Fuel '02 V6 - Fuel Pump Fuse Popping After Pump Motor And Ccrm Replacement

Good evening, all,

I've replaced both the CCRM and fuel pump motor in my son's '02 coupe, but now have the underhood fuel pump fuse (F1.14) blowing every time I move the key to the on/run position (before pushing it forward to start).

I alternated disconnecting first the CCRM then the pump, trying the key after each, and the fuse pops only when the pump is connected (C463 connector behind the bumper). With a good fuse installed, though, I get continuity on the harness-side of C463.

When only the CCRM is connected, I hear the integrated FP relay click when the key is engaged, which leads me to think it's okay. I also, though, sent 12v through pins 6 & 7 of the tank-side C463 connector and heard the new pump run fine.

Am I right in assuming the pump shouldn't run if the short was in the pump itself or tank-side connection? I lowered the tank to ensure the tank harness wan't binding on anything, with no luck. Again, though, it runs fine and indefinitely with power applied to connector.

Any suggestions for chasing this apparent short would be greatly appreciated.

Thanks,

Ramon
 
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Am I right in assuming the pump shouldn't run if the short was in the pump itself or tank-side connection? I lowered the tank to ensure the tank harness wan't binding on anything, with no luck. Again, though, it runs fine and indefinitely with power applied to connector.
This assumption isn't quite correct. I can think of a case that would cause this set of symptoms. How about the fuel pump positive power wire pinched between the gas tank and fuel basket ring?

I have helped more than one person that has done something similar. I even helped someone that dropped the tank more than once to test the fuel pump. Each time the fuel pump tested fine. However what this person didn't understand is the gas tank isn't well grounded to the car body when it has been dropped. When the tank was not grounded it tested fine. But as soon as the tank was fully installed the problem re-started.

Depending upon which fuel pump wire is grounded will determine the symptom. IF the positive supply is grounded, blown fuse. If the negative return line is grounded, the fuel pump will run all of the time.

With C463 disconnected, measure the Ohms through the fuel pump. Be sure to zero the VOM and use a fresh battery. This will give the resistance of the FP coil winding and confirm the FP isn't shorted internally. Now with the gas tank in place measure the resistance between each C463 fuel pump lead an a KNOWN good ground. With C463 disconnected this reading should be very high. Anything not in the kilo or mega Ohm reading confirms the diagnosis.

The reason your test is working is because the temporary supply isn't referenced to a working car ground. I'm suspecting that IF you grounded the FP return line your test maybe very different. Note, I recommend doing the VOM resistance test first. Don't needlessly risk burning sometime up with the "blow fuse" test method.

Note, the Ohm meter may not give the best results for a power circuit as the Ohm meter does not load the circuit. However in this case IF the Ohm meter shows low resistance to ground, the test is valid.

Other possible causes could be a bad fuel pump driver module (FPDM). IMO based upon your symptoms this seems less likely to me. it seems to me that a bad FPDM would blow the fuse every time.

If the VOM test doesn't confirm the diagnosis you would be well served to learn how to perform voltage drop tests as this is the gold standard test for this sort of electrical problem. Here's some information to get you started.

Howto perform charging system voltage drop test
https://www.stangnet.com/mustang-fo...perform-charging-system-voltage-drop-test.56/
 
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Thanks a ton for the detailed feedback @wmburns !

Depending upon which fuel pump wire is grounded will determine the symptom. IF the positive supply is grounded, blown fuse. If the negative return line is grounded, the fuel pump will run all of the time.

Since the symptom is blowing fuse versus constant operation, sounds like the potential suspect is grounded postive supply.

With gas tank still in place, I set my VOM to both kilo- and mega-ohms and probed the fuel pump (6 and 7 pins). Each time the reading dropped to near zero.

Connecting one probe to either pin and the other to multiple nearby metal reinforcement points (not the tank) returned an open (OL) reading. How does open compare to high resistance in this case?

Other possible causes could be a bad fuel pump driver module (FPDM). IMO based upon your symptoms this seems less likely to me. it seems to me that a bad FPDM would blow the fuse every time.

At the time I wrote the question, I wasn't aware of another module in the circuit (the FPDM). Since the fuse is blowing every time, I'm wondering if it's the cause and will look for posts describing how to test it.

