Hello, new to this forum, I'm from Belgium, I recently bought a VANDEN PLAS XJ12 from 1984 (5.3 HE) the car is equipped with gas. Unable to start the vehicle on petrol that the engine is hot or cold. All electrical circuits have been tested. When I hold the pump relay in hand, in 'contact' position the pump turns and engine works, but if I release the relay, the motor stops. Someone knows it this problem and can give me some leads to follow .thank you
sorry for my poor basic english.

 

Hidden switch....Cold there be one to interrupt the fuel pump because of the conversion?


Let the fun begin!

 

thank's for your answer, but when i say gas i talk of natural gas, and when i say petrol, i talk of carburant gas

 

I'm not sure if I fully understand the problem. However, I think you may have a problem with the ECU/computer.


The fuel pump circuit is energized by (among other things) the ECU/computer. The ECU grounds/earth the orange wire at the fuel pump relay. It's common for this internal circuit of the ECU to give trouble.

I suggest locating the orange wire at the pump relay socket and grounding it independantly. The pump should now run, and stay running, whenever the igntion key is "on".

Now try running the engine.

Report back with results

Cheers
DD