ab56452001
NAXJA Forum User
- Location
- Australia
Seen an example today , at around 13 volts pump put out 50psi at 11volts 30psi , I think this could be my problem.
1996 XJ fuel pump and pressure regulator repair details
- Thread starter Anak
- Start date
- Location
- In a strange land
From another thread, fuel pump/sending unit pinout:
Could be useful for diagnostic purposes.
Could be useful for diagnostic purposes.
pstanstill
NAXJA Forum User
- Location
- tallahassee
great thread, a lot of info in one place. I'm trying to help the mechanic in tampa who "fixed " my daughters 96. Fuel pump and regulator were replaced but pressure leaks down quickly. It runs fine once started but takes several key turns to prime up. I dont know if tank o-ring was replaced, also wondering about that flat rubber washer that didnt come with your new regulator. What else could be causing loss of pressure ( assuming new pump and regulator were installed properly.
- Location
- In a strange land
You could lose pressure at the engine end. A leaky injector (or two) could cause that, but I doubt it would take multiple efforts at priming in order to overcome that.
A leak external to the system (fuel line leak, fuel filter leak) should be easily identified by your nose.
That leaves us with a leak in the tank itself. A bad hose or a bad connection on a hose would be one failure mode. A defective check valve in either the new regulator and/or pump would be another mode (From what I have read both of those are supposed to have check valves, but it would seem both would have to be bad in order for this problem to occur. Not having dissected either I can't say with certainty whether they both do or not.).
If it were me I would drive it down to a quarter tank or so and then pull the assembly back out and check for issues with the hoses on the inside. If those all look good I would then get another regulator and try that. Another pump would be the last resort option.
Dealing with a shop is another matter entirely. While they should have the advantage of experience, I am consistently disappointed in the level of attention to detail. It is a rare thing anymore that I let any shop touch my vehicles. Best of luck.
A leak external to the system (fuel line leak, fuel filter leak) should be easily identified by your nose.
That leaves us with a leak in the tank itself. A bad hose or a bad connection on a hose would be one failure mode. A defective check valve in either the new regulator and/or pump would be another mode (From what I have read both of those are supposed to have check valves, but it would seem both would have to be bad in order for this problem to occur. Not having dissected either I can't say with certainty whether they both do or not.).
If it were me I would drive it down to a quarter tank or so and then pull the assembly back out and check for issues with the hoses on the inside. If those all look good I would then get another regulator and try that. Another pump would be the last resort option.
Dealing with a shop is another matter entirely. While they should have the advantage of experience, I am consistently disappointed in the level of attention to detail. It is a rare thing anymore that I let any shop touch my vehicles. Best of luck.
pstanstill
NAXJA Forum User
- Location
- tallahassee
Thanks,anak. my daughter had to take the car back to school so I will have to encourage the shop- as best I can. To clarify my limited understanding of fuel pressure, the pump only pressurizes the fuel line, not the tank itself?A pinhole leak in the tank or the tank o-ring shouldnt matter?
- Location
- In a strange land
Correct.
Edit to add: This does beg the question, is your daughter smelling fuel back there?
If yes, then it would increase the suspicion about a leaking line, perhaps in the vicinity of the fuel filter.
However, I will also note that my '96 has something fishy with regard to tank venting and occasionally smells of fuel vapors in the vicinity of the tank. I suspect the vent grommets at the top of the tank, but have yet to get around to dropping the tank just for the fun of checking them.
Edit to add: This does beg the question, is your daughter smelling fuel back there?
If yes, then it would increase the suspicion about a leaking line, perhaps in the vicinity of the fuel filter.
However, I will also note that my '96 has something fishy with regard to tank venting and occasionally smells of fuel vapors in the vicinity of the tank. I suspect the vent grommets at the top of the tank, but have yet to get around to dropping the tank just for the fun of checking them.
Last edited:
pstanstill
NAXJA Forum User
- Location
- tallahassee
A brief update, Turns out the mechanic in tampa left off the nut that holds the pump to the bracket, so the pump was hanging by the hose, far enough out of plumb to activate the rollover check valve, allowing fuel to drain back to the tank. I know its obvious but, DONT FORGET THE NUT.
