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Defender 90 V8 with possible fuel delivery problem. Can anyone help?


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Can anyobne point me in the right direction please?

I have a 50th anniversay defender 90. It has the factory fit 3.9L V8 engine and has aftermarket LPG.

On LPG it drives brilliantly.

When I switch over to petrol it really struggles.

Its just had new lambda sensors and a MAF sensor fitted and ti much improved - however it still starts to stutter +++ at about 3000 revs when on petrol.

Recently I broke down and was rescued by the AA (out of LPG gas and so using petrol at the time).

It just wouldn't start.

The very nice man from the AA got it going by spraying sure start into the air filter and I was able to get to a garage and get LPG again.

He also pointed out there is a whining noise coming from the petrol tank and a bit of a slurping sound.

So...

is it the fuel pump perhaps? A blockage eg fuel filter? or some other thing? I think they have a fuel delivery unit as well as a pump dont they??

I have spent a lot with garages who cannot work out what wrong already and have replaced lots of bits sometimes without any real benefit at all. Plugging him into the garage computer shows no faults at all.

I wonder if the symptoms are obvious to someone who knows these well?

- He is absolutely fine on LPG

- Quite a lot of black exhaust fumes when switching over to petrol - but much better since the new sensors were fitted.

- Struggling to idle without cutting out - but better since new sensors were fitted

- Old lambda sensors absolutely black with soot.

- Once you get him going he's okay but struggles at about 3000 revs and becomes quite "blustery".

- When driving he feels restricted if using petrol. If you switch over to LPG from petrol its like you let the handbrake off while driving and he's fine (til you run out of LPG!).

- He only eer broke down after replacing all the sensors. Before that everything was really sluggish - now its not - but he cut out and would not start again.

- After being left for about an hour (waiting for the AA) he started first go, but then cut out again and would not start at all until the man used some Holts Easy Start in the air filter.

- There is a bit of a high pitched whining noise from the petrol tank which continues so long as its on petrol mode. It stops when you switch over to LPG.

- There is a separate slurping sound from the petrol tank sometimes - like he's low on petrol perhaps - but he isn't.

- When driving along on both petrol and LPG - the fuel gauge is a bit bouncy.

Thanks for any help

:o)

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Strange.. However I'm sure the 'adults' will have some ideas.

It may help if you tell us what LPG system it has - is it a single point mixer system or sexy multi point injection?

With reference to your very last point, FWIW my carbed V8 will not run on 'both' fuels at once (that's what you meant when you said "driving along on both petrol and LPG", right?), when I switch to gas I have to wait for the float chambers to empty fully before switching the gas on otherwise the poor thing coughs, splutters and sounds generally sick.

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Coolant temperature sender, hence black lambdas, test it, change it out if necessary, buy a decent one!

If plugs are in equally a sooty state, change them, new NGK BPR6ES, the only ones worth running in RV8's.

That said, if still struggling up above 3000rpm, you may find that the fuel pump is on it's way out, easy to change if so, but probably ~£100 as it is an anniversary model....

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