Vincent Milone

Hi guys,
I have a new to me Cherokee that has an intermittent (more often than not) long crank. The "poor mans prime" trick all over this forum doesn't seem to make a difference in my case. Interestingly though, fuel pressure reads high for a 1994 at 45PSI idle, and drops to zero after 20-30 minutes, though one key prime brings it right up to 45. Not sure why my pressure isn't the spec 31.

Anyway, new battery. New starter. It will crank and crank and crank (and fast!) until it a) eventually catches itself and slowly literally stumbles to life b) the cranking starts to bother me and I floor the gas pedal.

Every time I floor the pedal it starts right up. Runs and drives AWESOME.

There is so much hubbub about the check valve, fuel pump, CPS etc on the forum but not too much pointing in a specific direction involving the clue that slamming the accelerator down starts it up. When I press the gas and crank it might stumble for a second but it fires up every time I do this and then idles nearly immediatly fine around 750rpm or so. I believe electronically this tells the computer to stop feeding the injectors? I'm not sure what else it might mean, but can anyone more definitively say what might be up? I don't like parts replacing and if I can trouble shoot this Id rather.

I've cleaned the IAC and throttle body. I've plugged and unplugged/contact cleaned CPS, MAP, and temperature sensors...

I've cleaned dipstick, block, firewall, and fender grounds. Tomorrow I'm running new champion copper plus plugs, premium wires, brass cap and rotor. I have a new fuel filter as well. I have 2AWG cable upgrade enroute.

If I turn it off after I get it running and turn it over again, itll fire up immediately fine.

Thoughts? Thanks in advance!

PatHenry

Do you HEAR the pump prime when turn it to "ON" prior to starting?

Dave51

See what the plugs look like and if the new ones make a difference.

Red1992XJ

Honestly, it is worth it to at least do plugs, wires, cap and rotor. I know you don't want to throw parts at it, I don't usually endorse doing that. It is also good to do things like the fuel filter, and when you put in a new one, cut the old one and take a look at the inside. The fuel pump could be suspect in this situation, do you have any info as to when it was last, if ever replaced?

How long have you had the truck, have you ever had to put gas in it?

Vincent Milone

TL;DR--> Did the tune up, no difference. Injectors don't appear to be leaking. Cranks for about 10 seconds and actually does start without stepping on accelerator but it stumbles to life. See video.

Video example after tune up, without pressing accelerator---> https://www.youtube.com/watch?v=IC4G...ature=youtu.be
In the video, also notice my temp gauge flies up when cranking and then goes back down when it finally starts. Strange electrical.
------

Pump primes OK. Though today I did notice with gauge on it she primes to 33PSI or so first, then a second prime gets it to 45PSI and it goes no further. Though despite two primes, she still long cranks....

Did the tune up today: Plugs champion 412 coppers, premium wires cap and rotor, air filter, fuel filter

I have run about 1/2-3/4 a tank through it since I bought it. Added a can of seafoam. No difference.

Additionally- I figured leaking injectors might be the trouble so I pulled the rail. Found I have Ford 710 4 hole injectors with the 45PSI pressure regulator. Though they're missing the pintle caps, no visible external leaks. New O rings installed.I cleaned each injector by blowing seafoam through. Also pressure tested to 45PSI or so using my compressor, and no obvious leaks on each individual one. Spray patterns seemed generally OK.

When I removed the old plugs to change, they were black dirty despite me just cleaning them a week prior before I got tune up parts. Seemed almost wet, oily or maybe gassy. The threads of 2-3 of the plugs had oil on them. Might be valve cover gasket.

It has 270K miles on it. But it's not blowing smoke. Oil and coolant are clean. Idles awesome and quiet. No ticks, nothing. And once it starts I can't keep the damn thing under 60mph. Very peppy. No lack of power I feel.

Anyway- not sure where to turn next. My opinion is this is electrical. But I don't know anything. Lol

Thanks so much.

Brendan Tracy

My 94 has the same problem, with a slight twist. Everytime I disconnect the battery and reset the pcm, it will crank on the first touch for two or three starts. I just installed the k suspension 2awg upgrade yesterday, and same result. Started like a champ the first two times, then this morning going to work it's long crank again. I have the 4 hole injectors as well. I've replaced the starter, alternator, and the battery in the last 3 months, plus the wire upgrade, and the fuel pump and filter last year. Everything on mine points to the injectors, as it didn't have as bad of a problem before I switched them. I bought mine from Amazon, and replaced them twice, as I thought the first set had a leak. Oh I've also changed plugs and wires last year as well.

PatHenry

I had an issue with my 95 with the PCM in cold weather (obviously this was several months ago) - I would turn the key but NOT hear the fuel pump prime. Of course, this also meant a long "crank no start" condition.

Being I had the wrong PCM in there from a P.O., I was replacing the unit anyway after finding at a good price online. (The 95 with stick shift PCM is rarer than the auto PCMs) After changing it, the Jeep starts right up every time regardless of the outside temps.

For you auto folks, you can have the very common CPS thermal failure requiring a MOPAR replacement part, or a less common, but still a suspect, Camshaft position sensor (the one on the distributor) that some folks have had causing this same issue.

97grand4.0

What does your scan tool say for codes? Yes the Crank and Cam sensors should be changed to Mopar as a matter of maintenance, (and perhaps all of them Lol) they are slow to throw the code, but it could be anything from TPS to IAC motor stuck, ..Then I would check your long and short fuel trims, O2 sensor operation, and report back. .maybe an issue with the injectors being the wrong flow rate for the PCM?