Since I've owned my 98 xj it will not start on the 1st crank after sitting for any length of time no matter how long you crank it for.now as soon as I let off & crank again it starts right up...no cel or other issues.recent tune up also.

 

check the pressure at the fuel line.?

 

Turn the key to ON. Leave it there 5 seconds.
Turn key to OFF.
Try starting Jeep. See what happens.

The fuel pump only runs about 5 seconds, then waits for the engine to start before powering up again. If your anti-drainback valve is leaking that 5 seconds isn't enough to build sufficient pressure. You have to cycle it twice.
It's annoying, but harmless.

 

+1 I usually turn the key and let the pump prime before trying to start. Especially if it's been more than a day between starts. Also, careful on extended cranking. It's a good way to wear out the starter

 

Tried that before to no avail...always starts right up on 2nd crank so not really that much of an inconvince

 

I have a 1998 with the exact same problem. I posted about it a few weeks ago (in fact I thought this was my old post come back to life). I tried all the suggestions and have not come up with anything yet. I turned the key on and waited 5 seconds, 10 seconds, 30 seconds, it does not matter. The fuel pump comes on when I turn on the key. When the car is warm, no problems. I am stumped. I just live with it right now. Let me know if you come up with anything.

 

X2 & I ill let you know if I do

 

The check valves (there are two of them; one on the fuel pressure regulator and another on the fuel pump) are part of the fuel pump assembly on 95.5-2001 vintage 4.0 XJs. When a check valve starts to fail, it can reduce fuel pressure to a point where an extended cranking time 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) first step in helping you 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 about 2 seconds. Be sure to wait until it stops running.
3. Turn key to OFF position
4. Repeat above steps 1-3 two more times
5. NOW crank the engine over

If the engine starts quickly and cleanly after performing this procedure, you may have a check valve issue. If it starts and runs poorly for a few seconds, it could also be a leaky fuel injector resulting in the fuel pressure leaking down and the subsequent 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 starting symptoms as well. Have your battery load tested (any parts store will do this for free) if you have any doubt; your XJ does NOT like low available battery voltage. Be sure battery connections and posts are CLEAN.

Some troubleshooting tips for extended crank times. You will need a fuel pressure gauge. Many parts stores will rent you this tool inexpensively.

*Hook up fuel pressure gauge on the schrader valve on the fuel rail under the hood

*Start engine and bring to normal operating temperature.

*Observe fuel pressure gauge. Normal operating pressure should be 49.2 psi (plus or minus 5 psi)

*Shut engine off.

*Observe pressure on gauge. Pressure should not fall below 30 psi for five minutes.

If pressure falls below 30 psi, it must be determined if a fuel injector, a check valve within the
fuel pump assembly, or a fuel tube/line is leaking. An adaptor tool/hose included with the fuel pressure gauge can help you with this. Consult the manual that comes with the fuel pressure gauge and the Factory Service Manual for your year XJ for more information on this exact procedure, 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 – most likely a check valve. If the pressure falls below 49 psi fairly rapidly then the problem is probably a leaky fuel injector.

**Note. Where check valve is suspect, a quick loss of fuel pressure is often the fuel pressure regulator check valve and a slow loss of pressure is often the fuel pump check valve. But keep in mind that either or both check valves can be to blame.

You can limp a check valve problem along indefinitely if you like, as it doesn't mean the fuel pump itself is going to fail. Perform the “poor mans prime” before cranking to speed up your starts. However, if you have a check valve issue and want to resolve it, it is recommended that you replace the entire fuel pump assembly for two reasons. First, you have to drop the gas tank to access the assembly. Secondly, with two check valves, replacing just the fuel pressure regulator where one of the check valve resides may or may not resolve your problem; remember there are two check valves; the other one is on the fuel pump.

The fuel pump assembly consists of fuel pump, fuel pressure regulator, fuel gauge sending unit, fuel gauge float, pickup filter and pigtail wiring harness. If you do replace the fuel pump assembly, purchase a high quality unit; you do get what you pay for here. Some cheap aftermarket assemblies have been known to fail prematurely. I personally prefer Bosch fuel pumps as they manufacture the best fuel pump assemblies for the XJ. Carter is my second choice. Airtex is my least favorite choice and I will not recommend or install them.

 

Thanks for all the good information! I am troubleshooting a similar problem on my '92 XJ: it will crank for a long time without turning over, but then will start on the 2nd or 3rd try. Sometimes it helps to give it a little bit of throttle when cranking, and occasionally it will sputter along after turning over until I rev the motor over 2k. Once it's started and been revved up a bit it idles fine and hasn't stalled out yet.

This is only a problem when the car hasn't been started for at least several hours, and was not an issue over the summer. I've trying to figure out whether I need to replace the fuel pump assembly or if the injectors could be the problem. (The chunky idle it sometimes has right after turning over makes me think it could be an injector... but as the gas gauge is dead a new fuel pump assembly wouldn't be a bad idea anyway.)

I'm definitely going to try the pressure check you mentioned. Since I haven't rented the tool yet I haven't read the manual and it may be that that answers my question. But I'm not quite clear on what you mean at this step:
"*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. "

Where do you mean to clamp the fuel line?

Thanks for the help!

 

My 1997 XJ does the same thing.

Use a "Poor Man's Prime", turn the ignition on a few times before engaging the starter motor, should start quickly.

I believe that in order to solve vapor lock, the fuel is continually circulated back to the tank. If a check valve were installed, the fuel in the line near the hot engine risks turning to vapor so it drains back to the tank. No vapor lock but slow starts after sitting for an hour.