401 Ignition Issues

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ainokea
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401 Ignition Issues

Post by ainokea » Tue Nov 23, 2021 8:20 pm

'75 Cherokee S (Chief) - 401 cid
Not sure exactly what the question is but here's the problem:

Started working on installing a new fuel filler tube, which lead to me repairing the electric back window roller upper, which caused me to inadvertently leave the ignition switch on. Prior to that she started and ran fantastic.

I was thinking coil (no checked out fine), points condenser (maybe but bought the wrong one - maybe), ignition module (can't locate it).

No spark at the plug(s) but have 12 volts to coil and 12 volts from coil to distributor.

The thing I am trying to figure out first and foremost is what distributor I may have, because I do not think it was original to the 401. Also trying to locate the ignition module. I have a black cube which I think is a relay mounted on the fender, but no ignition module that I can find. Struggling to find a new cap and rotor and points and condenser since I can't identify the distributor - which at this point do not seem to be the issue, although the points are fairly burned - so it needs to be done anyway.
Last edited by ainokea on Wed Nov 24, 2021 10:22 am, edited 1 time in total.
'75 Cherokee S (Chief) Levi, '99 XJ Classic, '00 XJ Sport, '16 KL Trailhawk
'86 Porsche 944, '56 GMC 1.5 ton flatbed, '78 Yamaha DT 175, '16 VW Golf

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Stuka
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Re: 401 Ignition Issues

Post by Stuka » Tue Nov 23, 2021 10:42 pm

'75 won't have points from the factory. It should have a Prestolite ignition. These have a plastic, dual-diaphragm vacuum advance. It will look like this one here: https://www.napaonline.com/en/p/NRD484690

This is an electronic ignition distributer that uses a hall effect sensor. They are also considered to be the worst ignition to ever be used in a Jeep. Most people swap them out for points or HEI.

And as it happens, these ignitions will destroy themselves if they key is left on. I did this very thing with my '75 once. Trying to recall (this was about 20 years ago), if it was the ignition module (gold box on passenger side fender). Ultimately after this ignition left me stranded several times (the ignition modules are especially bad), I switched to points, and then ultimately HEI.

Now, perhaps a previous owner swapped in a points distributer for the very reasons I mention above. If that's the case, the points probably got burned up and you will need to replace them. When doing so you have to set the dwell. This requires a dwell meter to set correctly. BUT, you can get dang close by setting the gap with a matchbook. Or, I think the TSM has a gap size to start with.
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Re: 401 Ignition Issues

Post by tgreese » Wed Nov 24, 2021 5:15 am

Stuka mostly covers it -

If you have the original ignition parts, look at page 3-41 forward in the '76 TSM here: https://oljeep.com/edge_76_tsm.html Jeep used the Prestolite BID (breakerless inductive discharge) ignition 1975-1977. The '76 and '77 TSMs will cover this system, and should be helpful.

Jeep supplied Delco points ignition in 1974, and that TSM is also on the site I linked above.

You can get some of the parts for the BID system, but most owners would replace it. It's unique in how it generates the spark trigger, and not compatible with any of the other ignition types that can be used with this engine. There are several possibilities for replacement, if you choose to go that way.

All the GM HEI distributors for these engines are aftermarket parts. From 1978 on, Jeep used the Motorcraft Duraspark distributor and ignition module, which is another possible substitute for the BID. I am running the Duraspark distributor with a HEI ignition module in my CJ-6. Many other mixing and matching options are possible.
Tim Reese
Maine beekeeper's truck: '77 J10 LWB, 258/T15/D20/3.54 bone stock, low options (delete radio), PS/PDB, hubcaps.
Browless and proud: '82 J20 360/T18/NP208/3.73, Destination A/Ts, 7600 GVWR
Copper Polly: '75 CJ-6, 304/T15, PS, BFG KM2s, soft top
GTI without the badges: '95 VW Golf Sport 2000cc 2D
Dual Everything: '15 FCA Jeep Cherokee KL Trailhawk, ECO Green
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will e
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Re: 401 Ignition Issues

