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Unread 12-10-2007, 05:34 PM   #1
toms93grand
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93 Grand cherokee fuel pump

93 grand 4.0L, fuel pump does not cycle on during cold start. fuel pump replaced, relay is good. If key left in run position while checking under hood after a few minutes I can hear the fuel pump relay chatter and then close, pump comes on for a few seconds to charge fuel manifold and then I can start. The relay is known functional by swapping with starter relay(same pn#) removed case from relay to mechanically engage contacts, fuel pump runs however even if i charge up manifold this way, will not start.

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Unread 12-10-2007, 10:51 PM   #2
-Joe-
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Some have noted this can be caused by bad capacitors in the pcm.

You could pull and check for swollen or leaking caps.
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Unread 12-11-2007, 03:19 PM   #3
greasefingers
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Yep that’s a lazy PCM powering-up. Replace it or tear it apart and replace the three capacitors that Joe is speaking about.
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Unread 12-11-2007, 08:35 PM   #4
-Joe-
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I just replaced like 12 of them on an old motherboard.
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'95 Jeep Grand Cherokee Laredo I6 4.0L
242TC - Extreme Engineering 2" Front Lift/1.75" Rear Lift - ES9000 Shocks + JKS BPEs
Moog Cargo Control Springs
Magnaflow Converter - Dynomax Muffler
235/75/15 AT Uniroyal Liberator Tires
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Unread 12-12-2007, 08:00 PM   #5
toms93grand
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Thanks a lot guys, I will take a look at the caps in PCM, or see if I can get one from a junkie. Is there any issue with swaping the PCM with a used one that I should know about?

thanks! Tom
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Unread 12-15-2007, 10:22 AM   #6
toms93grand
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Thats It!!!

You guys were right on the money! Pulled the PCM and 1 of the 3 large caps was swollen.

Now I know root cause of this issue

Thanks a lot
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Unread 12-15-2007, 10:33 AM   #7
indept
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Quote:
Originally Posted by toms93grand
You guys were right on the money! Pulled the PCM and 1 of the 3 large caps was swollen.

Now I know root cause of this issue

Thanks a lot
I found rubbing make the swelling go down
How about some pics showing which capacitor
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Unread 12-30-2007, 05:49 PM   #8
toms93grand
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Quote:
Originally Posted by indept
I found rubbing make the swelling go down
How about some pics showing which capacitor
Left myself open for that one! Still laughing

Replaced the 220uF cap and the thing is now alive again...

Like how Jeep pots the motherboard so you can't work on it!
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