1968 J3000 -Ignition and Fuel Tune Up

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Harry Dawg
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Re: 1968 J3000 -Ignition and Fuel Tune Up

Post by Harry Dawg »

So I have a theory on the fuel pump.

I tested the fuel pump previously when I was having ignition issues, and was getting 6-7 PSI on a rough idle.

I think the PSI is fine, but what I am concerned with is volume. Being that this pump was designed to support a carb with roughly half the CFM, I don't think it is pushing enough fuel to keep up with new fuel demand.

450 CFM is at WOT, but even at idle I am sure it is pulling more fuel than the Holley 2209 ever demanded.

To test this theory, I am going to cut a block off plate from some sheet metal and remove the mechanical pump for the time being.

Using the already installed inline electric fuel pump I use for priming, I will just have it running full time.

Will see what this does.

I am guessing I just randomly had the perfect amount of excess fuel in the bowl when I test fired it the first time which allowed it to run for a minute or so.

*EDIT - I replaced the entire fuel system including lines, tank, rebuilt fuel pump, sending unit, filters etc.
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sierrablue
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Re: 1968 J3000 -Ignition and Fuel Tune Up

Post by sierrablue »

I don't think your problem is the volume with the fuel pump. The CFM vs. the idle circuit are two totally different ball parks. The idle circuit is minimal for making a difference in CFM, and it's the same engine--if the idle mixture is right, it should be fine. And if it has enough fuel under throttle, it has plenty of fuel at idle.
'71 Wagoneer (DD)
-B350 (HEI, iron 4-barrel, Edelbrock 1406), TH400, D20
-'74 D44 front (nonpower discs)
-custom headliner
-Front shoulder belts (rears eventually)

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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 Harry Dawg »

Alright.

I had some of my dad's buddies who are Air Force mechanics come over and take a look at it. Between the 3 of us and 4 hours of screwing around, we still couldn't get it to run correctly.

SO. New plan is to reinstall the factory Holley 2209 and 2BBL for the time being. I might take another crack at it down the road, but I need the garage space to start body work on my Cheyenne project.

I rebuilt the carb yesterday, and replaced the gaskets and cleaned everything out.

Mikes Carburetor Parts has a ton of hard to find rebuild kits, and are great to work with.

Lots of curmudgeons in the fuel bowl, but all of the passages were surprisingly clear.

I couldn't get the power piston out due to requiring special tool, but it seemed to be functioning well enough.

I did rebuild the accelerator pump and tuned everything to factory spec.

Will install intake and carb after work today and check back in tommorow.
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Re: 1968 J3000 -Ignition and Fuel Tune Up

Post by sierrablue »

Sounds good.
'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 Harry Dawg »

So I got the factory intake and carb installed, go to fire it up and nothing.

I pull the ignition coil lead and no spark.

At this point, I'm like WTF?! Is this still an ignition issue? Was there ever anything wrong with my 4BBL carb? Was the coil on its way out and now it's just dead, which would explain the erratic idle?
(Rhetorical questions- just explaining my thinking)

Test ignition positive wire and I am getting power from ballast resistor to primary coil lead, but no spark from ignition coil output.

While trouble shooting, I noticed that there is some sludge / melted plastic around the negative terminal of the coil. So obviously my ignition coil is bad, but it's not just bad...it's burned.

Continue tracing wires and get to the primary distributor lead... Well, the points and primary lead are totally fried.

The only thing I can think of is the continuous cranking when fooling with carb never let the circuit switch over to muted 10V via ballast resistor and was giving it the full 12V for too long.

Alternatively, the ignition switch or my wire routing from the ballast resistor is incorrect.

Either way, I'm pretty much at a loss here. I don't want to install $100 in new ignition parts only to have it get fried again.

All my new parts will be in on Monday, so tomorrow I am going to double check wiring on the whole ignition system against TSM.

Hope y'all are having a better weekend than me!

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Re: 1968 J3000 -Ignition and Fuel Tune Up

Post by sierrablue »

Well, glad you finally found the problem.

Last year I had a coil on mine (before I put the HEI on) that worked REALLY well, I was so happy with it, and then it started stumbling and giving me fits. Took forever, but the positive 12V post had a crack in the plastic under it, and was slowly leaking fluid. Talk about hard to find 🙄

I got to install an electric fuel pump this weekend, as my mechanical one gave out 🤪 I feel your pain
'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 Harry Dawg »

Good news everyone!
(Futurama reference... If ya know, ya know)

I finally have a running and smooth idling J-truck!

It turns out something in the ignition system was the culprit this whole time.

After adding in an Accel Super Stock coil, new points and condenser, and a new wire it fired right up.

https://youtu.be/MxCaE_1xoB8

I think I had the ignition coil wired to the wrong side of the ballast resistor as well. I switched it over to the side that has the starter solenoid lead running to it since that is where the original ignition coil got power from.

Maybe that is what caused the melt down?

Either way, it's finally running!!!

I won't lie though, there were a few points where I thought about burning it down and collecting the insurance money lol.

Anyways, a few more items to do before I can call this thread "closed".