Post by will e » Wed Nov 24, 2021 7:00 am

Welcome to the board. A few pics of your setup will help a lot.
81 Waggy 'WILL E' Retired
82 Cherokee WT - SOA/SF/high steer/Alcan springs/agr box/Borgeson steering shaft/AMC 401/performer/holley TA/HEI/BeCool/727/ALTAS (2.0/2.72/5.44)/D60 Snofighter(Yukon Zip,hubs,stubs,4.56)/14 Bolt (FF,BF shave, Discs, ARB,Artec Truss)/MTR 37X12.5/Corbeau XRS Baja & 5 point retractable harness/Hella Aux lights/tuffy console/killer32 sliders/Evil Twin bumpers, rack and roll cage/WARN 8000/TT Fabworks steering brace/dual batts/custom TC skid plate/ARB fridge

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Re: 401 Ignition Issues

Post by ainokea » Wed Nov 24, 2021 1:58 pm

Thanks will e! I have gained a lot from this site already on the tailgate window repair. That was FUN!

Here are some photos of my distributor for reference. Was a struggle for me getting the photos uploaded. Hoping I become a little more proficient next time.

Cheers! And thanks for all the input so far!
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'75 Cherokee S (Chief) Levi, '99 XJ Classic, '00 XJ Sport, '16 KL Trailhawk
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Re: 401 Ignition Issues

Post by Stuka » Wed Nov 24, 2021 3:00 pm

Ok, so the distributer has definitely been converted to points. Did you just put in those points?

As for the black box, that's definitely not stock, even for an FSJ that came with points. It looks like a transformer inside. I wonder if its setup to send a higher voltage to the coil when the ignition switch is in the start position? In a stock setup, the starter solenoid did this. There should be two ports out the front, one has an I, and one has an S. The S would bypass the ballast resistor, and send a straight 12V. But then when just running, I would supply 7-8V. Running a straight 12V will kill the points pretty quick. But it does give a hotter spark that makes cold starts easier.

Do you have a multimeter? I think your next step is to trace out voltages at various points. Something is open someplace. You can also measure the resistance of the coil to find out if its bad.
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Pevious Jeeps: 1981 J10, 1975 Cherokee, 2008 JK, 2005 KJ, 1989 XJ


letank
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Re: 401 Ignition Issues

Post by letank » Wed Nov 24, 2021 5:28 pm

Welcome,

Image

this looks like the external voltage regulator, see section 3 from Tom's site, here: https://oljeep.com/edge_76_tsm.html figure 3-6

check the wires Green, Black and Yellow
Michel
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Re: 401 Ignition Issues

Post by tgreese » Wed Nov 24, 2021 7:08 pm

The Motorcraft alternator Jeep supplied with V8s in 1976 does indeed use a mechanical voltage regulator. This appears to be a mechanical voltage regulator.

However, a '75 with a V8 should have the Motorola alternator, which comes with a transistorized (solid state) voltage regulator. No coils and contacts like the OP's regulator. Additionally, this regulator looks like an antique compared to the Motorcraft regulators I've seen.

Motorcraft-type regulators: https://www.rockauto.com/en/catalog/jee ... lator,4884

Motorola-type regulators: https://www.rockauto.com/en/catalog/jee ... lator,4884

Suggest the OP post some pictures of his alternator. You can mix and match alternators and regulators if you know what you are doing, but the original equipment would have been specific to the plug on the harness and the holes in the inner fender. A direct replacement of factory equipment, no wire splicing and such.
Last edited by tgreese on Thu Nov 25, 2021 7:35 am, edited 2 times in total.
Tim Reese
Maine beekeeper's truck: '77 J10 LWB, 258/T15/D20/3.54 bone stock, low options (delete radio), PS/PDB, hubcaps.
Browless and proud: '82 J20 360/T18/NP208/3.73, Destination A/Ts, 7600 GVWR
Copper Polly: '75 CJ-6, 304/T15, PS, BFG KM2s, soft top
GTI without the badges: '95 VW Golf Sport 2000cc 2D
Dual Everything: '15 FCA Jeep Cherokee KL Trailhawk, ECO Green
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Re: 401 Ignition Issues

Post by Stuka » Wed Nov 24, 2021 7:09 pm

letank wrote:
Wed Nov 24, 2021 5:28 pm
Welcome,

Image

this looks like the external voltage regulator, see section 3 from Tom's site, here: https://oljeep.com/edge_76_tsm.html figure 3-6

check the wires Green, Black and Yellow
That crossed my mind, but its connected to the ignition?