Thanks so much again,
 
With gas tank still in place, I set my VOM to both kilo- and mega-ohms and probed the fuel pump (6 and 7 pins). Each time the reading dropped to near zero.
Well........The above test results would indicate the problem is in the fuel pump itself. The resistance of the FP coil shouldn't be near zero.

There has to be some resistance of at least 1.5 Ohms which should give a current flow of 8 amps at 12 volts.

But it's possible that the Ohm scale has been set too high to see a low value such as 1.5-2 Ohms.

One of the other details missing from this thread is HOW many amps the fuel pump actually drew during the functional test. With the F1.14 being a 20 amp fuse would mean that the min fuel pump coil resistance has to be greater than 0.6 Ohms.
 
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Thanks again! Your description helped me understand the formula/relationship between voltage, amperage and resistance. I retested, understanding also now the low scale involved.

I set VOM to 600Ω and touched the probes to zero the meter: this produced a reading of 0.4Ω. I then re-probed connectors 6 and 7 of tank side of c463: the reading fluctuated between 0.9 and 0.8Ω.

Subtracting the 0.4Ω baseline from the readings results in a range of 0.5-0.4Ω. Dividing either of these by 12v results in 24-30 amps, either of which would blow a 20a fuse.

Am I interpreting this correctly? I have a second VOM and will check with it as well.
 
I set VOM to 600Ω and touched the probes to zero the meter: this produced a reading of 0.4Ω. I then re-probed connectors 6 and 7 of tank side of c463: the reading fluctuated between 0.9 and 0.8Ω.

Subtracting the 0.4Ω baseline from the readings results in a range of 0.5-0.4Ω. Dividing either of these by 12v results in 24-30 amps, either of which would blow a 20a fuse.

Am I interpreting this correctly? I have a second VOM and will check with it as well.
Good work!

Just wondering. What happened to cause the fuel pump and CCRM to be replaced in the first place.

Where did the replacement Fuel pump come from? Are you sure it's the correct fuel pump for the application? As a reminder that the fuel pump is different for a return-less vs a return system.
 
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Thanks for the encouragement - now for the confession (-:

This adventure started about 18 months ago with a recurring P0457 EVAP leak code coupled with a random no-start. After reading that EVAP leaks could keep the car from starting, I (myopically, in retrospect) focused on it as the source of the then-still random no-start. After three gas caps and a filler neck grommet replacement by a mechanic, I learned about the Vapor Canister Purge Solenioid.

In preparing to check it, I discovered that the fenderwell splash shield was missing, and that the VCPS was covered with road debris and one of the mounting ears had broken off. It's bad physical condition was enough for me to change it, so I did, and I picked up a used shield from a salvage yard.

Certain that the P0457 was now fixed, I turned the key...and no dice, and no longer random.

Before this, I'd suspected a PATS issue - and my wife was certain that jiggling the steering wheel once corrected a no-start - but finding no voltage at the harness-side of C463 (bad test, again in retrospect) let me to suspect the CCRM. Discovering thereafter that it also lived in the exposed right wheelwell led me to suspect it might be damaged. I replaced it, but again no dice.

Ulitmately, 12v right to the pump with no results confirmed for me that it must have been dying (I still have it, and with what you've taught me, I'm going to check it's resistance). The P0457 was, then, related, but not the cause.

The new pump is a Delphi CFE0443 from Autozone, and shows to be a match.

Though I want to go back and practice testing them to learn more, I'm honestly not overly worried about replacing parts that might have been okay. The car has 180k and sooner or later these parts were going to fail.

Weather's bad in Houston today to drop the tank, will likely do so tomorrow.

Thanks again for your in-depth knowledge-sharing, man!
 
I have doubts that a P0457 could ever "cause" a no start condition.

FWIIW, a 1999-2004 PATS problem will not "cause" the fuel pump to not run. PATS works by withholding the fuel injector pulse. PATS does NOT affect how the fuel pump works/operates. The fuel pump should always run for a few seconds each time the key is cycled on/pause/off. It may help to have a buddy listen for the fuel pump to run.

Here's some more information.

1996+ Crank with no start check list
http://www.allfordmustangs.com/forums/4-6l-tech/336452-1997-mustang-wont-ignite.html#2984838

Pay attention to the part about how PATS is "proved out". Knowing if PATS has "proved out" will take the guess work out of if this is a PATS issue or not. Also pay attention to the part about IF the check engine light goes out during cranking.

