How is the wiring for the petrol and the LPG related?

[Frontier1]

Hi All,

Well my petrol fuel pump has gone again even though there is a full tank. Since I have LPG as well, I have been running on that but I now have a problem where the engine will not idle properly. When this first happened, the idle on LPG was high (over 2000rpm), for about 3 days, now it idles VERY low.

The fuels both share connections to the injectors but apart from that, I'm at a loss to explain how one not working can affect the engine idle for the other.

When the petrol pump is working there is no problem whatsoever.

Any thoughts?

Cheers, Pete'

[Lotz-A-Landies]

Hi All,

Well my petrol fuel pump has gone again even though there is a full tank. Since I have LPG as well, I have been running on that but I now have a problem where the engine will not idle properly. When this first happened, the idle on LPG was high (over 2000rpm), for about 3 days, now it idles VERY low.

The fuels both share connections to the injectors but apart from that, I'm at a loss to explain how one not working can affect the engine idle for the other.

When the petrol pump is working there is no problem whatsoever.

Any thoughts?

Cheers, Pete'
Pete

It will depend what type of LPG system and whether you have a fuel injected vehicle or not. Many dual fuel systems also start on petrol and switch to LPG (open the LPG shut-off valve) when the revs hit a certain point.

If fuel injected, there will be an injector shut off, which would normally mean that petrol fuel still flows past your injectors and returns to the tank while running on LPG although they are never commanded to open.

You may need to increase the idle flow on the LPG unit and make sure there are no holes in or missing vacuum tubes on your manifold or plenum chamber.

Diana

[Frontier1]

Hi Diana,

Yeah, as I mention in my post, they do both share the injectors so it is efi.

Mine is setup with a switch on my dash so I can choose what I start on rather than the auto petrol to lpg valve. Thank god too otherwise I would not be able to start since it is the petrol pump that is not functioning!

Re holes or missing vacuum hoses, since it runs fine on lpg when the petrol pump is fine but not running, I can't see how it could be that either, but I will take a gander at the hoses to and from the plenum chamber just in case.

Cheers, Pete'

[Lotz-A-Landies]

Hi Diana,

Yeah, as I mention in my post, ....
Stupid Stupid me -

I read that bit and was explaining the connections mine has for both LPG and petrol.

It is a case of: Make sure Brain is engaged before putting mouth in gear (or at least fingers!) :D

Diana

[Frontier1]

It's all cool! :)

This is the 4th or 5th one (I forget since there's been that many!), thats gone south and this is why I think it must be an electrical gremlin rather than a mechanical failure of some sort.

Will be pulling this one out today and will post pics if there is anything interesting.

Pete'