And its a different size and shape than the factory Motorola voltage regulator.
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Re: 401 Ignition Issues

Post by tgreese » Wed Nov 24, 2021 7:53 pm

It might be a lighting relay. The relay coil wire seems very fine for a mechanical voltage regulator. And an old-school voltage regulator has two contacts and coils, IIRC. Maybe. Trace through what it connects to.
Tim Reese
Maine beekeeper's truck: '77 J10 LWB, 258/T15/D20/3.54 bone stock, low options (delete radio), PS/PDB, hubcaps.
Browless and proud: '82 J20 360/T18/NP208/3.73, Destination A/Ts, 7600 GVWR
Copper Polly: '75 CJ-6, 304/T15, PS, BFG KM2s, soft top
GTI without the badges: '95 VW Golf Sport 2000cc 2D
Dual Everything: '15 FCA Jeep Cherokee KL Trailhawk, ECO Green
Blockchain the vote.


will e
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Re: 401 Ignition Issues

Post by will e » Wed Nov 24, 2021 8:38 pm

Lots to digest. Thanks for the pictures that does help!

Guys, correct me if I am wrong but a dwell meter can help him diagnose if the points are the problem?

Regarding the 'use without external resistor' on the coil. Some coils have an internal resistor and others do not. Most, if not all, of our jeeps had a resistor wire from the ignition to the coil. You'll want to take a volt meter and compare the voltage at the battery and the voltage on the positive side of the coil (with the negative of the volt meter on the battery). Do this with the ignition switch in the ON position. The voltages will either be close or there will be a drop of several volts at the coil if there is a resistor wire in the circuit. You'll want to check this fairly soon.

Do you have a basic understanding of how a points ignition system works? This video is pretty good:

https://www.youtube.com/watch?v=HAQXlhOog2s

They are super simple but mechanical so they do require proper setting. However, to get the engine to idle the gap does NOT have to be 'perfect'. Proper gap is more important at higher RPM, so don't panic too much getting them set perfect to get the engine running. There shouldn't be any 'ignition box' associated with a point ignition.
81 Waggy 'WILL E' Retired
82 Cherokee WT - SOA/SF/high steer/Alcan springs/agr box/Borgeson steering shaft/AMC 401/performer/holley TA/HEI/BeCool/727/ALTAS (2.0/2.72/5.44)/D60 Snofighter(Yukon Zip,hubs,stubs,4.56)/14 Bolt (FF,BF shave, Discs, ARB,Artec Truss)/MTR 37X12.5/Corbeau XRS Baja & 5 point retractable harness/Hella Aux lights/tuffy console/killer32 sliders/Evil Twin bumpers, rack and roll cage/WARN 8000/TT Fabworks steering brace/dual batts/custom TC skid plate/ARB fridge

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Re: 401 Ignition Issues

Post by ainokea » Fri Nov 26, 2021 8:23 pm

Well...I thought I understood how the ignition system worked. I was a little off. That's a great video and forced me to draw out how I think it works, which helped, and got me to draw the wiring out as well. I'm not sure what I did to get the truck running but going through the process above, and checking voltage as I went, I finally got spark back to the points. The engine still wouldn't fire so I suspected weak spark. So I put the new points back in, and installed (another) new condenser. After that it fired right off! I guess me leaving the ignition on burned up the points and condenser, as you all suggested. This would not have been so tough if I knew what the distributor and other parts were so I could have gotten correct replacement parts.

So...I ended up with new points, cap, rotor, condenser. Put the old coil back in for now, since I don't have an in-line ballast resistor. Sure was good to hear it fire up. I went for a drive and rolled up the tailgate window, and then filled the tank with gas! A big day!

Time to work on the '99 XJ for a bit then back to replace the ignition system on the Chief. I'm sure I'll be coming back to this post to implement what you all suggested.

Thanks so much for all the help!!

