to find out whether it's the diaphragm or the solenoid valve.

[garett]

lpg still needs a cat. not looking for leaks with the test i suggested was looking for a partly blocked cat or muffler. seen it a couple times not a real common issue but its easy ish to check. re running the vac test is probably the better way to check it ...

[mudnut]

Post number 31 explains the FICD operation.

[dom14]

lpg still needs a cat. not looking for leaks with the test i suggested was looking for a partly blocked cat or muffler. seen it a couple times not a real common issue but its easy ish to check. re running the vac test is probably the better way to check it ...

Thanx mate. Couldn't do it today 'cos of the noise at early or late hour. will do tomorrow.
I did the vacuum test at dizzy vacuum line with quick revving today while the engine was running cold start.
Funnily enough, it produced 10 In-Hg steady and went to zero and back to 10 when I quick rev the engine.

I tried sucking on the dizzy vacuum hose. It just filled my lungs, no resistance.
No feeling of vacuum there.
But, before that I pulled dizzy vacuum line while the engine was cold running.
RPM dropped a bit and came back to normal when I plugged it back in.

I pulled the dizzy cap tried sucking on the vacuum line.
I couldn't see any movement of the lever inside the dizzy.
I think I blew at it once or twice as well(with the hope that clears any jamming.

Then I got distracted and accidentally cranked the engine while the dizzy cap and rotor was out.
Some old memory said to me that I wasn't suppose to do that.

Anyway, I put everything back and tried to start the engine.
No luck.
pulled the dizzy cap out again and checked and put it back and cranked again.
No luck.

Then I thought I blew the ignition coil or something, so I checked with multimeter, it's good.

Then I sucked hard of the dizzy vaccum line again, Wow!
Here I feels the vacuum now(never before)
It's a miracle!

Tried starting the engine.
It started

No idea what I did or did not right.

I'm hoping the whole story makes sense to you.

Cheers

[dom14]

This is the exhaust leak at the cat converter-manifold joint.
The gasket is fairly new.
Bolts are tight.
Not sure the reason for the leak.
I'm planning to pull it out tomorrow.

[dom14]

I'm planning to pull out the dizzy and dismantle it, hopefully tomorrow.
I need to read some guides in the manual first, as I haven't done this before.

These are the dizzy pictures
I'm just wondering whether this is a stock dizzy or an after market enhanced one.

[dom14]

Post number 31 explains the FICD operation.

Thanks mate. I just need to learn to read. :D
It's a pretty informative post.
I reckon I might have to remove some of the gibberish I wrote at the start of this thread,
'cos before I had no idea what it does.
Now I do. :)

[mudnut]

That is the exhaust manifold to
engine pipe joint. I have only
recently had the engine pipe
replaced as the flange was
warped because it was made
with thin steel.
The gasket on that join blew
out during the drive home
from the exhaust shop.
The guy spent ages refitting
a new gasket which blew out
as soon as the engine started.
On closer inspection we found
the new pipe was fouling inside
the manifold so the gasket
wasn't getting clamped.
He ground off the protruding
pipe and fitted a flat gasket.

My '94 RB30 doesn't run a
Catalytic converter and I was
told 4x4s were not required
to run them until a few years
after mine was built.

[dom14]

That is the exhaust manifold to engine pipe joint. I have only recently had the engine pipe replaced as the flange was warped because it was made with thin steel.The gasket on that join blew out during the drive home from the exhaust shop.The guy spent ages refitting a new gasket which blew out as soon as the engine started.On closer inspection we found the new pipe was fouling inside the manifold so the gasket wasn't getting clamped. He ground off the protruding pipe and fitted a flat gasket.

My '94 RB30 doesn't run a Catalytic converter and I was told 4x4s were not required to run them until a few years after mine was built.

Hi mate,
If that's the case, I don't think mine has a cat converter either. It's a 1990 model RB30.
There's the muffler and then the resonator at the end of exhaust. But can't remember having another cylinder between the muffler & manifold.
I need to double check under chassis to confirm.

As you can see in the picture, the flange is around half a centimetre thick on both ends.
Do you think it's possible it's warped?
Sounds like I have the same problem as yours.
Also wondering if there's a heat resistant sealant that we can thinly cake between the gasket and flange.

When my broken EGR pipe at the exhaust was giving me crxp, I kept caking some exhaust paste once a week or so, which kept going that way, before I pulled whole pipe out and effectively removing the EGR system. It was a PITA job 'cos very hard to access both ends of the pipe without removing both inlet and exhaust manifolds. Even after that, the pipe was practically welded to the two manifolds over year of heat, I ended up ruining the whole pipe and joint in the process, hence the decision to get rid of EGR for good, since the LPG doesn't require EGR as far as law concerns.
I'm wondering whether there's similar sealant I can apply between the gasket and flange as an interim measure(not the paste I used to cake over the joint though, that's messy and short lasting)

[garett]

you can get a putty for that exact task. ask at you local parts store they should have it in stock. its like clay paste in a tube

[dom14]

you can get a putty for that exact task. ask at you local parts store they should have it in stock. its like clay paste in a tube

Cool, mate. I'll drop into Supercheap or Burson.
Cheers

[dom14]

Just updating,
There's no catalytic converter in my GQ RB30(carby, 1990).

