no start 90 XJ

Help me I'm at my witts end. :bawl:
My 90 XJ won't start my buddie Mark and I have read the thread here on this site for no start and still nothing. We where getting a bad reading off the MAP sensor so we replace it, still nothing. CPS checks out ok, we even pulled it out and cleaned the flywheel with a small wire brush. We cleaned the wires at the fuel pump relays, adjusted the throtle postion sensor. All I seam to do is throw money at sensors, the MAP is new, the CPS is new, and so is the TPS. The fuel pump is new as well as the fuel pressure regulator and my fuel pressure is in specs. The XJ will start when we spray some starting fuild down the throtle body and run just fine. I even can drive it around town. It will also restart on it's own if it doesn't sit more than a hour. If it sit for more than an hour, it won't start and we have to spary it again. We checked the Injector pulse and we don't have any until the engine starts. Can anyone help???

Have you checked the ballast resister to the fuel pump?

Check or replace the fuel pump relay.

Obviously you have spark as you mentioned that when you help your XJ start with starting fluid, it will fire up and stay running. So you have to concentrate on fuel delivery.

Did you check the fuel pressure with both engine off and engine running? Are you checking it with a fuel pressure gauge on the schrader valve of the fuel rail? Really need static/dynamic pressure readings.

Try the "poor man's prime test" ...turn key to on position (not start), listen for fuel pump to energize and pump will run for a few seconds. Turn key off. Repeat above twice more. NOW try to start the XJ. If priming helps to start it, you still have a fuel delivery problem. Just because the pump and regulator are pretty new doesn't mean you can't have an early death of one of them; it happens.

Also, have you changed the fuel filter? A restriction there may cause this type of symptom....easy and cheap to change on your vintage XJ. Good luck and post back what you find!

xjtrailrider said:

Have you checked the ballast resister to the fuel pump?

Check or replace the fuel pump relay.

Click to expand...

X2 and dont forget about checking the fuse aswell. When you turn the key to the on position do you hear the pump prime? If not check the above.

Thanks for the help, but still nothing. I still have all kinds of spark and no injector pluse. I can only get the fuel pressure to about 32 psi. I also can't maintain that pressure, it starts to leak down almost as soon as I turn off the key. I have read my Haynes manual and it says to pinch off the return line and the pressure should hold. No such luck, I'm still losing fuel presure. I have heard there is a check ball to keep the fuel from bleeing back to the tank. Is this true, where is it located? The fuel pump is new as is the regulator, but I did buy them at Auto Zone. Does the fuel pressure have to be in the specs in order to for the injector to fire? Please help.

Also I can hear the fuel pump working, and the filter is new

I'm mark the other one trying to help out. When it starts up manually it has about 32 psi. The injectors do pulse and fire. We even pulled one by one off as it was running and they all checked out. Then left ito sit and the pressure bleeds off and it will not start. We did all this off the fuel rail with a gauge. Once it starts it stays at the same psi. Which souds to me like the pump is working. The question is if there is a min amount of pressure required for it to start. Also what tells the injectors to start in the first place. The cam sensor is new as well as the distributor. The other sensors as mentioned are within specs. The computer is working once the thing starts. It just does not seem to know that with out dumping gas or ether into the throttle body.Any thought or help would be appreciated.

Just a quick thought here...
I have read that the ECM will shut off the injectors if you have the throttle wide open...sort of a feature built in to help start a Jeep that is flooded...is this a 2.5L motor?
Does it have the WOT (wide open throttle) switch? If so maybe that circuit wiring or switch is causing a start problem...

just a quick question have you checked the oil? because on my old 90 which i sold to some guy complained to me that it wouldn't start after i sold it to him. there was water in the oil which caused it not to start...just a suggestion

it's a 4.0 liter. we tried that too, We took the plugs out, pushed the pedal to the floor and turned it over. Cleaned the plugs and put them back in. Same old chit, no start. Give it a shot of gas and it started and run great. No shot of gas, no start. Could it be the ECU??

I'll give it a try. Thanks

I wasn't thinking it was flooded....I was thinking maybe the ECM thinks it is at WOT and therefore not firing the injectors... I would do an advanced search on "fuel pressure" and "renix files" and read through them... I think there are some fuel pressure tests to help you decide were to go next...you might need an ECM...

Thanks McQue, I wasn't trying to be a butt, it's just that we have tried everything we can think of, twice. I think I'll just push it in the river. I just remember that the ECU was repalced at some point. We pulled it and it's a reman. I'll do the search and see what it says.

no problemo...I'll do some more research too...if I find a good thread to read I'll post it...

you guys on this site are da bonb. I wouldn't even know where or how to figure it out with out you

thats what i said when they helped me figure out my no start problem haha they have been thru it all and should prolly become some of the top ASE mechanics hahaha

You get a start signal to the ECU and a ballast resistor bypass from the Starter relay. The orange wire with the black stripe or the BAL pin on the starter relay (most times, though it is sometimes marked differently).
An easy test would be to hold a volt meter to one of the ballast resistor pins to chassis ground and see what happens when you try to start. There should be current (between 10 and 13 volts normally depending on which end of the ballast resistor you test) during cranking.
You should also get a 2-3 second pulse at the same location when the key is first turned to run, the ECU should pulse the fuel pump relay and supply current and prime to the fuel system.
Kind of in the middle of the system, but may tell you something.

Your not the only one on the board with low fuel pressure problems. Some causes I can think of are. Low voltage to the pump, poor ground to the pump, low amperage to the pump, bearings seizing in the pump. Less likely is the screen at the pump is clogged, the filter is clogged, the rubber supply line from the pump to the outlet has a hole in it. I don't know exactly what the rubber stopper does at the end of the return line, it has been discussed but I'm pulling a blank right now.
The check valve is in the pump, I've never disassembled a pump so I really don't know the exact setup well.
Failing check valves are fairly common, search fuel pump and BMW. I posted a BMW check valve a long time ago that was a fairly easy install in the return line just before the pump. But lost the numbers in a hard drive crash. I have one in my 88, it helps the long starts somewhat, mine starts about twice as fast as before (half as many revolutions on the starter).
As a last resort reverse the power and ground wires to your pump, contrary to popular belief a pump wired backwards does run in reverse but still pumps in the same direction, though poorly. It may have been wired in reverse from the factory, I've never seen it on the pump wiring but there was a rash of windshield wiper motors that were wired bassackwords in the past.
A little far out there, but something I've seen before. Have somebody jump up and down on the rear bumper and listen for the sound of ice cubes bouncing around inside the tank. Not as far out there as you would think. Gas tank deicer and an overnight in a heated garage may be the cure.

some good info in this thread...some of it may pertain to your problem

http://www.naxja.org/forum/showthread.php?t=942835&highlight=fuel+pressure

The BMW fuel check valve part number 16 14 9 068 988.

I have read that the ECU needs to see a starting RPM of at least 300 RPM before it will
syncronize spark and enable the injectors...

How strong is your battery and starter? Is itr cranking the motor at a good speed?