Curious 79 FJ40 Project Runs Very Rough - Ideas?

[CruiserInProgress]

OK, I did some experimenting and have some info -

- there may have been more symptoms related to my non-oem distributor than just missing on #1 cylinder. With the repaired oem distributor cap and rotor the engine now seems to run and rev without backfiring when NOT using the vacuum line.

Progress made, but I am still confused about the large delta between static and dynamic timing settings, and the negative effect the vacuum advance plays in running rough.

Here's some new info -

- ported vacuum on the carb shows around 15 psi at idle, double that when cracking the throttle. So, it's definitely having an effect on the vacuum advance.

- that vacuum, when connected to the distributor advances the timing quite a bit, from my static timing mark to a couple degrees beyond the BB, 7-10 degrees?

- included is a pic of my two timing settings relative to an arbitrary line on my pushrod cover (for illustration only). The line on the right is my static timing setting The line on the left is my dynamic timing setting. Seems to be an awfully large delta between the two.

- the engine now seems to run OK at either position WITHOUT the vacuum line used, but the highest idle is midway between the two timing settings.

Oh, one more curious thing regarding the after dark spark test suggested. I wasn't able to do that test during the day, but kept getting shocked when touching the fresh air intake line from the firewall to the distributor. It's a rubber hose! I disconnected it and no more shocks. What's that about?

Not sure what that all means, but I found it interesting. Any observations or ideas on any of this?

 

[mattressking]

OK, I did some experimenting and have some info -

- there may have been more symptoms related to my non-oem distributor than just missing on #1 cylinder. With the repaired oem distributor and rotor the engine now seems to run and rev without backfiring when NOT using the vacuum line. Ditch the aftermarket junk, too many variables.

Progress made, but I am still confused about the large delta between static and dynamic timing settings, and the negative effect the vacuum advance plays in running rough.

Here's some new info -

- ported vacuum on the carb shows around 15 psi at idle, double that when cracking the throttle. So, it's definitely having an effect on the vacuum advance. Ported vacuum should show ZERO inches of mercury (NOT PSI) at idle, you have an issue with your butterfly being open. If you see 15inHg at idle, clarify your elevation where you live with the truck.

- that vacuum, when connected to the distributor advances the timing quite a bit, from my static timing mark to a couple degrees beyond the BB, 7-10 degrees? Again, you have an issue with primary butterfly open causing ported vac to have 15inHg at idle. Fix this. Base timing should be 7*. Bumping timing can be done and dependent on if the truck has smog equipment, elevation and if HAC is intact.

- included is a pic of my two timing settings relative to an arbitrary line on my pushrod cover. The line on the right is my static timing setting The line on the left is my dynamic timing setting. Seems to be an awfully large delta between the two. Do not use those as 'timing marks'. Use the BB on the flywheel to confirm your timing settings at 7* for initial fact finding.

- the engine now seems to run OK at either position WITHOUT the vacuum line used, but the highest idle is midway between the two timing settings. By advancing the timing, you are masking your issue*. *Again if you have HAC intact, if you live at 4,000ft AGL, your base timing is set at 7*, then your timing will be raised an additional 6 degrees. If you are above 4,000ft AGL, do not have HAC and base timing is 7*, increase timing an additional 6*.

Oh, one more curious thing regarding the after dark spark test suggested. I wasn't able to do that test during the day, but kept getting shocked when touching the fresh air intake line from the firewall to the distributor. It's a rubber hose! I disconnected it and no more shocks. What's that about? The hose from distributor cap to firewall is for distributor cap venting. If you are getting shocked, you have an electrical issue that needs sorting because that hose does not interact with any electrical.

Not sure what that all means, but I found it interesting. Any observations or ideas on any of this?

View attachment 3690522

 

[CruiserInProgress]

Thanks for the detailed input.

I agree on the non-oem junk problems. Unfortunately, OEM distributor caps for my year (79) seem to be unavailable. Fortunately, repairing the original OEM cap seems to have dramatically improved things.

Fyi, my truck is completely desmogged and I'm at 2500 ft elevation.

About the timing marks in the photo they were only intended for illustration. I use flywheel timing marks as you suggest to set timing.

About the ported vacuum, yes, I meant 15 inches of mercury, steady, which would be fine if it was manifold vacuum.

But, you raise an interesting point. I quickly adjusted the idle screw early on to keep the engine running, which would have cracked the butterfly a bit. The ported vacuum draws from a point immediately above where the butterfly seats, so I can now see that any opening of the butterfly would create a vacuum when the engine is running, activating the vacuum advance. I'll back that throttle screw out and use the idle mixture screw instead?

I'll dig into your suggestions tomorrow and see what happens.

Thanks!