Here's the wiring diagram as far as I took it, and a few other photos for what it's worth.
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'75 Cherokee S (Chief) Levi, '99 XJ Classic, '00 XJ Sport, '16 KL Trailhawk
'86 Porsche 944, '56 GMC 1.5 ton flatbed, '78 Yamaha DT 175, '16 VW Golf

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Re: 401 Ignition Issues

Post by tgreese » Sat Nov 27, 2021 5:24 am

JMO - it's really hard to measure low resistances, like the primary of an ignition coil, with an inexpensive multimeter. I suggest you use buy a spare ignition coil and swap it in to test. A spare coil is a replacement part you'll want to carry anyway, if you use this Jeep as a Jeep and go remote places.

The box with the nichrome resistors on the bottom is definitely an older type mechanical voltage regulator. It regulates the alternator current to recharge the battery after starting. You have a mix of parts from different vehicles.

1974 was the last year for points ignition in a Jeep. If you look at the '74 wiring diagram, and read the legend that goes with the wire numbers, you will see they used a resistance wire as a ballast resistor for the ignition coil. The easiest sub for this IMO is a ballast resistor that you can mount on the firewall and run the coil wire through. You can ask for a ballast resistor for a '70s Dodge, and that will work - like a Standard RU-37 - https://www.rockauto.com/en/catalog/dod ... istor,7052
Tim Reese
Maine beekeeper's truck: '77 J10 LWB, 258/T15/D20/3.54 bone stock, low options (delete radio), PS/PDB, hubcaps.
Browless and proud: '82 J20 360/T18/NP208/3.73, Destination A/Ts, 7600 GVWR
Copper Polly: '75 CJ-6, 304/T15, PS, BFG KM2s, soft top
GTI without the badges: '95 VW Golf Sport 2000cc 2D
Dual Everything: '15 FCA Jeep Cherokee KL Trailhawk, ECO Green
Blockchain the vote.


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Re: 401 Ignition Issues

Post by will e » Sat Nov 27, 2021 7:38 am

That's awesome that you got it running AND learned a bit more about how it works. How exciting for you when it fired up. I've been there and done that and the feeling of joy and relief is amazing.

In the drawing, what is the 'switch'?

What I would do is measure the volts at the coil with the engine running. Put the red lead on the positive and the negative lead on the battery. Then move the positive to the battery. If the voltages are about the same you do not have a resistor wire.
81 Waggy 'WILL E' Retired
82 Cherokee WT - SOA/SF/high steer/Alcan springs/agr box/Borgeson steering shaft/AMC 401/performer/holley TA/HEI/BeCool/727/ALTAS (2.0/2.72/5.44)/D60 Snofighter(Yukon Zip,hubs,stubs,4.56)/14 Bolt (FF,BF shave, Discs, ARB,Artec Truss)/MTR 37X12.5/Corbeau XRS Baja & 5 point retractable harness/Hella Aux lights/tuffy console/killer32 sliders/Evil Twin bumpers, rack and roll cage/WARN 8000/TT Fabworks steering brace/dual batts/custom TC skid plate/ARB fridge

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Re: 401 Ignition Issues

Post by Stuka » Sat Nov 27, 2021 9:45 am

Glad you got it running!
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Re: 401 Ignition Issues

Post by tgreese » Sat Nov 27, 2021 9:55 am

will e wrote:
Sat Nov 27, 2021 7:38 am
... If the voltages are about the same you do not have a resistor wire.
Just pointing out - a '75 does not have a resistance wire. The Prestolite stuff does not have a ballast resistor.

Also, you can look at the wire that should be a resistance wire in the '74 TSM wiring diagram. This is wire #38. A resistance wire is a single-stranded nichrome wire, which looks completely different from the stranded copper wire used in the rest of the Jeep. Like the bard says, you can see a lot by looking. Second, I would measure the resistance of the wire with my multimeter. You may not get an accurate measurement of the couple of ohms resistance of the resistance wire, but you can easily tell the difference between the resistance wire and a piece of plain copper wire. Touch the probes together, then compare the wire resistance to that reading. Plain copper wire will show very close to no difference. Resistance wire will be different by at least an ohm, maybe two.
Tim Reese
Maine beekeeper's truck: '77 J10 LWB, 258/T15/D20/3.54 bone stock, low options (delete radio), PS/PDB, hubcaps.
Browless and proud: '82 J20 360/T18/NP208/3.73, Destination A/Ts, 7600 GVWR
Copper Polly: '75 CJ-6, 304/T15, PS, BFG KM2s, soft top
GTI without the badges: '95 VW Golf Sport 2000cc 2D
Dual Everything: '15 FCA Jeep Cherokee KL Trailhawk, ECO Green
Blockchain the vote.

