1968 J3000 -Ignition and Fuel Tune Up

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Re: Rough/ Erratic Idle on Cold Start

Post by Harry Dawg »




Last edited by Harry Dawg on Sun Dec 11, 2022 7:29 am, edited 1 time in total.
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Re: 1968 J3000 -Ignition and Fuel Tune Up

Post by Harry Dawg »

Also editing the title incase it makes it easier for another person to find this info in the future.

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Re: Rough/ Erratic Idle on Cold Start

Post by tgreese »

This is a Buick? I've noticed Jeep recycles their TSM drawings, even though the details aren't exactly right. The exploded drawing looks right to me. Look on RockAuto at ca 1970 Buicks with the 350, and you'll see your distributor design. Your distributor should have Delco stamped on it somewhere if it's OEM (which I think it is).

Dwell on these distributors is really easy to adjust. A 1/8" hex key on a flexible shaft with screwdriver handle is the special tool for it, but any 1/8" hex key will work. Beware the shock hazard. The special tool is handy, both for reach and insulation. You'll also need a meter.

In principle you can get in the ball park of dwell angle with a feeler gauge, but with how hidden the contacts are in situ, that may be difficult in this case. Note that dwell also affects your timing setting.

I would make another trip to Harbor Freight and buy their multimeter with dwell/tachometer built in. Summit or Amazon will have a wider choice, if you want to wait.
Tim Reese
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Browless and proud: '82 J20 360/T18/NP208/3.73, Destination A/Ts, 7600 GVWR
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Re: 1968 J3000 -Ignition and Fuel Tune Up

Post by Harry Dawg »

This is an AMC 327.

I removed the post related to the distributor components, as the blown out diagram I posted was for the "High Torque" engines, and not the Vigilante.

Here is the distributor diagram for the 327, which has the cams positioned above the condenser. Image

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Re: 1968 J3000 -Ignition and Fuel Tune Up

Post by tgreese »

Same story for the 327 -

https://www.rockauto.com/en/moreinfo.ph ... 08&jsn=548

It's a Delco distributor. Looks like it shares a distributor cap with the small block Chevy.
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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
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Re: 1968 J3000 -Ignition and Fuel Tune Up

Post by Harry Dawg »

As far as dwell angle, points gap, and a few other things go, I am still contemplating how I will move forward.

To adjust these settings the circuit breaker assembly must be installed. Being that the cams are positioned above all this makes it more difficult.

I don't know that it will be possible to set using a feeler gage once installed, but I believe you must set this manually to start off. According to the TSM "After replacing the contact set, rotate the crankshaft until the distributor cam holds the distributor points to a wide open position. If the point gap is not .16", loosen the contact set mounting screw and adjust the point gap to the proper dimension.

To throw one more monkey wrench in the plan, the contact set is different from the factory, and I have an unknown wire in the mix.

As you can see from the photo, my condenser does not have a lead hold down screw, and I only removed one wire versus the 3 shown in TSM. I also am lacking the "condenser lead" wire Image

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Re: 1968 J3000 -Ignition and Fuel Tune Up

Post by Harry Dawg »

One of the mystery wires has been located. Looks like it grounds out to the distributor housing.

I guess this unit just doesn't use a condenser lead...

Next is to reinstall points and attempt to set gap with a feeler gauge.

Still thinking about dwell as I work to understand the concept. Image

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Re: 1968 J3000 -Ignition and Fuel Tune Up

Post by tgreese »

That design of points is interchangeable with the separate points and condensor, as I recall. I'd say that's not an issue here.

JMO - these points retain their setting when removed; if the engine runs at all, I would skip the feeler gauge and set the dwell from a meter. IMO you need to own a dwell meter to tune up points ignition. The dwell defines how the rotation is divided between charge and discharge for the coil. The slower the engine runs, the less difference this makes, and setting the gap is meant to get you into a range where the engine will run.

Condensors do fail (modern condensors seem particularly crappy), and it's hard to test them beyond trying a replacement. Looking at RockAuto ('66 AMC Ambassador 327 with Delco ignition), these consumable ignition parts are the same as most Chevy V8s. Widely available, if you want to replace them.

I'd start with plugs, wires, cap, rotor, points, condensor if I had never tuned the car before. IME wires are particularly suspect; often (usually) neglected. You want to know these parts history, and what you have now can be trail spares.
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
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Re: 1968 J3000 -Ignition and Fuel Tune Up

Post by Yeller »

They do look good. The contacts in the points are what really matter. Very minute deposits create misfires sitting is very hard on them. In my opinion unless you just enjoy tinkering with ignition install a Pertronics module and put the points in the glovebox just in case.

https://pertronixbrands.com/collections ... gK81PD_BwE
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Re: 1968 J3000 -Ignition and Fuel Tune Up

Post by Harry Dawg »

I reinstalled the points and condenser.
Still had a misfire. I adjusted the dwell according to TSM (1/2 turn counter clockwise once the engine is misfiring), and it made it even worse. It did look like the points were too close together at widest point, but I couldn't get a feeler gauge in there to confirm (too tight with cam weights on top).

