Ground issue?

I'm about ready to drive this friggin MJ off a cliff... it's been one thing after another with this thing, and recently I had some sort of ground issue, at least I'm assuming.

Last time I was out, my gauges started going haywire... it started with the Fuel gauge. It was showing a full tank, which I had, but then it started to peg out fuller and fuller. By the time I got to the dirt (about an hour of road driving) I was reading 2 and a half tanks of fuel. I figured something must be wrong with the sender, and continued. Then the temp started... it slowly started to climb until finally it hit red. I pulled over, popped my hood and looked for the exploded renix bottle... but nothing, no boiling, no dripping, no steam, no nothing. Hell my engine didn't even feel hot.

Confident that my junk wasn't overheating, I continued on my way to meet up with the rest of the crew. As I continue, the rest of my gauges started going nuts. My oil pressure was damn near pegged, temp gauge pegged, fuel gauge pegged. The only thing working correctly was the speedometer, which later broke when we pulled out the gauge cluster.

I continued throughout the day with the attitude of "eff it" if it blows it blows. I was at a race and wasn't going to let it bother me. I ran all day, and into the night without problems, even ran my two 9" soltek lights all night. On the way home was a different story. I stopped for gas, filled up and went to leave and had NO power. I completely drained my battery. Jumped it, it ran fine... turned on my offroad lights, bam, it's dead. I limped her home and parked it. I'm finally starting to get around to working on it.

I checked the alternator, it tested good at vato zone, also charged my battery. I fixed a wire going to my starter solenoid that appeared to be grounding out on the motor mount, started it up, still acting up. I replaced the gauge cluster as well, still NOTHING working, it immediately pegged my gauges. So here I sit... frustrated with this stupid ass renix, wires EVERYWHERE, and not sure where to check. Any ideas?

I would start by cleaning the grounds on the firewall, engine block, and behind the driver side tail light, and I would also add a ground from the battery to the front fender.

Back tail light? Really?


Also, update, I just hooked up jumper cables from negative on the battery to the block (engine mount) and also from the negative on the battery to the firewall. Tried different combinations, no difference, still bonkers

Do the grounds as Icehawk recommends and also scrape the paint from under the braided strap where it attaches to the firewall.

Not sure of your year--somewhere between 86-92? Just asking because many of the chain store alternator testers can't seem to handle the Nippon Denso PCM controlled alternators, returning false "good" results. Have you measured the voltage? Static battery voltage between the terminals--how many volts? Voltage between the terminals with the engine running? Have you tested for voltage drop on the main cables? Your fuel gauge, does the sender read 0 ohms = empty, 44 ohms = 1/2, 88 ohms = full, or do you have the reversed gauge--another reason knowing the YEAR is important.

Good luck.

crazyjim said:

I'm about ready to drive this friggin MJ off a cliff... it's been one thing after another with this thing, and recently I had some sort of ground issue, at least I'm assuming.

Last time I was out, my gauges started going haywire... it started with the Fuel gauge. It was showing a full tank, which I had, but then it started to peg out fuller and fuller. By the time I got to the dirt (about an hour of road driving) I was reading 2 and a half tanks of fuel. I figured something must be wrong with the sender, and continued. Then the temp started... it slowly started to climb until finally it hit red. I pulled over, popped my hood and looked for the exploded renix bottle... but nothing, no boiling, no dripping, no steam, no nothing. Hell my engine didn't even feel hot.

Confident that my junk wasn't overheating, I continued on my way to meet up with the rest of the crew. As I continue, the rest of my gauges started going nuts. My oil pressure was damn near pegged, temp gauge pegged, fuel gauge pegged. The only thing working correctly was the speedometer, which later broke when we pulled out the gauge cluster.

I continued throughout the day with the attitude of "eff it" if it blows it blows. I was at a race and wasn't going to let it bother me. I ran all day, and into the night without problems, even ran my two 9" soltek lights all night. On the way home was a different story. I stopped for gas, filled up and went to leave and had NO power. I completely drained my battery. Jumped it, it ran fine... turned on my offroad lights, bam, it's dead. I limped her home and parked it. I'm finally starting to get around to working on it.

