304 distributer and spark questions

[Petescj]

The top two pics are of my dizzy. Supposedly the only thing keeping my Scrambler from firing is low spark. The wiring diagram he sent was for '74-'75. Does that look like the right one for those years?





What are these two boxes for?





And finally in this spot is usually that motorcraft box with the two plugs. Is that deleted for the earlier years. I'm thinking about dropping a DUI dizzy in it to see if that'll cure my spark woes. Any additional information would be welcome.

 

[lutry]

I think that this is a Prestolite Distributor, as I know, Motorcraft came 1979.
What is the build date of the engine?
If the engine is from 74-75, it should be fine.
Could you post your wiring diagram?
The blue box does not seem to be factory...

 

[Posi]

Prestolite distributor
Blue box is voltage reg
Second box (below) is ignition module
Vac advance is not hooked up
Could be a bad ground causing the low spark among other things.

 

[Petescj]

I think that this is a Prestolite Distributor, as I know, Motorcraft came 1979.
What is the build date of the engine?
If the engine is from 74-75, it should be fine.
Could you post your wiring diagram?
The blue box does not seem to be factory...

My 78 CJ5 used the Motorcraft and I thought I read somewhere that Prestolite lasted till 77. I also remember the Prestolite not getting rave reviews. I was just going by what year the previous owner told me it was a '75 AMC 304 . I'll get a picture of the wiring diagram after work.

Prestolite distributor
Blue box is voltage reg
Second box (below) is ignition module
Vac advance is not hooked up
Could be a bad ground causing the low spark among other things.

By getting the DUI distributer I can cut all that out and run just a hot wire to the distributer correct? Where do I check for grounds or add one? Electrical is easily my greatest weakness by far.

 

[Hedgehog]

Petescj - I'm a big believer in the DUI I put on my 360. The usual warning applies, use the stock gear on your distributor. It's an easy change over. Yes, even though the DUI gear is supposed to be okay, if for no other reason do it for peace of mind. Check the stock gear closely though, you never know you might have a toasted cam gear. I wired directly to the ignition switch, but that won't be easy with the GM column you have. Trace the wire going to your ignition back past the resister to where you get a solid 12v and you are good to go. Another piece of excitement is installing your DUI so it doesn't hit your power steering pump. I installed mine as a distributor normally is located, saw that the wire plug in box on the side of the distributor wouldn't allow it to be properly timed. So I jumped the gear one tooth. This brought the timing around, but the vacuum can hit the water pump hose you can see in your pictures. You probably won't have any problem with that. My engine still has it's air conditioning pump in the way so there was another hurtle for me to jump that you likely won't have trouble with. You can spend crazy money for HEI spark plug wires. I used universal MSD wires. A great kit with the proper HEI wire ends and a crimping tool included.

 

[Torxhead]

Pete, from what I have read thru the years in the CJ type forums, the best replacement for the Prestolite is a DUI. As for for grounds maybe start another post, I for one think the CJ was poorly grounded to save money and can benefit by adding a few plus adding some larger wires in some locations. You should probably look closer at that blue box as it does appear to be some sort of add on looking at those crimp connectors.

 

[Hedgehog]

I don't really think the grounding was bad on a new CJ, I think the grounding can be bad 40 years later. After all no mater what they say metal is metal and electricity will run through metal just fine. I would run the battery ground wire to a nice clean spot on the frame, from that spot run a battery cable with eyes on both ends to a bolt on the engine. It wouldn't hurt to run a similar cable between the heads, you will find empty threaded holes on the back the heads, I use those. Most battery cables will have an extra heavy gauge wire at the clamp. I use that wire to ground the body. From there you can go nuts running ground wires to the dash and maybe one to the rear of your CJ, but since electricity will run in metal I run a ground wire from a frame rail to the rear portion of the body. Where the tail lights are grounded is a good spot. A lot of folks like to run more ground wires all over the place, I'm not a believer, but they are and it certainly can give you piece of mind knowing that your CJ is well grounded. I'll also add a disclaimer, I live in the desert south west, but came from the Adirondacks so I know from what I speak. We don't have the rust you will be dealing with in Pa. While my frame is old and might have cracks in it, there is absolutely no rust on it.

 

[lutry]

This is what the parts book says:

Ignition wiring 74-78



Ignition wiring 79-



Distributor



Parts list

 

[lutry]

Found this for 1974:

http://oljeep.com/gw/74_tsm/3-Electrical(3-1to3-40).pdf

http://oljeep.com/gw/74_tsm/3-Electrical(3-41toEnd).pdf

 

[Petescj]

Petescj - I'm a big believer in the DUI I put on my 360. The usual warning applies, use the stock gear on your distributor. It's an easy change over. Yes, even though the DUI gear is supposed to be okay, if for no other reason do it for peace of mind. Check the stock gear closely though, you never know you might have a toasted cam gear. I wired directly to the ignition switch, but that won't be easy with the GM column you have. Trace the wire going to your ignition back past the resister to where you get a solid 12v and you are good to go. Another piece of excitement is installing your DUI so it doesn't hit your power steering pump. I installed mine as a distributor normally is located, saw that the wire plug in box on the side of the distributor wouldn't allow it to be properly timed. So I jumped the gear one tooth. This brought the timing around, but the vacuum can hit the water pump hose you can see in your pictures. You probably won't have any problem with that. My engine still has it's air conditioning pump in the way so there was another hurtle for me to jump that you likely won't have trouble with. You can spend crazy money for HEI spark plug wires. I used universal MSD wires. A great kit with the proper HEI wire ends and a crimping tool included.