.
.
- Location
- Rainy side of Washington
Great thread! I kinda miss my 96 making me learn things like this constantly.
I had the same issue with the gauge being accurate once I swapped to a 97-01 tank. Never got around to solving it, it was a beat up woods rig by the time I was thinking about it.
I had the same issue with the gauge being accurate once I swapped to a 97-01 tank. Never got around to solving it, it was a beat up woods rig by the time I was thinking about it.
nukem69
NAXJA Forum User
- Location
- Fort Worth, TX
First post here. Building a XJ for a ranch ride. Cheaper than a utv and has a heater and windows !
I realize this is a old thread, but thought I would share my results. Replaced fuel pump and FPR with ones purchased from pepboys. Sorry don't have the part numbers, but will try to post later. Ended up with 39 psi at rail. Going to pull out tonight and put the old FPR back in while I wait for the crown FPR. As a side note the jeep runs fine however I am getting a code 0171 which is a lean A/F condition. Not sure if this is due to the 39 psi pressure or something else. Figure I would start here anyway.
I realize this is a old thread, but thought I would share my results. Replaced fuel pump and FPR with ones purchased from pepboys. Sorry don't have the part numbers, but will try to post later. Ended up with 39 psi at rail. Going to pull out tonight and put the old FPR back in while I wait for the crown FPR. As a side note the jeep runs fine however I am getting a code 0171 which is a lean A/F condition. Not sure if this is due to the 39 psi pressure or something else. Figure I would start here anyway.
keith.hasselstrom
NAXJA Forum User
- Location
- CO
Anak :cheers: - thank for very much for this write up !!
Let me quickly recap what our situation was with the 96 XJ:
Became increasingly hard to start - would have to prime the system (turn key to on position so pump will kick in for a few seconds) several times. This worked for a while -- but after 6 months became nearly impossible to start.
Troubleshooting Fuel system from tank to cylinder:
We hooked up a fuel pressure gauge at the rail and identified that the fuel pressure would get to the 49 (+/- 5) psi spec when the key was turned to "on" several times - but would immediately fall very quickly. At this point, we needed to identify where this pressure was being lost. We pinched off the fuel line (between the tank and the fuel filter) and we could now see the pressure hold when we primed. So we knew the problem was in the tank --- likely check valve / fuel pressure regulator not working. If the pressure would not have held, we would have looked at a problem at the rail -- fuel injectors. For prosperity, we actually did remove and clean all fuel injectors and verified no leaks.
Resolution:
This is where the huge thanks to Anak comes in. We read about this 96 being a one off solution and that the fuel pressure regulator was not serviceable AND that the whole assembly is near impossible to find. His post clearly walks you through how it can be serviced. The key part was that Crown 53030001 fuel pressure regulator ($45 via Amazon). The regulator, under vacuum, is rated at 39 psi (out of spec); however, when not used with a vacuum, as in our in tank setup, it will get you to the 49 (+/- 5) psi. We did not replace the pump or any other component -- just the FPR. It's fairly easy to get the old regulator off and put this new one in -- direct fit. Vehicle now is holding 52 psi at the rail (verified) when primed. Normally, we would have changed the pump when doing this -- but it was so easy to get the fuel pump assembly out -- that we decided to wait for a pump issue before spending that $$.
Lessons / Tips:
When we put the pump assembly back in, the large O-ring/seal was not seated properly. We filled the tank up -- and noticed a leak. Cleaning where the seal sits and holding in place with some tacky substance should do the trick. In order to service this leak, we drained the tank by disconnecting fuel line at the fuel filter .. placing hose in a gas container .. and jumped the fuel pressure relay. This drained 9/10 gallons of gas in about 10 minutes or so. If anyone has tips on getting these seals to stay in place .. please share
This could be an argument for dropping the tank where it would then be much much easier to get that seal in place. I'd recommend filling the tank only half way after you put the assembly back on -- and then watch for leaking gas after you drive a bit.
Let me quickly recap what our situation was with the 96 XJ:
Became increasingly hard to start - would have to prime the system (turn key to on position so pump will kick in for a few seconds) several times. This worked for a while -- but after 6 months became nearly impossible to start.
