Pappy C

Hello all. In anticipation of the "Try using the Search Function" Ninjas, let me preface this with the statement that I have used the Search tool ad nauseum both on this forum and on (*gasp* *choke*) the other boards, but have not yet found a resolution to my problem. That being said, I may have overlooked something, and if I have I truly apologize. But, I need help.

I needed to replace the NSS in my son's 98 XJ (4.0L, AT), so in order to see the bottom of the vehicle I had a top and bottom steam clean. Blew out the distributor, plugs, leads, etc...all the usual suspects. Cranked right up at the detail shop and drove about 3 miles with no issue. Made a U-turn to get a closer look at a 1951 Dodge pickup like the one I'm restoring, and the thing just plain quit on me. Tried to restart with no joy. Cranks like a champ, but won't turn over. Towed back to the house, popped the hood and ran through a whole series of diagnostics (no moisture, fuses in tact, etc.) Replaced the ignition coil b/c the original was cracked, but still getting no spark between the ignition coil and the distributor. No spark from distributor to plugs.

Gotta send my son back to college this weekend, so need help soonest. Anything ring any bells with anyone?

- Pappy

sthon

If it turns over NSS is not the issue. NSS will prevent the starter from running.

sthon

If it was steam cleaned I would be looking at the TPS, and CPS. Neither like water.

sthon

Since your original problem could have been NSS related, no need to replace. Pull it off and clean it up. http://www.bc4x4.com/tech/2010/jeep-...ty-switch-nss/

1976Mustang

Did it die while making the turn? If so I would say a wire became exposed somewhere during the cleaning and it shorted out while turning. I would start with trying to check all the wires visually, check continuity to the TPS and Crank PS if you have a multimeter.

Radi

^^ CPS in particular if there's no spark.

Pappy C

Thanks gang. Looking to swap Crankshaft Position Sensor...have the part, now I just need to figure out how to get to it :-/.

Will probably swap the TPS also, after I get over the $130 price tag. I traced all of the wires as best I could, and didn't find any protruding from the shrouds, so I don't think it's that.

The NSS is a known issue. That was going to be the initial repair as he was stranded at the practice field with no starter kick until I told him to wiggle the shifter and kick it again. NSS is definitely bad, but not feeding this issue.

What has me flummoxed is that I'm getting an OL (infinity) multimeter reading from both the CKP sensor and the TPS. Wouldn't that signify that both are operating within spec?

Edit: Another question, does the new CKP have to be bolted in place to the bell housing in order to test it? I.E. if I just unplug the old one and plug in the new one without mounting it, shouldn't that tell me if it is the culprit?

1976Mustang

Only accurate way to test the sensors is with a scope while the engine is turning over. A meter will tell you if it's working, but not if it's working correctly. Next best way from what I know is to replace with a known good sensor, which is what you're doing.

On the NSS, usually shifting into Neutral will resolve it until you can get it fixed.

sthon

CPS can be a pain. A few wobble extensions and a universal or two. It also helps to have someone above to help guide the mess of extensions to the bolts.

Radi

That's an incorrect reading for the TPS, TPS is nothing but a three-terminal potentiometer and should have a definite resistance reading, not open-circuit.
CPS OTOH should read extremely high resistance but that does not mean it's good, just means it isn't shorted.
Mine read normally on a multimeter but still worked intermittently. Agreed the only accurate way to test it is with an oscilloscope. Or by substitution. It will not work plugged in but not mounted, it has to sense teeth cut into the edge of the flywheel/flexplate.

To get at it you'll use about 3' of extension, up over the transmission crossmember. If you have a friend with small hands, having them reach down from the top to hold the bolts/CPS in place while you work from underneath makes it easier.

Pappy C

Oh, and if it helps at all with diagnosis, I just checked and the engine is throwing a P0320 code.

sthon

That would be the CPS.

Pappy C

Thanks for the catch Radi and sorry for the misstatement. The TPS is, in fact giving a definite read. Next step is go ahead and *try* to remove/replace the CKP since I have the replacement part anyway.