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1991 XJ Will not start HELP!!

WeeTodd

NAXJA Forum User
Location
Ontario Canada
Ok so I just got a 1991 Cherokee inline 6 4.0L HO for $300 It was not running when I got it and is still not running.
I'm stumped it has all the things it needs to run but it won't.

I have a new fuel pump. I checked the fuel at the rail and there is pressure
I have over 120 psi per cylinder
I have spark at all 6 cylinders
and I have air
I think the timing may be out but not sure how to change it or if it is even possible

so I have all the things I need to run but it does not run

I tried changing the ecu but that did not help
I also unplugged the CPS and then there was no spark and reconnected it and the spark came back.
I TDC the crank and the rotor and cap line up with #1 cylinder
I also tried quick start and that did nothing so it’s not a fuel problem cause I could smell it on the plugs when I pulled them
 
Air, fuel, compression, spark--what else could you ask for? Having all of the above at the right time and place.

Check the CPS/CMP (camshaft position sensor), it provides a synch signal for firing the injectors.

Have you tried a NOID light to see if the injectors are in fact firing?
 
Even though timing mark and cap/rotor line up, the distributor could be 180 degrees out of phase with the crankshaft. It has to be TDC on compression stroke. This can be verified by checking at the spark plug hole for pressure or removing valve cover and checking that #1 exhaust and intake valves are closed.
 
Installed a new CPS

Checked if it was 180deg out of phase it is not

Installed a used rotor/distributor/cam shaft sensor

and it wont fire!!!!

there must be something up with the timeing I spray quick start in it and nothing happens so it is not a fule problem!!!

I just dont know????:dunno:
 
Installed a new CPS

Checked if it was 180deg out of phase it is not

Installed a used rotor/distributor/cam shaft sensor

and it wont fire!!!!

there must be something up with the timeing I spray quick start in it and nothing happens so it is not a fule problem!!!

I just dont know????:dunno:

OK, back to basics.

Hook a multimeter to the battery terminals. What is the static voltage?
What is the voltage when cranking?
 
12v static
11v cranking

Ok, that is good. Reason I asked is you can have plenty of amps for cranking but too little voltage for the engine's electronics. Less than 9 volts things don't work like they should.

Again, basics.

Condition of the spark? Blue, really snaps or yellow?
 
I also unpluged the
MAP no change
IAC a couple times it woud fire while I am cranking but woud not start
TPS no change

unpluged all of them Nothing
 
I also unpluged the
MAP no change
IAC a couple times it woud fire while I am cranking but woud not start
TPS no change

unpluged all of them Nothing

Ok. You are saying it is firing when cranking but dies when the key returns to the RUN position?
 
Most of the time it wont fire but there was a hand full of times when I was cranking that it would fire but when I stop cranking there was nothing

it is hard to discribe maybe I can take a video

the guy who had it before me said that he drove it parked it at work and when he went to leave it woud not start. so it totally sounds like a sensor or some electrical isue
 
Ok.

Basics here.

XJ fuel pump 101 (disclaimer, the following is Renix info, not sure if it has changed):

When you turn the key to the ON position power to the fuel pump comes through the B Latch relay (later models called ASD relay), this is bypassing the ballast resistor and providing a full 12v. When at the START position, power to the fuel pump comes from the starter relay, bypassing the ballast resistor and providing a full 12v. When in the RUN position power to the fuel pump is through the fuel pump relay, then through the ballast resistor where it is reduced to approximately 6v. When at WOT power to the fuel pump is through the oxygen heater relay, bypassing the ballast resistor and providing a full 12v.

So lets see if you have 12v to the pump in the ON position--lasts about 3 seconds. Then check power to the pump in the START position, and then check it in the RUN position.

Post back.
 
EDIT: Oops! Joe beat me to the ballast resistor...

When you say you changed the CPS, was it the Crank Position Sensor, the one on the bellhousing? Or the Cam Position Sensor, the one in the distributor?

:)
 
I put a new Crank Position Sensor in and I also changed out the distrbutor/Cam Position Sensor with a used one out of my friends parts jeep

Joe if it was a fule problem I would think that I shoud be able to get it to run on the quick start when I spray it in an crank it over?????
 
Most of the time it wont fire but there was a hand full of times when I was cranking that it would fire but when I stop cranking there was nothing

Ok, we can only work off of what you tell us.

Yes, I would expect it to fire when spraying ether into the intake.

You have said it tried to fire then stopped when you stopped cranking.

I can understand your frustration, and it is always easier to "jump" around, because it feels like your getting something done.

Do the basics. Test and confirm. "A journey of a thousand miles begins with a single step" is what some old Chinese dude said.
 
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