4.0 doesnt start right up?
Thread Starter
Junior Member
Joined: May 2011
Posts: 47
Likes: 0
From: Pittsburgh
Year: 1998
Model: Cherokee
Engine: 4.0L
4.0 doesnt start right up?
My Cherokee does not start immediately unless I put the key to the on position for about 3 seconds and then start it. But if I drive it let it sit for a couple of hours it will start up like it was brand new. So it seems to me it likes it when the engines still warm not cold. When the engine is cold and I don't put the key to the on position it takes about 5 seconds of cranking for it to start. What do I need to replace in order for it to start correctly?
CF Veteran
Joined: Aug 2011
Posts: 10,489
Likes: 24
From: Nor-Cal Coast
Year: 90,84
Model: Cherokee
Engine: 4.0,2.5
I gather that's a check valve in the fuel pump. Mine does it too. I bet it's crud in there and might try to clean it someday. I saw a post about installing a check valve for a BMW. I saw another post saying don't bother, doesn't help. So there's that! Good luck, D.
CF Veteran
Joined: Aug 2011
Posts: 10,489
Likes: 24
From: Nor-Cal Coast
Year: 90,84
Model: Cherokee
Engine: 4.0,2.5
I think it's in the pump, so it would be the cost of a new pump. I haven't seen anyone saying they have successfully cleaned one. Actually I have one I cut open in my barn. maybe tomorrow I'll look and see if I can tell what's up with the check valve.
CF Veteran
Joined: Aug 2011
Posts: 10,489
Likes: 24
From: Nor-Cal Coast
Year: 90,84
Model: Cherokee
Engine: 4.0,2.5
Fuel pump check valve. Fuel pump impeller drive pin.
Looks like MAYBE a blast of compressed air, (through the right way of course), might help. Since the fuel runs right around the windings I wouldn't experiment with solvent or "cleaner" in an electric device that goes into a fuel tank. It may well eat the insulation and result in a short, overheating/fire, big bang, making the evening news. Maybe with some diesel in there, then blast air through. I would check it before and after. (I would blast it on a paper towel to see what I got).
I destroyed the little spring retainer ripping it out with a needle nose. If a guy was really hell-bent on it I suppose there might be a way to put it back. I wouldn't go there myself. Would probably end up with bits of retainer and a spring stuck somewhere else in the system. Just took this one apart for fun.
This pump failed when the hollow rolled steel impeller drive pin wore out. Wonder why they made it that way?
I destroyed the little spring retainer ripping it out with a needle nose. If a guy was really hell-bent on it I suppose there might be a way to put it back. I wouldn't go there myself. Would probably end up with bits of retainer and a spring stuck somewhere else in the system. Just took this one apart for fun.
This pump failed when the hollow rolled steel impeller drive pin wore out. Wonder why they made it that way?
Last edited by DFlintstone; Oct 7, 2011 at 10:58 PM.
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CF Veteran
Joined: Jan 2011
Posts: 1,894
Likes: 4
From: Las Vegas
Year: 1999
Model: Cherokee
Engine: 4.0
I was having exact same problem with my 00 and 99.
Change the fuel pressure regulator (is like $73 from rockauto) and it starts up once everytime
.
Checklist
Here is a good write-up.
GL.
Change the fuel pressure regulator (is like $73 from rockauto) and it starts up once everytime
.Checklist
The check valve is located on top of the gas tank and is part of the fuel pump assembly on 95.5-2001 vintage 4.0 XJs. When the check valve starts to fail, it reduces fuel pressure to a point where an extended crank is needed to start the engine. It is a very common failure. I experienced it on my 99 at around 75K.
A good (and simple) way to troubleshoot this problem is called “the poor mans prime”
1. Turn key to ON position (do not crank the engine!)
2. The fuel pump will energize and run for a couple of seconds
3. Turn key to OFF position
4. Repeat above a two more times
5. NOW crank the engine over
If the engine starts quickly and cleanly after performing this procedure, you may have the check valve issue. If it starts and runs poorly for a few seconds, it could also be a leaky fuel injector resulting in the bleed down and the stumble upon startup is the engine clearing the excess fuel that has leaked into the cylinder because of the faulty injector.
Also be aware that a bad battery can give you this symptom. Sounds strange but it definitely does happen. Have battery load tested if you have any questions; your XJ does NOT like low available battery voltage. Be sure battery connections and posts are CLEAN.
