89 MJ bulkhead connector issues

The MJ that I just got done fixing from the roll over has a connection issue and a cracked cover. If I tighten the connector it looses power to the fuel pump. If I loosen it a little it works just fine but the connection is intermittent. What are my options?

I will post a picture as soon as I can

Let me correct my previous post: The bulkhead connector is secured tightly to the back of the fuse block but the fuse block is loose to the bulkhead. If I tighten down the fuse block then I loose power to the fuel pump and radio.

Here is a pic of the cracked housing;



Any ideas why I can not tighten the fuse block down and not loose power to the fuel pump/radio?

there's a 1/4" (IIRC, could be metric...5-6mm) bolt in the center of that bundle of wiring. It's a pain to get to, but check to make sure it's tight and/or it's not shorting out a wire in there. Might be the cause.

HTH,
Jeff

edit: I've got the pinout for that connector but it's not near to me at the moment.....I'll post it up tonight when I get home tonight if you need it.

yes, you access the bolt from the inside. Torque spec is low. I tighten them up just until I feel the connector seat, otherwise you risk it cracking like that.


I have bypassed the connector for the high amerapge wires as they caused intermittent no starts for me. That may be an option for you as well.

The connector was cracked when we got the truck. The connector is tight to the back of the fuse block but the fuse block is loose to the bulkhead. If i tighten the fuse block up, I loose the fuel pump?

87manche, you have the old style connector correct? Mine is just like the one on my newer XJ's.

Can you post up pics as to how you bypassed the connector, especially for the fuel pump.

Thanks!

pull the fuse block completely off. Check that it's not got contacts falling out of it or wires pinched. There are jumper wires that run on the back of it, it fyou pinch one I could see it shorting out when it was tightened.

Just to be certain I'm on the same page. The bulkhead connector is tightened with the center bolt, but when you tighten the two phillips head screws that hold the fuse block on the firewall it shorts?

I made the assumption that yours is just like mine, did you do an HO swap on that? I didn't keep up with the build thread, just looked at the pretty pictures.

87manche said:

pull the fuse block completely off. Check that it's not got contacts falling out of it or wires pinched. There are jumper wires that run on the back of it, it fyou pinch one I could see it shorting out when it was tightened.

Just to be certain I'm on the same page. The bulkhead connector is tightened with the center bolt, but when you tighten the two phillips head screws that hold the fuse block on the firewall it shorts?

I made the assumption that yours is just like mine, did you do an HO swap on that? I didn't keep up with the build thread, just looked at the pretty pictures.

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No, its still all RENIX. My connector has the single center screw, which is tight. Its when i tighten the fuse block down to the bulkhead/firewall with the two screws is when I start having issues.

ok. Yeah, pull it off, you'll see a rats nest of jumper wires and such. mine also had a few loose contacts.

You're going to be appalled when you see the back.

AMC did not do great wiring.

Since you say the radio and the fuel pump are quitting then it's a power issue going to the ignition switch most likely. The Renix ECU controls the pump. The radio is wired straight through the fuse block to the ignition switch. The top two big orange wires are the primary source of power for the fuse block. mine are bypassed at the bulkhead connector because of wire fatigue there causing intermittent "oh the Jeep's dead" issues.

We had a similar issue on Rob Mayercik's XJ a few years back on the trail - fiddling with the connector would make it work for a little while. Turns out a few pins inside it were horribly corroded.

The dielectric grease they put in them at the factory has almost always congealed into what might as well be a solid mass of roofing tar by this point. Even cleaning it out with contact cleaner is a real bear, it took me something like an hour to clean one up enough to troubleshoot it a while ago.

You might try very carefully tightening up the female side of the terminal with a dental pick - basically just retension the terminals so they grab the spades harder. Shouldn't even need to pull them out of the housing.

IIRC it is a 1/4" hex head. Had to pull it apart on an 87 YJ recently so I could pull an unnecessary pin out and swap it into the right spot to energize the fuel pump when doing an EFI conversion, the body harness had the fuel pump power wiring (since the 2.5 used a lifter pump) but the engine harness didn't since it was a carbed 258 vehicle originally. If you are real careful with a dental pick you can release the pins from the housing but I don't think you will even need to unless you find some of them are badly corroded.

This is why Chrysler moved the bulkhead connector from the firewall to under the dash on later years - made it so they could get away without any dielectric grease and still not have any corrosion problems. 97 and later just have a rubber grommet at the firewall and then the harness connection itself is about 6" further in under the dashboard.

Ok, this sounds like its just going to be way too much fun LOL! Why would they squeeze jumpers between the connector and the fuse block?

That is probably where the issue is at. If I wiggle the connector(engine bay side) I can make the fuel pump shut off.

The rigs with manual transmissions are the worst, as the clutch MC leaks brake fluid from just above and eats the metal connectors like zombie brain food, LOL. 90% of that block is by passed on my 85 now.

xjtrailrider said:

Why would they squeeze jumpers between the connector and the fuse block?

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Cause AMC.

same reason there's duct tape in the factory wire harness to protect factory crimps.

mine was having VERY similar issues to yours, and bypassing the two primary wires at the top of the connector fixed it. I ended up doing that after I replaced the ignition switch and spent a while tracking it down as something with the in cab wiring.

kastein said:

We had a similar issue on Rob Mayercik's XJ a few years back on the trail - fiddling with the connector would make it work for a little while. Turns out a few pins inside it were horribly corroded.

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"Horribly corroded" is an understatement - the crimp end of the terminals on at least two of the wires in my connector were flat out GONE. One of those was the 10-gauge wire that is probably the mains line into the cabin. I still don't know how I got it home like that, drove it a couple weeks more, then went to that junkyard M&G and back. By all rights, it should never have been able to get home from the trails on the day Ken mentions under its own power, let alone to that junkyard and back.

kastein said:

The dielectric grease they put in them at the factory has almost always congealed into what might as well be a solid mass of roofing tar by this point. Even cleaning it out with contact cleaner is a real bear, it took me something like an hour to clean one up enough to troubleshoot it a while ago.

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No kidding - I spent a bit of time and work prepping the replacement connector I installed because of this.

TrailRider, is that crack in the "dust cover", or is it the connector itself? If the second, perhaps you'd be better off finding a good one in a junkyard truck, cutting it out (with as much wire as you can get to), and replacing the whole thing?

Rob

Rob Mayercik said:

TrailRider, is that crack in the "dust cover", or is it the connector itself? If the second, perhaps you'd be better off finding a good one in a junkyard truck, cutting it out (with as much wire as you can get to), and replacing the whole thing?

Rob

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I think its just the dust cover. I have a local wheeler coming over this week to look it over. He is a MJ owner and also happens to be a chassis electrical guru. He said he could fix it easily.

Its been running just fone for 5 days now since getting it back on the road but I really want to get the issue fixed permanently.

This issue was forgotten about(LOL!) until tonight when the truck would not start(crank, no start) but wiggling the bulkhead connector got it going again.

Some one please show me pics of the two primary power wires and how you bypassed the connector(How do you bypass a connector this big?). I'm reluctant to dig into this as I do not like chassis electrical. I would rather rebuild a AW4 than take that damn bulkhead connector loose LOL!