Fuel pump seems to keep running when on gas..

[Crash76]

Hi, another one in a long list of questions....


My 1994 classic is on direct vapour gas injection. It has to start on petrol, then when its ok, it turns itself to gas. BUT it starts like a bugger on petrol, and idles bad, and when you give it a rev, sometimes it revs then kind of sputters. Othertimes it wants to cut out from idle, and I feather the throttle a bit. sometimes it works, sometimes it cuts out.


so I've been trying to get the car to run on petrol, and I have found that when its on gas I can still hear the fuel pump running in the tank.


Is that an indication the fuel pump could be faulty, hence not wanting to run on petrol?


Its a half size petrol tank, so not the normal place and assuming its not the normal pump.

[billsdefender1996]

Hi there, your engine should run perfectly on petrol. If not you have a problem with the EFI on the car. The only other reason that could cause it to run as described is that the gas is being injected at the same time causing the engine to run very rich and rough. Turn the gas off at the tank and try it then. If the problem still continues then you have a fault with the petrol injection. If you have a pressure gauge you can tap into the fuel rail and check the fuel pressure.

In answer to your question about the electric fuel pump, it depends on the system fitted. Some systems shut the fuel pump off when they change to gas and some the pump runs all the time to keep the fuel in the fuel rail cool. On my car the fuel pump cuts out when on gas. You should be able to find this info on the web for the particular system you have fitted.

My mechanic said that if it runs properly on petrol then that is 90% of the work done!

Hope that this helps

Cheers Bill

[bee utey]

EFI pumps are designed to run continuously for up to 200 000km and so don't need turning off. Your fuel rail would empty if the pump wasn't on and you were running a long distance on gas. Those half sized petrol tanks echo like buggery and a pump will always sound louder in one. However if your pump is worn or has ingested some crap it won't hold pressure for long and be hard to start in the mornings. Drop the half sized tank, replace the efi pump with a new one, and be meticulous in cleaning the tank interior while it's accessible. You can use a universal VN Commodore style pump, priced around $100 or less depending on which crooks you buy it from.

Once you've replaced the pump then have the system pressure checked at the fuel rail. The petrol system should run fine if in good condition.