Was there something wrong with checking the continuity of the injector wires from the ECU to the injectors before shotguning an ECU?

Haven't heard a peep from the OP about doing this.

Maybe it is time to just start throwing parts at it.

 

Im horrible with electronics. I just went and started it again. ran like a top. I shut it off after about 2 minutes. when i immediately restarted it was missing again. I do need to check continuity but it fires them on some starts and not others. not arguing just trying to figure this out. this jeep sat for many years due to a bad tranny. It ran good up till the tranny problem and sitting for about 7 years.

 

No offense intended but mate, in the OPs last two or three posts above mine, it has been mentioned that he tested the wiring. Maybe not in great detail but that's what he should have done after cruiser's posts.

And my post also had an 'if' condition that IF the wiring checks out fine THEN try a known working ecu.

 

You won't figure this out until you stick a probe into the problematic injector (s) and their respective ends at the ECU.. after this as mentioned by cruiser start wiggling the harness until you identify the point where it loses continuity..

 

I will do some wire testing when it gets light enough outside. thanks guys for helping me trouble shoot this.

 

I thought I might add that the cps wires were burnt on the manifold it appeared and were separated during the tranny swap but went unnoticed until later after I tried getting it running. It had broke in an area above the bracket that holds it at the back of the head, therefore still appeared attached when re installing the transmission. they weren't burnt due to hot electrical issues if that might help rule out ecu. while doing my checking today is there anything else that could give a signal to the injectors to fire? im curious what triggers the ecu? cps, or some other sensor ? I realize the cps controls the spark but something has to tell it the proper time to fire the injectors also. Maybe I could also trace those wires back if there is any thing else.

 

the burnt CPS wires can be shorted with the body which can also cause damage to the ECU but anyways..


the CPS determines spark timing as followed:

1 and 6 cylinder on top
2 and 5 cylinder on top
3 and 4 cylinder on top

and position number of the injector to fire is given out by the CAMSHAFT position sensor inside the distributor (CMP).

even if the CMP is disconnected your jeep should run, maybe a little rough but still have power pulses to all of the injectors.


you need to confirm that you don't have a bad injector wiring harness by the methods mentioned above.

 

ok sounds good. still pretty dark here right now but ill let you guys know what I find.

 

Not to distract, but you can check a Renix CPS in about the time it takes to tie your shoes. I'd check mine if the radio didn't work, that trickster can do about anything.

AC voltage CPS test; Small clips on the meter leads really helps. (you need contact with those little pins while it cranks)

Unplug the connector at the back of the manifold with wires going down to the bell-housing/cps. (it's a three wire plug, with only two wires)
Probe the two wires to the cps with the digital meter set on AC volts, a 200 scale on mine. Your meter may have a lower, (2 Volt), or “auto range”.
Crank the engine and note the voltage. (jump it if your battery is low) .35 is minimum. >.4 to .8 is more like it.