Finding the dead cylinder culprit

[ShiftTheDrift]

We had a dead cylinder a couple days ago and in all our testing we got down to the injectors and found "before" preignition, injectors 4 and 6 were on for some reason and maintaining 10v at all times. The rest of the injectors were seen with 3v but not always on such as 4 and 6.

If you look at the ECU wiring diagram, it's the only thing between the injectors and the ECU itself that is or could influence voltage.. that is unless we're clearly mistaken; this is very possible.

The ECU has had a JMS custom chip installed for roughly 4 weeks and when doing testing, we removed the chip and reinstalled the J4J1 by itself and the problem was still present (eliminating the chip theory).

As best as we figure, the ECU must be the culprit. What do you guys think?

 

[rockin_rick]

The engine harness connector C104 is between the EEC and the injector. Maybe it's dirty/wet and shorting those out.

What caused the dead cyl.? Was it 4 or 6? What do you mean by "before" preignition? Was it a steady 10V? What diagnostics have you done to determine this?

I don't really know, but I'll give it a eductated guess.

Rick

 

[ShiftTheDrift]

The engine harness connector C104 is between the EEC and the injector. Maybe it's dirty/wet and shorting those out.

It would just seem kinda weird for both injectors to do this at the same time.

What caused the dead cyl.? Was it 4 or 6? What do you mean by "before" preignition? Was it a steady 10V? What diagnostics have you done to determine this?

The #6 cyl was found to have it's injector stuck closed and tracking down how much voltage should be before pre-ignition was wrong. The voltage on injectors 4 and 6 were holding steady at 10v while others were at 3v and not on at all times. We determined by using a digital voltmeter.

I don't really know, but I'll give it a eductated guess.

Thanks dude!

Rick

Bill

 

[rockin_rick]

Yeah, I doubt it's the connector. I honestly don't know what's wrong. Could be the ECM, but still it seems like there would be something that caused it to go bad in the first place. Have you tried swapping injectors and retesting?

Rick

 

[Slow5.0]

Sorry to bring old topic
ShiftTheDrift do you have 94-95 EEC wiring diagram

 

[ShiftTheDrift]

I sent you a pm...

 

[black945.0]

there has to be a short in there with some kind of resistance or else it would see batt voltage not 10v check all the injectors to see if they have enough voltage other than that i have no idea

 

[donjohn]

well, this was a long time ago, so hopefully ShiftTheDrift figured it out by now

 

[ShiftTheDrift]

Sure did fellas. ...Jeez, that was a while ago.