I have 98 Xj with 4.0, aw4, np231, dana 30 and 8.24'' rear. My jeep used to have be hard to start in Park 6-7 sometimes requiring more than one attemp, but would crank up fast in N on the first try in 2-3 sec. I replaced the NSS on the tranny with a new one from crown. It cranks in P and N and the reverse lights work but it takes awhile to start in P and N sometimes requiring cranking more than once. Im not sure If I need to adjust NSS again or look at something else. Battery is new, starter relay is new, Had recent tuneup this year.
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Jeep Starting problem
- Thread starter sfg454
- Start date
- Location
- Rainy side of Washington
If it cranks in P and N, but just takes a while, that's not an NSS issue - an NSS issue would keep it from cranking altogether, or let it crank in the wrong positions. I'd check a few other things -
* check if you're getting a good hot spark - snapping blue, not weak and yellow.
* check your fuel pressure and check valve - try holding the key in Run for a few seconds before starting it. If it starts instantly after that, you can either continue using this method or replace the fuel pressure regulator mounted on top of the fuel pump on top of the tank. Have fun dropping the tank, I would personally just live with it. As for fuel pressure, put a gauge on the test port on the fuel rail, I believe you should see about 49PSI on a 1998.
There are probably other things I'm forgetting as well...
* check if you're getting a good hot spark - snapping blue, not weak and yellow.
* check your fuel pressure and check valve - try holding the key in Run for a few seconds before starting it. If it starts instantly after that, you can either continue using this method or replace the fuel pressure regulator mounted on top of the fuel pump on top of the tank. Have fun dropping the tank, I would personally just live with it. As for fuel pressure, put a gauge on the test port on the fuel rail, I believe you should see about 49PSI on a 1998.
There are probably other things I'm forgetting as well...
birchlakeXJ
NAXJA Forum User
- Location
- Melrose, MN
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.
Some troubleshooting tips for extended crank times:
1. Connect the gauge at the fuel rail and start the engine. The gauge should read 49 psi plus or minus 5 psi.
2. Turn the engine off and immediately clamp the fuel line just ahead of the fuel tank. 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 - probably the check valve. If the pressure falls below 49 psi fairly rapidly then the problem is probably a leaky 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.
Some troubleshooting tips for extended crank times:
1. Connect the gauge at the fuel rail and start the engine. The gauge should read 49 psi plus or minus 5 psi.
2. Turn the engine off and immediately clamp the fuel line just ahead of the fuel tank. 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 - probably the check valve. If the pressure falls below 49 psi fairly rapidly then the problem is probably a leaky 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.
MJR
NAXJA Forum User
- Location
- Costa Mesa, CA
The 97-up with the plastic fuel tanks it's on top of the tank and is replaceable (part #4798301). On a 96 it's part of and only sold with the fuel pump module. 87-95 it's on the fuel injection rail.
On 87-95 the check valve is part of the fuel pump, on 96 it's part of the fuel pump module. On 97-01 it's part of the serviceable fuel filter pressure regulator.
Your problem is most likely that the fuel pressure is bleeding off due to a bad valve (more noticeable after it sits longer).