Help us help you. By posting the year, make, model and engine near the beginning of your help request, followed by the symptoms (no start, high idle, misfire etc.) Along with any prevalent Diagnostic Trouble Codes, aka DTCs, other forum members will be able to help you get to a solution more quickly and easily!
1990 Bronco II crank no start. Will run on carb cleaner. Good fuel pressure. Back probed injector and attached a test light. Blinks a couple times then stops. So I'm thinking it has a shorted injector. This engine is batch fire. One wire for 3 injectors, other wire for other 3. Checked all 6 injectors and they all check out good. So after checking powers and grounds I put a ECM in it. Didn't fix it. Start back over. Hooked up the pico. Amp clamp on power feed for injectors, back probed power feed, and back probed 2 injectors( one for each driver). All looks good, so now I'm thinking the test light must have over loaded the injector drivers. So next step is check for plugged injectors or plugged fuel rail. But really? Less than 200 mA added to the wire for 3 fuel injectors. Does that make sense to anyone?
Has it been sitting a long time?
Wondering about fuel quality and the possibility of the fuel system getting gummed up.
I don't think back probing an injector control wire with a test light would have over loaded the driver.
No I don't think it has been sitting. But they have been working on it their self. Replaced TPS, fuel pump and fuel pressure regulator. Thinking maybe they left the regulator off for to long and something got in there.
I wouldn't have thought so either. I have used a test light like that on other injectors before and it worked just fine. Boss had me push it out to work on other stuff. I'll add to this post when they have me get back to it
I agree, I don't think adding the test light did anything to the driver.
How long is the cranking pulse width on the Pico? Wondering if it's becoming too short after the first couple pulses, and no fuel ends up getting injected. I figure you'd have seen a lack of saturation in the current ramps if it was there, mostly just thinking out loud.
Realized that I never updated this post. The truck is fixed. Ended up being the MAP sensor. Never seen one cause a no start like this before, but then I haven't diagnosed many EEC-IV systems. I've seen a bad MAP cause a start stall but not a no start like this one was doing.
Still don't understand why the test light was shutting down the coil drivers. Even checked with a scope and when I would add the test light it would shut the drivers down. But it runs and is gone.
Topic Author