Troubleshooting Fuel system from tank to cylinder:
We hooked up a fuel pressure gauge at the rail and identified that the fuel pressure would get to the 49 (+/- 5) psi spec when the key was turned to "on" several times - but would immediately fall very quickly. At this point, we needed to identify where this pressure was being lost. We pinched off the fuel line (between the tank and the fuel filter) and we could now see the pressure hold when we primed. So we knew the problem was in the tank --- likely check valve / fuel pressure regulator not working. If the pressure would not have held, we would have looked at a problem at the rail -- fuel injectors. For prosperity, we actually did remove and clean all fuel injectors and verified no leaks.
Resolution:
This is where the huge thanks to Anak comes in. We read about this 96 being a one off solution and that the fuel pressure regulator was not serviceable AND that the whole assembly is near impossible to find. His post clearly walks you through how it can be serviced. The key part was that Crown 53030001 fuel pressure regulator ($45 via Amazon). The regulator, under vacuum, is rated at 39 psi (out of spec); however, when not used with a vacuum, as in our in tank setup, it will get you to the 49 (+/- 5) psi. We did not replace the pump or any other component -- just the FPR. It's fairly easy to get the old regulator off and put this new one in -- direct fit. Vehicle now is holding 52 psi at the rail (verified) when primed. Normally, we would have changed the pump when doing this -- but it was so easy to get the fuel pump assembly out -- that we decided to wait for a pump issue before spending that $$.
Lessons / Tips:
When we put the pump assembly back in, the large O-ring/seal was not seated properly. We filled the tank up -- and noticed a leak. Cleaning where the seal sits and holding in place with some tacky substance should do the trick. In order to service this leak, we drained the tank by disconnecting fuel line at the fuel filter .. placing hose in a gas container .. and jumped the fuel pressure relay. This drained 9/10 gallons of gas in about 10 minutes or so. If anyone has tips on getting these seals to stay in place .. please share
This could be an argument for dropping the tank where it would then be much much easier to get that seal in place. I'd recommend filling the tank only half way after you put the assembly back on -- and then watch for leaking gas after you drive a bit.
- Location
- Rainy side of Washington
Buying a new lockring and O-ring kit is extremely cheap and they're in stock basically everywhere. It doesn't come up in some parts cross-refs, but the Spectra Premium LO01 is what you want. (That's L, letter O, number zero, number 1. If you have the autozone counter guy plug it in, expect to have to explain this.)
A little bit of axle grease or vaseline should do the trick holding it in place while you get the sender assembly and lockring installed. Don't go too heavy on it and it'll be no problem, both dissolve in gas and burn readily.
A little bit of axle grease or vaseline should do the trick holding it in place while you get the sender assembly and lockring installed. Don't go too heavy on it and it'll be no problem, both dissolve in gas and burn readily.
- Location
- In a strange land
It is nice to see this is stll proving useful.
Thank you for the detailed response.
Thank you for the detailed response.
nukem69
NAXJA Forum User
- Location
- Fort Worth, TX
Finally got around installing the Crown 53030001 FPR and that bumped the fuel pressure up to 58 PSI. Is this going to be a problem? I did test my pressure gauge and it is reading correctly. Thoughts ? I am just about ready to break down and buy a new sending unit.
keith.hasselstrom
NAXJA Forum User
- Location
- CO
Just to follow up on our tank leaking issue after reassembly. We were using the LO01 spectra ring. We never tried the new lock 'nut' as the old one looked in great shape and was much heavier duty. The new ring still leaked after 3 times. We took the assembly completely out and took off the new LO01 ring and compared with the old ring.... oddly .. the old ring was a tiny bit smaller and it felt a little heavier. It was still in very good shape and we put that back in. Leak is gone. Maybe this new O-ring was bad / wrong size from the factory -- i'm still baffled.
- Location
- In a strange land
Here is a Youtube video in which the clamps between the fuel pump and the pressure regulator were loose, causing a loss of pressure: Hard to diagnose '96 XJ fuel pressure issue
