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[stuvaux]

Not unknown for new GM crank sensors to be faulty

Surely it wouldn't run well on LPG if crank sensor was faulty....or am I wrong in thinking this?

Electrically the only difference between petrol and lpg is which injectors are working, so unlikely to be crank sensor, hence my fuel suggestion

Generally lpg is much more sensitive to weak or failing sensors than petrol, so I doubt it's a sensor issue

Thanks, that is what I was thinking. Going to get some fresh petrol to try that. Also ordered a fuel filter which should be here by next Tuesday. Luckily I have my Bedford CF2 to keep me mobile in the meantime! 

[stuvaux]

Quick update. Fresh fuel didn't make any difference 

Next step fuel filter, as soon as it gets here

[martin42]

Ive not driven a cf2 in a few years ....

[05omegav6]

Quick update. Fresh fuel didn't make any difference 

Next step fuel filter, as soon as it gets here

How much fuel did you add?

[stuvaux]

Ive not driven a cf2 in a few years ....

Still as great as ever....better than any modern van  . I have owned it for 14 years, only recently got it back on the road. I now use it almost daily as part of my business 

[stuvaux]

Quick update. Fresh fuel didn't make any difference 

Next step fuel filter, as soon as it gets here

How much fuel did you add?

10 litres.....it did start initially but then same problem happened after a minute or so of ticking over

[05omegav6]

If you look under the car at the tank you'll see a round patch on the right hand side towards the middle...

Give this a thump with your fist as someone cranks the car... fuel pumps can stick when they're on the way out

To add, try and get the car as level as possible, any slope, especially to the left, and the fuel is away from the pickup.

If it starts when level, you need more fuel in it, when they run dry they take alot more than you think to get going

If it doesn't start, the whack the tank as above whilst cranking. If it fires and runs then budget for a new pump...

It will likely be one of those two things

[stuvaux]

If you look under the car at the tank you'll see a round patch on the right hand side towards the middle...

Give this a thump with your fist as someone cranks the car... fuel pumps can stick when they're on the way out

To add, try and get the car as level as possible, any slope, especially to the left, and the fuel is away from the pickup.

If it starts when level, you need more fuel in it, when they run dry they take alot more than you think to get going

If it doesn't start, the whack the tank as above whilst cranking. If it fires and runs then budget for a new pump...

It will likely be one of those two things

Great tip, will give that a try thanks 

It is parked on level ground so I'm thinking there must be enough fuel in there now. I won't be back to the car until Tuesday now, but will definitely give that pump a whack when I get chance 

[stuvaux]

Update - changed fuel filter. Car ran for a few minutes, then went really choppy and cut out. I then noticed that the fuel tank had "sucked in" on itself! When I opened the fuel cap loads of air came out (this also happened last week but I assumed it may have been that I had left a vac pipe off....). the tank then returned to normal.

Is it possible that there is a small hole in the pipes above the fuel pump? I have had a look at them - there is some surface rust but no obvious holes. I'm thinking it must be drawing air in somewhere.

[Entwood]

Update - changed fuel filter. Car ran for a few minutes, then went really choppy and cut out. I then noticed that the fuel tank had "sucked in" on itself! When I opened the fuel cap loads of air came out (this also happened last week but I assumed it may have been that I had left a vac pipe off....). the tank then returned to normal.

Is it possible that there is a small hole in the pipes above the fuel pump? I have had a look at them - there is some surface rust but no obvious holes. I'm thinking it must be drawing air in somewhere.

That can't happen ...   if the tank "sucks in" as you call it, when you open the cap then air will ENTER the tank to relieve the vacuum .. which is IMHO the cause of your problem !!  If a vacuum builds up in the tank then no fuel will leave it... so  suggestion #1 ... try running the engine with the fuel cap OFF if it works ok that proves the problem, you then need to find out why the fuel vent system is not working as it should, it is a sealed system to prevent pollution , but the system will replace used fuel with air via the vent pipe .. which yours does not appear to be doing

[terry paget]

Might be water in the fuel tank occasionally sloshing into the pump intake. I always wondered in the fuel filter would trap it as it lies horizontally and water would collect in the bottom. Could be faulty MAF  Test for that is to unplug it and see if the fault disappears. But that would still misbehave on LPG.

[stuvaux]

Update - changed fuel filter. Car ran for a few minutes, then went really choppy and cut out. I then noticed that the fuel tank had "sucked in" on itself! When I opened the fuel cap loads of air came out (this also happened last week but I assumed it may have been that I had left a vac pipe off....). the tank then returned to normal.

Is it possible that there is a small hole in the pipes above the fuel pump? I have had a look at them - there is some surface rust but no obvious holes. I'm thinking it must be drawing air in somewhere.

That can't happen ...   if the tank "sucks in" as you call it, when you open the cap then air will ENTER the tank to relieve the vacuum .. which is IMHO the cause of your problem !!  If a vacuum builds up in the tank then no fuel will leave it... so  suggestion #1 ... try running the engine with the fuel cap OFF if it works ok that proves the problem, you then need to find out why the fuel vent system is not working as it should, it is a sealed system to prevent pollution , but the system will replace used fuel with air via the vent pipe .. which yours does not appear to be doing

Thanks for the explanation.

Right, car runs with fuel cap off. So where would I start in trying to find out why the fuel vent system is not working?

[05omegav6]

Has it been pranged recently causing the vent pipe to become pinched? Only real way to check is to drop the tank

[stuvaux]

Has it been pranged recently causing the vent pipe to become pinched? Only real way to check is to drop the tank

No prang recently and no work done anywhere near there either.....its really odd!

[Entwood]

Not certain if this thread helps.... I know you haven't got a warning light on, but it does, to some extent, describe the vent system, I have a strong feeling you have a blockage somewhere ... perhaps in the purge valve or the carbon canister ??

http://oldsite.omegaowners.com//forum/YaBB.pl?num=1180455423