Have Jeep Questions? Ask a Jeep Repair Expert for Answers
Hello and welcome to just answer. Have you verified that there is good continuity on the injector driver circuit between the injector connector and the PCM connector?
Ok, then you may have a slightly spread terminal at the PCM connector, or at the injector connector. Do you have access to an OBD 1 scan tool that can check for codes or look at sensor data? If not can you rent one?
Okay, besides the crank sensor, the cam sensor in the distributor will affect the injector ground pulse, You may want to check that.
This is a 1990 right?
It should look like the picture in the link below.
You are right my mistake. 91 and up. Okay, then the crank sensor on that engine provides a signal to the PCM for spark and fuel injector pulse. The MAP sensor will determine how much the pulse should be. Try disconnecting the MAP sensor and see if it will run.
Ok, I may be off line for a couple of hours, but will check back later.
Yes, at this point probably a good idea. I would send you a wiring diagram, but I only have the older diagrams at work. If you need it, I can send it to you next week.
Gotcha good luck, and I will look for your reply tomorrow,
Well that is normal because the ASD relay will send 12 volts to the injector, through the injector coil, and if the PCM is not grounding the injector, you will see 12 volts. If the PCM grounds that circuit, then the voltage reading on that circuit will be zero.
Ok I see it. That should not really cause the no injector pulse if that fuse blows based on that diagram. Something else is causing the no injector pulse.
Yes, That can and will cause a no injector pulse. Have you disconnected the MAP sensor connector and PCM connector, then check for a short to ground in that circuit?
Ok, well check for a short by disconnecting PCM and MAP sensor, then set your meter to ohms, ground the black lead of the ohm meter and then probe the map sensor terminals one wire will show continuity, but the signal wire should not. If it does, then that circuit is shorted to ground. Try that and get back to me.
Well actually if the PCM connector is disconnected then you should have no continuity to ground. If you plug in the PCM then you would see continuity.
At this point, it is time for a scan tool to help us diagnose this. The Snap On MT 2500 would be a good one to use on your Jeep, but you will also need the appropriate adapter to connect to the data link connectors under the hood. See if you can get/rent one and then get back to me.
Okay, check it with the sensor disconnected. I will look for you tomorrow.
You are welcome!
This is a strange one indeed. let's back track a bit. If you disconnect the injector connector, and the PCM connector. Use your ohm meter and place one test probe from the meter onto the injector driver terminal at the injector connector, and the other test probe onto the corresponding injector driver terminal at the PCM connector. Tell me what the resistance reading on the meter is.
It is not common, but I have seen that before. I will look for your reply today.
I know.. Good luck and keep me up to date!