no signal to injectors
09-17-2011, 09:07 PM
#1
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Year: 87
Model: Cherokee
Engine: 4.0
no signal to injectors
I have an 87 with the inline 6 and have no start problems. I have spark and fuel but no signal at the injectors. Any ideas I have already replaced the ecm. Thanks
09-17-2011, 09:27 PM
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Year: 87
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I have fuel at the rail not sure on pressure but I just put in a new pump. I pulled the plugs and they are bone dry.
09-17-2011, 09:32 PM
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pull your injectors and make sure they're not stuck. simplest way to test them is with a 9v battery and some wire. if they're not stuck, you'll hear a "click" come from the injector when you touch the wires (connected to the 9v battery) to the electrical pins in the injector.
Another possibility is that your not getting any electrical feed to the ev1 connections on the injectors. Use a volt meter to check each of those as well.
Another possibility is that your not getting any electrical feed to the ev1 connections on the injectors. Use a volt meter to check each of those as well.
09-18-2011, 07:16 AM
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Sounds like the wiring for the injector connections is the place to start. Trace the wiring, make sure it's all good - no breaks, rubbing of exposed wires, or corrosion.
09-18-2011, 08:20 PM
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Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
It was common on the Renix models to have the injector harness chafe at the rear of the engine near the firewall.
Another thing to do as a preventative measure is to clean out the C101 connector. It's located on the firewall above the brake booster. Almost every communication between sensors, injectors, and the ECU pass through this connector. Unbolt the two halves, clean out the black tar crap with a small pick or screwdriver. Then flush everything with contact cleaner and dab out with a cloth. Repeat another time or two. Take a small pick and tweak the male receptacles so they will hold the pins tighter. applu dielectric grease and bolt it back together.
Another thing to do as a preventative measure is to clean out the C101 connector. It's located on the firewall above the brake booster. Almost every communication between sensors, injectors, and the ECU pass through this connector. Unbolt the two halves, clean out the black tar crap with a small pick or screwdriver. Then flush everything with contact cleaner and dab out with a cloth. Repeat another time or two. Take a small pick and tweak the male receptacles so they will hold the pins tighter. applu dielectric grease and bolt it back together.
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09-19-2011, 12:22 AM
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Year: 87
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I think my jeep knew I was about to take it to a shop so now its starts, but when it runs it idles high. I will look into the harness and I have cleaned the c101 but think i may cut it out.
09-19-2011, 06:49 AM
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Year: 1990
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After that, with the engine running, wiggle the harness that carries the injector wires from the C101 connector up to the front of the engine. If something changes, you're on the right track.
09-19-2011, 09:31 AM
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Year: 1990
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Engine: The venerable 4.0
Originally Posted by cruiser54
It was common on the Renix models to have the injector harness chafe at the rear of the engine near the firewall.
Another thing to do as a preventative measure is to clean out the C101 connector. It's located on the firewall above the brake booster. Almost every communication between sensors, injectors, and the ECU pass through this connector. Unbolt the two halves, clean out the black tar crap with a small pick or screwdriver. Then flush everything with contact cleaner and dab out with a cloth. Repeat another time or two. Take a small pick and tweak the male receptacles so they will hold the pins tighter. applu dielectric grease and bolt it back together.
Another thing to do as a preventative measure is to clean out the C101 connector. It's located on the firewall above the brake booster. Almost every communication between sensors, injectors, and the ECU pass through this connector. Unbolt the two halves, clean out the black tar crap with a small pick or screwdriver. Then flush everything with contact cleaner and dab out with a cloth. Repeat another time or two. Take a small pick and tweak the male receptacles so they will hold the pins tighter. applu dielectric grease and bolt it back together.
09-19-2011, 10:06 PM
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Year: 87
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Messed with it a little bit more today. Got it started let it warm up and the battery charged. Shut it off, started again, shut it off then no start. I gave th idle air controller a couple taps and then it started. Will a bad IAC cause no signals to the injectors?
09-19-2011, 10:40 PM
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Year: 1990
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Nope. How did you check the CPS? Did you check resistance in ohms or AC millivolts?