Going to purchase new points and condenser, rotor, cap, plug wires. While I am at it, I figured I'd replace the ignition coil too. I just tested the ignition coil and got the following ohm reading.

Primary coil: .6 OHM @ 200 range setting
Secondary coil: 4.06 OHM @20K range setting.

I couldn't find any specifications for acceptable ranges in the TSM, plus it's aftermarket so I don't know that really helps me narrow it down.

Trying to trace the rats nest of wiring to each part so I can determine what the most safe, reliable and simple path forward is.

The Pertronix kit looks like it would tuck up nicely under the cam weights, which would eliminate the current issue of lack of access to the circuit breaker assembly.

Not our of the question, but I need to better understand it's function before making a decision. Going to watch so YouTube videos on a setup like this.


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Re: 1968 J3000 -Ignition and Fuel Tune Up

Post by tgreese »

Re the coil, do you really mean 4 ohms? I would measure 4 ohms on the lowest setting. The secondary is from the center post to the positive of the primary.

First I would look that the coil makes a strong blue-white spark. Usually when they fade away the spark gets yellowish and barely jumps a 1/4" gap. Don't you have a CD box too? That will make the spark stronger, and may mask a weak coil.

May as well get the coil. Any Jeeper should carry a spare coil IMO. BTDT.

Those the have the Pertronix kit like it. Seems pretty reliable. It replaces the points with a big transistor, and does not do anything to change timing or spark strength. Lower maintenance mostly.
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
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Re: 1968 J3000 -Ignition and Fuel Tune Up

Post by sierrablue »

Also just something to be aware of--since it's a Delco points distributor, it only has about 6-8 degrees of mechanical advance. I'm not sure how the AMC 327s are with timing, but for the B350, this is nowhere NEAR enough advance there, causing an incredibly irritating stumble on acceleration. Not sure if you can, but if you can get an HEI distributor for it, that'd be a cheap/easy way to upgrade it. They run for like $100, and I think you should be able to swap the gear on the bottom. And then if you want to set the curve and adjust the vacuum advance and such down the road, you can. On those the coil goes in the cap. You can also gap the plugs farther with the hotter spark and such.

When I swapped to HEI it made it consistent--the erratic idle, hard starts, occasional missing, and stumble (that was due to the timing though) all went away. Now, that's not all HEI specific--but the consistency an electronic ignition thing.

It's entirely possible that I had a weak coil but it shouldn't matter--most of the time, if a coil is bad, it just dies. And in my case the points were burning up so I don't think the coil was the problem.
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Re: 1968 J3000 -Ignition and Fuel Tune Up

Post by Harry Dawg »

Sorry. I am not well versed in electrical terminology.

That is correct. It appears to be 4K ohms.

On the lowest setting (200) I don't get any ohm read out at all.

Primary is .6 ohms on the 200 range read out.

I tested it using a spark testing tool ( one of those that catches it in a glass ) and it was making solid, consistent spark.

ImageImage

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Re: 1968 J3000 -Ignition and Fuel Tune Up

Post by tgreese »

This is a hot aftermarket coil (similar to the Ford TFI or GM HEI coil) of some kind. 4K is reasonable for the secondary, I think. On the primary, that includes your lead resistance. Touch the leads together and subtract that from your reading. Is that your capacitor discharge unit on the inner fender? Any brand showing?

There's no aftermarket distributor (HEI or otherwise) available for the AMC 327 that I know of. If you have a good OEM distributor, I'd expect that's about the best you can do aside from some custom machined solution. The AMC forum may know of something ... https://theamcforum.com/forum/forums.html

I suspect the ignition is working like it's supposed to. You just have something out of tune or mixed up, like the ignition wires out of order or such. Did this truck run smoothly when it came to you? Points ignition can be static tuned to get in the ballpark. Done all the time for VWs; look online for instructions.
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 Chryco Jeep Cherokee KL Trailhawk, ECO Green
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Re: 1968 J3000 -Ignition and Fuel Tune Up

Post by Harry Dawg »

Yes.

This is a Summit Street and Strip Multi-Spark Capacitive Discharge Ignition System.

I did see one Mallory Mini-Mag on eBay that the seller claimed to fit this motor, but with a $200 price tag for an untested part I am not willing to roll the dice.

I'd rather avoid removing distributor anyways.

The CD box is wired as shown below as far as I can tell.

The truck was in running condition when I got it. It had the mechanical fuel pump and 2 BBL carb.

Image

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Re: 1968 J3000 -Ignition and Fuel Tune Up

Post by letank »

recheck and clean your ground from battery to MSD unit.

