03 Liberty Sport fuel pump 35-40 psi /running lean...

[jettrue]

Hi!

I've had this issue before with my daughter's jeep. It was throwing "lean" codes for a while. I used to have a code reader to plug in, but have since misplaced it. I'm not sure if it was a coincidence, but I ran some fuel injector cleaner through the gas tank and it went away for a while, maybe about 6 months.

Fast forward to yesterday, she's been driving it more often, she has a delivery job, starting and stopping a lot. The check engine light came on. I brought it to Firestone, and they called back saying it was showing lean codes, after diagnostics, they guy said the fuel pressure was 35-40 psi when it should be 60, so that's the problem.

But my gut is telling me not to throw down $650 to replace the fuel pump without asking other people first. Is that really too low of a fuel pressure? Perhaps it's some other issue? She did just fill it up with gas.

 

[CalcityRenegade]

I would ask them how the tested the fuel pressure to be sure that it is the pump causing the issue. If it is can you replace it yourself? Fuel pumps are not all that expensive to buy and fairly simple to replace. I've replaced a couple including a Jeep GC.

 

[LibertyTC]

What was the exact code number/s?
How many miles on the KJ?
Besides a bad pump, A fuel filter can reduce psi if restricted as well.
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Note a 4 connector PCM block fuel pressure spec is 59.2 psi.
58392[/ATTACH]"]

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And only 49.2 psi for a 2 connector PCM block.
LINK to good read & info & uss2defiant posted how 2 filter change: http://www.jeepkj.com/forum/f196/fuel-delivery-questions-thoughts-folks-58071/

 

[uss2defiant]

Eric @ south main auto recently did a video. only early models have this service port.

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[jettrue]

Thanks guys.

I picked it up, I don't want to rush into fixing anything (like I did with my transmission if you look at my post from 2015) :winner_third_h4h:

The paperwork says "Long term fuel trim at 33%, short term fuel trim at 3%. Measured fuel pressure between 35 and 40 PSI, manufacturer's spec is 60 psi"

I asked them if they checked the voltage to the pump, they said "we checked it all, he's sure it's the pump".

It is both codes P0171 and P0174.

Like I said, I've had these codes with this jeep before and a tank of injector cleaner seemed to clear it up, though not saying the pump isn't going bad now.

It's got 130K miles on it.

 

[tjkj2002]

If your only running 35-40psi at the rail for fuel pressure then yes it can cause the P0171/P0174 codes.

The fuel pressure needs to be fixed 1st before any further testing should be done.

The correct spec is 49.2 +/- 5psi

 

[jettrue]

If your only running 35-40psi at the rail for fuel pressure then yes it can cause the P0171/P0174 codes.

The fuel pressure needs to be fixed 1st before any further testing should be done.

The correct spec is 49.2 +/- 5psi

What are you suggesting? You say the fuel pressure needs to be fixed first, they are suggesting the fuel pump is the fuel pressure issue.

 

[tjkj2002]

What are you suggesting? You say the fuel pressure needs to be fixed first, they are suggesting the fuel pump is the fuel pressure issue.

If your fuel pressure is low like they say then yes you must fix the fuel pressure issue 1st before any further testing can be done for lean codes.If it's the pump then the pump needs to be replaced and the system cleared and retested(long term/short term FT's).

I know a little bit about this stuff being a 20 year ASE Master Tech.