won't start
06-01-2012, 11:29 PM
#2
CF Veteran
Does it crank and not start or does it not crank? If it cranks then it could be a number of things but most likely a fuel deliver issue. If it doesn't crank it could be your NSS or ignition switch or an issue with your starter. We'll narrow it down with a little more info.
Let us know what transmission you have, too.
And, what the hell, how 'bout engine while you're at it.
Let us know what transmission you have, too.
And, what the hell, how 'bout engine while you're at it.
06-02-2012, 05:28 AM
#3
CF Veteran
Join Date: Apr 2008
Location: Smiths Station, Al
Posts: 7,661
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Year: 87
Model: Wagoneer
Engine: 4.0 I6
My thought is you have a poor/ degraded CPS signal. But the guy anove is right. We need more input and any troubleshooting you have already done.
06-02-2012, 06:52 AM
#4
MJ>XJ
Join Date: Mar 2009
Location: Griffin, G.A.
Posts: 17,836
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Year: 1990
Model: Comanche
Engine: 4.0 I6
If it cranks and dont start and then crank a couple seconds later it does start then its a common issue... Either the fuel pump check valve is.bad or u have a leak in the fuel system... When u bump the starter the pump will run 30 seconds or so... Pushing fluid to the rail... When it sits the fuel will run back to the tank if the valve is gone or the pressure side of that system is drawing air from a leak...
06-04-2012, 02:37 AM
#6
CF Veteran
Okay. Now that we know that we can narrow it down a little. I'm going to assume you've got a 4.0. Here are the things to check...
#1 When you turn the key to the run position (not start), do you hear the fuel pump prime? It should run for 2 to 3 seconds and then shut off. If yes then see #2, if no, check for 12v at the fuel pump, if it has power then you probably need a new fuel pump, if it doesn't, check fuses and fuel pump relay(s).
#2 Check for spark by pulling one of the plugs, reattaching it to the plug wire and grounding it to the engine block while someone cranks the motor. You should have a strong blue spark. If yes, see #3, if no, check your Crank Position Sensor. I believe the '00s had coil packs so no coil or cap and rotor to check, someone who is more familiar with the ignition system on a '00 will have to chime in, I've got a Renix... completely different.
#3 Rent a fuel pressure gauge and check pressure at the fuel rail. I'm not sure what it's supposed to be but someone here does and they'll be along any moment to tell you.
#4 Make sure it has gas in the tank.
#1 When you turn the key to the run position (not start), do you hear the fuel pump prime? It should run for 2 to 3 seconds and then shut off. If yes then see #2, if no, check for 12v at the fuel pump, if it has power then you probably need a new fuel pump, if it doesn't, check fuses and fuel pump relay(s).
#2 Check for spark by pulling one of the plugs, reattaching it to the plug wire and grounding it to the engine block while someone cranks the motor. You should have a strong blue spark. If yes, see #3, if no, check your Crank Position Sensor. I believe the '00s had coil packs so no coil or cap and rotor to check, someone who is more familiar with the ignition system on a '00 will have to chime in, I've got a Renix... completely different.
#3 Rent a fuel pressure gauge and check pressure at the fuel rail. I'm not sure what it's supposed to be but someone here does and they'll be along any moment to tell you.
#4 Make sure it has gas in the tank.
06-04-2012, 05:25 AM
#7
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Join Date: Nov 2010
Location: In the middle of Minnesota!
Posts: 5,804
Received 99 Likes
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Year: 1999
Model: Cherokee
Engine: 4.0
Primary suspect here is a check valve issue on the fuel pump assembly. Here's more.
--------------------------------------------------------
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 a couple of seconds
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.
--------------------------------------------------------
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 a couple of seconds
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.
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