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Stock XJ Cherokee Tech. All XJ Non-modified/stock questions go hereXJ (84-01)
All OEM related XJ specific tech. Examples, no start, general maintenance or anything that's stock.
Jeep was running fine, parked it and a few days later went to start it but only cranks no start. Cranks strong but nothing.
Checked for spark, I get a white spark which seems plenty strong but allot of searches say must be a blue spark?
I stuck a voltmeter on the crank position sensor and it showed infinite resistance in terms of ohms
Fuel pump you can hear prime and is a month old Carter pump. I can push in the shrader valve on the rail and get fuel.
Plugs are not soaked with fuel or anything out of the ordinary.
Pulled the Dizzy cap, rotor (which are both a month old) to pull the cam sensor to inspect. It looks new and is clean of any signs of wear or cracks. Not really sure how to test it though.
Battery is an old Optima redtop which I can drop into my foxbody mustang with a 331 and start it no problem. However static measurement I just took of it with a voltmeter reads 12.1 to 12.2 volts. I guess from all the turning of the key. I'll stick a charger on that later
I did happy to notice the only way to get the jeep to fire up is to hold the gas peddle to the floor while you crank the engine. It only revs then dies instantly though.
So what should be my next steps in troubleshooting this?
*edit, Just put the voltmeter to a few of the injector pig tails with key on and no 12v at all..... So I'm guessing no injector fire. Where does this lead me? the ecu?
Guess I should do what everyone does on f cebook and through money at it first in the form of a crank position sensor then move down the line to the crank sensor and possibly the TPS
On a '99, the injectors get 12v through Fuse 21 in the PDC, so check the fuse. The fuse gets power from the ASD relay. You could try swapping the ASD relay for another one in the PDC like the fan relay next to it. You should check fuel pressure using a gauge. These are things you can do without buying any parts.
Having said that, the CPS is always a prime suspect for a crank/no start but you said your say spark and it will fire at WOT.
On a '99, the injectors get 12v through Fuse 21 in the PDC, so check the fuse. The fuse gets power from the ASD relay. You could try swapping the ASD relay for another one in the PDC like the fan relay next to it. You should check fuel pressure using a gauge. These are things you can do without buying any parts.
Having said that, the CPS is always a prime suspect for a crank/no start but you said your say spark and it will fire at WOT.
Is you CEL on? Have you pulled any codes?
Yah wish it was just a fuse but they are all clear in both boxes. I did swap the ASD relay just for the hell of it with the starter relay so I would be able to tell easily if the relay was the problem. It's still cranking fine.
I verified that the crank position sensor is functioning fine.
I haven't verified fuel pressure yet because of the lack of 12v at the injector plugs.
The only time I have had cherokees not start but turn over were a extremely weak battery, ignition rotor, ignition coil, distributor out of time, bad fuel pump, spark plug wires wrong, cps sensor, and bad battery ground.
So update, I replaced the ignition coil since it looked pretty bad visually. It did however check out fine resistance wise but I don't want to worry about it anytime soon.
Also replaced the cam sensor and the Cherokee fired right up. So I'm chalking it up to the cam sensor taking a dump being the problem
04-13-2023, 01:02 PM
99 Crank No start
