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Discussion Starter · #1 ·
Hi All,
First time poster her. I'm nearing the end of a frame-off rebuild on an '89 YJ. I stripped her down to the frame, removed as much rust as I could, welded new frame end pieces on her, and repainted the frame. I replaced the old rusted tub with a solid undercoated and bedlinered '93 one and put on new front fenders. New shocks and spring shackles, and new brake lines. I left the wiring harness intact as much as possible, only disconnecting to remove the dash and replace the body, and only cut wires at splices for the rear lights. It's a 4.0L engine with a weber carb, but still had all the old emissions stuff hooked up and the ECM was connected when I started the project. It started and ran fine at the beginning of the project.



My plan was to get it running, then do a nutter bypass and remove as much of the old emission stuff and simplify as much as the vacuum mess as I could get away with. The problem is now it appears that I am not getting any power to my fuse panel, so it obviously won't start. I checked and cleaned the grounds and connectors leading from the battery to the fuse panel plug. The plug at the back of the fuse panel (engine side of the firewall) has 12V power coming into one of the pins that leads into the back of the fuse box, and another pin reads about 6V, but I have no idea which pins should be powered and which shouldn't. I'm not picking up any voltage across any fuses in the fuse panel itself.



Am I missing something obvious here? Hoping someone with experience in YJ electronics can provide a simple fix, or give me something else to try. Any advice is appreciated.
 

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Welcome to the Forum DIrtdoc72,

Find a post by Got it at last. Look in his signature for a link to several Factory Service Manuals. The schematics are most likely in the electrical troubleshooting section.

Good Luck, L.M.
 

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When you find the schematics that LM is talking about you need to concentrate on the Relay that is supposed to be attached to your firewall on the passenger side below your battery box. When you turn your key to on and start that relay is what sends all your power to your power distribution and fuzes. On your bulkhead connector left side as you face it from the front of the jeep you will have 2 12gauge red wires, 1 12 gauge red w/white stripe, and 1 14 gauge orange w/white stripe. Those should be going to that relay on your firewall. I would imagine your 89 is identical to mine when it comes to wiring. If you removed that relay during your restoration you need to find it and get it back into your wiring. That little relay is the most important part of your engine compartment wiring. Hope that helps.
 

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starter relay

I don't know how to find the reference to "got in last" as mentioned above (I am new to the forum). I am trying to trouble shoot my recently purchased 88 yj...I've been working on upgrades with new motorcraft 2150 carb and HEI ignition...Jeep has been running fine (except for a choke issue)...yesterday while pulling into garage, the engine stopped...when I tried to start it everything was dead in the ignition system (head lights work fine, battery is good)...ignition fuse under the dash is ok...I suspected some sort of fusible link in the circuit but needed an electrical diagram of an '88...I did a google search and found some but not so legible. Then I saw your posting about the starter relay. I checked my jeep and found that I have an inline fuse in the line from the battery to the relay. I have power coming out of the inline fuse so I know its good. This leads me to the relay. I have a basic question, "do these relays go bad" and "what could cause them to fail"...they are not very expensive so I'm inclined to just buy a new one. I am concerned about what could cause it to fail. Any thoughts or insight would be appreciated. The existing relay markings are : MB402-12V 40A In the pic of the relay, can you explain the circuit notation on the bottom of the relay? 87 -->30 and 86 --> 85 tks in advance
 

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Welcome to the Forum Dogbreth46,

"Got it at last" is a forum member that often posts. Look through other threads for a post by him.
His signature is the few lines at the bottom of his posts that tell a bit about him and his Jeep. The link is the part that's underlined.
Click on that link and then click on the Factory Service Manual that fits your year jeep. The schematics should be in the electrical troubleshooting section.

It would be best to start your own thread about your particular issue. That way the answering posts don't get confusing.

Good Luck, L.M.
 

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'89 YJ 4.2 with MC-2150 Carb & HEI, 2-1/2" Ex. AX-15, NP231 SYE, Adams shafts, F&R ARB, 3
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Welcome D-Doc. FSM Link is at the bottom of my Sig below.

Am I correct in assuming that you are running a '93 Tub with all the '93 wiring cab, engine and computer, OR are you running an '89 electrical under the hood with '93 in the cab? 89 is wired for the power distribution from fuse panel in cab bye-brake, '93 power comes from PDC by the battery. you could be having some compatibility issues here which is gonna require tracking everything down circuit by circuit.

You're gonna want to pull up and look at both wiring diagrams ('89 and '93) to compare.
 

