Hi,
So When I bought my 2000 XJ it took two cranks to start, and the previous owner said that it was the fuel pressure regulator that was the problem. Well last night I replaced it and the problem has gotten worse. Now it's two cranks followed by a rough start. I just ran a pressure test and it's 5 psi when turned to on, 49-50 while idle, and 5 again when it's turned off. I want to say that it is probably the fuel pump but that is a shot in the dark. I'm new to mechanics so any help would be appreciated. Thank you.

First question is what brand of fuel pump assembly did you install?

49 is the correct fuel pressure for your 2000, but it should NOT bleed down to 5 psi quickly. That indicates a pretty serious pressure leakdown; it should not fall below 30 psi for at least 5 minutes.

Here is some information from my file that may be helpful to you in troubleshooting and isolating this.
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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. I specifically seek out Bosch fuel pumps as they are the best in the business. Stay away from Airtex, as IMHO, they have a bigtime reliability problem.

Thank you, that's exactly the information I was looking for. In order to test though I need tool number 6631 and I can't rent it from o'reillys. Is there any where else that I can rent it? I'd prefer to rent it but if I had to buy it I would. The fuel pressure regulator that I bought was BWD number 23079. Thanks again.

I don't know what tool number 6631 is exactly, I guess the fuel pressure tester.. oreillys might not have that exact tool, but i'd bet they have one that would work. Did you try asking for just a generic fuel pres. tester?

Does your test has erratic fuel pressure like in the video?
http://youtu.be/7v0gBcsmSTQ

Hello just curious if you ever figured out your fuel issue? I'm having a similar issue with my 99 XJ only mine starts fine, ever once in a it cuts out. When I did the fuel pressure test mine drops to zero immediately after turning off the key, I have to cycle the key to get the fuel pressure back.