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im thinking fuel pump, how bout you??

H

hammerheadxj

NAXJA Forum User
Location
latham
96 xj,,,, stock,,,,, started stalling while driving then restarting itself,,,,, then got worse would stall, put in neutral while driving and started right up, 30 seconds later same thing,,,,, did this for a week,seemed when it got hot it wstarted but not all the time,,,,, then got worse now got power and turns over fine, just no starting so its no fuel or no spark,,,,,, 140k so prob the fuel pump,,,, prob gotta drop the tank?????
 
1. Determine the missing element--fuel or spark. That is your starting point, otherwise you are p/ing into the wind, and we all know what that is like.

2. If it is spark, then a thermal failure of the crank sensor (CPS/CKP) is likely.

3. If it is fuel, it could be a weak fuel pump relay. Check with a fuel pressure gauge and post up the psi numbers.
 
pump is winding when key turns on, then clicks at the engine,,,, and stops,, minor pressure at the shrader valve and then nothing, a few drops of gas,,,,,
 
Low pressure at the schrader valve isn't good. You can put a fuel pressure gauge on it to confirm but it sounds like the fuel pump is probably going south.....
 
But if there's no spark that's also something to look into. Both of those things happening at the same time could quite possibly be a bad CPS. Never hurts to do a little dubbing around before you go dropping money on parts that might not be bad.
 
OK, back to basics. Once you prime the pump by turning on the key, the system should hold fuel pressure for an hour or more. If it isn't holding pressure, it is caused by a one way valve in the pump. Not holding pressure isn't a good indicator that the pump isn't pumping.

Bottom line is that you need to monitor the fuel pressure with a gauge.

Another little known fact is that if the CPS quits putting out pulses, the computer will turn off the pump. So if you start cranking and the CPS isn't giving a signal, the computer will not necessarily turn on the pump. This is how they get away from having an impact switch. If the engine isn't running, the fuel pump isn't pressurizing the system.
 
With the fuel pump energizing, you should have good pressure at the fuel rail. Gotta start with a fuel pressure gauge on the schrader valve.

You can test for spark in about 10 minutes by removing a plug, keep it attached to the plug wire, place the plug electrode near a good engine ground. Have a buddy crank the engine while you watch. You're looking for a strong, blue snapping spark.

If you have spark and the fuel pump comes on and runs for about 2 seconds when the key is turned to the on position and you are not getting up to full fuel pressure at the rail, the pump isn't doing its job or you have a leak somewhere else in the line.
 
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Not sure what the problem is, but on a 96 and earlier you can get the pump out without dropping the tank. Not fun but it's possible.
 
My bets are on the CPS, but I have also seen a couple of bad coils. Good Luck.
 
No spark I always start with the crank sensor, then ASD relay, coil, harness, PCM.
 
Ok, do you have 12 volts to the coil?
 
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