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Cheapamanche

Starter relay blown fusible link

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I have a blown fusible link coming off of my starter relay. It's the one that splits off into 4 red wires. When I repaired it the engine wouldn't shut off with key off. I think one of the wires goes to the fuel pump because touching the 2 ends of the link make the pump prime. Even with the key off... 

I thought I was a pretty good shade tree mechanic until this comanche. Its giving me a run for my money, and running off with my money.

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Based on your posts-

 

You have a mess, you need to begin cleaning up your mess. 

You need to attack your mess methodically. 

Your mess is not uncommon with MJs or XJs of the era. 

 

Yes, your MJ will runaway with some of your money. 

 

As for fusible links- I've addressed here several times and here is a solution-

 

 

 

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did you repair what caused the fuse link to blow? Have you checked the fuel pump relay? it could be stuck closed.

wire.xps

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15 minutes ago, jdog said:

did you repair what caused the fuse link to blow? Have you checked the fuel pump relay? it could be stuck closed.

wire.xps 1.42 MB · 1 download

 

 

He needs to review Cruiser's Tips, then-

 

He needs to replace all his battery cables.

Delete C101.

Replace fuse block.

Replace ignition switch. 

Improve all grounds (ALL).

Add more grounds. 

Inspect and clean all connectors. 

Inspect and repair all wiring harnesses. 

He will likely end up replacing all sensors. 

 

Until then.............chasing gremlins.

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Thanks for the quick replies. I have refreshed all my grounds and added grounds, cleaned every connector, cleaned my c101 connector which is on my list to replace soon. I fixed all my vacuum leaks, replaced all sensors that didnt test right including IAC, O2 sensor, cts. I still need to replace my headlight switch. My TPS is set to 17% and the sweep is smooth from closed to open throttle. Still, I ordered a replacement tps from rock auto. I remember cruiser54 saying somewhere that just because it tests right doesnt mean it is functioning right. Front blinkers are still buggy. Throttle body is clean. Relays all check good. Fuel pump still primes with key on. 

   You are right it is a mess under here. I'm trying to figure out where the 4 red wires go from my blown fusable link so I can figure out why it tripped. I have a Haynes but my ability to follow electrical diagrams is poor.

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13 minutes ago, Cheapamanche said:

Thanks for the quick replies. I have refreshed all my grounds and added grounds, cleaned every connector, cleaned my c101 connector which is on my list to replace soon. I fixed all my vacuum leaks, replaced all sensors that didnt test right including IAC, O2 sensor, cts. I still need to replace my headlight switch. My TPS is set to 17% and the sweep is smooth from closed to open throttle. Still, I ordered a replacement tps from rock auto. I remember cruiser54 saying somewhere that just because it tests right doesnt mean it is functioning right. Front blinkers are still buggy. Throttle body is clean. Relays all check good. Fuel pump still primes with key on. 

   You are right it is a mess under here. I'm trying to figure out where the 4 red wires go from my blown fusable link so I can figure out why it tripped. I have a Haynes but my ability to follow electrical diagrams is poor.

C101 gets eliminated not cleaned or replaced. 

 

Have you got a test light? If not, get one. 

 

Make a fused jumper. Jump from the pos bat post to each of the red wires. Test to see which circuit comes to life.........one circuit at a time.

If any one of the red wires fries the fuse........you will know which circuit of the four has the problem. 

 

You will need to replace your headlight switch.......cheap, like $14 anywhere. Inspect the connector, if the switch is fried it's likely the connector is too. 

Ignition switch, inspect, clean, adjust.........or replace. Inspect wires at ignition switch. 

 

Throw the Haynes in the trash where it belongs. 

 

There is an excellent wiring diagram here, someone will post, download it. 

 

Chances are your problem lies in your fuse block and headlight switch and ignition switch. 

Also, light harness at rad support driver's side is generally problematic. 

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I'm sure the problem is in my fuse block. I had a mc leaking on it when I bought it. I do have a test light. A fused jumper is a great idea. Thank you.

The hay es for it is junk. I buy a book for every vehicle I own but this has proven to be the least useful off all the books I have purchased. Come to think of it, I usually buy Chiltons but all I could find at my local parts stores were haynes... 

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52 minutes ago, Jeep Driver said:

Electrical manual is here- 

 

 

Wow this is really helpful. Thank you. So it looks like I'm getting no power to my orange and black wire on my starter relay. I believe this is my fuel pump. When I fixed the fusable link it would send power to my fuel pump and cause it to prime. Then after starting it I was unable to kill the engine unless I pulled one of the wires to my fuel pump resister. What's confusing is that my fuel pump still primes and runs without the power to it... am I missing something?

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1 hour ago, Jeep Driver said:

C101 gets eliminated not cleaned or replaced. 

I’ve cleaned the connection. I mean it’s not the most cleanest setup creating electrical power loss I’m sure over 32 years but my truck starts and runs fine. Eliminating is an option. One step at a time.

 

1 hour ago, Jeep Driver said:

Throw the Haynes in the trash where it belongs

Don’t. There’s good basic info in there. Yes it’s not a Chiltons.

A leak onto the fuse block was/is a common problem. It sounds like you’re doing a good job trying to locate electrical problems. I’m sure if you PMd Cruiser he’d point you in the right direction. He’s helped many members in the past. He patiently literally walked me through(held my hand!) in how to properly diagnose a headlight problem.

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16 minutes ago, Cheapamanche said:

So it looks like I'm getting no power to my orange and black wire on my starter relay.

During engine CRANK (starter relay engaged) the ORN/BLK becomes HOT and bypasses the ballast resistor for straight 12vdc to the fuel pump.

