Bettler

About 2 weeks ago, i noticed my '95 XJ (stock) just started to get harder and harder to turn over. First the optima from 7 years ago started to die, so i bought a new battery, thinking maybe it just needed more juice.. still no luck, before it took maybe 3 cranks to get it fired, even in the cold. Now winter is starting to set in and it's taking prolly twice if not triple that to get it cranked over. Any ideas? Just did the plugs, and valve cover because i was leaking oil, injectors maybe? It's not that big of an issue, just wondering what the hell it could be.

dukie564

cranking harder like cranking slower? Mine had an issue for a while with cranking very slowly. A new battery did not fix it. turned out I needed to remove the starter and clean the mating services between the starter and the engine block and reinstall the starter. the starter uses the engine block as a ground so the surfaces need to be clean and shiny for the starter to work properly. I would also invest in new battery terminals.

belvedere

If it cranks longer before it starts, maybe the fuel pressure is bleeding off.

Bettler

It just takes many more cranks to actually start up, but times like this morning, it went back to taking 2 cranks.. got to work, came out, back to taking 6-8 cranks. I'm stumped.

How would i diagnose that?

dukie564

try turning the key to "on" for a few seconds, then turn it to crank.

If the check valve in the pump is going bad or getting stuck open it will let fuel go back into the tank when you shut the truck off, and will take longer to prime the system when you turn the key.

belvedere

Yes, key to "on" for a few seconds, back to "off", then to "on" again for a couple seconds, then start. This will prime the fuel system if the pressure is dropping.

To truly diagnose it, put a fuel pressure gauge on the rail, and watch to see if the pressure holds after you shut off the engine.

tjwalker

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.

Bettler

So, i tried this and it did seem to help, it wasn't back to 2 cranks, but it was faster than just starting it regularly. So it could either be an injector or check valve.. gotta check my little black book for the last time the injectors were done!