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yet another no start 1990

Lightfoot

NAXJA Forum User
Location
fort collins co
Alright, so i bought a 90 4.0 that wasnt running, so i know nothing about the conditions that caused it to stop running. The guy said it just wouldnt start one morning. I have searched for hours on here looking for tips, and so far nothing has worked. Here is what ive got. turn key, fuel pump cycles for 2 seconds. fuel does squirt out of rail when i push the valve. I also tried the carb cleaner down the intake, and still nothing. So i dont think its fuel. The engine cranks, and seems to sputter a tiny bit sometimes. I took out a plug and stuck it into the coil wire, and grounded it and had a friend crank the engine. I got spark but it was not blue, and was weak. I tested the cps and it was within the range of good. I cleaned a bunch of grounds, and connections, unplugged and replugged a bunch of ssensors. I put in new plugs, and a new coil that I had. I am jumping the jeep from my other jeep wich has a good battery. I tested voltage at the yellow wire below the coil, and it came back two volts lower than at the battery.
This jeep has been messed with before, the wiring under the dash was all labeled like it had been disconnected, and the vaccuum hoses under the hood are all messed up. could these hoses cause the no start?
I am out of ideas on what would cause weak spark. anyone have any sugestions?
Thank you
Lightfoot
 
You can try starting fluid to see if it try and run. Just try it once or twice.

Do a compression check . May have a blown headgasket.

Good luck

Nick
 
How are the cap and rotor? I'm not sure about Jeeps (sorry), but most '90 vehicles still had cap and rotor. Sometimes you can see arcing on the rotor to the distributor shaft. There used to be a thing too about the polarity of the spark wire from the coil to the distributor where you couldn't reverse it after it had been used for a while one way. Like hanaxj87 said, check compression. I messed arould for days with a Fiero that just wouldn't run one (cold) day even though it had gas and spark. Compression was under low on all cylinders and it wouldn't run until we put in new rings.
 
I'm not a RENIX guy but along with the coil, I believe your vintage has an "ignition control module" that may be suspect? Looking for something responsible for creating the weak spark does seem to be a good strategy here. Spark should be strong/blue/snapping; orange and yellow color spark is probably not going to be enough to fire the engine.
 
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