Questions about replacing fuel pump

ike_hike

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My LJ refused to start in the Lowe's parking lot. It will crank at a normal level but will not start. I had it towed home, and here it sits.

Background. I have read all of the threads I can find about "crank won't start," and I believe that my problem is the fuel pump.

1) There are no relevant CEL codes. [I do get P0218 "High Temperature Mode Activated" which I think means a stuck thermostat. However, the CEL is not actually on, and I replaced the thermostat last year after getting the code. Maybe it's still in the memory somewhere, or maybe the thermostat is bad. But anyway, not relevant to this problem I don't believe.]

2) When the key turns to the on position, I can hear the fuel pump run for a second or two. It's not whining per se, but the whirring sound does seem louder than normal to me. You can hear it clearly standing anywhere around the Jeep.

3) My battery is good and all of the electronics are working.

4) The trick of initiating the pump 10-12 times in a row has no effect.

5) When I put some starter fluid into the throttle body, it ran for a couple of seconds and died. This suggests that it's not anything electronic.


Questions.

1) Could it still be the crankshaft position sensor? Would that necessarily throw a CEL?

2) Is it clear enough that the problem is the fuel pump, or do I need to do an actual fuel pressure test? The reason I ask is that I don't have a tester and I would also need to rig up the extra tubing to get around the no-schrader-valve problem.

3) The tank is about 2/3 full. Would you drop it and then siphon out fuel before you raise it? Or maybe try to do everything with fuel in it? [I have read that a siphon tube will not go through the fill hole into the tank?]

Thanks so much! The bolts are stewing in Kroil as I type.

Bryan
 

TJ4Jim

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Give the TB a shot of starter fluid and see if she fires momentarily . Sounds like it could be a crank sensor which will not usually throw a code.
 
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ike_hike

ike_hike

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I did put starter fluid into the throttle body, and it fired for a second. I interpreted that to mean that it must be the fuel pump. Is that not correct?
 

TJ4Jim

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I did put starter fluid into the throttle body, and it fired for a second. I interpreted that to mean that it must be the fuel pump. Is that not correct?

Do you hear the pump prime when the key is turned to the run position. It should run for about 2 seconds and you should be able to hear it near the drivers side rear tire.
 

pagrey

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Regarding your third question, if you do decide to pull the tank I'd just do it with gas in it. It's only 75 lbs extra and with a jack it just takes some care to keep it level. Extra hands help. The pump can be pulled with fuel in the tank as well. I've done it on an 06 close to full. I left the filler neck on, it is more difficult but keeps it almost sealed. I'd research replacement fuel line clips before you start, they break easily. The Rokmen skid install video is very helpful for the 05-06. My 04 is different but I think 05-06 are the same.

 
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ike_hike

ike_hike

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Do you hear the pump prime when the key is turned to the run position. It should run for about 2 seconds and you should be able to hear it near the drivers side rear tire.

Yes, I can hear it. It's loud enough that you can hear it even from the engine bay.
 

AjRagno

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P0218 is transmission temp, not engine. Being that this is the only code you have, I would start here. The transmission (PCM) goes into over temp mode at 240 degrees. If you don’t have any reason to believe this has occurred, then you have an issue with a sensor, wiring or ground, or the PCM.

The PCM, and most of the sensors, ground to the stud on the passenger side of the engine block. Make sure the ground is clean and also check the wiring harness loom for chafing.
 
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ike_hike

ike_hike

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P0218 is transmission temp, not engine. Being that this is the only code you have, I would start here. The transmission (PCM) goes into over temp mode at 240 degrees. If you don’t have any reason to believe this has occurred, then you have an issue with a sensor, wiring or ground, or the PCM.

The PCM, and most of the sensors, ground to the stud on the passenger side of the engine block. Make sure the ground is clean and also check the wiring harness loom for chafing.

Thanks for that nudge. I'll do some research in that direction.

I guess I should also just go ahead and do a pressure test before I fool with the pump, if it comes to that.
 
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ike_hike

ike_hike

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P0218 is transmission temp, not engine. Being that this is the only code you have, I would start here. The transmission (PCM) goes into over temp mode at 240 degrees. If you don’t have any reason to believe this has occurred, then you have an issue with a sensor, wiring or ground, or the PCM.

The PCM, and most of the sensors, ground to the stud on the passenger side of the engine block. Make sure the ground is clean and also check the wiring harness loom for chafing.

I should say, I had the transmission rebuilt last fall and it's been running like a top since then. I would be surprised to hear that it was overheating. I definitely haven't seen any signs of it, and I haven't been doing any hard wheeling or trailer pulling, etc.

I'm still learning about all of this. Would a failure in the PCM prevent fuel from being sent into the cranking process, even though the pump is good?
 

AjRagno

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Thanks for that nudge. I'll do some research in that direction.

I guess I should also just go ahead and do a pressure test before I fool with the pump, if it comes to that.

Yes, and really it’s about proper diagnosis before replacing parts. Also: With our 15+ year old Jeeps, a lot of issues come up with the wires shorting to ground.

The fuel pump is no joy to replace. If it comes down to it, get the OE Bosch fuel pump.

If you have fuel pressure, you may not have spark, which would suggest the crankshaft or camshaft position sensors or circuit.
 
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ike_hike

ike_hike

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If you have fuel pressure, you may not have spark, which would suggest the crankshaft or camshaft position sensors or circuit.

Thanks so much for your help. What about the fact that it ran for two seconds with starter fluid through the throttle body? Does that mean I have spark, or maybe not?
 
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ike_hike

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Update:
I bought a tester and rigged it up to the fuel rail, and as expected, 0 pressure. So, I dropped the fuel tank and replaced the pump with a Bosch. (I also replaced the diff oil and gasket while I was back there.) I managed to get it back up, hook everything in, and voilà!, it works.

I siphoned the gas into a clean container after I dropped the tank, and then siphoned it back into the tank after it was back up. That part worked out well; I was happy to have that weight gone when I was trying to get the bolts lined up.

One thing that was curious is that on my LJ, there was no disconnect for the electrical line near where the fuel line and breather tube are connected (by the driver rear tire.). I had to reach in and disconnect it right on top of the pump, which was definitely a challenge. That part was different from the videos I watched.

Also, the retainer ring around the pump on the top of the tank was metal and not the white plastic one I was expecting. The tool I bought for the purpose didn't fit, and so I had to use the screwdriver/mallet technique, which worked ok.

Thanks for the help thinking through this project, everyone.
 
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ike_hike

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Oh, I meant to say, I also took the opportunity to file down the ridges on the fuel tank's inlet check valve, which is supposed to stop the gas from shooting out when the tank is full. Fingers crossed on that one.