Confused on Cranking

Generally my 1997 XJ has to wind over several times before it cranks if it has set for an hour or so. I've read some forums and got the idea that maybe the injectors were losing vacuum over a period of time because my cruise control and A/C vents stopped working too. But today it did something very strange. I had a battery charger on it because I left the door ajar all night. The charger was on it for most of the afternoon and when I went out to crank it, it barely turned over before firing right up. In the two years I've owned it, it has never cranked that fast. Even after driving it for a while, killing it and then starting it right back, it still turned over a few RPM's before cranking. Does this indicate that I have an electrical problem and not a fuel delivery problem as once thought?

A fuel pump "check valve" is still a primary suspect here.......more on that
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The check valve 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.

JARaney7186 said:

Generally my 1997 XJ has to wind over several times before it cranks if it has set for an hour or so. I've read some forums and got the idea that maybe the injectors were losing vacuum over a period of time because my cruise control and A/C vents stopped working too. But today it did something very strange. I had a battery charger on it because I left the door ajar all night. The charger was on it for most of the afternoon and when I went out to crank it, it barely turned over before firing right up. In the two years I've owned it, it has never cranked that fast. Even after driving it for a while, killing it and then starting it right back, it still turned over a few RPM's before cranking. Does this indicate that I have an electrical problem and not a fuel delivery problem as once thought?

Click to expand...

First off you need to pay closer attention to how you some of the technical terms you are trying use, Like "still turned over a few RPM's before cranking" ???????

What is "wind over"

Sounds like a cables issue, at least part of the problem.

Vacuum has NOTHING to do with injectors!

The battery could also be on its last legs, but time will tell.

I filled up my Jeep for the first time the other day. Before gas pump sut off, gas started coming out from the top of the tank. I haven't had time to check and see where it is coming from yet. Do you think this could be causing the fuel system to lose prime?

Overflowing gas should not cause the pump to lose prime. IN any case it cannot lose prime unless you run out of gas, because it is submerged in the fuel. What may be happening is that it's losing pressure upstream after it shuts off, because a check valve is not holding pressure. When that happens, it may take a little more cranking before it fires.

Please note that when your engine turns over with the starter, that's "cranking." What you seem to be describing is that it cranks too long before it starts. It's not uncommon. One thing you can do to test it is to turn on the ignition and wait about 5 seconds before you try to start. If that helps, it is probably a matter of pressure loss in the fuel rail. If it helps some but not enough, you can try turning the ignition on, wait five seconds, turn it off, turn it back on, wait another five seconds, then crank. When you first turn the ignition on, the fuel pump runs for a few seconds to pressurize the system, then shuts off. Waiting, or doing it twice, helps to pressurize the system a bit more.

If simply waiting a few seconds before you crank makes it start reliably, then you may be better off ignoring the problem. It won't affect running.

Ecomike said:

First off you need to pay closer attention to how you some of the technical terms you are trying use, Like "still turned over a few RPM's before cranking" ???????

What is "wind over"

Sounds like a cables issue, at least part of the problem.

Vacuum has NOTHING to do with injectors!

The battery could also be on its last legs, but time will tell.

Click to expand...

English/Arkansas Translation

Wind over = Crank

Crank = Start

Fire = Start

Kill = turn off

...crank a few RPM's requires at least one M for the R's to be measured.

LOL, now we need a Texican:Cajon and Texican:TexMex and Cajon:Arkansas version to complete the translations for the Red River chapter folks!!!

Also if you ever take the time to watch the engine while you crank, what you guys commonly call one revolution is actually only one piston going though its compression stroke.