TJ Fuel Pump?

[Marco]

Hey guys/gals.  i have an issue im thinking could be a fuel pump in my 97 tj 4.0

cold start- turns over several times before finnaly starting
                  -if i turn key on for 5-6 seconds before engaging starter first it fires right away
                 -idles fine
                 -drives fine with smaller throttle demand
                 -stuttering uphill with heavy throttle demand
                 -HAS to warm up for a bit or wont even move before stuttering and quits.


warmed up -fires right away unless its been sitting for several hours
                    -idles fine
                 -drives fine with smaller throttle demand
                 -stuttering uphill with heavy throttle demand

are these decent enough symptoms to put a fuel pump in? i can hear it priming but not sure if its to its full health.200k and assuming its original. thanks for any input before i buy one.

[birdo]

Might me worth getting a fuel rail pressure test. Replacing a fuel pump can be expensive as the unit is in the gas tank and it has to be dropped to get at it.
The part itself is not cheap either. A fuel rail pressure test is fast and easy. The pressure should be about 48 to 50 psi. Anything less might indicate a problem with the pump.
The other culprit might be the fuel filter. It too is in the tank.

Be careful if you take it into a dealer. Insist on the fuel rail test first. My dealer replaced my entire fuel sender/pump/filter assembly and billed me over $800.00 for it and it wasn't the issue.....they refused to investigate further and screwed me over good. A good 4x4 shop should be able to help. Take it to Lemon Aid Jay's Shop. They are very good.

[birdo]

E-Mortal Customs is the name of Jay's shop.

[Marco]

awsome thanks. im going to buy a pressure testor. seems handy to have in the shop anyway. Is that pressure reading when i turn the key, running or both? how about when i shut it off, is it supposed to stay presurized or slowly dissipate to zero eventually? thanks for the tips!

[yellowjeep101]

It will always hold pressure, but it may be lower than 48 to50 if its been sitting.  Jeep injectors are known to leak which would cause a lower reading over time. So test while running. Also a quick google search could also lead to other people with the same issue, and maybe it could be unrelated to your fuel pump. If you have to drop the tank, make sure you lube the bolts well.

[esi]

Not sure if you have a two line fuel system(with return) or a single system. If its a dual it could be your fuel pressure regulator. ceaper than a fuel pump and should be located on the rail. you can google what the rail pressures should be with it connected and disconected to seee if its working properly. Usually I found that a pump works or it doesn't. But not always.

[LLYJ]

Inspect your vacuum lines as well - My YJ has a line that runs from the vapour cannister to a module of some sorts on the firewall, sorry can't remember all the tech particulars but if that line is leaking it causes exactly what you are describing (on a YJ anyway), can't imaging the TJ set up is a whole lot different.  Sorry not sure if that vacuum diaphram switch at the end of the fuel rail is part of that system too but best check that line too, if your TJ has that. - just a few easy things to check before going to shop rates.

[BUKI]

Inspect your vacuum lines as well - My YJ has a line that runs from the vapour cannister to a module of some sorts on the firewall, sorry can't remember all the tech particulars but if that line is leaking it causes exactly what you are describing (on a YJ anyway), can't imaging the TJ set up is a whole lot different.  Sorry not sure if that vacuum diaphram switch at the end of the fuel rail is part of that system too but best check that line too, if your TJ has that. - just a few easy things to check before going to shop rates.

Are talking about the MAP?  Prob not a sensor issue or he would have a CEL. I'm assuming you've checked codes. Fuel pressure gauge taped to windshield. drive around so you can see if pressure drops when you get symptoms. That would be the first step I'd take.


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[Marco]

great.thanks. all very useful. i will post up after my investigation

[LLYJ]

No not referring to map system - again speaking of yj's, there is sensor that tells a control that the vapour canister is saturated and directs vacuum to the canister to evacuate vapour to the manifold - anyway when there is a leak in that system the fuel supply diaphram limits the fuel to the rail - not sure why but its a common complaint with the same symtoms reported by guys that have tried to remove their vapour canisters - anyway had the same issue a few years back and replacing the vac line from the canister to the module on the firewall solved the problem - didn't feel a need to understand it cause problem was fixed. I could read up on it but probably easier for the op to check the lines


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[LLYJ]

Oh yeah - don't know if i had a code or not - no engine light came on so i never checked


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[BUKI]

Obd2 is a little more intuitive than our old school stuff. Our systems are so redundant (easier to fix though) compared to theirs. Hell they even tell you individual misfires on left right bank etc. we have to do it the old fashioned way.  I'm sure if this was the case. The cel would be going off like crazy. But worth checking anyways. I personally redid all my vacuum lines with washer tubing. Cost like 9$ or something. Op something you might want to do when you got extra time.


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[LLYJ]

Great idea !  Was gonna pony up for some high end silicone but will give that some serious thought.

Can't wait to start the CJ3A the whole wiring diagram fits on one page lol


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