• NAXJA is having its 18th annual March Membership Drive!!!
    Everyone who joins or renews during March will be entered into a drawing!
    More Information - Join/Renew
  • Welcome to the new NAXJA Forum! If your password does not work, please use "Forgot your password?" link on the log-in page. Please feel free to reach out to [email protected] if we can provide any assistance.

No start yesterday, starts today

Dirk Pitt

Adam Dowling
Location
Salem, IN
'96 XJ, 4.0, AW4...

Drove to work yesterday fine. Heading out for lunch it cranks strong, but won't start. Also, could not hear the fuel pump energize when turning the key to the on position.

At this point I assume it's a bad fuel pump and buy one.

Today, after work I come home and start to tear it down but try to start just for chits and giggles.

Fires right up.

At this point, there has got to be a troubleshooting procedure to follow. Is it the fuel pump or something else? Any suggestions?

I swapped the AC relay with the fuel pump relay yesterday and it still didn't start so I think I can eliminate the relay as the culprit.

I really would rather not change the pump if I don't have to, since it's a pain in the ass. There is no check engine light.

Any help would be appreciated.
 
w_howey said:
Had the same exact symptoms on my 90.....

Turned out it was the CPS..

Yeah, but the 1990 control setup is a bit different from the 1996...

Dirk, when you hit the key, listen for the fuel pump first. Don't crank if you don't hear it - it should run for 2-3 seconds without cranking to pressurise the system. If you don't hear it, start thinking about checking the exposed wiring to the thing to make sure it hasn't taken a hit.

If you do hear it, remove the spark plugs and have a helper crank the engine - you should see a fine mist and smell fuel (if you don't, then it's a fuel injection issue.) See if you see a mist from all holes.

If you do, put the plugs back in and let the engine bay air out for a few minutes. Remove the coil wire, insert an old spark plug (if you have one. What do you mean you don't keep an old spark plug?!?) and rest the shell against the engine block. Have the helper crank again, while you look for spark at the plug. You should see quite a few - you're going to see the coil file for each cylinder! Take a few minutes to examine the underside of the cap and the rotor tip, and possibly apply a point file or a coarse emery board to the tip of the rotor - sometimes, carbon buildup or HV erosion can cause an intermittent "no-start." (It's rare, but I've seen it just enough to look for it.)

Fuel, heat, oxygen - the fire triangle. We can assume you've no trouble getting oxygen, since that's mechanical (and once it starts up, it runs just fine.) So, check the other two for possible failures...
 
Triple post, see below.
 
Last edited:
I added a second post to this thread a bit ago but for some reason it's not here now.

For the past few weeks when I start it in the morning and pull out of the driveway, the thing sometimes feels like loses power for a second under acceleration, then after a second goes right back to normal. It doesn't do this every time, just maybe once or twice a week. I just haven't had time to think about it.

Jon, yesterday I could not hear the fuel pump kick on but today I can. That's what led me to believe it was the pump and why I'm second guessing now since it seems to be working fine.
 
Triple post...
 
Last edited:
Dirk Pitt said:
I added a second post to this thread a bit ago but for some reason it's not here now.

For the past few weeks when I start it in the morning and pull out of the driveway, the thing sometimes feels like loses power for a second under acceleration, then after a second goes right back to normal. It doesn't do this every time, just maybe once or twice a week. I just haven't had time to think about it.

Jon, yesterday I could not hear the fuel pump kick on but today I can. That's what led me to believe it was the pump and why I'm second guessing now since it seems to be working fine.

Check the wiring for the fuel pump, then. The pumps themselves rarely fail intermittently, but I've lost count of the number of intermittent WIRING failures I've had to track down...

If all the relays are still DIN relays (the 1" cubes with five terminals,) it will really help to have spares - especially since they're cheap. Sounds like I need to get going on this relay tester I'm thinking about (tests and identifies standard DIN relays...) Right after I get going on this headlamp harness, which I'm getting things lined up for (damn, I hate moving...)
 
Alright, so it finally happened again a few times and I was able to play with it a little bit. (Hard to diagnose it when it seems to be running fine).

Same symptoms as last time, could not hear the fuel pump come on with key in "on" position. Crank but no start.

I replaced plug wires, plugs, rotor, and cap. Swapped relays. All with no change after the last time it happened.

I put a plug in the coil wire to check spark and it definitely has spark.

Logic tells me it's a fuel pump or the wiring (I traced the wiring and it seems to be in good shape), but research tells me it could be the CPS or ASD relay not signalling the pump send fuel.

In the '96, what signals the pump to come on? Is the CPS involved? I have the test procedure for the CPS somewhere, but I can't locate it. If it was the CPS or some sensor or even the ECU, wouldn't I get some sort of check engine light? I don't get a check engine light.