[dom14]

I'm planning to pull out the dizzy and dismantle it, hopefully tomorrow.
I need to read some guides in the manual first, as I haven't done this before.

These are the dizzy pictures
I'm just wondering whether this is a stock dizzy or an after market enhanced one.

When I bought the car, there was dizzy points in the left hand side box.
I thought the guy upgraded from points to magnetic-electronic unit as appears in the dizzy now.
But, I've been told this is the stock dizzy with all the components in it.
If that's correct, the guy must have bought the points by mistake?
Did the GQ RB30 stock dizzy come with points or no points?
I would be grateful to find out.
Thanks guys

[mudnut]

I tried that paste and
it blew out within a
week.

Mine was fitted with
an electronic ignition
and the vehicle was
bog stock standard.
It is strange that the
engine started after
you sucked on the
vacuum advance line.

[dom14]

I tried that paste and
it blew out within a
week.

Mine was fitted with
an electronic ignition
and the vehicle was
bog stock standard.
It is strange that the
engine started after
you sucked on the
vacuum advance line.

Yes, it's strange. And strange it refused to start when I opened the dizzy up to the point of taking off the rotor and then put it back the way it was.
I blew moderately hard on the dizzy vacuum line once or twice with the hope unjamming any stuck parts of it.
If that's the cause of not being able to start, then I need to find out why.
At first, I felt no vacuum from the diaphragm, then in the end I did, which is weird.
I reckon the diaphragm(and perhaps the internal lever mechanism as well) is dodgy.
I was going to pull apart the dizzy today, but wanted to go through the manual first.
I'll update as I go.

Did you say you tried the external ceramic paste or the paste that is supposedly applied between the flange and the gasket?

I saw a picture of somebody applied some sort of silicon looking paste inside the surface of the gasket(manifold gasket in that case). The thread is somewhere in the forum. I need to find that thread.
I think the flange surface is bit pitted on mine. That's why I thought some kind of sealant paste might help it as a temporary measure.
I didn't get a chance to go to Burson and find out what they have for something like that.
Will do tomorrow.
Cheers

[dom14]

Hey guys,
Let me quote the below line from Haynes manual before I start yapping.

" 3.0 litre engines are equipped with a vacuum switch which will not allow engine vacuum to reach the vacuum
advance unit until the engine is warm".

This is obviously the thermal vacuum switch on top of the cylinder head-radiator hose spot.
The same thermal vacuum switch opens and cuts the vacuum to EGR vacuum line as well.

I found the vacuum test(when engine running cold) at the dizzy vacuum line produces something completely opposite to what the Haynes manual says above.

When I did the engine cold running vacuum test at the dizzy(again today) the vacuum says 10 In-Hg.
Then once the engine is warm the vacuum cuts out.

Complete opposite of what Haynes says above.

It looks like the vacuum lines are swapped, accidentally?
I'm guessing it must be me!

Only thing that confuses me is that

more advance when cold and
less when warm

is what LPG needs, doesn't it?!

So, should I leave the thermal vacuum switch lines as it is now or should I swap it to produce the result as in the Haynes manual??!!

Thanks for any tips.

[mudnut]

Yep tried the cement and also
a bandage, The pipe must've
been moving and crumbled
the paste.

[Robo]

vac needs to be supplied as per mr nissan design.
search manual, you should be able to find vac line diagrams.
and these diagrams should also show direction of flow/vac.

firstly, don't be worried about lpg needs more as ya mentioned.
vac lines and vac switches needs to plumbed and working correctly first.

vac advance is later on in the tuning process.
for lpg, adjusting the dizzy advanced a few deg,
each engine and owners specs vary the amount of advance slightly.
eg to much advance and you'll lose top end power,
to little and you have trouble getting lpg to preform efficiently.
cheers

[dom14]

Ok, cool. I was thinking whether somebody purposely swapped the vacuum lines on thermal switch to get an advantage for LPG ignition.
Not a good idea to fiddle with vacuum lines without knowing it's mechanics.
It wasn't me for sure, unless I accidentally did it while under the influence of booze.cBang Head :D
The reason, I've been doing all the fixing and tuning on LPG, 'cos I drive on LPG all the time.
But, apparently not the best approach when diagnosing problems of course.
Thanx mate

P.S. couldn't find vacuum diagrams on Haynes or Factory one. That's why I drew the funny looking diagram above.
I should look harder in the factory manual I reckon. It should be there somewhere :)

[dom14]

I swapped the vacuum lines on the thermal vacuum switch.
Then did a vacuum test on dizzy vacuum line.
It behaves as the Haynes manual suggested now.
Which means, there's no vacuum in the dizzy vacuum line(until engine is warmed up).
But, by swapping the above vacuum lines to be the way it suppose to be, it dropped
the cold idling even lower to around 450-500rpm, it picks up once warmed up.
But, obviously not good. ATM, it's no affect on stalling the engine, 'cos A/C is not running.

I'm planning to get hold of the vacuum pump and do a proper vacuum test on dizzy vacuum diaphragm,
as well as dismantle the dizzy slowly and look for any issues inside.
Apparently this stock RB30 dizzy has a mechanical advance as well as vacuum advance, according to the
patrol(Haynes) manual.

Just trying to test the resistance on leads and spark plugs.
I can't find the specifications on the manual.
Do you guys know where it is in the manual or do you remember?

[Robo]

try the tuning section.
usually near front of manuals