DADS55

Ok,
I have been having this problem with my 91 LX 5.0, it runs real rich, I troubleshot it down to #1, I pull the plug and it is drenched with fuel, checked spark, and compression and all is good, I replaced plugs, wires, cap, and rotor. I thought maybe it was a bad injector, so I replaced #1 injector...NO JOY. Today I decided to check the fuel injector leads and sure enough they all pulse except for #1 which is a constant 14.92 VDC. Does any one have any ideas.
Thank you.
Mark
P.S. I am a new guy here, so if I posted this in the wrong spot, please let me know.

Portmaster

Is that 14.92 voltage with the engine running? I'm a bit confused because if the injector didn't pulse there would be no fuel in the cylinder. You should have the same battery voltage at the injector as you have at the battery (or real close) the ECA controls the ground and cycles the injector. Check to see if there is a constant ground at that injector. take your test light and go from one pin to the other at the injector connection and see if you have a solid light. Also check to see if you have spark at the plug on the same cyl. I'll check back with you later

DADS55

Sorry about that, it is with the car running, and the spark plug fires...I checked all leads with the car running, and they all open, and close with the exception of the #1 which is the same voltage as the battery, actually the alternantor because it is in the 14 volt range. I checked the wires (#1) and one of them has continuity to ground.
Thank you.
Mark

Portmaster

If the ground side of the injector connector (unpluged from the injector) is grounded you either have a ground before the ECU or it has a grounded driver inside the ECU (ECA, Computer). You can pull the ecu out and unbolt the 60 pin connector at the ECU with a 10mm wrench. You will need to check the terminal after you disconnect it where #1 injector enters the ECU. I think it is terminal #58 and should be a tan wire (I'm not 100% suree of this and you may want to hunt up a diagram to see for sure) I use a break-out box so it's a little harder doing it your way). If the tan wire is grounded you have a short to ground before the ECU. If it isn't grounded you have a bad driver in the ECU and will need to be replaced. This is the best diagnosis I can give you on line. It's tough enough to diagnose these problems when you have the car in front of you even worse in a one dementional forum. maybe someone else will chime in with a more favorable diagnosis that I'm missing.

DADS55

Thank you,
I will give it a shot and get back to you. I do have a 87 GT ECU, I wounder if I should just plug it in and see if it works, and if not start chasing wires.
I do appreciate your help.
Have a great day.
Mark

DADS55

Just wanted to update everyone.....my problem was the ECU, plugged my 87 McLaren ECU in and everything is good, although I do have a check engine light, but I figure its looking for some thing that is not there, no big deal, I do need to find a compatible ECU for my 91.
Thank you all for your help.
Mark