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Comanche not starting


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Went by Auto Zone last weekend looking for a horn relay and some fuses, got back in my truck and she wouldn't start. Not cranking at all :blush: luckily there was a mechanic across the street who took a look for me, tested the battery, and said he thought it was the starter relay. I couldn't find a new relay that day so he showed me how to touch the green wire to the nut on the relay to get it going in the meantime. I just got the new relay and swapped it in this evening. I cleaned the grime with electronic cleaner, applied dielectric grease. Pretty sure I got all the wires back on correctly, except for the orange wire for the fuel pump, which had ripped off the old relay, and is nowhere to be seen. The wires under the hood are kind of a mess in general. So. I was hoping it would start, but still nada. Is the missing orange wire my problem?

 

Trying to think what else it could be! I had poked around and pulled out the horn relay before it started giving me trouble. Could I have moved something under the dash that would be causing the issue? Once we got it going with the wire my very worn key fell out of the key lock and the engine kept running. Could the worn key be the culprit? And am I gonna mess stuff up if I keep using this wire to nut starting hack? 

 

This is a manual transmission, 4.0 liter inline six engine.

 

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This is on your 89 MJ Right?

 

There are not many spare wires. I'm somewhat new to Renix but it looks like the starter relay provides power to the fuel pump (while cranking). If the orange wire that goes on the fuel pump ballast resistor terminal is not in place, you should have cranking but no start, since the fuel pump will not run. Find and install that orange wire. It does not appear to be a fusible link so it can't have disappeared.

 

The ignition switch / lock cylinder is obviously a critical part of the starting system. If it is known to be faulty then it can't hurt to replace it, but it is normally better to develop an understanding of the electrical system and troubleshoot rather than throwing parts at a problem.

 

Btw, any time you have a no start condition, it is helpful to say whether you have no cranking, or cracking but no start.

 

 

 

 

 

 

 

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Yep this is on my 89 MJ. There is no cranking when I turn the key.

 

I looked for an orange wire floating around near the origin of the black/white and green but all I see is a whole slew of colored wires that look like they’ve lost their original bunches, all bunched together in the area below the relay. I’ll try looking some more!
 

For troubleshooting, would next step be measuring voltage at the terminals on the relay? I have a multimeter but not a lot of experience using it. Any recs for starting to study the electrical system?

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It is possible that you may have more than one issue. That orange wire being disconnected should not prevent cranking from what i understand.

 

I would begin my measuring voltage at the battery terminals. Then observe voltage while attempting to start, to make sure there is not a big voltage drop.

 

Next look for battery voltage between the negative battery terminal and the terminal on the starter relay labeled "fuel pump ballast resistor terminal" while cranking. It will only have battery voltage while cranking.

 

The Haynes manual isn't too bad for wiring diagrams. I'm sure the guys here have something better in digital format.

 

The next step might be testing the fusable links

This thread has a good procedure for checking all of the fusible links that come off of the starter relay.

https://www.cherokeeforum.com/f2/1989-xj-won't-stay-running-unless-fuel-pump-relay-jumped-227111/index3/

 

 

 

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Thanks for the tips @EUREKA! I think I’m going to take some time watching videos and picking apart what’s described in the thread you shared above. I also have a copy of the factory electrical service manual. All new territory for me which is exciting albeit a little intimidating haha. So I take it you’re in Eureka? I’m new to NorCal, and hoping to plan a visit over to Arcata soon.
 

 

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