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Re: 401 Ignition Issues

Post by ainokea » Sat Nov 27, 2021 6:34 pm

Yes it's been confusing for me with the whole "use without external resistor" thing. I'm wondering if one of the previous owners had a tractor he cannibalized for parts. On a side note - when I was a kid a had '75 Ramcharger, with a 440 Magnum (originally a 318 truck I think - not that displacement matters as far as ignition goes - right?), that had an ignition module and ballast resistor, both mounted on the firewall, and no points (it had a magnetic pick up). I used to have to change the ign. module out quite a bit. I also had to frequently retard the timing to get it to start it was so cold blooded, but I digress. I've been called a "parts changer" and that's typically what I do, but it doesn't go well when I don't know what I have. I'm still not sure what I have.

I don't think I have a resistor wire, but will do that voltage test anyway that will e recommended.

Will e - also the switch in the drawing is for the ignition switch. I may have it wrong.

I'm thinking HEI is the way I'll go, but for now will take Tim's advice and get a ballast resistor and use one of the two new coils I bought (long story why I have two but I do), then I'll have a spare. I do like having spare parts in the truck and do plan on taking her off road. Would love to drive over Engineer Pass and get some nice photos...someday.

This truck does not have a lot of power, which will be a topic for a future search or new thread, but maybe I have weak spark and it is related to the ignition? Are the 401s just too under powered? The guy I bought it from put 33 inch tires on it, which I know doesn't help, but dang she is SLOW. Reminds me of the same year Ramchargers and Traildusters with 440 boat anchors in them. Mine was a '70 440 Magnum which had tons of horsepower (the manual transmission helped too I think). Sorry getting a little sidetracked, and again a topic for a different forum, but what is the best "spark related" way to get the 401 running a little stronger. I also has a buddy who is into AMXs and had some pretty strong 390s! Although the most powerful one had a Chevy 454 in it, oh I miss those cars! TMI? Anyway - looking forward to try and get my 401 a little more hp. Might as well start with the ignition system right? I have new plugs and wires too...just need to put 'em in!
'75 Cherokee S (Chief) Levi, '99 XJ Classic, '00 XJ Sport, '16 KL Trailhawk
'86 Porsche 944, '56 GMC 1.5 ton flatbed, '78 Yamaha DT 175, '16 VW Golf

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Re: 401 Ignition Issues

Post by tgreese » Sun Nov 28, 2021 8:59 am

You understand the resistor? The resistor limits current to the coil. You can put the resistor anywhere in the circuit - between the ignition switch and the points - and it will have the same effect. The factory circuit will bypass the resistor for starting, improving the spark for starting. Putting the resistor inside the coil is one option, but it eliminates the resistor-bypass feature for starting.

What's your axle ratio? Tall tires plus tall gears do not help performance. I would make sure my engine was tuned up and not tired before I started adding aftermarket gear to improve performance. Compression test, wet and dry, plus oil pressure, full-hot idle and at cruise.

That said, there are plenty of ignition upgrades available for these engines. You could keep the points distributor and add a capacitor discharge module like the MSD 6A to get a hotter spark. The 6A will trigger from the points signal, and then relieves the points from switching the coil. Relieved of their coil-switching duty, the points will last a looong time, until the fiber block on the points wears out. Also, if the module ever fails, you can go back to points ignition with some wiring changes and get back to civilization or to work or wherever.
Tim Reese
Maine beekeeper's truck: '77 J10 LWB, 258/T15/D20/3.54 bone stock, low options (delete radio), PS/PDB, hubcaps.
Browless and proud: '82 J20 360/T18/NP208/3.73, Destination A/Ts, 7600 GVWR
Copper Polly: '75 CJ-6, 304/T15, PS, BFG KM2s, soft top
GTI without the badges: '95 VW Golf Sport 2000cc 2D
Dual Everything: '15 FCA Jeep Cherokee KL Trailhawk, ECO Green
Blockchain the vote.

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