'89 Cherokee will run but randomly dies
03-18-2016, 12:06 PM
#61
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I think we have different issues, Mine stalls when it's cold. once it warms up, no more stalling. I was having a problem with it not starting, but that was fixed with the nss rebuild.
03-18-2016, 03:27 PM
#62
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Year: 1997
Model: Cherokee
Engine: 4.0
Aroundincircles, I feel your pain. I was hoping I had our problem wiped too. Cleaned the NSS and replaced the fuel pump ballast resister. Took it out for a drive, and no problem. Have driven it about 150 miles, took it out this afternoon, and about 2 miles from the house it died. This time I was able to check to see if there was fuel at the schrader valve on the fuel rail. No fuel came out. But was able to get it started and drove it home.
I have completed tips 1 and 2-8, 11 and 14
replaced and adjusted TPS,
replaced CPS,
replaced fuel pump, fuel filter, and fuel pump ballast resister
replaced ECU (before I found this site), and
replaced IAC.
Seems like I've done more, but that is all I can remember now.
Any ideas what could be causing fuel pressure to drop to nothing? As described above in my original post, I started out checking the fuel pressure idling in the garage
"At idle pressure is 30 psi, if rev motor to about 2000RPM (a guess with no tach) quickly rose to 32, then dropped to about 29 psi. Let idle for hour with back end sticking out of the garage hoping it would die so could watch the pressure gauge. But it never dies, and the pressures never changed. Just for fun I kept pressure gauge hooked up, and put car in drive and revved engine while standing on brakes until tires started to spin. Fuel pressure rose to about 38 psi."
Ideas? Thanks! Mike
I have completed tips 1 and 2-8, 11 and 14
replaced and adjusted TPS,
replaced CPS,
replaced fuel pump, fuel filter, and fuel pump ballast resister
replaced ECU (before I found this site), and
replaced IAC.
Seems like I've done more, but that is all I can remember now.
Any ideas what could be causing fuel pressure to drop to nothing? As described above in my original post, I started out checking the fuel pressure idling in the garage
"At idle pressure is 30 psi, if rev motor to about 2000RPM (a guess with no tach) quickly rose to 32, then dropped to about 29 psi. Let idle for hour with back end sticking out of the garage hoping it would die so could watch the pressure gauge. But it never dies, and the pressures never changed. Just for fun I kept pressure gauge hooked up, and put car in drive and revved engine while standing on brakes until tires started to spin. Fuel pressure rose to about 38 psi."
Ideas? Thanks! Mike
Yes I said that. lol
A wiggle test. Start motor, wiggle all the key electronics connectors. I would start with the connector on the CPS. Then get under it and reach in there and wiggle the wires to the pump. Follow them and wiggle intermittently along the path.
Do that with all the key wires you find. Even the ones you see coming and going from the computers.
Reason being I have seen on more than one occasion a simple wire cause this problem. On one vehicle the wire going from the computer to an ignition module was up against the frame and rubbed raw. When the engine flexed just right, it would hit the frame and short out cutting the engine. It would then crank right back up usually and drive fine until it happened again sometimes weeks later. Electrical tape over the wire and no more problems. That guy had put three fuel pumps in and spent hundreds on diagnostic fees for something I found in fifteen minutes doing the wiggle test.....
03-18-2016, 05:55 PM
#63
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Have you done a wiggle test?
Yes I said that. lol
A wiggle test. Start motor, wiggle all the key electronics connectors. I would start with the connector on the CPS. Then get under it and reach in there and wiggle the wires to the pump. Follow them and wiggle intermittently along the path.
Do that with all the key wires you find. Even the ones you see coming and going from the computers.
Reason being I have seen on more than one occasion a simple wire cause this problem. On one vehicle the wire going from the computer to an ignition module was up against the frame and rubbed raw. When the engine flexed just right, it would hit the frame and short out cutting the engine. It would then crank right back up usually and drive fine until it happened again sometimes weeks later. Electrical tape over the wire and no more problems. That guy had put three fuel pumps in and spent hundreds on diagnostic fees for something I found in fifteen minutes doing the wiggle test.....
Yes I said that. lol
A wiggle test. Start motor, wiggle all the key electronics connectors. I would start with the connector on the CPS. Then get under it and reach in there and wiggle the wires to the pump. Follow them and wiggle intermittently along the path.
Do that with all the key wires you find. Even the ones you see coming and going from the computers.
Reason being I have seen on more than one occasion a simple wire cause this problem. On one vehicle the wire going from the computer to an ignition module was up against the frame and rubbed raw. When the engine flexed just right, it would hit the frame and short out cutting the engine. It would then crank right back up usually and drive fine until it happened again sometimes weeks later. Electrical tape over the wire and no more problems. That guy had put three fuel pumps in and spent hundreds on diagnostic fees for something I found in fifteen minutes doing the wiggle test.....
