90XJ no start

Will crank, sometimes will backfire through the intake. Usually cranks 3-5 times and will skip then crank again. Has good fuel pressure, relay switches and pump runs with key on, has spark at coil, cap and plugs. New CPS, Fuel pump, fuel filter, injectors, bypassed resistor. Most other sensors are new in the last year, IAC, TPS, MAP (shows 5.03v at supply terminal C but only .01v at terminal B), starter and starter relay, cap, plugs and wires. Head gasket was replaced about 2 years ago and the oil shows no signs of coolent contamination. Have not replaced MAT, EGR sol., EGR valve is 2 or 3 years old. Problem came on suddenly. Did it twice but would start and run REAL rough and would cut out if I tried to drive right away.

i said this twice before today... check your gorunds mine did the same thing with the backfire was the firewall ground from the back drivers side corner of the engine to the firewall

Alright, any other ideas.

thecozmo65 said:

(shows 5.03v at supply terminal C but only .01v at terminal B),

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This is were the problem is --> with key on, voltage at B should be between 4-5 volts. If all wiring is good, replace the map sensor.

I rechecked it and came out at about 4.9v so I dont think the MAP is it.

You might want to check the distrubtor too. I have a 90 XJ also... I went on vacation once and came back 2 weeks later and my XJ wouldn't start. Changed alot of electronic stuff, ICM, Ingnition Coil, etc. It turned out to be that the shaft on the distrubtor was worn and cause the rotor to rotate and tilt abit. This cause the timing to be off slightly and weak spark also. Just an idea if you're at a dead end right now.

Doug

Well, the damnedest thing just happened. I just went out to start checking ground wires so I tryed starting it. The bitch fired right up. I swear its like having an old Jag.

Even more evidence for the grounding theory.... Undo and clean each ground point, smear with ox-gard, reattach.

-Skip

skipc said:

Even more evidence for the grounding theory.... Undo and clean each ground point, smear with ox-gard, reattach.

-Skip

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can anyone tell me where they all are. I want to make sure I get them all.