1990 Cherokee 4.0 Renix burning fuel pump ballast wire
#62
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That wire was cooked through or cut by the PO but I spliced it back together. Just wonder if it was cooked it may have damaged more. It's the thick red one coming off the starter solenoid.
#64
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I work a half day today and I am heading to the junkyard. I found a mostly compete XJ and just wondering what parts I should raid and give it a shot. Going to check the grounds today. The map vacuum line looked. Going to get an ignition coil for sure. Where is the ECU located on this beast?
Interior parts that break like vents, ***** etc.
TCU/ECU and Cruise module
Driver seat if not broken
Seat belts (if you need them)
Trailer Hitch (if it has one)
All the hard plastic tubes in the engine compartment, vacuum ball
Fuel injectors, fuel rail, throttle body, air filter box
Radiator fan
#65
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The starter solenoid is on the starter and has a thick red cable to the batt + post. The starter relay has a post that is used as a junction since it's so close to the battery, could be anywhere.
GMC reminded me...The TCU's are known to have problems, also the TPS can fail easy. I really wouldn't spend much at all to buy something that isn't broken though.
GMC reminded me...The TCU's are known to have problems, also the TPS can fail easy. I really wouldn't spend much at all to buy something that isn't broken though.
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Year: 1988
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Note from DJ
I’m including a diagram of Battery, Alternator, Starting Solenoid, Starter Relay and their wiring just for clarification.
The nut on the threaded post on the Starter Relay is the attachment point for all of the Fuse Links.
Your cut blue wire was a Fuse Link that protected the alternator from being overloaded.
I’m including a diagram of Battery, Alternator, Starting Solenoid, Starter Relay and their wiring just for clarification.
The nut on the threaded post on the Starter Relay is the attachment point for all of the Fuse Links.
Your cut blue wire was a Fuse Link that protected the alternator from being overloaded.
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Dustin, now that you are an old hand with your meter I've got one for you. Resistance is measured in Ohms. What we do with that is normally hella simple, you just use to see if, and how well something is connected. It's the section on the meter with the symbol that looks like little headphones. Slight glitch is selecting the rite scale if it's not an "auto ranging" meter. (we don't want anything with a K, or a triangle diode symbol) The range going up to 200 ohms is common for most of us.
See it just shows a "1". Now just touch the leads together and it will measure the resistance of your leads. (oddly that's always something other than zero which annoies me, ignore that) Now you could, say put one lead on the engine anywhere and the other on Battery Negative. There you would hope to see close to 1 ohm resistance. (1.2-1.5...), telling you your engine and hopefully starter are well connected to the battery.
Cruiser has taught and emphasized the importance of having the sensor, and other grounds reliable. Same test, but you access the sensor ground "web" at the TPS in his tips. (same wire is easier to reach at the MAP, but that is past some connections)
Now to the point of all this yack. The coil is mounted to the ICM with two torx screws. Those two major pins on it are the connections to the primary windings, (which are what fails). If you see more than the above mentioned resistance, (> 1.2 ohms)(or about), for sure it's bad. Unfortunately it checking good doesn't mean it's always good though.
Got spark? (two man job). Put a small Philips in the coil wire that went to the dizy. Carefully hold it so the shaft of the screwdriver is 1/8-1/4" from metal, like the valve cover. Have someone crank it. Should be a crisp, sharp blue spark. Mine will go 5/8" at least. If you get zapped it should be "profoundly noticeable". (It won't actually hurt you, unless you flinch and whack your elbo or something) I'll actually test a questionable spark by just holding it
See it just shows a "1". Now just touch the leads together and it will measure the resistance of your leads. (oddly that's always something other than zero which annoies me, ignore that) Now you could, say put one lead on the engine anywhere and the other on Battery Negative. There you would hope to see close to 1 ohm resistance. (1.2-1.5...), telling you your engine and hopefully starter are well connected to the battery.
Cruiser has taught and emphasized the importance of having the sensor, and other grounds reliable. Same test, but you access the sensor ground "web" at the TPS in his tips. (same wire is easier to reach at the MAP, but that is past some connections)
Now to the point of all this yack. The coil is mounted to the ICM with two torx screws. Those two major pins on it are the connections to the primary windings, (which are what fails). If you see more than the above mentioned resistance, (> 1.2 ohms)(or about), for sure it's bad. Unfortunately it checking good doesn't mean it's always good though.
Got spark? (two man job). Put a small Philips in the coil wire that went to the dizy. Carefully hold it so the shaft of the screwdriver is 1/8-1/4" from metal, like the valve cover. Have someone crank it. Should be a crisp, sharp blue spark. Mine will go 5/8" at least. If you get zapped it should be "profoundly noticeable". (It won't actually hurt you, unless you flinch and whack your elbo or something) I'll actually test a questionable spark by just holding it
Last edited by DFlintstone; 07-22-2017 at 09:38 PM. Reason: rite
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unhook batt
unhook batt when doing ohms/resistance readings or your readings will be whacky if ANY current is flowing anywhere. you can also blow your meter or its fuse if it has one.
also 1 ohm in a ground or hot wire would be high.
i ohm with just 12 amps would drop 12 volts.
.1 ohm in a starter circuit could drop ?8-10 volts.
check ohms law, it cant be broken!!!
also 1 ohm in a ground or hot wire would be high.
i ohm with just 12 amps would drop 12 volts.
.1 ohm in a starter circuit could drop ?8-10 volts.
check ohms law, it cant be broken!!!
Last edited by nujeepguy; 07-22-2017 at 02:26 PM.
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Dustin, just do it with the engine off, and normally the ign also. Near one ohm is expected and normal. Leave the battery connected. Jeepguy knows things, but they don't apply here.
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Alright the latest in the saga after digging through everything. There is no power to the injectors at all. I am going to hit all the grounds and go from there. Anymore feedback what else to check for would be appreciated.
#75
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Yellow box is the cruise control module. Won't be causing any issue with injectors. Work on the grounds-You'll go far. Not sure about the red wire but I'd move on to other more basic things at this point. It might be just powering up your brake controller or something else (brake controller, non-jeep stereo, aftermarket lights etc), but it wouldn't be a Jeep installed item.
Make sure your battery is fully charged. If the engine doesn't crank the right number of revolutions per minute, it won't start. I can't remember if you said it would run on starter fluid or not. You might want to post all the other updates and what is working and what isn't. There's a lot of posts from others but not many from you so we would like to see what you've fixed, replaced etc.
Good work so far.
Make sure your battery is fully charged. If the engine doesn't crank the right number of revolutions per minute, it won't start. I can't remember if you said it would run on starter fluid or not. You might want to post all the other updates and what is working and what isn't. There's a lot of posts from others but not many from you so we would like to see what you've fixed, replaced etc.
Good work so far.
Last edited by 67 GMC; 07-25-2017 at 06:59 AM.