Excellent. I was waiting for you to chime in. I thought you had a thread about the Prestolite awhile back but the search isn't working. Couldn't remember if you got the DUI or not. Thanks for the extra information from your experience.

 

[Petescj]

Pete, from what I have read thru the years in the CJ type forums, the best replacement for the Prestolite is a DUI. As for for grounds maybe start another post, I for one think the CJ was poorly grounded to save money and can benefit by adding a few plus adding some larger wires in some locations. You should probably look closer at that blue box as it does appear to be some sort of add on looking at those crimp connectors.

Thanks for the endorsement on the DUI. Back to the grounds. I looked over the engine compartment and found one ground strap. It went from the frame to the driver side head. I doubt it's doing a good job considering its bolted through the aluminum power steering bracket.

 

[Petescj]

I don't really think the grounding was bad on a new CJ, I think the grounding can be bad 40 years later. After all no mater what they say metal is metal and electricity will run through metal just fine. I would run the battery ground wire to a nice clean spot on the frame, from that spot run a battery cable with eyes on both ends to a bolt on the engine. It wouldn't hurt to run a similar cable between the heads, you will find empty threaded holes on the back the heads, I use those. Most battery cables will have an extra heavy gauge wire at the clamp. I use that wire to ground the body. From there you can go nuts running ground wires to the dash and maybe one to the rear of your CJ, but since electricity will run in metal I run a ground wire from a frame rail to the rear portion of the body. Where the tail lights are grounded is a good spot. A lot of folks like to run more ground wires all over the place, I'm not a believer, but they are and it certainly can give you piece of mind knowing that your CJ is well grounded. I'll also add a disclaimer, I live in the desert south west, but came from the Adirondacks so I know from what I speak. We don't have the rust you will be dealing with in Pa. While my frame is old and might have cracks in it, there is absolutely no rust on it.

I've done the double eye ended battery cable ground before. I'll add that to this project. The wire that comes of the negative battery Cale I usually run to a cleaned spot on the firewall. I'm pretty lucky with my frame considering the shape of the floors. The frame is clean and solid and should make a great grounding point just about anywhere.

 

[Petescj]

Found this for 1974:

http://oljeep.com/gw/74_tsm/3-Electrical(3-1to3-40).pdf

http://oljeep.com/gw/74_tsm/3-Electrical(3-41toEnd).pdf

Thanks for the info. What they have listed for '79 was exactly what I had in my '78. Maybe my '78 was late '78. AMC back then, total crapshoot

 

[Petescj]

Thanks to all of you guys for your responses. Looks like I'm spending some cash on the DUI along with a 600 CFM Edelbrock carb. hopefully I'll get her to fire with your advice and those couple pieces.

 

[Posi]

The 78-79 stock v8 distributor with a gm module is another option as well.
Just a thought on low voltage, I would check to see if it has the 83 factory resistor wire connected in any way to the ignition system. Reason, your replacement 74-75 ignition system does not use one.

 

[Petescj]

Any tips on how to find this wire asks the electrically challenged guy.

 

[lutry]

Maybe this can help:
BASIC WIRING 101, Getting You Started! - JeepForum.com

A bit to read, but seems helpful...

You have to scroll down to end at the ignition wiring.
Or maybe if you do a Google Picture search with:
jeep cj motorcraft ignition resistor
You find a lot of drawings, but for me, it is hard to say which one will fit your Needs.

 

[Posi]

The resister wire (1.35 resistance) is a brown thicker wire running from the dash connector (13f). It then splices into the solenoid/coil wire (red with white tracer).

The way the resistor wire works, when the key is on and engine off it reduces the voltage to the coil to 6v, plus or minus .5. When the key is turned to start position it sends batt voltage to the coil. However, there is not a need to use this resistance with your older distributor, and who knows if or how it is wired up, if at all.

Side note: the above wiring is for my 79 the wiring color/codes for your newer CJ may be different.

Edit: an 82 6 cyl engine bay wiring would be the same 13f dash connector and resistor wire setup.

 

[Petescj]

The resister wire (1.35 resistance) is a brown thicker wire running from the dash connector (13f). It then splices into the solenoid/coil wire (red with white tracer).

The way the resistor wire works, when the key is on and engine off it reduces the voltage to the coil to 6v, plus or minus .5. When the key is turned to start position it sends batt voltage to the coil. However, there is not a need to use this resistance with your older distributor, and who knows if or how it is wired up, if at all.

Side note: the above wiring is for my 79 the wiring color/codes for your newer CJ may be different.

Edit: an 82 6 cyl engine bay wiring would be the same 13f dash connector and resistor wire setup.

Thanks a bunch. I'll look into it after work.

 

[Neuner]

Back to the grounds. I looked over the engine compartment and found one ground strap. It went from the frame to the driver side head. I doubt it's doing a good job considering its bolted through the aluminum power steering bracket.

Not familiar with the V8s but that does seem really odd. I've only seen ground straps connected at or around the engine mounts.