I also noticed the other day that it will not start in neutral and I have no reverse lights, which means dirty/bad NSS. I cleaned it about a year ago but it is obviously needing another cleaning or adjusting. Could this also be the culprit for the no start?

Any ideas?
 
Dirk Pitt said:
.....In the '96, what signals the pump to come on? Is the CPS involved? I have the test procedure for the CPS somewhere, but I can't locate it. If it was the CPS or some sensor or even the ECU, wouldn't I get some sort of check engine light? I don't get a check engine light.

I also noticed the other day that it will not start in neutral and I have no reverse lights, which means dirty/bad NSS. I cleaned it about a year ago but it is obviously needing another cleaning or adjusting. Could this also be the culprit for the no start?

Any ideas?
Hi Dirk. I also have a 96 OBD II. The NSS problems are most likely separate, and have no bearing on the pump not running.
If the CPS was not sending a signal, you should have a CEL on, and a code stored. A bad or intermittant fuel pump won't show a code or light. My best guess is it's a bad pump. How many miles are on it?

The pump isn't really that hard to change. Getting the rear wheels up on blocks for access is the hardest part. Then it's just a matter of removing the retaining ring, then the pump. You can do it with the tank in place......
 
Runnin'OnEmpty said:
Hi Dirk. I also have a 96 OBD II. The NSS problems are most likely separate, and have no bearing on the pump not running.
If the CPS was not sending a signal, you should have a CEL on, and a code stored. A bad or intermittant fuel pump won't show a code or light. My best guess is it's a bad pump. How many miles are on it?

The pump isn't really that hard to change. Getting the rear wheels up on blocks for access is the hardest part. Then it's just a matter of removing the retaining ring, then the pump. You can do it with the tank in place......

It has ~140k miles. A fuel pump R&R seems easy, it's just that I don't want to replace it if not necessary.

From what I'm reading so far, the CPS could cause no spark, but not no fuel. Sound right to you?
 
That's true.
Your no-start symptoms are a classic indication of a bad CPS, and that's the usual cause, BUT....the fact that the fuel pump dosen't pulse when the key is turned leads me to believe it's a bad pump.

The CPS dosen't give a signal until the engine starts turning, but the fuel pump is energized when the key is turned on. By the way, the pump will only tick for 2-3 seconds when the key is turned, and then stop, so you have to listen closely for it.

When it dosen't start, you can spray starter fluid down the throttle body; if it starts for a few seconds that confirms a bad pump. You can also of course take a pressure reading off the schrader vavle on the fuel rail.

You OBD II system will give codes for just about everything 'except' the fuel pump, and that's another reason I suspect the pump.
 
Runnin'OnEmpty said:
That's true.
Your no-start symptoms are a classic indication of a bad CPS, and that's the usual cause, BUT....the fact that the fuel pump dosen't pulse when the key is turned leads me to believe it's a bad pump.

The CPS dosen't give a signal until the engine starts turning, but the fuel pump is energized when the key is turned on. By the way, the pump will only tick for 2-3 seconds when the key is turned, and then stop, so you have to listen closely for it.

When it dosen't start, you can spray starter fluid down the throttle body; if it starts for a few seconds that confirms a bad pump. You can also of course take a pressure reading off the schrader vavle on the fuel rail.

You OBD II system will give codes for just about everything 'except' the fuel pump, and that's another reason I suspect the pump.

Yeah, I can tell clearly when the pump turns on or off by sound. I did not know the CPS didn't give a signal until engine revolution, so that confirms my suspicions that it's the pump. That and the fact that (like you said) the OBD system has a CEL code for everything else.

Thanks.
 
Adam, If you are not getting a CEL when you turn the key on & the pump isn't kicking on it's probably the CPS. That's what mine was. I checked the pump by using an extra batt. & jumper wires at the pump. I also jumped the ASD & fuel pump relays. The pump would come on when I had the jumper wires hooked up at any of the 3 spots. Unplug the CPS & turn on the key & see if you get a CEL. If you do change the CPS. I was told they can short out internally & basically shut down the computer so nothing gets toasted. JIM.
 
recently went through the same thing last week, first suspecting the fuel pump, but I could hear it prime up with the key turned to accessory. At first I ignored any sensor issue cause my CEL never came on. So just because you don't have an engine light come on, doesn't eliminate the CPS. It turned over right away with a new sensor in. There's a black knob/button on the fuel rail towards the front that should give a little spray if your pump is pushing fuel. Prices vary a lot for the CPS, but it sure can't hurt to have a spare on hand. Luckily this is my first sensor issue, but I have heard that the OBD II isn't all that sensitive to all engine issues.
 
Back
Top