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Fuel Pump Failing?

Wheeler

TJ Enthusiast
Joined
Oct 18, 2021
Messages
211
Location
Georgia
Took a thirty minute trip last weekend to meet a buddy. About an hour and a half later we parted ways. My 97 SE fired right up made it about 300’ and started bucking, surging, and then died. I had it towed back to the house, and it started right up so I could put it in the garage.

I’m fairly certain the fuel pump is failing but I wanted to see if there were other things to test before dropping the gas tank…again.

Battery is good. Starter will crank and crank and crank.

Will start when the fuel gauge registers gas in the tank. I checked the electrical connector to the pump and it was seated firmly and no exposed or damaged wires that I could see.

If the fuel gauge doesn’t register then no start.

I recently replaced the gas tank. The fuel pump that came with the tank would not pump. I put the pump from the old tank in and it has worked for the past three months however, I’ve noticed some power loss going up hills and under “hard” acceleration. I’ve also had warm start issues.

Prior to this incident it would fire right up after sitting for a week. Would also fire right up when hot.

I have not seen any leaks.

Suggestions?

9EB678DF-EC89-4E60-8261-3C0C37908561.jpeg
 

Jerry Bransford

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If your 2.5's fuel rail has a Schrader test port like is on this 4.0 fuel rail, screw a fuel pressure gauge onto it and see what the pressure is when you turn the key on and while you're trying to start it. Normal is at or close to 49 psi. Many auto parts stores like Autozone have a tool loan program and most have fuel pressure testers available to loan or rent. Autozone doesn't charge for the use.

A Schrader valve is like an oversized tire stem valve.

Schrader Valve.jpg
 

DougyintheBushies

TJ Enthusiast
Joined
Nov 15, 2021
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423
Location
Chickamauga, Ga
If your 2.5's fuel rail has a Schrader test port like is on this 4.0 fuel rail, screw a fuel pressure gauge onto it and see what the pressure is when you turn the key on and while you're trying to start it. Normal is at or close to 49 psi. Many auto parts stores like Autozone have a tool loan program and most have fuel pressure testers available to loan or rent. Autozone doesn't charge for the use.

A Schrader valve is like an oversized tire stem valve.

View attachment 337809

My Autozone charges for the tool but refunds your money when you return the tool. Sometimes I just keep the tool.
 
OP
Wheeler

Wheeler

TJ Enthusiast
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Oct 18, 2021
Messages
211
Location
Georgia
I was finally able to circle back around to testing this.

Fuel Pressure is 41-42 PSI with engine off and 46 PSI at idle and at 2500 RPM… as I was typing this the engine just died. PSI was still at 46.

Any suggestions?
 
OP
Wheeler

Wheeler

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Oct 18, 2021
Messages
211
Location
Georgia
Swapped out the crank position sensor. It starts, idles, will hold RPMs but still has extended crank when the engine is warm.
 

Jerry Bransford

TJ Guru Moderator
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Swapped out the crank position sensor. It starts, idles, will hold RPMs but still has extended crank when the engine is warm.
Did you install the new fuel pump from NAPA you mentioned just above?

Slow starts that happen after the engine was recently shut off, like after getting gas or going into a store are often caused by a bad fuel pressure regulator. Slow starts after extended times of sitting usually means the check valve in the fuel pump has gone bad meaning a new fuel pump.
 
OP
Wheeler

Wheeler

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Oct 18, 2021
Messages
211
Location
Georgia
Did you install the new fuel pump from NAPA you mentioned just above?

Slow starts that happen after the engine was recently shut off, like after getting gas or going into a store are often caused by a bad fuel pressure regulator. Slow starts after extended times of sitting usually means the check valve in the fuel pump has gone bad meaning a new fuel pump.
What we discussed above from NAPA was the CPS. Fuel pressure is fine after an extended period of sitting.

Cranks right up after an extended period as well. If I run it, then let it sit for 30 or so minutes, it doesn’t want to start, usually requires 4-6 seconds of cranking.

It will start right up while engine is hot as well.
 

Jerry Bransford

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Kinda sounds like it could be heat soak, but I'm not sure if the 2.5 engine is susceptible to that or not like the 4.0 can be.

Any 2.5L engine owners with heat soak knowledge? Is there a heat soak fuel injector insulation kit made for it like there is for the 4.0?
 
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Wheeler

Wheeler

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Oct 18, 2021
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211
Location
Georgia
It was mentioned in another thread that the coil casing could be cracked and causing a similar symptom.

Just to verify, I’m going to hook the fuel pressure gauge back up and check it about 30 minutes after I’ve ran the engine, just to eliminate that possibility.
 
OP
Wheeler

Wheeler

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Oct 18, 2021
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Location
Georgia
I replaced the crank position sensor yesterday. I started and let it idle for 45 minutes and then took it for a short drive, maybe 10-12 miles. Shut it down, let it sit for an hour and then tried to start. It cranked right up this time however, now the fuel pressure tester is reading erratic pressure.

I let it sit until this morning, checked pressure with key in ignition and am reading 44PSI. I get the same result when it’s idling, erratic pressure. Hopefully you can see in the attached video.

It DID NOT do this before installing the new CPS.
 

TJ4Jim

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Dec 9, 2015
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Brookings, Oregon
Kinda sounds like it could be heat soak, but I'm not sure if the 2.5 engine is susceptible to that or not like the 4.0 can be.

Any 2.5L engine owners with heat soak knowledge? Is there a heat soak fuel injector insulation kit made for it like there is for the 4.0?
Never really experienced any heat soak on my 2.5 nor am I aware that there was ever an issue.
 
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Wheeler

Wheeler

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Oct 18, 2021
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Location
Georgia
I’m guessing the lack of response is a good indication that my situation is unique. I’m not quite sure how I feel about that…😂
 

SSTJ

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Aug 24, 2019
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South Carolina
I wish I had any advice to offer. I'm watching, and if you learn anything unique about the 2.5, let me know and I'll add it to the other thread.

I wonder if @Wildman has any thoughts.
 
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TJ4Jim

TJ Expert
Lifetime Supporting Member
Joined
Dec 9, 2015
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3,545
Location
Brookings, Oregon
It was mentioned in another thread that the coil casing could be cracked and causing a similar symptom.

Just to verify, I’m going to hook the fuel pressure gauge back up and check it about 30 minutes after I’ve ran the engine, just to eliminate that possibility.

Yes the 2.5 coils are known to split open with age so take a look.
 
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