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I have been down the path you are on now. If I was doing it again I would pull the fuse box apart clean and check all the wires going to it. There are multiple wires in the fuel pump circuit. I found shorts in 4 or more wires. 

mj1988electricalmanual_(1).pdf

This is the 88 electrical manual. I would save it so it's easily accessible. I even printed it all out. You going to need a decent multimeter, time, and patience.

IMG_20190818_134715617.jpg.e7b2296e7d66799faf6d8eac42b6a481.jpg

The PO had installed this switch to $#!& of the fuel pump. I drive it that way while I fixed the rats nest of wiring.

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So I traced the burnt green fusible link to my ignition switch. Looks like I know what I'll be replacing. The confusing thing is that even with it blown I can start and kill the engine. I'm guessing that the ignition has been hotwired somehow. I didn't mention that the cylinder comes out with the key. I'm guessing I'll find another mess once I have replaced the ignition... crapola... my guess is that they wired it into my headlight switch somehow because I can't kill the engine if my headlights are on. Why do people try to do these stupid hack jobs instead of fixing it right? It would have been so much easier for them and me.

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2 minutes ago, JMO413 said:

I have been down the path you are on now. If I was doing it again I would pull the fuse box apart clean and check all the wires going to it. There are multiple wires in the fuel pump circuit. I found shorts in 4 or more wires. 

mj1988electricalmanual_(1).pdf 8.04 MB · 0 downloads

This is the 88 electrical manual. I would save it so it's easily accessible. I even printed it all out. You going to need a decent multimeter, time, and patience.

IMG_20190818_134715617.jpg.e7b2296e7d66799faf6d8eac42b6a481.jpg

The PO had installed this switch to $#!& of the fuel pump. I drive it that way while I fixed the rats nest of wiring.

Your right, I need to tear into the fuse box. I have been putting it off but it looks like I can't anymore. I'll go through your old thread. 

    As a side note, I just ordered some comancheclub stickers! I really appreciate all the help from you folks. As I get more experience I'll be able to return the favor some day. You guys are really cool and I'm happy to be a part of this group.

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21 minutes ago, Cheapamanche said:

I can't kill the engine if my headlights are on

 

 

It's possible, none of us are there so..........just guessing............

 

If the headlight switch has melted down, it could be back-feeding a 12v circuit, the ignition circuit somehow.

 

 

 

It's aggravation, I know, but you are just going to have to start stripping it down and chasing and inspecting. 

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14 minutes ago, Jeep Driver said:

 

 

It's possible, none of us are there so..........just guessing............

 

If the headlight switch has melted down, it could be back-feeding a 12v circuit, the ignition circuit somehow.

 

 

 

It's aggravation, I know, but you are just going to have to start stripping it down and chasing and inspecting. 

If I had a little more cash I could deal with it a little better. I'm going to have to get it good enough for work for a couple of weeks because I just don't have the funds to replace anything else for a while. Fortunately chasing shorts is free. I did pull back my fuse box and didnt find any bad wires. A couple of the connections were loose and I tightened them with a pick. Will be cleaning it as the day goes on.

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3 hours ago, Cheapamanche said:

I have a blown fusible link coming off of my starter relay. It's the one that splits off into 4 red wires

Isn't that ORG fusible link?

1 hour ago, Cheapamanche said:

So I traced the burnt green fusible link to my ignition switch.

Which fusible link was blown?

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21 minutes ago, Ωhm said:

Isn't that ORG fusible link?

Which fusible link was blown?

It's one of the green fusable links coming off my starter relay. According to the manual it's the link connected to my ignition switch. My orange link to the fuel pump and the ecu is fine.

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16 minutes ago, Cheapamanche said:

According to the manual it's the link connected to my ignition switch.

That's fusible link F.

 

21 minutes ago, Cheapamanche said:

It branched off into 3 red wires.

Could it be fusible link H?

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FWIW-

 

I have no idea what the values are of the fused links.


I've asked here in the past and no one else seemed to know. 

 

Links are available, at least at independent stores here and I've asked what the values are, no one here knows either.

 

So, ask again, maybe someone will come up with something. 

 

I decided to go another route. 

 

Guess you'll need to decide also........maybe you can buy used ones from someone here?  Or create your own fused panel?

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4 minutes ago, Jeep Driver said:

I have no idea what the values are of the fused links.


I've asked here in the past and no one else seemed to know.

 

You can take a reasonable guess by looking at what they power and what gauge the wire is...  At the end of the day the fuse is not protecting the device it is hooked to, it's protecting the truck from burning down.

 

I think I replaced most of them with 20A fuses, save for the alternator one.   But I'd have to look.  My harness has about half of it cut out, so it's not exactly a fair representation either. :dunno:

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8 minutes ago, Jeep Driver said:

I've asked here in the past and no one else seemed to know. 

True. Seems to be a tough question to answer. Go low and work your way up.

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I don't think its link h because I have radio and clock power. I don't have an engine bay light and my dog lamps are not hooked up but last I knew they had power. Let me check real quick... so the fog lights still have power. I don't think it's the H fuse link.

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Are there any general guidelines for choosing a suitable fusible link?
Typically, a given harness segment is protected by fusible link that is four gauge numbers smaller. A 14-gauge wire would be protected by an 18-gauge fusible link. A 6-gauge wire would be protected by a 10-gauge link, and so on. Odd number wire gauge sizes like 19, 15, 13 and 11 are counted when sizing a link. The length of a fusible link should not exceed 9".
 

This is the best I could come up with. It seems nobody wants to tell you how to switch to fuses for liability reasons.

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