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Old 09-11-2019, 05:45 PM
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Join Date: Sep 2019
Posts: 6
TJ Starting Issues...fuel pump?

First let me apologize for another starting issue thread. However, I am looking to confirm that my suspicions of a bad fuel pump are the problem before I tackle such an in depth job.

My Wrangler: 1998, 4.0, 5 speed, 160k miles, 33" Tires

Ever since I have owned the Jeep (6 years now) it has had the long start issue. So I had have been anticipating the fuel pump going out for some time now. Just recently, within the last month, my Jeep has been hesitant to accelerate upon first drive of the day. After about 10 minutes of driving the Jeep would drive completely fine and be able to accelerate full throttle, half throttle, any position really. A week ago, after having sat for 4 days, I drove the Jeep home (about 10 minutes) and it was very hesitant (felt like not getting enough fuel under load) and especially when flooring the gas pedal it simply would not provide what I assume is adequate fuel to accelerate. I parked it when I got home and it sat for another 3 days. This morning (after sitting for 3 days) I went to start it and on first crank a loud pop came from the exhaust and it would not start. I feared a drop valve or something of the sort so I started checking oil for discoloration. Nothing. I did notice while checking under the hood there was some white smoke coming from my cold air intake. While I was under the hood I checked, spark plug wires were seated, and all of the throttle body sensors were seated. I think checked CPS and it was seated as well. I got back in the jeep and cranked the engine with the gas pedal floored. It started and I left it alone for about 5 minutes. After idling for 5 minutes I tried to Rev it up and it immediately died. I left it for about 6 hours after that and came back to it. 6 hours later it now starts and rev's but with a lot of stutter. I haven't driven it under load in gear for fear of it leaving me stranded. However I have shut it down and started it multiple times since then and it now starts and runs, and will rev, but with some stutter sometimes and a lot of stutter others. It seems to idle perfectly when I am not touching the gas pedal.

I am very torn about what it is. I replaced the CPS about 3 years ago with a Duralast (I know, not good) but it has been fine ever since. I don't know if it could be the Duralast has finally quit on me, or if it has something to do with the throttle body sensors? Spark plugs are champion generics and are about 4/5 years old with maybe 25k miles on them. I pulled one and it was fairly worn, certainly time to do plugs but I don't know if these symptoms point to plugs? I am cleaning the throttle body tonight, and replacing the air filter. Doubt that will do the trick but doing those 2 things doesn't hurt.

There are currently no CEL's at all.

Any advice is greatly appreciated. If it comes down to fuel pump, which pump do I get with the Bosch now being impossible to find? Thank you again for the help!


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Old 09-12-2019, 03:19 PM
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Went out today and bought a fuel pressure tester. Cleaned the throttle body and cold air intake filter and then ran the pressure test. Just turning the key on, the pump put out 30 PSI but started to slowly drain back. Started the Jeep and it held around 41 PSI. I rev'd it up while it was running and it would dip to 37 PSI for a quick second and then jump right back up to 41 PSI. Jeep seemed to be running better today, all though it was mid day so temp was right around 65. I know 41 PSI is about 8 PSI lower then its supposed to be. Should I still be thinking pump? Maybe time to do plugs, wires, cap and rotor and see what result that yields?

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Old 09-13-2019, 11:28 AM
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ran another series of tests today, when primed the fuel pump will pressurize the rail to 30 psi no matter how many times the key is shut on then off. When started today the Jeep held pressure at 42 while running and when rev'd would dip just below 40 psi and jump right back up to 42.

When turned off the psi dropped to 30 in 2 minutes and 30 seconds. Then 20 psi in 5 minutes and 30 seconds, then at 10 minutes was at 14 psi, then 10 psi at 16 minutes, 5 psi at 30 minutes, and will eventually bleed all the way down to 0.

Is it time to change the pump? My main worry changing the pump is that since the complete Bosch unit is nearly impossible to find now, that I will be changing pumps again in the next 12 months.

If it is time to change the pump, what is the best complete sending unit to get other than the OEM Bosch unit that can not be found anymore?

Thank you again!
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Old 09-13-2019, 01:43 PM   #4
Join Date: Sep 2019
Location: Denver
Posts: 20
67659 This is the Bosch fuel pump part number from Autozone, its the complete module set up and its for the 15 gallon tank.

5012952AD this is the mopar part number I found in Alldata for the 19 gallon tank, Autozone does not show a Bosch cross over, only the Delphi part which is not a bad part. I put this part number into and its shows its available for 441.35 plus shipping.
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Old 09-16-2019, 01:07 PM   #5
Join Date: Jan 2019
Location: Round Rock, TX
Posts: 210
I don't think your issue is the fuel pump. Sounds like the check valve in it might not be the best but that isn't your hesitation issue if you are holding high 30s, low 40s psi.

The way you describe the idle being fine, but won't accelerate...maybe it's a plugged cat. Or bad timing or do you have bad compression on a cylinder or two.

The white smoke out of the intake, is there coolant leaking into the head?

I'd start ruling things out. Check for back pressure in an O2 sensor port to test for cat blockage. Do a compression test on the cylinders to see if there are any head leaks. Maybe verify timing?
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Old 09-16-2019, 03:29 PM
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Join Date: Sep 2019
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ended up replacing the fuel pump which fixed a whole slew of issues. Previous owner had obviously had the tank out at least once before. The plastic lock ring was barely even on there (which explains my leaking fuel when completely filling the tank). Ended up going with a Delphi 1353, only have 20 miles on it since it was just installed so I can not comment on the longevity obviously. But the wrangler is now running better then ever before. Thank you everyone for the comments.

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