Cranking no start, no fuel pump prime, no fuel gauge activity - JeepForum.com
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post #1 of 20 Old 07-29-2021, 08:38 PM Thread Starter
Coledbernstein
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Cranking no start, no fuel pump prime, no fuel gauge activity

Hey y'all, haven't posted yet here, thought I'd give it a shot. 2002 Jeep Grand Cherokee 4.7. Ran great until it didnt. Came out in the morning to start er up and go to work - nothing. Just cranked and cranked. No fuel pump prime noise, no pressure at shraeder valve. Already replaced Crankshaft Position Sensor and Camshaft Sensor, IAC, crankcase breather tube, new starter, new battery, cleaned all grounds EVERYWHERE. PCM terminal and ground terminals all sparkling and clean. New lifters and rocker arms, valve springs gaskets etc. Been bored, so f it. Everything except starter and battery was done before the problem started. And it ran fine for weeks after doing this. I've seen thousands of threads on this, only a few resolved with PCM replacement or CPS replacement, but those test ok. Anyone find the magical cause of this yet? I've ran through my wiring and replaced anything worn out. Also, key light is solid. Any suggestions would be much appreciated. Thanks!

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post #2 of 20 Old 07-29-2021, 08:47 PM
cDee63
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Mine did this last summer. Drove me MAD, did the same as you. Turned out to be internal to the connector underneath that is rosebud clipped to the fuel tank skid plate/tray, it's on the drivers side on the back side of the tray. It connects the fuel pump/level wiring to the vehicle harness. The wires for it come through the floor under the back seat along with the speed sensor wires. I bypassed mine completely and have not had a problem since AND I have a new cam position, crank position, PCM!! And spares!!

2004 Limited, 4.7 modded slightly, IRO 3" RockLink LA front, adjustable SA rear, Bilsteins, Addco bar, JKS disconnects. Coming attractions include 242hd, IRO SYE and Woods DS right after the new engine/trans..
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post #3 of 20 Old 07-29-2021, 08:59 PM Thread Starter
Coledbernstein
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Good to know, thanks for the reply. I'll find it in the morning and see what I can do. When you say bypass it, you just cut it out of the equation?
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post #4 of 20 Old 07-29-2021, 11:38 PM
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If it's electric & it don't work, check it's got power is always good advice.
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post #5 of 20 Old 07-30-2021, 06:50 AM
jtec
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What checks/diagnostics have you done?

Codes?
do you have a test light and wiring diagrams?

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 20 Old 07-30-2021, 07:42 AM Thread Starter
Coledbernstein
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No codes. My scanner does connect to OBDII just fine. I've worked my way with my multimeter all the way from engine bay to airbag system under center console so far. Checked everything, it's all good. If I jump fuel pump directly it primes.
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post #7 of 20 Old 07-30-2021, 07:45 AM Thread Starter
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Also, I've done fuel pressure test, compression test for the heck of it...I'm about at my wits end but I'm gonna check the wiring forward from fuel pump today I guess. I've also checked all fuses, and made sure everything that needs 5v is getting it, confirmed voltage at spinouts on pcm also.
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post #8 of 20 Old 07-30-2021, 09:39 AM
JGCJeep
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Check to see if there’s any shorts to the 5v reference wires on the crank sensor. I had a bunch of wires melted together next to the throttle body(4.0). It would crank, but the pump wouldn’t prime or run. Same as yours, the pump primed when jumped.
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post #9 of 20 Old 07-30-2021, 10:27 AM Thread Starter
Coledbernstein
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Ok, I'll check that also, thanks.
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post #10 of 20 Old 07-30-2021, 10:37 AM
JGCJeep
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Quote:
Originally Posted by Coledbernstein View Post
Ok, I'll check that also, thanks.
You’re welcome. Diagnosing it was tricky. It’s been a while, but what I think I wound up doing was disconnecting all the connectors at the pcm and I was still getting continuity between the reference wire and reference ground.
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post #11 of 20 Old 07-30-2021, 10:57 AM
jtec
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OK the scanner will communicate - any chance you can view live data?

Some simple tests that will tell alot,
1) with your test light will the injectors pulse when cranking?
2) with a 4.7L you could also check the coil primary (12v) to see if it flashes as cranking.
C) fuel pressure PSI ?
4) as someone cranks engine spray some carb cleaner into TB - did eng fire and try to run on spray?

When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.

Last edited by jtec; 07-30-2021 at 12:15 PM. Reason: typo injector to coil
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post #12 of 20 Old 07-30-2021, 12:00 PM Thread Starter
Coledbernstein
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Live test on scan tool only showed TPS at 12%...literally nothing else which is strange. Tried to start it with fluid and obviously have no spark, didnt get anything. Fuel pump alone would not cause a no spark. Keyfob works, all overhead and dash tests show good, but I'm starting to wonder if its Immobilized from SKIM or something similar.
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post #13 of 20 Old 07-30-2021, 12:02 PM Thread Starter
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Fuel pressure psi is very very low, at 14psi. I have to run around for a bit, I will check the rest and get back to yall
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post #14 of 20 Old 07-30-2021, 12:24 PM
jtec
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above post #11 do test 1 & 2 - see if inj and coil are getting 12v and pulsing. A fast and easy test, unplug any coil or injector and jump terminal with test light it should flash as engine is cranked.

As fr the low fuel pressure - lets check (don't just look at) fuse #12 in cab fuse block and the PDC fuse #23.

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 #15 of 20 Old 07-30-2021, 01:16 PM Thread Starter
Coledbernstein
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No pulse on coil one, injector has proper Ohm reading though if that helps. All fuses are ok and show good when key is on
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