Thread: 3.5 RUNNING ON LPG BUT NOT ON FUEL

Injectors frequently fail when an EFI engine is run without petrol for any length of time. On one memorable occasion I had a Falcon ED which had been run on gas only for 1 year, I replaced the fuel pump, and it only had one single injector that still worked. A similar thing happened to my bro's RRC when his fuel pump died and was driven for some months on gas only.

Your injectors are very similar to early 90's Falcon and Holden injectors, a handful of these from non-lpg wrecks can be used in the LR engine to get it going. Or you purchase upgrade injectors from ebay US or local to suit your budget.

Thanks for your reply.

Is is common for injectors to fail and stop the vehicle whilst driving. Is there any indicators to know that they are the problem before i pull them out?

Thanks in advance

I'm not going to mention that LPG is actually fuel!

It is unusual that all the injectors should fail at the same time.

Have you checked to see if there is:

• petrol pumping up to the fuel manifold?
• current to the injectors when switched to petrol?

On my dual fuel RRc V8, the petrol pump continues to operate even on gas and only the injectors are switched off. The switch over to petrol re-connects the injector harness wire and shuts off the LPG solenoid. A couple of times the wire to the change over relay came off the terminal so even though the LPG was shut-off the injector circuit was not restored and would not run on petrol. Was merely a case of checking the connections and reinstating the disconnection.

Originally Posted by discont

Thanks for your reply.

Is is common for injectors to fail and stop the vehicle whilst driving. Is there any indicators to know that they are the problem before i pull them out?

Thanks in advance

It is very unlikely that all 8 injectors fail at the same time. A failed fuel pump or a failed relay (for disconnecting the fuel when on gas) could stop the petrol side working. Also the negative side of the coil has an ECU connection (white wire, black stripe), if this falls off the car will stop injecting petrol. But as you say there is something happening on petrol so I would start with fitting a fuel pressure gauge to the high pressure side of the fuel rail, read the pressure and see if there's enough (30 psi or more) with the engine running. If your pressure is good, you can run the engine on gas with most of the injectors unplugged, tickle them with 6-12V from a battery and see if they drown the engine on that cylinder. Or take them out and do the same and see if they blow through. Use an old injector plug without its spring clip to do the testing, and do it for very short bursts only.