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96 4.0 Cranks, No Start, Has Fuel At Rail


NAXJA Forum User

Finally got my 96 4.0 XJ cranking by bypassing the NSS, now it won't start! SMH! The last time I worked on it I was diagnosing the no crank and when I added a jumper wire from the starter relay to ground it would crank and start right up, now not having touched it in a week or two it will crank but not start. I did try starting it with the distributor harness unplugged and three grounds at the passenger side rear block accidently because I had it disconnected while cleaning other harnesses and grounds, but when I plugged it back in..no go. There are two harnesses by the passenger side fire wall that have exposed wires due to the insulation literally crumbling away (one squarish with 6 pins and another that is round inside with 4 round pins), I haven't repaired them yet but plan to tomorrow. I'm in the process of installing an external voltage regulator, replacing the "big 7" with 2 awg and a few other upgrades but hadn't started before trying to start it to move it. Any ideas? I need to get this thing running ASAP to move it. Thank you!
You say it has fuel at the rail, but what is the fuel pressure? Just pressing the Schrader valve does not rule out a fuel delivery problem.

Have you checked for an injector signal with a noid light?

Have you confirmed spark?

Any codes?

Pics of the wiring issue could help. Is there crumbling insulation elsewhere? What caused the crumbing insulation? That is not a typical situation (at least not yet). Underhood fire?

Another approach, have you tried spraying starter fluid in the throttle body? That may help separate spark from fuel issues.
At this time I don't know what the fuel pressure is. I did press the valve and fuel sprayed out.

I have not checked injector signal, I'm not sure how to do that. I do have a test light and multimeter.

Have not confirmed spark. Spark was what I was suspecting after seeing fuel at the rail and that's when I found that I forgot to plug the distributor back in. I was hoping that was the problem, but plugging it back in changed nothing. Three grounds (at passenger side/rear block) were also disconnected when I initially tried to start it and at the same time the distributor was unplugged.

I do not have a scan tool to read codes and unfortunately can't start it to drive to a local parts store to have them read at this time.

The harnesses/connectors with crumbled insulation are two of 4 or so in a "bundle" coming from the main harness on the firewall and both appear to be going under the vehicle towards the transmission. They are in the area of the dip stick/heater control valve, all are soaked with oil. I'm guessing possibly a combination of oil saturation and heat over many years? Nothing appears to be burned, the exposed copper is relatively clean and corrosion free having been oil soaked. Wires are definitely touching each other. I sprayed them down with electrical parts cleaner and removed as much of the brittle insulation as possible, tomorrow I will try to install marine heatshrink to keep them from shorting. Both harnesses/connectors were disconnected at the time of initial starting attempt.

I started removing cables to install the "big 7" power/ground cables, new battery terminals etc. and hope to have that done tomorrow. Once I get those main power/grounds in, I will try spraying a fuel into the intake and starting it.
CPS is on the driver's side. Its connector/pigtail comes out of the bundle which includes all the sensors attached to the throttle body.

My guess is that your bundle of damaged wires involves the Neutral Safety Switch. That is an automatic transmission thing. I have an AX-15, so I am not as familiar with that bunch of wires. I would think if you have a problem with the NSS it would not even crank over, but again, not something I have had to get much acquainted with. Varmint #1 had to pull the NSS to clean it up so his '92 would start in the winter, but that was a job I let him figure out pretty much all on his own. But if bare wires are touching each other that would be something to take care of and then reassess the situation.

A fuel pressure gauge is not particularly expensive and is probably something you could "rent" from the auto parts store. Likewise for a noid light to test for an injector pulse. As to a code reader, you really should set yourself up with something in that department. I think the cheapest option is something that interfaces with a cell phone. I hate cell phones, but most folks seem to have them.

I would say fix your wiring first. If that doesn't take care of it, try a snort of ether down the throttle body. If that doesn't at least get it to try to start, get your hands on a FP gauge, a noid light and a code reader. See what information that gets you.
I will add, in case you aren't aware, 1996 is the first year for OBDII (at least for an XJ). That is to your advantage. OBDII makes life pretty easy when it comes to codes, and it is the easiest for which to find a code reader.
Yeah looking up CPS, that definitely is not it (at least concerning the bare wires). I think they may be NSS and one of the O2 sensors (possibly downstream O2) Last time I worked on the XJ and it started everytime without issue (about a week or two ago) I had the NSS bypassed. I do think there is something wrong with the NSS (my previous no crank issue) but I don't think it would cause it to crank but not to start (I could be wrong).

I may be able to track down a fuel pressure test gauge tomorrow, if I can I will definitely run the test and post the results. Not sure on noid tester, I will have to look that up.

I'm hoping to get those harness/connector wires isolated from each other tomorrow, finish installing new power/ground cables and then trying to get this figured out.
This XJ is son of a gun..96 bastard year could have any combination of 91-96 (?) and 97 + parts. On top of that the engine is not original and I'm not sure what model and year it came out of. The PDC does not match the layout described in the 96 XJ owners manual; it also has two posts (battery and alternator +) with a fusible link bridging them rather than a fusible link between the alternator + cable and PDC and both the battery and alternator + going to a single post at the PDC. I have no idea what is going on here lol.

I think I'm going to test for voltage at the feed wire going to the coil and see if I get spark from the secondary coming out of the coil, then at the spark plugs if it leads me that far.
If some of those wires involve an O2 sensor that could indeed be the problem. A grounded O2 sensor is as good as a kill switch.
So doing some more looking around while I'm installing these "big 7" cables, the fuse that I believe is associated with the ASD circuit is blown. I hear it's posdible that a shorted O2 sensor can blow that fuse. If the connector with exposed wires is in fact an O2 connector that would make sense. I've got alot going on at once; installing "big 7", external voltage regulator, headlight harness, finishing electric fans and installing water temp gauge. Once I finish the " big 7" and external voltage regulator (hopefully in the next few hours), I will do a temp repair to those exposed wires and switch the fuse for a new one. Hopefully it will start!
An update: I temp repaired (isolated the exposed wires) on both connectors, the XJ now cranks and starts without issue. I do still have my NSS bypassed with a jumper wire at pin 10 with the relay installed in the PDC to ground.