Wire missing from ignition fuse by battery

My 91 XJ 4.0L 4WD base model w/o ABS had a no-start issue yesterday. I ended up getting it towed home because cleaning corrosion and attempting to jump-start and tapping the solenoid didn't let it start. Before pulling the starter I verified there was 12V at the high-amps post and, when the key was in start position, also to the solenoid terminal. I pulled the starter last night and got it tested at Autozone. It passed, surprisingly, but since this Cherokee has been in the family since '95 and service records don't show any changed starter motor, I figured it was about due and bought one.

I'm cleaning up the wires and connections and since battery terminals were very corroded and connection were very dirty. To figure out how to get the short fat wire to the fuse/relay block (aka junction box?) off to clean or change, I ended up removing the junction box and took a look at it from underneath. Surprisingly, I discovered there is no wire attached to the terminal of the 15A mini-fuse that is supposedly "ignition". To the other terminal of this fuse (the one nearest the firewall) there is a blue wire with a white stripe. This is mysterious. I don't have a shop manual for this vehicle and haven't located a diagram on the Internet that shows how it originally was wired. I'm guessing there was a modification to the wiring of this vehicle sometime in the first 4 years before our family got it. I wonder if there is any common modification that would account for this (perhaps removal/disabling of ABS?) There's a connector for the missing wire, but no disconnected wire crimped in are anywhere nearby nor wire strands left over (it's as though the connector was crimped without a wire in place). All connections look very professional like they were done at the factory.

I'll get going on my starter-motor-related connector clean-up now, but while I have junction/fuse box serviceable I'd be interested to know if anyone here has insight about why this wire might be missing and if necessary how it should be corrected.

Well I ignored the missing wire (I'm sure it was missing before!) but got the starter changed. Also changed the battery terminals - I went to the brass type. And got the connections all real clean (used degreaser, 400 grit sand paper & contact cleaner). Now it cranks fine but still doesn't start.

I read through Old_Man's no start diagnosis post here which helped me once before, and low-an-behold, I have no fuel pressure. I hear the pump for a couple seconds when key is in ON position, but there's no gas that comes out when I depress the Schrader valve. I checked fuel rails and everything looks good all the way from the pump to the engine. I guess it's off to get a new fuel filter, but the one in it is only 6 1/2 months old. I suppose stranger things have happened. The pump can't "loose its prime" or something like that, could it? The tank was almost empty when it arrived at the gas station yesterday, after which it wouldn't crank. But two no-start causes simultaneously? Very unlikely. Yet I have looked carefully and don't think I bothered anything, and was not working on the side near the fuel system portion. I hear the pump run, so how can it not have fuel in the fuel rail other than a defective pump or a very clogged fuel filter? The pump is less than 3 years old. It's a brand that I later saw not spoken of very highly (I'd have to look up what it was). The pump has been getting a bit noisy lately but I do hear the motor and it sounds no different when it runs for a few seconds before an attempted start.

Any ideas anyone? This is baffling.

Spoke too early - it wasn't the fuel system. Still don't know what it is, but when I depress the Schrader valve while someone else cranks it, fuel comes out. I'm remembering (I think) from when I had fuel system problems before, that the fuel rail should hold the pressure. Is that right? So I guess I can go on to check for spark, but something happens to release the fuel pressure very quickly. Is that abnormal?

I probably knocked something off or broke a wire or vacuum hose or something like that. No fun...

Well, cleaning up some more I found a very dumb mistake :shocked:: what I thought was the air intake end of the vacuum pump or some such thing, was the contact point for the central distributor wire! I suppose I moved it out the way and where I tucked it hid it too well, and memory must have failed me too.

I noticed the "extra" distributor wire when I was cleaning up the cam position sensor plug, because I wanted to re-route it so the wires didn't go right alongside the engine were it gets so hot (even if they are in heat-shield casing). The various cranking I had done had flooded the engine, but holding the gas pedal to the floor while cranking it started in about 10 seconds and since then has started right up. I think I still have some issue to be concerned about related to it not holding fuel pressure like it should - my fuel pump is probably getting overworked. So it was good exercise to go through the diagnostics.

As for the missing wire in the junction/relay fuse box, I did a further investigation of that, but didn't get to the point of a sane explanation. I checked for voltage with engine & key off (no voltage). I then checked for continuity to ground using an ohmmeter, and (with 15A ignition fuse out) the terminal nearest the battery measured about 10 ohms to ground. So somehow it is connected - it's not an open circuit there. The resistance between the other terminal of that fuse was different (18 ohms if I recall). In any case, just for grins, I left the ignition fuse out and tried to start the engine - and it started, no problem! Plastic that provides a 10 ohm path to ground? Creepy :shiver:. There must be an interior location where the connection to that terminal is located.