1) Mount ignition coil to the firewall with a shorter coil lead ( will look cleaner)
2) Organize spark plug wires with a wiring loom
3) Set dwell
4) Check timing
5) Do a final carb tune with the vacuum gauge. She's already about at the highest reading, but I just want to check it again.

For those wondering, it did run with the 2BBL on there, but was leaking fuel out of the side of the carb near the curb idle screw. I am guessing the shaft that the butterfly valves attach to wallowed out the carb body and it was running down the shaft to the outside.

Special thanks to TGreese for all of his patience and sharing of knowledge.

Will update y'all once I tidy all of the wiring up.

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Re: 1968 J3000 -Ignition and Fuel Tune Up

Post by Harry Dawg »

Checked the timing today. Looks like it jumped time, as it's definitely not at 5 degrees BTDC.

https://youtube.com/shorts/au0gWfprlOU?feature=share

The vacuum gauge says late timing, but I would think that it's early since it's flashing before the marks on the crank get to the indicator pin.

The indicator pin is just behind the hose clamp at the outlet of the fuel pump. You can barely see it on the video.

Probably need to do a timing chain, and I read these have a plastic timing gear which would explain why it slipped.

I found this one on Speedway.

Says it fits an AMC 327, but that sounds too good to be true.

https://www.speedwaymotors.com/Edelbroc ... 11330.html

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Re: 1968 J3000 -Ignition and Fuel Tune Up

Post by Harry Dawg »

It was too good to be true!

Product summary says it will fit a 327, but if you click more details it excludes this motor in the application list.

Gonna have to shop around some more.

In the interim, I am going to adjust the timing tomorrow and hope that gets me by until I can find the chain.

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Re: 1968 J3000 -Ignition and Fuel Tune Up

Post by Harry Dawg »

Advanced the timing so that the marks on the crank line up with the indicator at 5 degree BTDC, and reset the dwell to approximately 22-24 degrees.

Was still running like crap, so I hooked the vacuum gauge to it thinking I would dial in the carb.

Now it's reading way lower, only about 10 -15 HG of vacuum and indicating late valve timing as opposed to late timing.

Seems like I just can't get a head up with this truck.

I also read another thread on the AMC forum where a 327 Ambassador had a timing issue and bent the pushrods and valves.

Hopefully that isn't the case for mine.

I am going to give it a rest for the night, as it has sufficiently aggravated me for the day lol.
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Re: 1968 J3000 -Ignition and Fuel Tune Up

Post by Harry Dawg »

Fired it up. I had normal vacuum reading until the choke came off.

This would indicate a vacuum leak, but I double checked everything and no leaks from what I can tell.

I turned the idle speed screw in a little and got it to level out, but only at high idle (1,000 RPM)

Going to investigate a little more after work today.
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Re: 1968 J3000 -Ignition and Fuel Tune Up

Post by tgreese »

I understand that 1000 is above the idle circuit. That is, idle mixture should have little effect at that speed.

At idle, you should be able to kill the engine with either the idle stop or the idle mixture. With a big leak, the idle stop may have no effect below a certain speed.

Too much history here. Can't read all the old thread right now. Maybe you can recap where you are? Likely that will help elicit suggestions from others too.
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Re: 1968 J3000 -Ignition and Fuel Tune Up

Post by Harry Dawg »

Noted on the idle circuit.

Basically that was the only way I could get it to stay running is by turning up the idle until there was significant pressure on the throttle cam.

That would explain why the idle screws did not have any affect here in getting the idle down.

Previously I was chasing an ignition issue which turned out to be a combination of poorly set dwell and a bad ignition coil.

Got the truck running, but it had a high idle.

After hooking the vacuum gauge to it, it was indicating late timing so I checked timing with a Zeon light.

Was about 20-30 degrees retarted, which to me indicated that it jumped time (presumably worn out chain or gear).

I advanced the timing via the distributor, and reset dwell but still poor idle.

Basically the only way I can get it to stay running is if I give it gas or if the speed screw is turned in past where it should be.

I tried unhooking all vacuum accessories which had no impact. Still runs rough
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Re: 1968 J3000 -Ignition and Fuel Tune Up

Post by Harry Dawg »

Got it running better.

The float was off and it was starving for fuel at idle,which is why it only ran with the idle screw turned in.

Currently in the green on the vacuum gauge - getting the "normal motor" reading.

Timing is dead on also.

Still not a super steady idle, and the needle bounces around a bit.

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Re: 1968 J3000 -Ignition and Fuel Tune Up

Post by Harry Dawg »

I also nailed down another mystery today.

Drove it to work (first time road driving it) which is about 8 miles away. A good 20 min drive with traffic to warm it up.

When I pulled it into the garage I popped the hood just to see if anything was going on, and I noticed there was movement in the fuel filter.

Gas looked to be boiling and it was forcing it's way into the bowl, gradually filling it up.

This explains why the float always appeared to need constant adjusting.

I think I actually need to raise the float and back off the idle screw just a touch to level out the idle.

I will reset tomorrow with the truck running.

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