Cranks... but doesn't start... sometimes...

Krayzie949 · 01-27-2010, 07:45 PM

My 96 Jeep Grand Cherokee starts up great in the morning and it starts up fine if I shut it off for a minute and then get back in it and start it right back up. My problem is after the Jeep warms up. If I shut the Jeep off for 5+ minutes while I go into a store, I come back out and most of the time the jeep will just crank and crank but won't start. It used to just crank and crank forever on the first try. Then the second time I would turn the key and it would start up immediately. Well today that didn't happen. I had to wait a little until it cooled down and then it started right up. Any idea on what could be wrong. I thought the CPS, but I can't explain why it starts up just fine when its cold. I do need to replace a coolant sensor and oxygen sensor, but could that cause this problem? Please let me know. Thanks.

Brian

ZeeJay1997 · 01-27-2010, 07:59 PM

Checked your fuel pressure?

Krayzie949 · 01-27-2010, 08:34 PM

No, I haven't checked that. I assumed since it started fine when it was cold the fuel pressure should be ok. I'll check that out tomorrow though. Thanks. Any other ideas.

Krayzie949 · 01-28-2010, 06:52 AM

Anybody?

ZeeJay1997 · 01-28-2010, 07:39 PM

Quote:

Originally Posted by Krayzie949

Then the second time I would turn the key and it would start up immediately. Well today that didn't happen. I had to wait a little until it cooled down and then it started right up.

Sounds like a fuel delivery problem. Swap fuel pump relay with another relay. It could be getting hot and failing. The pump could be drawing too much current when it gets hot. The only way to eliminate is to check the pressure when you're having problems.

ThePinkBaron · 01-28-2010, 10:02 PM

That is the exact issue I had with my 93 ZJ ltd. I replaced 2 fuel filters, which helped the slight drop in fuel pressure I had, but in the end I had to replace the PCM as it was sending false signals out, and causing the jeep to just crank crank crank with no spark. And it only did it after it had been driven for awhile and turned off. Eventually it let go all together and my tach started spiking when I turned the key on and no matter what I could not get it to start.

Anyhow, I digress, it could be anything from your fuel system to your coilpack, all the way to your PCM, hell it could be your security system malfunctioning.

Check your fuel pressure, do you have spark at the distributor? If you are not getting fuel OR spark, then its likely something to do with your computer system (same issue as mine) or a malfunctioning security system.

If you have one but not the other then well, might be a bad fuel pump relay like already stated, could be a coil issue (doubtful but if it got cracked and got some water in there it can really mess things up)

Doubt I helped much, but I went through all of this garbage to find out that it was the computer, lets hope you find it faster.

Krayzie949 · 01-29-2010, 10:12 AM

Quote:

Originally Posted by ThePinkBaron

That is the exact issue I had with my 93 ZJ ltd. I replaced 2 fuel filters, which helped the slight drop in fuel pressure I had, but in the end I had to replace the PCM as it was sending false signals out, and causing the jeep to just crank crank crank with no spark. And it only did it after it had been driven for awhile and turned off. Eventually it let go all together and my tach started spiking when I turned the key on and no matter what I could not get it to start.

Anyhow, I digress, it could be anything from your fuel system to your coilpack, all the way to your PCM, hell it could be your security system malfunctioning.

Check your fuel pressure, do you have spark at the distributor? If you are not getting fuel OR spark, then its likely something to do with your computer system (same issue as mine) or a malfunctioning security system.

If you have one but not the other then well, might be a bad fuel pump relay like already stated, could be a coil issue (doubtful but if it got cracked and got some water in there it can really mess things up)

Doubt I helped much, but I went through all of this garbage to find out that it was the computer, lets hope you find it faster.

Just curious, did you replace your CPS while this was all happening or would the jeep not start at all if the CPS was bad?

Krayzie949 · 01-29-2010, 10:26 AM

New development. Now it won't start. This morning it would not start at all. Right now, it started for literally five seconds and died.

ThePinkBaron · 01-29-2010, 10:38 AM

Quote:

Originally Posted by Krayzie949

Just curious, did you replace your CPS while this was all happening or would the jeep not start at all if the CPS was bad?

Well I tried the PCM before the CPS though it seemed a lot of my google searches warranted CPS failure, it just didnt seem like the symptoms matched me.

