AU2 No fuel injector pulse

bighendo81 · 12-03-2014, 10:30 PM

Hi all, I have just replaced the engine in my AU2 with a low km engine from an AU1. I changed the bbm upper and map sensor over, I changed the TPS over and the throttle body, as the car is dual fuel and had the mixer ring setup.

Where I'm at now is that the car won't start on petrol. It will start and run on what little LPG is left in the tank and when set to petrol it will fire with some starting spray down the throttle body, but as soon as I stop spraying she dies, so I am sure it has to be an injection issue.

I connected a test light to both terminals of an injector plug and got a pulse, albeit not overly strong. My multimeter couldn't pick up the voltage during the quick pulses. I pulled the rail out and cranked the car over and no fuel came out of the injectors.

Where to now?

Any advice greatly appreciated. I'm no auto electrician but any advice is greatly appreciated, as long as you don't mind explaining it if I don't understand.

Cheers,
Matt

foxtrot3 · 12-03-2014, 11:02 PM

Hi. The pulse will be too short for a digital multimeter to pick up. You might get a reading with a test light but the right thing to use is a "noid light". Have you checked the fuel pump is working and if you disconnected the fuel hoses have you got them the right way round? Cheers MD

bighendo81 · 12-03-2014, 11:46 PM

Thanks. Yep I checked the fuel lines by running them into a bottle so I have them the right way around, and it pumped fuel out so I'm assuming the pump is working.

I just saw some thing on the net suggesting I check the cam sensor but that seems to check out fine. I also just checked for constant 12v at the injectors with the ignition on and that was there too.

With a test light on the injector terminals they lit it up in pulses, although the brightness didn't seem consistent, but I suppose that might be due to the speed of the pulse through a cheap test light.

Is there another way I can test the injectors to see if they are getting the power/signals that they need? Would a blockage of the entire rail be a possibility? I could swap the rail from the old engine but I wouldn't have thought it likely that the whole lot would block up.

Cheers,
Matt

bighendo81 · 14-03-2014, 03:28 PM

Tested Cam Angle Sensor, Crank sensor, all seem ok.

Does anyone have any other ideas or stuff I should check?

Otherwise it might be off to the mechanic to have codes checked I guess.

Cheers,
Matt

foxtrot3 · 14-03-2014, 09:38 PM

Hi. Are they your old injectors or the ones that came with the gas engine? If the engine has run on gas only for the last 10 years they may be well and truly blocked. when you hooked up the fuel lines you did run the fuel pump to the rail and the return to the relief valve?. Cheers MD

Gaz · 23-03-2014, 07:14 PM

Test light or multimeter won't pick up injectors, your looking at a 2-3ms pulse time. Need an oscilloscope to test them correctly.

You may be able to hold a screwdriver to them and crank it and hear them opening and closing. as above, they could be well and truely blocked if they have been sitting for ages.

However, are you sure all the wiring is correct? because of duel fuel the injectors have to be shut off on gas, not familiar with all the LPG systems, but I believe most have a module to trick the ECU into thinking the injectors are firing, when running on gas, sounds like there might be an issue there?

bighendo81 · 30-03-2014, 11:39 PM

Thanks for the replies fellas. To add some closure, it ended up being the fuel rail blocked. I eventually managed to get it firing, which just left me with blocked injectors, but by swapping some from the old engine and new, and by cleaning them out, out of the vehicle using carby cleaner and a battery, I managed to get it firing on all six, albeit still rough. I'm now confident that a new set of injectors will have it running smooth as. Thanks again for the advice.