Otherwise as said the pertronix is the way to go, a bit annoying to install when checking the clearance between the magnet and the distributor, but you will not have to fiddle with point adjustment. I had one on the 74 for many many years... the day after I installed the pertronix, when I picked up the kids from school... they said that the engine must have been replaced because it was a lot quieter.
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Re: 1968 J3000 -Ignition and Fuel Tune Up

Post by sierrablue »

There are two reasons I'm not big on the Pertronix (it's what the Jeep had when I got it). Number one, it doesn't fix the stumble you get from a tiny mechanical advance, and number two, I put a Ford high-output coil (from like an early '90s truck) on it, super low resistance, and it made up for the lack of timing. Trouble is Pertronix needs more than 3 ohms of resistance to operate w/o getting fried. So that'd be my only concern with it for you is that booster system you have might be too much for it.
'71 Wagoneer (DD)
-B350 (HEI, iron 4-barrel, Edelbrock 1406), TH400, D20
-'74 D44 front (nonpower discs)
-custom headliner
-Front shoulder belts (rears eventually)

viewtopic.php?t=23070

There are 2 major differences between new Wranglers and FSJs. FSJs are meant to be both utilitarian and capable, not just capable. FSJs are also rarely initially recognized as Jeeps by the average American.
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Re: 1968 J3000 -Ignition and Fuel Tune Up

Post by tgreese »

With the Pertronix, does the magnet or reluctor wheel fit over the distributor cam? I expect, with this distributor, you'd need to pull the shaft out of the distributor body to put something over the cam.

I would run it the way it is. With that CDI system, the points only trigger the discharge of the box (switching a tiny current), and are relieved of switching the coil primary and its large inductive load. The points will last a long time, probably until the fiber block that contacts the cam wears out, and I'd guess the condensor does nothing - unless it were shorted. JMO - Pertronix adds negligible value when using this CDI box, and adds another electronic component that can fail.

With both the Pertronix and points, you can bypass the CDI box and fall back to conventional ignition if the CDI box ever fails. A second set of points in your trail spares is way cheaper than a second Pertronix unit.
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 Chryco Jeep Cherokee KL Trailhawk, ECO Green
Blockchain the vote.
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Re: 1968 J3000 -Ignition and Fuel Tune Up

Post by tgreese »

Harry Dawg wrote: Sun Dec 11, 2022 5:58 pm... The truck was in running condition when I got it. It had the mechanical fuel pump and 2 BBL carb. ...
Correct me if I'm wrong. The truck had this ignition system when you bought it, along with the OEM 2V carb and a mechanical fuel pump. It ran smoothly at idle. You have not changed the ignition system or timing.

You installed the new carburetor, and I presume an electric fuel pump and a new manifold, and now it does not run smoothly.

They say "show me where you've been, and I'll show you where the problem is." Given the history, it's exceedingly unlikely that the problem is with the ignition or timing. Instead it's something you've done by installing this new carburetor, manifold and fuel pump. Since this is a new carburetor, it's possible it was defective out of the box. It's also possible that you have a big vacuum leak that you have not detected.

Running at idle is not a very demanding task for a carburetor. There is a separate circuit in the carburetor that supplies fuel at idle, and everything else should be shut down. If you are actually running on the idle circuit, you should be able to kill the engine by backing out the idle stop (idle speed screw) or by closing down the idle mixture jets. If you do either of these, and the engine still runs (however badly), the idle circuit is not in control at idle.

Do you have a tachometer? Below say 800 RPM, you should have 100% idle circuit, nothing else.
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 Chryco Jeep Cherokee KL Trailhawk, ECO Green
Blockchain the vote.

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Re: 1968 J3000 -Ignition and Fuel Tune Up

Post by sierrablue »

tgreese wrote: Mon Dec 12, 2022 9:42 am With the Pertronix, does the magnet or reluctor wheel fit over the distributor cam? I expect, with this distributor, you'd need to pull the shaft out of the distributor body to put something over the cam.

I would run it the way it is. With that CDI system, the points only trigger the discharge of the box (switching a tiny current), and are relieved of switching the coil primary and its large inductive load. The points will last a long time, probably until the fiber block that contacts the cam wears out, and I'd guess the condensor does nothing - unless it were shorted. JMO - Pertronix adds negligible value when using this CDI box, and adds another electronic component that can fail.

With both the Pertronix and points, you can bypass the CDI box and fall back to conventional ignition if the CDI box ever fails. A second set of points in your trail spares is way cheaper than a second Pertronix unit.
The ring for the Pertronix can slip around the weights--you just have to get the angle right, then it goes in from the bottom. I will give Pertronix that it's better than buying new points, and pretty easy to install.

Like you said though, with that box pulling the load off the points, the points SHOULD be fine. Having burned a "high quality" set of points in <5000 miles with a ballast resistor and condenser, though, I wouldn't go with new points.

The reason I figured HEI would work is that I'm pretty sure the Delco distributors all have the same body, so the gear on the bottom should be the only unique part, and that just has a pin holding it in, so it should be easy enough to swap. Then it's just one unrestricted 12V wire and a tach wire if you want it.

Ditto on the idle circuit--also have you verified that the choke is coming all of the way off/nothing is binding up?
'71 Wagoneer (DD)
-B350 (HEI, iron 4-barrel, Edelbrock 1406), TH400, D20
-'74 D44 front (nonpower discs)
-custom headliner
-Front shoulder belts (rears eventually)

viewtopic.php?t=23070

There are 2 major differences between new Wranglers and FSJs. FSJs are meant to be both utilitarian and capable, not just capable. FSJs are also rarely initially recognized as Jeeps by the average American.
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