See if you can find someone with a CPS and/or PCM that matches your jeep, It only takes a second to plug it in and un plug it, and if yours fires up with theirs you know what is wrong. And you can order the part.

I got mine from OEM Computers For 1996 Jeep Grand Cherokee By Auto Computer Exchange I guess they are calling it an ECM, my mechanic called it a PCM as well, but either way it fixed me up alright. They take the exact drive train numbers from you, as new computers need to be flashed to your exact vehicle, VIN, mileage etc. And they will take your old computer back, and give you a 1 year warranty for returning it. Also best prices I was able to find. If you think about it, its not a bad deal, you do the work yourself it is much cheaper than replacing a fuel pump. (which it COULD also be, but I doubt it)

jeeper93436 · 01-29-2010, 08:57 PM

perfect now you can fix the problem.will it run if you hold the gas pedal slightly open? if not first check for fuel pressure and spark down to the wires. then get back at us

fivetears · 01-30-2010, 12:41 AM

Put on your "big boy panties" and check your fuel pressure! Take the adapter fitting cap off the injector feed line, get a machinist scribe or a long nail and depress the valve stem. If it sprays gas... then ya got pressure. Be smart about though; ya don't need to get yourself sprayed with gas; put a rag over your hand before you press the needle valve. No fuel spray; buy a pump.

Krayzie949 · 01-30-2010, 02:53 PM

Fuel pressure is good and I have spark. I'm thinking it's the PCM.

ThePinkBaron · 01-31-2010, 10:17 PM

Quote:

Originally Posted by fivetears

Put on your "big boy panties" and check your fuel pressure! Take the adapter fitting cap off the injector feed line, get a machinist scribe or a long nail and depress the valve stem. If it sprays gas... then ya got pressure. Be smart about though; ya don't need to get yourself sprayed with gas; put a rag over your hand before you press the needle valve. No fuel spray; buy a pump.

Or you can just unclip the inlet hose and place the hose in a bottle.

I am thinking PCM as well.

01-27-2010, 08:34 PM	#3
Krayzie949 Registered User Join Date: Dec 2006 Location: NEPA Posts: 106 Profile Gallery Classifieds My Jeeps	No, I haven't checked that. I assumed since it started fine when it was cold the fuel pressure should be ok. I'll check that out tomorrow though. Thanks. Any other ideas. __________________ 2001 Jeep Cherokee 4.5" RE Superflex Lift 1970 Buick GS 455 Stage 1 4-speed 1977 Trans Am (original owner)

01-28-2010, 06:52 AM	#4
Krayzie949 Registered User Join Date: Dec 2006 Location: NEPA Posts: 106 Profile Gallery Classifieds My Jeeps	Anybody? __________________ 2001 Jeep Cherokee 4.5" RE Superflex Lift 1970 Buick GS 455 Stage 1 4-speed 1977 Trans Am (original owner)

01-29-2010, 10:26 AM	#8
Krayzie949 Registered User Join Date: Dec 2006 Location: NEPA Posts: 106 Profile Gallery Classifieds My Jeeps	New development. Now it won't start. This morning it would not start at all. Right now, it started for literally five seconds and died. __________________ 2001 Jeep Cherokee 4.5" RE Superflex Lift 1970 Buick GS 455 Stage 1 4-speed 1977 Trans Am (original owner)

01-30-2010, 02:53 PM	#12
Krayzie949 Registered User Join Date: Dec 2006 Location: NEPA Posts: 106 Profile Gallery Classifieds My Jeeps	Fuel pressure is good and I have spark. I'm thinking it's the PCM. __________________ 2001 Jeep Cherokee 4.5" RE Superflex Lift 1970 Buick GS 455 Stage 1 4-speed 1977 Trans Am (original owner)

01-30-2010, 12:41 AM	#11
fivetears Registered User Join Date: Jan 2008 Location: Texas Posts: 2 Profile Gallery Classifieds My Jeeps	Put on your "big boy panties" and check your fuel pressure! Take the adapter fitting cap off the injector feed line, get a machinist scribe or a long nail and depress the valve stem. If it sprays gas... then ya got pressure. Be smart about though; ya don't need to get yourself sprayed with gas; put a rag over your hand before you press the needle valve. No fuel spray; buy a pump.