I am having problems with my 99 xj. I got in it the other night and it turns over but will not start. The next morning I checked the fuel pressure and had 50psi with the key on. Then I pulled the coil wire loose from the top of the cap and I have spark there. Can also pull a spark plug out and see spark there also, I am a stumped, I cleaned all my grounds while I was in there also. The coil has no visible cracks in it, new plugs wires and cap recently to. The only thing not stock on my engine is the injectors and air intake, they have been on there for about to years though.

 

Is your MAP sensor good still

 

Can you explain how to test it?

To the OP, is the spark blue or orange?

 

I can pull a plug out and lay it on the valve cover and turn over the engine and the spark I see is white, before that I pulled the coil wire loose and did the same thing and it looked orange. I dont know if it maybe the coil, if you turn it over for several seconds it will try to hit every now and then but wont start.

 

Any engine (CEL) codes?

 

Havnt put a code reader on, I dont have one, it wont run so not sure if the cel would stay on but its currently not on.

 

If you have good spark and proper fueling like it sounds you do.. The most likely reason is going to be in some way related to something having to do with the fuel injectors not opening. Because you have fuel at the rail does not mean the fuel injectors are opening to spray in the fuel.

With the ignition key turned into the run position the fuel injectors should all have battery voltage going to them. This is what I would be most interested to see wether or not this is happening (this is provided you do have good compression, which I am going to assume you do..)?

The PCM uses signals from the CkPS and Cam sensors for triggering pulses to occur with the fueling that will normally be happening at the injectors. This means something could be out of sync here too?

Also, the PCM fuel injector driver circuit provides the grounding necessary in order to energize the injectors while during normal operation. This means there could be something wrong with the ability of the PCM grounding to energize the fuel injectors? You could check at the PCM to see what is actually happening with it? Check to see if the PCM is providing a proper ground signal for the fuel injectors.. which is needed in order for them to be energized?

Those are two opposing directions you could investigate from, in order to see the fuel injectors are being energized, or not?

I would want to check at the fuel injectors themselves, and see if they are getting battery voltage when the key is turned into the run position? If they are not? I would next want to check from at the PCM side, to verify if they are able to be energized? It could be one of the connectors is faulty in some way? Or, maybe it could be in the wiring in-between these two portions of this part of the circuit has a fault?

It could be a fault with only just one of the fuel injectors... If a fuel injector has failed, it is often because the solenoid has shorted internally and it causes a drop in resistance. If the resistance is lowered the faulty fuel injector will often pull too much current. Too much current flow to any one of the fuel injectors may cause the PCM injector driver circuit to shut down. As a result, this will kill the other fuel injectors that also share this same driver circuit.

You could pull each individual fuel injector one at a time and try to start the engine. If there is one faulty fuel injector solenoid causing the issue.. after the faulty fuel injector has been pulled, the engine should start up for you. In that way you would know this injector that was unplugged is the shorted injector needing to be replaced. You could also check them all comparing their resistance readings to manufacturers specifications, as a way to check them all for a shorted solenoid too.

Make sure none of the fuses in the PDC are blown before you go digging too far into this issue. But, I am sure you have already looked into the fuses located both in the engine compartment, and inside of the Jeep checking on them all?

 

I am getting fuel I pulled some of the plugs after trying to start it for a while and they had fuel on them. It makes me wonder if its something that controls ignition, like its not firing at the right time. If you turn it over for 10 to 12 seconds it will try to hit every now and then. At first I thought it was most likely a CPS, I replaced it but it made no difference.

 

I almost forgot, may not should have done this but I did, I sprayed a little either down the throttle body at first thinking it was fuel related. No luck same thing hit every now and them but wouldnt start. I would think that it would have run rough for at least a second.

 

could you have gotten a bad tank of gas or water in it?

 

If you get fuel into the combustion chamber, air makes it through the throttle body, there is a good hot blue snapping spark, good compression, and the ignition timing is correct, it basically has to run.

Distributor shaft cracked (it has a distributor, right?)

Bad fuel.. Maybe drain the tank and refill with a gallon or two of new fuel to check.

Are you sure you are truly seeing a good hot blue snapping spark?

Do you think it could maybe be flooding? Are you sure all the fuel injectors are getting a pulse? You can check to see if power to them is continuous, or if it pulses?

Maybe you should verify compression at this point, to rule that out next..

 

Let’s get back on track here . We’ve got some suggestions that will take you down a rabbit hole . You need fuel, fire and compression to run . You said you have spark ... as long as you show spark while cranking on each cylinder we can rule out spark . You have fuel pressure but have not verified injector pulse . The easiest and quickest way to check is to get a noid light that plugs into your injector plug in . Buy one they’re cheap .. then crank the engine while it is plugged in if it flashes youre getting command to the injector to fire while cranking . If this happens we know we have fuel and spark so let’s check compression ... if we have decent compression across the board we can rule that out... my next suggestion would be to check for an obstruction in the exhaust specifically the catalytic converter. I just had a truck kick my butt last week that has fuel and spark and great compression but would not start turned out the cat was plugged up real good simple fix with a lot of head scratching .

 

Spark isnt blue its white not sure if this is my problem. Its got 3/4 tank of fuel and its been running fine on it so far. Everything was fine I drove it earlier Sunday and got in it that night and no start.

 

Blue and/or white spark is strong. Red or yellow is weak. It must have good spark then..

 

It does not really sound gas related to me either. I think it should have started for you when you poured that stuff down the throttle body.

All of this other.. it makes me think it is the timing may not be proper for some reason or another?

Cam sensor, Crank sensor, and the distributor would be where I would want to go to next, to further investigate at those places, and to make sure everything is correctly happening how it should with them.