Ecm/ecu

[95wrangler]

Is it possible for a bad injector to fri the electronic control module/unit? I recently changed injectors,ran the truck about 400 mi.In a two day time span,truck ran great.On the third day first start-up ,rough idle. #5 not firing.Pulled the plug ,cleand the plug, replaced the plug.Ran the truck 40mi.while driving the truck started missing on 1 or 2 cylinders for about 2mi.then it shut-down.would not restart,wanted to but no.key-on fuelpump pressured-up then pressure droped,would not hold.I pulled the fuel-rail with the injectors attached,#5 injector was leaking fuel.blew out the injector, replaced everthing.Injectors would not fire.Traced everything back to the ECM/ECU.pulled the unit,Opened the unit found something like a double-stack diode cooked.Anyone ever have this prob?

[95wrangler]

1990 4.0 aw4 4x4

[cruiser54]

I can't see that happening....

[95wrangler]

How common is it for ECM to go bad? I can't find anything shorted-out.Is there a fuel relay or fuse somewhere between the Injectors and the ECM?

[cruiser54]

EXTREMELY RARE.

[95wrangler]

Thanks cruiser,you are a fantastic sorce for info :thumbsup: Somewhere something took-out the ECM/U. I'll keep looking. :hmm:

[cruiser54]

What got moved during the injector installation? Any bare wires, harness crimped somewhere? 

[mnkyboy]

I had the same issue on my old XJ, I put In some LT1 injectors. A few hundred miles later I lost a cylinder, traced it back to the ECU were I found the transistor that I'm guessing pulsed the injector on the dead hole had let the smoke out.

 

I put in a new ECU and a fresh set of bosch yellow tops and never had another issue.

[95wrangler]

Thats exactly what happend.I got reworked injectors from precision auto injectors.They said they were for the year model I have.When I got there product I noticed they were 4-port,not single port.

[cruiser54]

You WANT 4 port.

[95wrangler]

Nothing was moved, No bare wires, I was very careful with the instal.

[95wrangler]

No sir, that's what they sent.I figured I'd try-em out.I'm in the process of putting the old ones back in.Also installed A1988 ECM.Still looking for A 89-90 ECM.

[cruiser54]

I've put the 4 port injectors in all my Renix Jeeps and in my neighbor's. . 

[mnkyboy]

The 4 ports is what I use as well.

[cruiser54]

Did you bust the line from your throttle body to MAP sensor on install? Go look.

[95wrangler]

All I know Is that the injector instal was the only thing I have done.So I'll go back where I started, With the old injectors.

[cruiser54]

Don't jump the gun. Go look at that hose/tube.

[95wrangler]

Not on the injector instal, On bleeding the air out of the closed cooling.I did splice the line with electrical tape.Can't look at anything, cause the truck is 200mi. from me at presant.

[cruiser54]

Gotta be perfect or the MAP is telling the eCM that the vacuum is low and to "add a bunch of fuel".

[95wrangler]

I work out of town,200mi. from my home. when the truck quit I got my son-in- law to trailer it to his shop.

[95wrangler]

10-4 I will replace asap.With the 88 ECM and the 4-port injectors the truck still has a miss.

[cruiser54]

Can you isolate it? 

[95wrangler]

I did not try to find the missing cylinder as of yet,Everything happend late sunday on my way back to the valley for work on monday.After the 88 ECM instal,and start-up, when it was still missing the time was 2am.I called it quits for for now.Trying to get info for the next round this weekend or relay info to the son-in- law.He can work on it when he has time.Thanks for your time & info :bowdown: 

[95wrangler]

One bad injector DiD take- out the ECM.

[cruiser54]

One bad injector DiD take- out the ECM.

How did you determine that?