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'89 YJ 4.2 with MC-2150 Carb & HEI, 2-1/2" Ex. AX-15, NP231 SYE, Adams shafts, F&R ARB, 3
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I don't know how to find the reference to "got in last" as mentioned above (I am new to the forum). I am trying to trouble shoot my recently purchased 88 yj...I've been working on upgrades with new motorcraft 2150 carb and HEI ignition...Jeep has been running fine (except for a choke issue)...yesterday while pulling into garage, the engine stopped...when I tried to start it everything was dead in the ignition system (head lights work fine, battery is good)...ignition fuse under the dash is ok...I suspected some sort of fusible link in the circuit but needed an electrical diagram of an '88...I did a google search and found some but not so legible. Then I saw your posting about the starter relay. I checked my jeep and found that I have an inline fuse in the line from the battery to the relay. I have power coming out of the inline fuse so I know its good. This leads me to the relay. I have a basic question, "do these relays go bad" and "what could cause them to fail"...they are not very expensive so I'm inclined to just buy a new one. I am concerned about what could cause it to fail. Any thoughts or insight would be appreciated. The existing relay markings are : MB402-12V 40A In the pic of the relay, can you explain the circuit notation on the bottom of the relay? 87 -->30 and 86 --> 85 tks in advance
Your HEI ignition is the one of the simplest fixes. Are you getting 12v (key on) power to the HEI and no Starter, or Starter turns and Jeep won't start, or none of the above?


We always start ignition diagnosis with checking your battery cable connections to both hot side and grounds. If your entire system is dead, Its 80% of the time corroded, poor or loose battery cables / connections
 
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The existing relay markings are : MB402-12V 40A In the pic of the relay, can you explain the circuit notation on the bottom of the relay? 87 -->30 and 86 --> 85 thanks in advance
86 - 85 is the relay coil, when supplied with 12 Volt DC, it will energize and closes the normally open contact between 87 - 30.
 

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Electrical --starter relay

Your HEI ignition is the one of the simplest fixes. Are you getting 12v (key on) power to the HEI and no Starter, or Starter turns and Jeep won't start, or none of the above?


We always start ignition diagnosis with checking your battery cable connections to both hot side and grounds. If your entire system is dead, Its 80% of the time corroded, poor or loose battery cables / connections
When I installed the new HEI, I ran a new wire from the HEI to the wire in the bundle that passes thru the firewall on the drivers side. If there was a problem with the HEI wire, it would (?) only affect the starting of the engine. My entire panel is dead as if the fuse were blown (fuse is good).The battery terminals are clean, new battery and good ground.

I ran a jumper from the positive side of the battery to the starter solenoid on the starter and the starter cranked. This tells me that the starter / solenoid is good and that I am not getting power to the solenoid.

I was able to download the files from your dropbox (tks)...I looked at the electrical diagram(s) and the image on panel #7 didn't make much sense to me--the colors didn't match either (I think most of the wires in my 88 are original)

EUREKA! just found the problem...found a broken wire inside the terminal connector on a wire wire from the battery...another left over from the previous owner... thanks everybody for their suggestions
 

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Discussion Starter · #10 ·
Thanks for the help. With the help of the electrical schematics in the FSM I tracked down the problem, it was a broken wire connector on the starter relay. Ended up getting a new starter relay and now I have power in the dash and the engine turns over. FYI I'm using the '89 wiring harness. The only thing that is '93 is the tub.
Now on to dealing with the vacuum mess and doing the nutter bypass. Know any good posts that diagram where the vacuum lines should go if removing the bowl and charcoal canister, and with a Weber carb?
 

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'89 YJ 4.2 with MC-2150 Carb & HEI, 2-1/2" Ex. AX-15, NP231 SYE, Adams shafts, F&R ARB, 3
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There are a few guys on here that have seen everything, I myself not so much on a carbed 4.0. I would leave the canister in as there is a vent line to the fuel tank and the PCV valve also ties into the Carb and Canister. You may end up with some wonky venting/vacuum issues. On the 4.2 you only need the vac advance to the dist, a fresh air breather cap, PCV to the air cleaner to re burn crankcase gases which tees to the canister, and a line from the CTO to the canister. If you are still using the CAD vacuum for your 4WD you will need to keep the vacuum line from the manifold teed off the line that goes into the cab to run your defrost gates.

I'm sure one of the guys that has done Carbed 4.0's will post up shortly, but in the meantime you can run through the vacuum diagram in the FSM and eliminate anything that ran off of an electrical solenoid valve
 
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