I have a 88 jeep Cherokee. when i go to start it, its not wanting to start right away. it will take 10-25 seconds before it starts, if im lucky. its even worse if i don't start it every day. Im running out of ideas on what to do about it. i put a new fuel pump and filter in it, distributor cap and rotor, spark plugs, coolant temp sensor and fuel pump relay. i need some ideas please! someone told me to replace the crank sensor??

 

Clean and tighten your grounds and battery cables if you haven't done so already.

​​​​​​​After that, a failing CPS is definitely a possible culprit.

 

You may also want to remove the starter and have a parts store test it. Might as well take in your battery and have that tested while you are there.

Hope this helps

 

i forgot to mention that i did get a new battery last month and the starter i replaced in October or November. so im not sure whats going on

 

im about to do the CPS will check on the grounds.

 

Make sure the new CPS is Mopar - these Jeeps are notoriously picky about the CPS.

Make sure the battery cables are clean and tight as well. You don't want to be messing around with the CPS if it's as simple as a loose cable.

 

I'm assuming that you mean you have an "extended crank period" before the engine actually fires and runs. If that is the case, this is not a problem with the starter/starting circuit. It's fuel or spark.

My gut feel is that this is a "fuel pressure" problem and that is where I would start if I were working on your XJ. I know you said you replaced the fuel pump but I didn't see any mention of the "fuel pressure regulator" under the hood. More on testing that later....

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
6. If it starts quickly this way, you have identified low fuel pressure or pressure leakdown as the vehicle sits.

To truly test fuel, it must be done with a fuel pressure test gauge. They can be rented inexpensively at many parts stores, call around for availability. You need approximately 31 psi for your engine to start. Hook up that test gauge and have a buddy help you. Watch the gauge, does it take a long time to build up sufficient fuel pressure and then the engine fires?

Also with engine running and if you are in the 31 psi range on the gauge, disconnect the vacuum line leading to the fuel pressure regulator and the pressure should jump to approximately 39 psi. Inspect that vacuum line closely for deterioration and if there is any raw fuel in the vacuum line, that means that the diaphragm for the fuel pressure regulator is ruptured and it would need to be replaced.

If all you are experiencing is an extended cranking time and if the engine runs well after it is started and doesn't die on you, this does not sound like a crankshaft position sensor problem to me.

The advice on freshening grounds is good. Your vintage XJ is particularly susceptible to poor grounds. You can't tell much by looking at them. Disassemble them, clean them with wire brush until shiny and reattach.

Good luck and keep us updated!

 

Renix era Jeep have a longer start time because of the different computer design. Upgradeing cables will help get more current to all circuits thus starter spins faster.

 

i did check the fuel pressure a few days a go and it was 31 psi. the CPS did not help

 

Clean the grounds, dont just check them.

 

Read b4 waisting money.....http://www.naxja.org/forum/showthread.php?t=1040424

 

I have recently checked the fuel pressure and it bleeds off completely with in about and hour and half.
here is a list of things i have replaced. I have probably forgotten a few.
fuel pump
fuel filter
cap and rotor
spark plugs
fuel pressure regulator
coolant temp sensor
crankshaft position sensor
fuel pump relay
idle air control valve
starter
i have also looked for draws and have found none!
im running out of ideas and hope!

 

I'd throw some new battery cables on before losing all hope.

You could PM Cruiser54, he was a chief mechanic for a Jeep dealership during the heyday of the Renix era XJs and I'm sure he'd love to help you.

 

This is an easy test. Open the boot from the idle air control valve. Pour a small amount of gasoline into there. Then start the vehicle. Alternatively, you can remove the spark plugs fairly easily and pour less than a spoonfull of gasoline into each cylinder. This determines whether delivery of fuel (presence of fuel) is the culprit.