If your Wife suspects that jiggling the ignition switch may have something to do with the crank with no start she may be on to something (a keeper). Next time it doesn't start test for +12 volts in/out of fuse F2.34, F2.2, and F2.8 with the key on using a KNOWN good ground. Where to focus next depends upon the test results.

If no voltage in F2.34, suspect an ignition switch problem.

If no voltage in fuse F2.2 and F2.8 suspect a CCRM problem.

1999-2004 MY fuse panel schedule:
http://www.allfordmustangs.com/foru...r-swap-wont-fire-please-help.html#post2669271

Recommend replacing fewer parts. Test. Don't guess.

Recommend using the $$ saved by not replacing good parts for better test and diagnostic gear (VOM and test light). Even better check out the Windows based ODB2 scanner:

ForScan ODB2 scanner w ELM327 USB
https://www.stangnet.com/mustang-forums/resources/forscan-odb2-scanner-w-elm327-usb.57/

OBTW, agreed about the Houston weather. It's projected to be real nice on Sunday.
 
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Hey, again,

I was reviewing another fuel-related, no-start thread (where you again gave great feedback!) and thought to recheck the pins on the tank-side of the c463 connector.


Here, pin 6 (nearest the angled connector) is black and 7 is pink/black. In earlier tests (before checking colors), I'd run 12v with a Powerprobe to 6 with ground to either 7 or on the chassis and could hear the pump.

I tried this again to empty the tank prior to dropping it and found that no gas was coming out. This and the validated wire colors seem to confirm that it is running backward, and 6 is the ground. Trying 12v to 7 instead trips the Powerprobe's breaker, confirming a (positive side?) short in the wiring, 2" wiring-to-spade-connector adapter or pump itself.

Now to drop the tank again |-:

Sidebar: I tested the old pumps' resistance, and it came in at 1.5Ω, which would generate a nice, low 8 amps. I then ran 12v through either side and reconfirmed that was siezed...
 
FWIIW my set of Ford wiring diagrams indicated connector C463 the wire colors are:

pin 7(RD/BK) Fuel pump, –
pin 6(BN/PK) Fuel pump, +

Did you have to field wire in the replacement pump into the basket? IF so it seems it would be wise to double check the pump wiring to be sure it's not wired backwards at the pump.

I have helped more than one person that accidentally pinched a wire between the fuel basket and gas tank hat when trying to stuff the basket into the tank.

IMO you should give yourself a pat on the back. Sometimes more than half the battle is the trouble shooting. Once the problem has been diagnosed the fix is often straight forward.
 
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So,

I lowered the tank again and checked the harness - no obvious signs of pinching or chafing. I then ran 12v through either pin and this time the pump ran in both directions.

I then rolled the tank back under the car, connected only the harness (c463 connector) and had the Mrs. turn the key to on/run - the pump primed and the fuse didn't blow!

I raised the tank and tested again, fuse still okay. I then connected the EVAP lines...then remembered i'd disconnected c463 after the test above. Plugged it back in, and the fuse blew.

I'm guessing the test with it lowered, grounded only by the black wire of the harness was flawed?
 
LOL, indeed! -though I was thinking more along the lines Schrödinger's cat: the + wire is both shorted and not shorted in the sealed housing (-:

Seriously, I should have inspected the pump at that point, but did not: the succesfull "no short when lowered but connected" test let me astray.

I lowered the tank again (I'm a pro '99-04 tank installer by now :- ) , unbolted the pump assembly, snaked the wiring out without lifting the pump and set the cover aside. Right off the bat, I could see the impression of a wire on the rubber gasket. Sure enough, I then checked the wiring-to-spade-connector adapter and found that the positive wire had a clear nick, plus what looked like compression chafing with a hint of copper visible.

Some heat shrink and zipties to secure the extra wiring - and 30 minutes of stepwise testing and reassembly - and she's running like a champ!

I appreciate the guidance, and am left with one question about it for future troubleshooting: I checked the resistance at the pump itself this time, and it was again 0.8Ω as it had been at the c463 connector before. As I discussed above, if I subtract my VOM's 0.4Ω baseline resistance, that would yield 0.4Ω and 30 amps - more than the 20a fuse for the curcuit. The fact the fuse isn't blowing anymore means the 20a limit is not being exceeded.

Should I not be subtracting the VOM's baseline resistance (12v/0.8Ω=15a)? Don't know if VOM quality is a factor: mine is a pretty good unit, I think.

Thanks again...