03-19-2016, 01:12 AM
#64
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Thanks Dude,
I have checked a few of the connections and parts of the wiring harness, but not all of it. I will go through the rest of it and give it a shot.
Cruiser54, The fuel pump and the fuel pump resister are new. I know having new parts is not a guarantee they are new, but can you give me any tips on how to check them?
Thanks!
Mike
I have checked a few of the connections and parts of the wiring harness, but not all of it. I will go through the rest of it and give it a shot.
Cruiser54, The fuel pump and the fuel pump resister are new. I know having new parts is not a guarantee they are new, but can you give me any tips on how to check them?
Thanks!
Mike
03-19-2016, 05:42 AM
#65
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Year: 1987
Model: Cherokee
Engine: 4.0
Thanks Dude,
I have checked a few of the connections and parts of the wiring harness, but not all of it. I will go through the rest of it and give it a shot.
Cruiser54, The fuel pump and the fuel pump resister are new. I know having new parts is not a guarantee they are new, but can you give me any tips on how to check them?
Thanks!
Mike
I have checked a few of the connections and parts of the wiring harness, but not all of it. I will go through the rest of it and give it a shot.
Cruiser54, The fuel pump and the fuel pump resister are new. I know having new parts is not a guarantee they are new, but can you give me any tips on how to check them?
Thanks!
Mike
03-19-2016, 07:16 AM
#66
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Year: 1990
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At idle, fuel pressure should be 31. Then you pull the vacuum hose off the fuel pressure regulator and it should shoot up to 39.
03-25-2016, 11:47 PM
#67
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Hey Dude,
Finally had some time off and wiggled every part of the wiring harness I could get to. Wiggled for over an hour. Nothing, then with 5 minutes left in the Gonzaga game, after I turned away from the Cherokee, not wiggling anything, it died. Darn thing is messing with me. I checked the fuel at the schraeder valve, and there was fuel. At least it started right back up.
I'll go to town tomorrow and rent the fuel tester gauge again, and see what I get. The one thing I didn't check the first time I checked fuel pressure was pull off the vacumm line to the fuel pressure regulator. I have replaced the fuel pump and the fuel pump ballast resister.
Thanks,
Finally had some time off and wiggled every part of the wiring harness I could get to. Wiggled for over an hour. Nothing, then with 5 minutes left in the Gonzaga game, after I turned away from the Cherokee, not wiggling anything, it died. Darn thing is messing with me. I checked the fuel at the schraeder valve, and there was fuel. At least it started right back up.
I'll go to town tomorrow and rent the fuel tester gauge again, and see what I get. The one thing I didn't check the first time I checked fuel pressure was pull off the vacumm line to the fuel pressure regulator. I have replaced the fuel pump and the fuel pump ballast resister.
Thanks,
03-27-2016, 12:43 AM
#68
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Checked the fuel pressure stayed right around 32 PSI then when removed the vacuum line from fuel pressure regulator and pressure went up to 39 psi. Reconnected vacuum line and revved up the motor and pressure increased, then dropped to about 28 and then went back up to 32 psi.
Before I started the motor I hooked up turned on the ignition switch with gauge hooked up to schraeder valve. Pressure was 35 psi, but then dropped to 30 over about 5 minutes. So I have a leak somewhere internally (no gas leaking externally). Most likely an injector?
Also, while I had the gauge hooked to to the schraeder valve, the car died. The pressure did not drop until after the car died, but then started to drop. Reached near zero in about it dropped in about 5 minutes. Again no external leaks. Ideas? Thanks
Before I started the motor I hooked up turned on the ignition switch with gauge hooked up to schraeder valve. Pressure was 35 psi, but then dropped to 30 over about 5 minutes. So I have a leak somewhere internally (no gas leaking externally). Most likely an injector?
Also, while I had the gauge hooked to to the schraeder valve, the car died. The pressure did not drop until after the car died, but then started to drop. Reached near zero in about it dropped in about 5 minutes. Again no external leaks. Ideas? Thanks
03-27-2016, 08:48 AM
#69
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Great job of testing. You may have more than one issue.
Your fuel pump MAY be weak. I wouldn't go down that road just yet.
I wonder if some electrical component is getting hot and failing. Check the connectors on your fuel pump ballast resistor for fun.
What is your CPS reading?
Your fuel pump MAY be weak. I wouldn't go down that road just yet.
I wonder if some electrical component is getting hot and failing. Check the connectors on your fuel pump ballast resistor for fun.
What is your CPS reading?
03-27-2016, 08:51 AM
#70
Senior Member
Mike-It sounds like you have done most of the usual suspects so just grasping at straws now.
I have a zip tie on my CPS connector to keep it tight.
When you say it "dies" I assume you mean that it is like you turned off the engine. Does it sputter before it dies like it's trying to stay running?
I wire-wheeled my grounds to bare metal. Make sure you are doing that when you're cleaning the grounds. The one from the back of the block to the firewall is important as is the instrument panel ground wire.
I'm still thinking CPS if it's just dying but you seem to have done everything you can.
What about the small hose to the MAP sensor off the throttle body? Replaced or checked that?
Sorry for not responding but the other replies seem to be logical so stayed out of threads.
I have a zip tie on my CPS connector to keep it tight.
When you say it "dies" I assume you mean that it is like you turned off the engine. Does it sputter before it dies like it's trying to stay running?
I wire-wheeled my grounds to bare metal. Make sure you are doing that when you're cleaning the grounds. The one from the back of the block to the firewall is important as is the instrument panel ground wire.
I'm still thinking CPS if it's just dying but you seem to have done everything you can.
What about the small hose to the MAP sensor off the throttle body? Replaced or checked that?
Sorry for not responding but the other replies seem to be logical so stayed out of threads.
03-27-2016, 08:45 PM
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Rechecked the CPS. My volt meter only reports in tenths of volts, but was registering 0.3, flickered 0.4 a couple times, but stayed mostly at 0.3. I've replaced it three times already, but based on tip #7, looks like I'll be replacing it again. Last time I replaced the CPS, I also used sandpaper and cleaned the outer edge of the flywheel. Not sure if it helped, but seemed like the slight rusty surface could have been interfering with the electricity generation. Also completed tip #18, and refreshed the instrument panel ground. With work, it will be Friday before I can work on the Cherokee again. Thanks for your help, and Happy Easter!
03-27-2016, 10:52 PM
#72
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I hesitate to suggest this... but have you thought of taking it to the dealer?
I chased and chased an intermittent stalling issue for weeks. Took it to the dealer, and in half an hour they called me on pick it up. 100$ for fixing the wiring harness that goes across the top of the engine on the firewall.
They said it's notorious for rubbing the wires raw and causing spontaneous and irregular stalling.
Even if you don't take it in, cut apart the black casing, being careful not to cause damage and check those wires.
Good luck.
I chased and chased an intermittent stalling issue for weeks. Took it to the dealer, and in half an hour they called me on pick it up. 100$ for fixing the wiring harness that goes across the top of the engine on the firewall.
They said it's notorious for rubbing the wires raw and causing spontaneous and irregular stalling.
Even if you don't take it in, cut apart the black casing, being careful not to cause damage and check those wires.
Good luck.
03-28-2016, 11:23 AM
#73
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I hesitate to suggest this... but have you thought of taking it to the dealer?
I chased and chased an intermittent stalling issue for weeks. Took it to the dealer, and in half an hour they called me on pick it up. 100$ for fixing the wiring harness that goes across the top of the engine on the firewall.
They said it's notorious for rubbing the wires raw and causing spontaneous and irregular stalling.
Even if you don't take it in, cut apart the black casing, being careful not to cause damage and check those wires.
Good luck.
I chased and chased an intermittent stalling issue for weeks. Took it to the dealer, and in half an hour they called me on pick it up. 100$ for fixing the wiring harness that goes across the top of the engine on the firewall.
They said it's notorious for rubbing the wires raw and causing spontaneous and irregular stalling.
Even if you don't take it in, cut apart the black casing, being careful not to cause damage and check those wires.
Good luck.
True story. Did you wiggle this wire too?
Also, when it dies, does it crank right back up?
If it dies and cranks right back up, maybe a problem in the coil getting hot.
Also as stated, no shame in taking it to the dealer after as much troubleshooting as you have done. An oscilloscope comes in mighty handy in these times and is usually too pricey for the home mechanic.
03-28-2016, 02:37 PM
#74
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Mine would die and not start back up. I didn't try the wiggle test on that harness. I didn't know they EVER had problems. I mean, who would even THINK that a wiring get harness, apparently very secured, and wrapped in that black plastic pipe protector could ever wear out? Especially that one?
This is where I learned to wiggle wiggle wiggle... cost me money I could've saved.
This is where I learned to wiggle wiggle wiggle... cost me money I could've saved.
04-07-2016, 03:55 PM
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I had the same problem. It's why my brother gave me the Cherokee. He never noticed it only happened on right turns and bumps. A wire had frayed ,and was hitting the engine and shorting it, and the jeep would die. We fixed that ,then the next problem was a iac valve. The idle would go so low it'd die, if have to whack it with a wrench and it'd start. I always keep a monkey wrench in my jeeps, lots of things to smash to get her going again 