91 Cherokee Won't Start

I have a 91 cherokee, Started fine 2 days ago. Went out to start it one morning and nothing. Turns over but wont start. I replaced plugs, wires, cap, rotor, I pulled the starter had it tested its fine. It almost seems like it isn't turning over fast enough to start. Put in a new battery, Acts the same. I unplugged the TDC sensor and back in, nothing. I tested fuel pressure on the rail and have no pressure, BUT it hasnt beed started for 4 days now. Will the fuel pump still pressureize the system without starting the jeep?

Any other clues would help


Thanks
Jayson

When you turn on the key you should hear the fuel pump pressurize the fuel system. If not, then check for a bad fuel pump or fuel pump relay.

Fuel system should always be under pressure, key ON or OFF. 39 psi is normal running pressure. Try starting it, then remove a spark plug to see if it's wet with fuel. I think the '91 still has the ceramic fuel pump ballast resistor on the fender, the part with orange wires that's supposed to drop the fuel pump voltage...a noise thing. Most people bypass it rather than replace it. Do you hear the fuel pump when you turn the key ON? If not, check the resistor and the pump relay before you assume the pump is dead.

Ok I'll check the resistor, I did check the voltage to the pump itself and it was WAY LOW. Like .700 of a volt. If I was checking it right there were three wires. Is the resistor on the drivers side fender? Oh and I allready swapped out the relay, with the AC relay.


Thanks
Jayson

Well when turning the key on the pump should cycle for 1 second reguardless if the ballast resistor is good, present, or missing, then after that 1 second it switches to the wire that contains the ballast resistor.
On my 91 the wires were green and the resistor is on the drivers side fender, just jump 2 terminals with a fuse or something or just butt connect them.

good luck

Well, I bypassed the resistor, Pump is definately running, for 1 second. It doest seem to pressureize the system though. I pulled the line from the pump and put it in a beer bottle it fills maybe 1/8th of the bottle. The fuel filter is fine I checked that too. I still don't get any pressure at the fuel rail, just a dribble of gas out of the check valve. Checked for spark again, definatley getting spark. I wonder if the fuel pump pickup could be clogged?

Thanks for the help
Jayson

Well, The fuel pump and filter is fine. I changed the starter because it was the original 112k miles. Still won't start. It definately sounds different now when i try to start, like theres some drag on the motor not letting it turn fast enough. When i check voltage at the battery I have 14.6v, at the starter 14.6v, When my wife turns it over at the starter the volts drop down to 2v but the starter still turns over. I hate to take it to the dealership but im lost, tried evrything I know!

This sucks!!

stupid idea....is the alternator bad?

Verifiy that you have spark, if not look at the CSP and the coil. Coils can be give intermintent problems when going out.


Added:
Fuel filter?

Alternator spins, not frozen, but it would start off the battery anyway. I am geting good spark. checked it 3 times now just to be sure. I tried to put some gas down the throttle body still didn't fire.

Well, The fuel pump and filter is fine. How do you figure?
Only a pressure test will tell for sure.
You need at least 31# at the fuel rail.

Ok, thats my next thing to try, I will test the pressure. Let me say this, the pump is running pushing fuel. It will only run for about 1 second and only fills about 1/8th of a cornona bottle. I am going to call up and see if I can rent a guage. When I push the fuel rail shrader valce down with a screwdriver I only get a small spray for like 1 second then it starts to dribble out.

Thanks for the help guys I'll let you know if thats it.

Well, I have fuel pressure. I can have my wife turn it over while I use starting fluid down the TB and nothing! Doesn't even try. I pull out a spark plug and ground it, I have spark, Its orange spark but spark. There IS compression, blows out the spark plug hole pretty good and ran like a champ last week. Maybe its a Cam posistion sensor? I am getting spark and Fuel, has to be timing related I guess.

It sounds timing related like its not turning over right, Like my subaru did when the timing belt skipped some teeth. Thats why I thought it was the starter not turning it over fast enough.


Any thoughts?

Thanks

Well timing related, OPS check the coil.

Its orange spark but spark thats not good.
It sounds to me like the sparks to week to light the fuel.
It should be blue and able to jump it least an inch.
It takes alot more spark under compression.

Tomorrow morning I will check the coil Via my haynes manual.

If it is a 4.0l, which I did not see any info on your engine, then here is your problem. Go and get a new crank shaft position sensor and pop that bad boy in. I already went through this routine. Nothing will work and the engine will just crank but never fire. No spark, no fuel, no nothing. If the computer does not know the position of the crank shaft then it will shut everything off. The part is 60 bucks from Autozone, and is a major pain in the arse to replace. It is ontop of the bell housing. You have to get under your jeep look up on the drivers side where the bellhousing meets the engine and you'll see a little black part with wires comming out of it. A 10mm(if I remember correctly) and one long or two or three short extensions are needed to get the two retaining bolts out. After you get it out look for the wire on the top by the rear of the intake manafold. Pull it out that way. Now attach the new one two the connector and feed it down through, do not attempt to put it in from the bottom cause fishing the wire out later is a pain(learned the hard way). Finsh up and turn it over and fire it up. I hope this helps.


BUT you could also have a cracked rotor cap its hard to tell. But your symptoms sound like what I had.

But Red he has spark so in this case it's not the CPS.

langer1 said:

But Red he has spark so in this case it's not the CPS.

Click to expand...

I just noticed he said it did. Sounds like the timing chain may have slipped, but it should still fire or attempt to. I have an orange spark on my jeep and that is with a new coil and wires and plugs(replaced all that when I had my issue). The coil is cheap and easily returnable if you don't install it completly just plug it up and see if that works. It is just odd that it would stop working like that. I didn't check, but could the rotor have turned? I don't think the rotor is adjustable but it's worth a look.

I know this sounds crazy, but you probably have a bad iac motor which is causing this problem.

I had all the same symptoms, checked the onboard diag and got no trouble codes. Replaced CPS and that wasnt it. Got spark, fuel, so i was like WTF? Try this: Pull out all your plugs and let the thing sit over nite because its probably flooded. then put your plugs back in and press the pedle to the floor and try to start it, see what happens. If you have spark and fuel, your probably lacking air so you need to floor it to allow air into the chamber otherwise with bad iac you will flood and suffocate your engine. Plus for some wierd reason if you unplug the IAC, alteast on mine, the vehicle will not run. I dont really understand it, but give it a shot.

My bet is that thing is really flooded, hope this helps, and dont worry it took me over 2 weeks to figure out that my iac would cause a no start.