I checked the alternator, it tested good at vato zone, also charged my battery. I fixed a wire going to my starter solenoid that appeared to be grounding out on the motor mount, started it up, still acting up. I replaced the gauge cluster as well, still NOTHING working, it immediately pegged my gauges. So here I sit... frustrated with this stupid ass renix, wires EVERYWHERE, and not sure where to check. Any ideas?

Click to expand...

Does the Renix powered MJ have the C101 connector (near the firewall slightly to the right of the valve cover) ?
If it does.... you might consider separating the connector and check the pins for oxidation.... Clean all pins and apply dielectric grease before reassembling.

CharlesS said:

Does the Renix powered MJ have the C101 connector (near the firewall slightly to the right of the valve cover) ?
If it does.... you might consider separating the connector and check the pins for oxidation.... Clean all pins and apply dielectric grease before reassembling.

Click to expand...

Yes it does if it's an 87 or 88. BTW, great suggestion if the c101 is there. They were agigantic source of issues when they were new. I doubt they've improved with age, unlike Joe Peters.:viking:

cruiser54 said:

Yes it does if it's an 87 or 88. BTW, great suggestion if the c101 is there. They were agigantic source of issues when they were new. I doubt they've improved with age, unlike Joe Peters.:viking:

Click to expand...

Like any fine wine, I have turned to vinegar.

joe_peters said:

Not sure of your year--somewhere between 86-92? Just asking because many of the chain store alternator testers can't seem to handle the Nippon Denso PCM controlled alternators, returning false "good" results. Have you measured the voltage? Static battery voltage between the terminals--how many volts? Voltage between the terminals with the engine running? Have you tested for voltage drop on the main cables? Your fuel gauge, does the sender read 0 ohms = empty, 44 ohms = 1/2, 88 ohms = full, or do you have the reversed gauge--another reason knowing the YEAR is important.

Good luck.

Click to expand...

It's an 87... I'll be buying a new alternator anyway, as this one has a cracked housing, problem is when I buy an alternator I'll be buying a higher amp alternator, along with upgrading wiring and relocating the battery.

As for the the rest of the post, I have not checked voltage on anything, as I don't have a voltage meter.

CharlesS said:

Does the Renix powered MJ have the C101 connector (near the firewall slightly to the right of the valve cover) ?
If it does.... you might consider separating the connector and check the pins for oxidation.... Clean all pins and apply dielectric grease before reassembling.

Click to expand...

Pics of what it looks like? I'll try that next

UPDATE: Checked grounds, still not the problem. I've checked and cleaned all the grounds I can find, and it hasn't cured the problem. I even went as far as to connect jumper cables from the battery to the firewall, and engine block, still no help.



However, I did find something ELSE wrong with this thing. It may or may not be related, I'm not sure. While poking around in wires, I saw a melted wire. It's melted to a connector on my starter relay.

No idea what they are, as they body dive back into the wiring harness.




This green wire (goes to the wire harness) is melted to this plug, the green wire, connects to a red wire through some rubber insulator, not sure if there's anything in it. But it seems to have been cooked inside, it feels swollen and hollow, and crumbled in my fingers when I massaged it.

sorry the pics are all effed, photobucket is stupid

The plug is going to the connector in the upper right of this picture.

On the starter relay is the PDC lug--big bolt, then IGN, SOL, and GRD male spade connectors. IGN is 12 volts from the ignition switch, SOL is the wire that carries 12 volts to the starter solenoid to energize it, and GRD is to the fenderwell or clutch switch (manual transmission), or to the NSS for an automatic transmission.

Those big lumpy wires to the PDC are fusible links, and they provide power for the unswitched circuits--headlights, brake lights, interior lights, basically anything that has power to it even if the key is OFF and removed from the cylinder. Even the aux fan circuit is powered all the time, it is triggered by a ground.

pwned!

I told you it was a ground issue.

crazyjim said:

Back tail light? Really?

Click to expand...

Yep, really, he's super serious on this one. The fuel level sender and fuel pump both ground through the rear driver side tail light as I recall.

:looney:

kastein said:

Yep, really, he's super serious on this one. The fuel level sender and fuel pump both ground through the rear driver side tail light as I recall.

:looney:

Click to expand...

What about those of us who no longer have those taillights and stil l have our fuel pumps work?

In that case clearly you are enough of a rocket scientist to fix it some other way :spin1: