No start issue - JeepForum.com
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  • 1 Post By kg6mov
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post #1 of 10 Old 07-14-2021, 11:32 AM Thread Starter
das13
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1994 ZJ 
 
Join Date: Jun 2016
Posts: 6
No start issue

Hello and thank you to all the amazing members here. I have used this site for the last 7+ years to keep my baby running. Unfortunately, she is not currently running. I'll list what I have done and am willing to take any and all suggestions. Thanks in advance.


1994 Grand Cherokee Laredo

5.2 engine
272k miles


The issue started with a stumble/hesitation off idle. When stopped at a light the engine would idle fine but upon initial throttle application would stumble a bit. After 1-2 seconds rpm's would increase and throttle response felt fine. No loss of power or stumble after the initial throttle tip in. This happened about 5-6 times in one trip, it hadn't happened before. I shut it off and restarted it about an hour later with the same issue. I was at the bottom of a large hill and hit the throttle to accelerate up the hill and the engine stopped. I coasted to a stop and could not restart the Jeep. It would crank but not catch.


I suspected the fuel pump was bad and replaced it. That resulted in no change, still cranks and will not start. When I turn the key to the on position I can hear the fuel pump powering on.


I attempted to pull codes with the key on-off-on-off-on and retrieved no flashing lights.
The check engine light stays on for about 3 seconds when I turn the key to on and then goes out.


I cleaned the battery terminals


I cleaned the ground located below the alternator on the passenger side of the block.


I removed the wire connector from the PCM and cleaned it. I wiggled the PCM.


I checked and cleaned all relays in the PDC and cleaned the positive wire attachment point


I have 11.5+ volts with the key on according to the dash. It drops below that when I attempt to start it but still cranks.


I have a half tank of known good gas.


I have replaced the fuel pump with a new Delphi unit


I was unable to test the coil but see no scoring or other indication of damage.


I am unable to access the distributor cap due to location. (If I need to be tougher or more monkey like, let me know).


I looked at the O2 sensor wiring as much as I could which isn't much and didn't see any issues.


Any suggestions would be greatly appreciated, thank you again and have a good one.


Jon

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post #2 of 10 Old 07-14-2021, 12:27 PM
kg6mov
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Location: Cupertino
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Yes, climb on into the engine bay and think thin thoughts then have after the cap and rotor. Go around the intake not over it.

I also don't see plugs on your list.

I'd basically throw an old school ignition tune up at it as a baseline.
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post #3 of 10 Old 07-14-2021, 01:26 PM Thread Starter
das13
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1994 ZJ 
 
Join Date: Jun 2016
Posts: 6
As I was sitting here I thought the same thing. Time to stop being a sissy. Thank you. I'll update after it is done.
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post #4 of 10 Old 07-15-2021, 04:16 AM
yjsaabman
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Location: Elizabethtown
Posts: 250
Diagnose, don't throw parts at it. Air, fuel, and spark are what the engine needs to run. You know you have fuel pumping, but is it getting to the rails? Do you have spark? Do you have injector pulse? When you pull the spark plugs pay close attention to the condition, are they fuel soaked?

No flash codes at all is odd, as it should at least give you the end code, even if there aren't any others.

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post #5 of 10 Old 07-15-2021, 04:35 AM
jtec
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spark check is there spark at several plugs. And as mentioned READ them.
Fuel pressure PSI- yes I see new pump but new ≠ good.

When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
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post #6 of 10 Old 07-15-2021, 04:56 AM
V8GCZJ
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Quote:
I attempted to pull codes with the key on-off-on-off-on and retrieved no flashing lights.
You may be doing it to slow or fast. Keep trying it you should get a 55 code meaning end of codes even if there are no codes set.
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post #7 of 10 Old 07-15-2021, 10:10 PM Thread Starter
das13
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1994 ZJ 
 
Join Date: Jun 2016
Posts: 6
Hello All and thanks for the responses so far. I didn't get a chance to do anything on the Jeep today. Tomorrow I'll try to retrieve codes again and pull the distributor cap to see if there are any issues there. I'll also see if I can get spark. Thanks again.
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post #8 of 10 Old 07-16-2021, 01:31 PM
HighLonesome
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You changed the fuel filter along with the pump I assume. There is a fuel regulator at the rail which can fail. I sort of recall it is vacuum driven, so give that a check. A pressure check at the rail will cover all that.

Sure diagnosis is best, but just replace the coil. They are cheap, and if it doesn't help, throw it under the rear seat as a spare. You may not 'see' anything wrong with a coil. What happens over time is the insulation on the internal wiring breaks down, and they short out. Or they become intermittent dependent on heat.
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post #9 of 10 Old 07-19-2021, 10:43 AM Thread Starter
das13
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1994 ZJ 
 
Join Date: Jun 2016
Posts: 6
Hello, I did replace the filter at the same time as the pump. I wasn't able to do anything on the Jeep this weekend. I'll update when something changes. Thanks again.
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post #10 of 10 Old 08-02-2021, 03:22 PM Thread Starter
das13
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1994 ZJ 
 
Join Date: Jun 2016
Posts: 6
Hello and thanks again for the help. Life got in the way and I wasn't able to do anything to the Jeep until this morning. I pulled a plug and had my wife crank the Jeep. Spark was weak and erratic. I replaced the coil and she started right up. 272k miles and the boy and I got ice cream. Life is good again in my Jeep. Thanks to everyone.
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