GQ RB30 Stalling

[lsmitti]

Hi all,

Having a bit of an interesting issue with the GQ RB30, I'm hoping someone may have had occur to them or may know what's the cause..

The car stalls / seems to run out of fuel when starting on a hill and taking off after being left for the day. Is reluctant to then start again until on flat ground.

I have changed the fuel filter, cleaned the inline fuel mesh on the banjo bolt On the carby and I have tested the return fuel solinoid resistance.

I first thought that the float may be stuck in the carby but lately the car has recently began stalling shortly after been refueled.

I have noticed a lot of pressure being released when removing the fuel cap.

Is it simply the fuel pump can't keep up and is too weak to get pressure back in the tank / lines?

Is there any other componet I'm missing here?

Cheers in advance..

[mudnut]

Is it pressure being released or air sucking in? I recently had to replace the fuel pump due to stalling etc. Has the carby been cleaned and a kit installed since you've had the vehicle?

Check the linkages and vacuum diaphragms. Make sure the second stage is operating properly. And make sure the internal screws that hold carby together are tight.

[lsmitti]

Thanks mudnut, I haven't had a carby kit put through it or thoroughly cleaned it in last 40k apart from a bit of carby cleaner down the throat of it. That aside the car runs well expect for those two scenarios, when starting on a hill or shortly after refueling. There has been the odd occasion it has seemed to run out of fuel while being on the hwy but thinking back that could have also been shortly after refueling. Based on this are we still thinking carby?

Being a long-range fuel tank I assume changing the fuel pump is going to be a pita?

I have noticed that the Gregory manual suggests pulling the fuel pump control fuse out to relieve pressure to replace the fuel filter but for me the car continues to run and never stalls ( can hear pump still running) can I assume someone previously changed the pump / wiring ? Or is this normal?

[PeeBee]

I would check your fuel tank breather, located up and behind the fuel tank filler. This is always moist from the relief operation and is a great place to catch all the dust that billows out from the rear wheels. The tank will pull a negative pressure if the volume of fuel is not replaced with air. It won't matter how good your fuel pump is - if the breather is blocked, which is indicated by the 'whooshing sound' when you open the tank, you will cease to draw fuel to the motor - seen it on 3 tanks so far. Also, you may find the vent line is plugged up with dirt as well, so the hose may need removing - don't just blow it clear with an airline whilst connected to the tank as the muck will go straight back into the tank.

[mudnut]

I would check your fuel tank breather, located up and behind the fuel tank filler. This is always moist from the relief operation and is a great place to catch all the dust that billows out from the rear wheels. The tank will pull a negative pressure if the volume of fuel is not replaced with air. It won't matter how good your fuel pump is - if the breather is blocked, which is indicated by the 'whooshing sound' when you open the tank, you will cease to draw fuel to the motor - seen it on 3 tanks so far. Also, you may find the vent line is plugged up with dirt as well, so the hose may need removing - don't just blow it clear with an airline whilst connected to the tank as the muck will go straight back into the tank.

That could be the case. Mine has no breather as such, except for the petrol cap. I'm interested to see if @Ismitti s tank is fitted with the breather.

[PeeBee]

Muddy, funny how the simple things get overlooked. I was troubleshooting a process at a food plant yesterday and the incoming air line for the vacuum convey system was 99% clogged with a globb-berg that not only stopped the airflow but had been festering away and generating mould spores that went straight into the product - funny enough they had been struggling with mould issues for the last 12 months - root cause is a great thing, problem resolved by way of faster/nameplate performance and no introduction of mould into the product.

[lsmitti]

Thank you, PeeBee and Mudnut. I'm hoping it's something as simple as this! The Old girl stalled at a set of lights a minute down the road from home this morning, So its progressivly getting worse.

Will take a look hopefully in the next day of two.

Thanks again

[lsmitti]

So, I have a breather which goes from the top of the tank to the filler flange which I assume is to assist with allowing air to escape when filling the tank. This line is breathing fine. The Fuel cap appears to have a value for negative pressure. If I apply negative pressure to the fuel cap it will allow for air to flow but not vent pressure as it should. There is Three lines heading from the tank to the front of the car. I assume one is the actual fuel feed line, the other a return fuel line and the last for positive pressure which goes to the canister on the passenger side of the radiator.

I checked that the one heading to the canister was free flowing which it is.

The car is now stalling shortly after every time it is started.

Car starts fine, idles well but if I watch the fuel window on the carby I can see the fuel slowly drain out of the bowl until it stalls. If I hold the ignition on an angle just enough for the fuel pump to go but without engaging I see that the fuel refills the bowl. Starting the car again and watch the fuel window I can see the fuel drain out again.

If I give the car a fuel revs as to simulate driving the fuel drops below the middle of the fuel sight but doesn't drain out and the fluctuates around. If you then let it idle it seems fine.

Now repeating all of the above, when first starting and the fuel is about to empty out the bowl if I remove the connector for the Return fuel solenoid the bowl quickly fills up and doesn't stall while idling and without giving any revs.

I assume this is causing more pressure at the carby.

Now I had checked the resistance on the fuel return solenoid and it was within spec and I can hear it click in and out with revs..

The only other thing that is non standard is the EGR pipe from the Exhaust manifold is urghh not connected.. after fitting extractors.

Does this all lead to either low pressure on the fuel line (I probably need to get the pressure checked, just don't have a pressure gauge) or that the carby is gumme up and needing more pressure than normal?

Any help would be a great help! Cheers

[PeeBee]

What happens if you leave the fuel cap off - does this improve the situation or does the bowl still empty to zero? The breather I am referring to is not the displaced air pipe for when you at are filling up - its a hose that allows the tank to suck air in when you are running to replace the volume of fuel removed - maybe this is one and the same on a petrol, however you say the cap does not seem to allow this negative pressure condition to be vented to atmosphere?

[lsmitti]

Thanks for the reply PeeBee.

I did try leaving fuel cap off but didn't seem to make a difference.

Looks to me that the fuel cap is the negative pressure relief for the tank. What I meant to say in my previous post is that the fuel cap doesn't vent positive pressure, this goes to the canister at the front to be burnt and negative pressure relief to me seems to be the valve in the fuel cap.

[lsmitti]

Hi all, ended up being the fuel pump.

For anyone else with a similar problem a simple test is to pull the fuel line off the top of the fuel filter. Attach a pipe to the top of the fuel filter and run it into a container. Turn the key enough to hear the fuel pump start and measure the amount that ends up in the container after 1 minute.

Mine had pumped a mere 200ml at most in 1 minute. From what I can find online it should be closer to 900ml - 1 litre in 60 seconds.

Based on this it seemed the fuel pump was the likely cause since I had replaced the fuel filter and left the fuel tank Cap off when testing to ensure there wasn't an issue with negative pressure etc.

If you get enough volume into the container I would then be looking at the fuel return solinoid, carby inline fuel mesh filter (banjo bolt) or the carby itself as these bits are all after the fuel filter which is where the above test tests up to.as such.