2002 Hard start issue

willrek

willrek

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Joined
Mar 11, 2022
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37
Location
El Campo, Texas
I don't want to bore you with another fuel pump story, but I have a question about the operation of this thing. I put a fuel pressure gauge on my 2002 4.0 to diagnose the hard starts. I had the fuel pump replaced by a shop a little over a year ago. Now it's doing it again. The pressure test showed zero pressure prior to starting. Zero pressure with the key in the "Run" position, and quickly built to 50lb as soon as I started cranking it. It started on the second try, as normal these days. When I shut it off, the pressure leaked back to zero within 15 seconds or so. I was thinking the pump would turn on with the key in the run position? Is this correct, or should I be diagnosing an electrical issue as well? I have ordered a new delphi pump and intend to drop the tank on Friday.

Thanks in advance for all your help.
God Bless,
will
 
willrek said:
I don't want to bore you with another fuel pump story, but I have a question about the operation of this thing. I put a fuel pressure gauge on my 2002 4.0 to diagnose the hard starts. I had the fuel pump replaced by a shop a little over a year ago. Now it's doing it again. The pressure test showed zero pressure prior to starting. Zero pressure with the key in the "Run" position, and quickly built to 50lb as soon as I started cranking it. It started on the second try, as normal these days. When I shut it off, the pressure leaked back to zero within 15 seconds or so. I was thinking the pump would turn on with the key in the run position? Is this correct, or should I be diagnosing an electrical issue as well? I have ordered a new delphi pump and intend to drop the tank on Friday.

Thanks in advance for all your help.
God Bless,
will
Click to expand...

The pump is initially energized for about 2 seconds to pressurize the fuel system when you turn the key to the run position.
 
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Any suggestions on what to check to determine why this is not happening? Reading that the ECU is what feeds the fuel pump relay. I'll put a meter on the lead after I drop the tank and check to see if anything is happening. Maybe I'm just not seeing the pressure build before it shuts back off. Hopefully the new pump will fix it.
 
All new parts are junk. I've had my fuel tank up and down four times. I finally put the almost cheapest fuel pump I could buy...a BrutePower from Rock Auto...and it's been good for two plus months.

I also installed a fuel pressure gauge using an adapter from Racetronix on my fuel rail so I can diagnose at a glance.

-Mac
 
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willrek said:
Any suggestions on what to check to determine why this is not happening? Reading that the ECU is what feeds the fuel pump relay. I'll put a meter on the lead after I drop the tank and check to see if anything is happening. Maybe I'm just not seeing the pressure build before it shuts back off. Hopefully the new pump will fix it.
Click to expand...

You should be able to hear the pump cycle near the drivers rear wheel.
 
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willrek said:
Any suggestions on what to check to determine why this is not happening? Reading that the ECU is what feeds the fuel pump relay. I'll put a meter on the lead after I drop the tank and check to see if anything is happening. Maybe I'm just not seeing the pressure build before it shuts back off. Hopefully the new pump will fix it.
Click to expand...

Nah, not necessary yet. Turn all accessories off and you should hear the buzzing when you turn the key on. You don't need to drop it for this. Weird issue. Are you testing this with the engine hot or cold? It won't prime consistently when hot.
 
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