Some troubleshooting tips for extended crank times:
Hook up fuel pressure gauge on the schrader valve on the fuel rail
Start engine and bring to normal operating temperature.
Observe test gauge. Normal operating pressure should be 49.2 psi (plus or minus 5 psi)
Shut engine off.
Pressure should not fall below 30 psi for five minutes.
If pressure falls below 30 psi, it must be determined if a fuel injector, the check valve within the
fuel pump module, or a fuel tube/line is leaking. An adaptor tool/hose included with the fuel pressure gauge can help you with this. Consult gauge manual for more information on this but here is basically how it works:
*Turn the engine off and immediately clamp the fuel line at the adaptor hose. Watch the pressure gauge and see how long it takes to lose pressure.
*If the pressure remains at 49 psi for an extended period of time then the problem is in the tank - possibly the check valve. If the pressure falls below 49 psi fairly rapidly then the problem is probably a leaky fuel injector.
You can limp a check valve problem along indefinitely if you wish as it doesn't mean the fuel pump itself is going bad. Normally, the check valve is replaced as an entire assembly as you have to drop the gas tank to access the assembly. Fuel pump assembly consists of fuel pump, regulator, check valve, filter. If you do replace the fuel pump assembly, purchase a high quality OEM style unit. Some cheap aftermarket assemblies don’t hold up and fail prematurely.
A good (and simple) way to troubleshoot this problem is called “the poor mans prime”
1. Turn key to ON position (do not crank the engine!)
2. The fuel pump will energize and run for a couple of seconds
3. Turn key to OFF position
4. Repeat above a two more times
5. NOW crank the engine over
If the engine starts quickly and cleanly after performing this procedure, you may have the check valve issue. If it starts and runs poorly for a few seconds, it could also be a leaky fuel injector resulting in the bleed down and the stumble upon startup is the engine clearing the excess fuel that has leaked into the cylinder because of the faulty injector.
Also be aware that a bad battery can give you this symptom. Sounds strange but it definitely does happen. Have battery load tested if you have any questions; your XJ does NOT like low available battery voltage. Be sure battery connections and posts are CLEAN.
Some troubleshooting tips for extended crank times:
Hook up fuel pressure gauge on the schrader valve on the fuel rail
Start engine and bring to normal operating temperature.
Observe test gauge. Normal operating pressure should be 49.2 psi (plus or minus 5 psi)
Shut engine off.
Pressure should not fall below 30 psi for five minutes.
If pressure falls below 30 psi, it must be determined if a fuel injector, the check valve within the
fuel pump module, or a fuel tube/line is leaking. An adaptor tool/hose included with the fuel pressure gauge can help you with this. Consult gauge manual for more information on this but here is basically how it works:
*Turn the engine off and immediately clamp the fuel line at the adaptor hose. Watch the pressure gauge and see how long it takes to lose pressure.
*If the pressure remains at 49 psi for an extended period of time then the problem is in the tank - possibly the check valve. If the pressure falls below 49 psi fairly rapidly then the problem is probably a leaky fuel injector.
You can limp a check valve problem along indefinitely if you wish as it doesn't mean the fuel pump itself is going bad. Normally, the check valve is replaced as an entire assembly as you have to drop the gas tank to access the assembly. Fuel pump assembly consists of fuel pump, regulator, check valve, filter. If you do replace the fuel pump assembly, purchase a high quality OEM style unit. Some cheap aftermarket assemblies don’t hold up and fail prematurely.
GL.
Last edited by BotakBeng; Oct 8, 2011 at 10:47 AM.
Thread Starter
Junior Member
Joined: May 2011
Posts: 47
Likes: 0
From: Pittsburgh
Year: 1998
Model: Cherokee
Engine: 4.0L
Thanks guys I think I fixed half the issue with the new check valve. I also think I need new injectors because it will stumble once it starts and then runs like it should after a couple of seconds.
CF Veteran
Joined: Aug 2011
Posts: 10,489
Likes: 24
From: Nor-Cal Coast
Year: 90,84
Model: Cherokee
Engine: 4.0,2.5
Ah..So..
, Those years have a separate valve that can be changed? Glad you got her goen right.
What I might try (for my 90), is blasting a fluid , through with compressed air. (although as TJ points out I may have a leak as opposed to a bad check valve).
Much thanks and happy trails.
, Those years have a separate valve that can be changed? Glad you got her goen right. What I might try (for my 90), is blasting a fluid , through with compressed air. (although as TJ points out I may have a leak as opposed to a bad check valve).
Much thanks and happy trails.
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