Diagnosing Hard Start Issue

Jesse_224

Member
Joined
Apr 9, 2020
Messages
33
Location
Oklahoma
Since I purchased my Jeep it has had a hard start issue. I have learned to live with it, no big deal. If I just try to start the Jeep right away, 90% of the time it will just crank and crank with no start. If I cycle the key on for a few seconds, back off, then try to start, it will start perfectly…that is until this weekend. I was out doing some light wheeling and I got up on top of some rocks for a good pic opportunity. I killed the Jeep to take pics and when I got back to the Jeep my cycling the key wouldn’t work. After cycling the key a few times I would get it to start but it would sputter and die after a couple of seconds. I finally got it started and drove home with no problems. Now it starts after cycling the key with no problems again. I can’t be breaking down like that on the trail so it’s time to fix it.

My gut feeling is that it’s the fuel pump. I hooked up a fuel pressure gauge to the fuel rail today and here are my results.

KOEO (First cycle) 2 psi
KOEO (2nd cycle) 12 psi
Engine started on 2nd cycle
Running at idle 48 psi
Under load (2k-2.5k RPM) 48 psi
Turn the engine off and the pressure immediately starts dropping. After 10 minutes I’m at less than 10 psi.

The pressure is definitely low with KOEO and it is leaking down too fast. Time for a new fuel pump, or any other suggestions first?

21DBEDC9-D8FB-4347-A7F7-AEC00A7541E7.jpeg
 
Since I purchased my Jeep it has had a hard start issue. I have learned to live with it, no big deal. If I just try to start the Jeep right away, 90% of the time it will just crank and crank with no start. If I cycle the key on for a few seconds, back off, then try to start, it will start perfectly…that is until this weekend. I was out doing some light wheeling and I got up on top of some rocks for a good pic opportunity. I killed the Jeep to take pics and when I got back to the Jeep my cycling the key wouldn’t work. After cycling the key a few times I would get it to start but it would sputter and die after a couple of seconds. I finally got it started and drove home with no problems. Now it starts after cycling the key with no problems again. I can’t be breaking down like that on the trail so it’s time to fix it.

My gut feeling is that it’s the fuel pump. I hooked up a fuel pressure gauge to the fuel rail today and here are my results.

KOEO (First cycle) 2 psi
KOEO (2nd cycle) 12 psi
Engine started on 2nd cycle
Running at idle 48 psi
Under load (2k-2.5k RPM) 48 psi
Turn the engine off and the pressure immediately starts dropping. After 10 minutes I’m at less than 10 psi.

The pressure is definitely low with KOEO and it is leaking down too fast. Time for a new fuel pump, or any other suggestions first?

View attachment 350768

When the pressure bleeds off like that generally it's the check in the pump that is leaking down. Delphi has been the go to for complete replacements or the pump and regulator can be individually replaced with oem Bosch.
 
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Just closing out this post.

I replaced the fuel pump with a Delphi FG1353 fuel pump assembly.
My new fuel pressure readings are as follows:
KOEO 22 psi
(Started on first try immediately)
Running at idle 55 psi
Under load (2k-2.5k RPM) 55 psi
Turn the engine off and wait 10 minutes 48 psi

This seems to have solved my problem.

I also installed a GenRight fuel pump access panel. I know some people think they are pointless (from reading reviews), but my money, my Jeep, and I dig it!
 
Since I purchased my Jeep it has had a hard start issue. I have learned to live with it, no big deal. If I just try to start the Jeep right away, 90% of the time it will just crank and crank with no start. If I cycle the key on for a few seconds, back off, then try to start, it will start perfectly…that is until this weekend. I was out doing some light wheeling and I got up on top of some rocks for a good pic opportunity. I killed the Jeep to take pics and when I got back to the Jeep my cycling the key wouldn’t work. After cycling the key a few times I would get it to start but it would sputter and die after a couple of seconds. I finally got it started and drove home with no problems. Now it starts after cycling the key with no problems again. I can’t be breaking down like that on the trail so it’s time to fix it.

My gut feeling is that it’s the fuel pump. I hooked up a fuel pressure gauge to the fuel rail today and here are my results.

KOEO (First cycle) 2 psi
KOEO (2nd cycle) 12 psi
Engine started on 2nd cycle
Running at idle 48 psi
Under load (2k-2.5k RPM) 48 psi
Turn the engine off and the pressure immediately starts dropping. After 10 minutes I’m at less than 10 psi.

The pressure is definitely low with KOEO and it is leaking down too fast. Time for a new fuel pump, or any other suggestions first?

View attachment 350768

I recently (today) replced thenpump with a bosch fuelnpump. I dont have to prime it 3-4 times but definitely still have to do it once so i too am facing the same issue. May have to do the entire assembly
 
I recently (today) replced thenpump with a bosch fuelnpump. I dont have to prime it 3-4 times but definitely still have to do it once so i too am facing the same issue. May have to do the entire assembly
When do you get the slow start? Only after it has not run for several hours like the 1st start of the day? Or even after being stopped for just for a few minutes like after getting gas?
 
I have had my TJ since 2014. I have had a hard start issue on and off for a couple of years with my 2002 4L. I had the mechanic replace the fuel pump assembly and it improved for a while but started acting up again. I checked the fuel pressure and it was about 50 psi, but when turned off it went directly to 0. I understand the check/ pressure relief valve (correct term?) goes bad on these assemblies often. I bought a Delphi fuel pump assembly (part#FG1353) and got good running pressure and it held to about 20psi when turned off. Unfortunately, the fuel gauge reads 1/3 tank when full and after a few months the pressure is dropping straight to zero when turned off. It still runs well and sometimes starts right up. Since Mopar and Bosch parts don’t seem to be available anymore, has anyone had a good with another brand?
 
I bought and installed a carquest fuel pump (part# m2510476) assembly from advanced auto. Running strong for a few weeks now. Are you throwing any codes? Typically it should throw an evap code. For a small leak. Mine went away after replacing it. It was doing the same thing.
 
Thank you for your reply. I did get an engine light, but that is more recent than the issue. I think the engine light might be related to me leaving the gas cap of when I topped off the tank and towed it about 20miles to our camp spot, but I will check for codes tomorrow.
 
I did get a P0456 evap system code. Since I think it is related to the gas cap I think I will clear the code and see if it comes back. I will be replacing the fuel pump assembly sometime soon.
 
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