No Start, no trouble codes, has spark/fuel

[TeXJ]

Okay, I've been through the threads and have found a lot ideas, but nothing that covers my problem, so if you have any suggestions I could definitely use them. I need my jeep back....

Okay, here's the deal:

'91 XJ
'00 4.0 block, intake, power steering
'91 everything else

It is very difficult to start. If it does start, it idles extremely rough (read bucking, backfiring in intake, so on) and then dies. I have spark and fuel to the fuel rail. I have no trouble codes -- checked with CEL and had a friend read the codes with diagnostic computer.

I just installed in the motor. Timing was correct (TDC on compression stroke), verified several times. Distributor was installed correctly. Firing order is correct. All grounds, wires, and connections checked several times.

I don't have any guages to check the pressure in the fuel rail, any other way to do it? How do I determine if injectors are pulsing? Could it be the CPS or cam position sensor even though its not giving any codes?

Anyway, any ideas would help. I need to get the Jeep running, its our only vehicle. :helpme:

 

[Matthew Currie]

Are you absolutely, positively sure the distributor is indexed correctly? It isn't that hard to experiment by moving it one tooth either way. When I was playing with my 87 a few years back, I found that one tooth forward gave very hard starts, but ran all right. One tooth back started and idled, but would not run, and spat back through the intake.

I don't think the CPS or cam position sensor would give you this problem without a code, but I could be wrong. It really sounds like a timing issue, but I suppose it might be possible that the CPS is weak but not quite dead, and sending a poor timing signal. I don't think the cam position sensor would mess you up like this if it starts at all.

The other thing that comes to mind, depending on who did the rebuild, and what you have or haven't confirmed with your own eyes, is whether or not the camshaft might be one tooth off.

 

[TeXJ]

Are you absolutely, positively sure the distributor is indexed correctly? It isn't that hard to experiment by moving it one tooth either way. When I was playing with my 87 a few years back, I found that one tooth forward gave very hard starts, but ran all right. One tooth back started and idled, but would not run, and spat back through the intake.

I'll pull the distributor again and check it.

I don't think the CPS or cam position sensor would give you this problem without a code, but I could be wrong. It really sounds like a timing issue, but I suppose it might be possible that the CPS is weak but not quite dead, and sending a poor timing signal. I don't think the cam position sensor would mess you up like this if it starts at all.

The other thing that comes to mind, depending on who did the rebuild, and what you have or haven't confirmed with your own eyes, is whether or not the camshaft might be one tooth off.

The short block wasn't rebuilt (low miles and clean as can be), but the head was. I installed a new cam (Crane) with a new timing chain set (Elgin). Unless there was an issue with the design of the cam and/or timing chain set, it should be installed correctly (according to specs/directions in my Haynes book). Timing marks lined up, rotate crank until cam mark is at 1 o'clock, count 15 pins -- done and verified twice.

Thanks for the help...

 

[old_man]

All I have ever done is to install the chain when the timing marks are pointing directly at each other. No indexing or anything of the sort. A bad or disconnected MAP can cause a virtual no start scenairo as well. Make sure the little rubber plug is inserted in the throttle body correctly. I think you can rotate it and get it plugged in upside down which renders the MAP inoperable.

On a head replacement, I have seen the intake not seated correctly and large vacuum leaks cause similar problems as well.

A quick and dirty check of fuel pressure is to turn on the key and let the fuel pump pressurize the system. Depress the Schrader valve on the fuel rail and you should get a very healthy squirt of gas.

 

[TeXJ]

Its fixed. :yelclap:

Matthew Currie, it was the distributor. One tooth off (back) just like you mentioned. I checked before I reset the distributor and it was right on the money according to Haynes. :smsoap:

Old_Man, I checked the valve, seemed a little weak (?) maybe, but it squirted.

Thanks for the help, I was actually a little shocked/surprised when it started...

This group is great... :cheers:

 

[TeXJ]

Okay, so I was a little premature on the fact that its fixed.

It started and sounded good, then... it got rough but kept running. If I give it gas it sounds good and smooth, if I let it idle it will gradually slow until it dies. If I put it in gear it will run okay, until I give it any gas to accelerate. Then it will start to die unless I keep giving it gas. Fuel delivery? Distributor still off?

Also, any reason why my Oil Pressure would be getting close to 80?? Thats what my guage has been reading.