Thread: Voltage issue with injectors

Tweet

OK, thanks guys for the help with the actuator. Lubed all the joints and top works some what better now.
Now I have a friend with a 1996 LT1 5.7 fuel injected motor with a 4L60 trans. For some reason he's losing voltage to the injectors. You ride a long and the tach drops to zero and then right back up. It's less than a second. The motor coughs and then runs fine. It happens when the car is warmed up. It does this numerous times while driving around. He has put a new relay in, checked all grounds, checked voltage to computer, changed computer and same thing happens. Had dist checked and that's OK. He has had to specialists look at this problem. But, since it's less than a second no error codes come up to tell what's wrong. Any ideas? As always Thank you for all your help!

Just a shot in the Dark, but I had a similar problem, and it was the Crank Sensor-mine also occurred after it was warm, no error codes, and it would just die without warning-it's a reasonably cheap part to try (if we're guessing here)-

Thanks will tell him and we will check it out!

I'd say the crank sensor is a good possibility. The first thing that popped into my head was "ignition switch". If he's got a contact going bad it might arc occasionally? Total shot in the dark, and I like the crank sensor idea better, or even the connector to the crank sensor.

Nope not crank sensor. Disconnected it completely and still skips a beat. Has us scratching our heads?

No disrespect meant, however my Car would not run without the Crank Sensor connected-yours will? I can't remember what it was, but there is a value (electrical-Ohms?) where the crank Sensor can be tested, and mine fell to the lower end of the range(s) given (and then we replaced it)-it was an intermittent issue, and got worse as time went on-not trying to beat a dead horse here (seriously), but I would check those values before moving forward (if I could)-

After that, rspears suggestion is a good one (GM had a real problem with Ignition Switches-especially in '99-07 Pickups)-beyond that I would check the Grounds to the ECU (again)-

Wait a minute, this engine has Opti-Spark (which is something like voodoo)-

I was wrong, on that engine you can run it without the Crank Sensor (the Crank Sensor only senses misfires, it doesn't have to work to run)-

After doing a bit of surfing, it appears that you have a low resolution signal and a high resolution signal that the ECM "sees" from the Optispark-if there is a high resolution signal it will run, but it won't without a low resolution signal-here is a bit more on the subject:

Diagnosing GM LT1 V8 Engines

And the Optispark is notorious for failing-I think you are off to find someone who has a Scope (to test the Optispark)-

Not sure what this is in, but this may also help:

C4 Corvette Diagnostic Code Recovery Techniques

Seems like a lot of these problems revolve around the Fuel Pump/Optispark/ICM-

Good luck, from what I've read these can be a bit of a nightmare-sounds like you need to find someone versed in these-a Corvette Shop maybe?

Optispark sucks. Ask me how I know . . . No, never mind, don't ask.

OK will check it out thanks.

Got a Corvette shop looking at it and he's pulling his hair out too.