skeltor

I am reassembling a jeep that the previous owner had taken down for restoration. It had previously had a TPI engine swap and ran fine. I installed the ECM and engine wiring harness but can't get the engine to start. When I turn the key to run, I don't hear the fuel pump, and the check engine light does not come on. I have checked 2 orange wires coming into the ECM and both have 12v. I have also checked the ground wires and it is grounded.
I think the ECM might be broken. Anything I can do to verify this? Any ideas are appreciated.

pimprs

Happened to me too...even had the same symptoms...bought an iroc wouldn't crank found another ecm with sams prom at the junkyard from a gta put the gta computer in the iroc fuel pumped primed and ses light came on...put the iroc computer back in nothing...took the iroc prom put it into another extra ecm from a v6 and plugged it in an worked

Six_Shooter

iTrader: (2)

Have you checked the ignition input?

skeltor

Sounds like a worth while thing to check. How do I check this?

Six_Shooter

iTrader: (2)

The same way you checked the battery inputs, you just need the key on...

skeltor

I checked the pink BAT wire going into the distributor (with the key on) and it is giving the distributor 12 volts. There are 4 wires coming from the distributor to the ECM. I assume one of these is the ignition signal, but I don't know which one. So I checked all 4 coming out of the distributor one has 0 volts and the others about 0.06 volts... I'm not sure what they are supposed to be, but I was expecting one of them to be 12 volt signal to the ECM.

skeltor

Six Shooter, which wire is the ignition signal? One of the four from the distributor?
Thanks

Six_Shooter

iTrader: (2)

No, the ignition wire to the ECM, the one that turns it on, the 12V switched ignition source....

It's difficult to test the signals between the ECM and the dizzy with a DMM, unless you know EXACTLY what you're looking for, which I can tell you're new to this so it would be difficult to explain what to look for there, and that's not what I'm suggesting to check anyway.

skeltor

You are right, I am new to this. Sorry for the ignorance. I installed the engine ecm harness and there is nothing that goes directly to the ignition. There is a wire from the ignition to the distributor and then the 4 wire connector to the engine harness. That's why I assumed it might get ignition "on" from the distributor. I have a wiring diagram from austinthirdgen.org 1991 5.7 L. I don't see anything direct from ignition. Do you know the pin ID for the ignition signal? Some other info to help me find it. Thanks for your help Six Shooter!

Six_Shooter

iTrader: (2)

There most definitely is an ignition input to the ECM. I don't recall the pin off hand, and it can be different depending on the ECM, usually it's in the A row of pins IIRC, sometimes there's two of them.... Usually it's pink or pink/black...

skeltor

Oh. Based on this diagram, I think it is A6 pink/black (hot in run). That makes sense. I'll go try it.

skeltor

I tested pin A6 on the ECM plug and sure enough no power with the ignition on. I didn't wire anything like Six Shooter was describing so I knew I was missing something. Tucked inside the wire loom, I found 3 pink wires with no connectors. One of the wires had continuity to A6. From the wiring diagram there is also pink wires (ignition on) for the injectors and some sensors. Looks like I need to wire these up to some fuses and then maybe it will work.
Thank you for your help Six Shooter!

skeltor

I connected the pink wires to some fuses then to the ignition source. That did the trick. The fuel pump turns on and the check engine light comes on.
Thanks for your help!

RBob

iTrader: (1)

Try one thing before you drive yourself insane, turn the key backwards to the ACC position. If the CEL lights up and the pump runs it is the wrong power source. It will go cold while cranking and hte engine won't start.

Need a power source that is hot with key-on (forward turn of key), but cold in the accessory position.

RBob.

skeltor

I was able to get it started today. I bought the thing in pieces and never seen it run. I was so excited see it work. Still a lot of work to do, but feels good to get to this milestone. 😃

Larbo Z

I'm a second gen owner so I hope you don't mind helping out. My 1990 S10 pickup (4.3 v6 auto) died on me going to work the other day. Would crank fine but no start. Had spark. Poured fuel in TBI truck ran until the fuel was gone. When checking fuel pump relay there was no signal on green/white wire from ECM. through testing I came to the same point as skeltor, no switched power to pin A6 pink/black wire. When I applied 12v power from battery to this wire something started to smoke under the hood so I immediately removed the 12v. This was in the area near the distributer. I did find a faulty oil pressure switch and replaced it. Engine will still not start. I'm a little afraid to apply 12v back to that wire again. Thank you in advance for any help.

skeltor

Larbo,
Not sure how much help I can offer. I am just learning my own set up. One difference between my situation an yours is that mine is a restoration project and when installing the harness, I missed the ignition-on wire that tells the ECM that the power is on. Sounds like yours was running fine until it died one day. There must be a fault somewhere. When the ignition is on, that wire should provide 12V to the ECM (assuming it is the same ECM as mine). I would check for an inline fuse along this wire and if that is good, check all connections to make sure nothing came loose. If it is not providing 12V with ignition on, it must be between the ECM and the ignition. Hopefully one of the other more knowledgeable members chime in. This forum is very helpful.

Larbo Z

skeltor,
Thank you for the reply. You make some good points, I never thought of a possible inline fuse. I will check that tomorrow as well as any other interruptions in the curcuit. I agree there are very knowledgeable and helpful people here. I do feel guilty posting here for a vehicle that is not 3rd gen F body but couldn't get much help elsewhere. I have searched the internet quite extensively and have learned more from this forum than anywhere else. I am a camero enthusiast but mine is a '73 Z28.