 

[Pighead]

I'll have to do more investigating to determine which direction the timing is moving with vacuum applied (advance or retard).

Yes, please do. Exactly what dizzy do you have right now? I think that I have "heard" that some dizzys can advance and retard. Make sure your baseplate moves in the correct (I believe counter-clockwise) when you apply vacuum. What happens when you use the other diaphragm?
Track down that bizarro ported vacuum thing, stop worrying about static timing, give us some wide shot pics of your engine

 

[CruiserInProgress]

Yes, please do. Exactly what dizzy do you have right now? I think that I have "heard" that some dizzys can advance and retard. Make sure your baseplate moves in the correct (I believe counter-clockwise) when you apply vacuum. What happens when you use the other diaphragm?
Track down that bizarro ported vacuum thing, stop worrying about static timing, give us some wide shot pics of your engine

I have the original electronic distributor for a 79 FJ40 2F. It's the smaller head that was only used for 2 years or so on the FJ40, being replaced by the larger head electronic distributor used on the FJ60.

I'm hoping Mattressking is on to something with my inadvertent cracking of the primary butterfly, introducing vacuum to the distributor at idle.

I'll attach a couple of engine pics from a while back, after I refurbished the rocker assembly and lifters. They were almost frozen in place. I have since replaced the carb with City Racer's Fuji. The 79 is on the right and my 69 SBC "FrankenCruiser" is on the left (that's another story)

It's pretty nasty everywhere, in and out from previous neglect and cobbling. But, it's got potential...to me anyway.

It's nice to hear it run and rev after sitting for so many years.

 

[fjc-man]

Where does the hose from the PCV check valve attach to the intake manifold?

 

[CruiserInProgress]

Where does the hose from the PCV check valve attach to the intake manifold?

It's been awhile since I pulled it off, but I'm pretty sure, on my 79 the pcv hose from the pushrod cover connects to the air cleaner.

 

[fjwagon]

Oh, one more curious thing regarding the after dark spark test suggested. I wasn't able to do that test during the day, but kept getting shocked when touching the fresh air intake line from the firewall to the distributor. It's a rubber hose! I disconnected it and no more shocks. What's that about?

Not sure what that all means, but I found it interesting. Any observations or ideas on any of this?

Try to find the source, I usually use silicon between the boot and wire on both ends especially the at the coil. It does not need a lot but enough to keep the voltage from leaking. I find it interesting that it's via a vacuum line. It usually travels through something with moisture or metal. Anyhow, back when TV tubes were a thing , we would apply silicon at the anode cable to from getting shocked high voltage.

 

[fjc-man]

Originally it would have been attached to the intake manifold below the carb, near the master cylinder.

 

[CruiserInProgress]

I ran out of time to diagnose that weird shock issue today. But I'll get back to it. The shocks were slight, almost like static charges. Maybe a ground issue somewhere? When the PO ripped out all the emissions gear out, he left the wiring harness behind with lots of hanging connectors and other wiring issues.

 

[fjc-man]

There was a flange with two pipes here, the smaller one was for the PCV and the larger one was EGR.

 

[CruiserInProgress]

Originally it would have been attached to the intake manifold below the carb, near the master cylinder.

Interesting. My 79 has been through a lot over the years. The headers are aftermarket, but the intake manifold and air cleaner seem modified, but original.

Thanks for clarifying with the photo. Yep, that looks like my intake manifold, but mine has an aftermarket fluid heat riser below, hence the huge red hoses in my photos.

When I'm done it won't be original, but hopefully it will be much neater and cleaner.

 

[CruiserInProgress]

Progress made!

Mattressking pointed out that ported vacuum should read 0 in hg at idle instead of the 15 in hg measured. That got me focused on the primary butterfly. After some guidance and a pic of the FSM page showing carb adjustments from City Racer, I removed the carb and had a quick look.

Sure enough, the primary butterfly was slightly open. I'm pretty embarrassed to say in my haste to test the shiny new carb, I neglected to go through the various checks and adjustments for the new carb before running it.

To make matters worse, I completely overlooked the throttle positioner screw that provides the stop for the primary butterfly. I couldn't see it post installation. So, to really confuse things, I tried adjusting the fast idle screw instead, which seemed to do something, but definitely not what I needed.

So, I now have a full FSM download compliments of this site and have no excuses for not doing all the required checks/adjustments before running my shiny new carb again.

Embarrassed, but optimistic!

 

[CruiserInProgress]

Update -

It's taken me a while to get to this point, but after adjusting my new carb to factory specs, flushing my fuel lines and tank (not a fun job), and planing my carb insulator to eliminate vacuum leaks, my long dormant 2F now idles and I get zero in hg on ported vacuum at idle.

I still have some weird issue with my vacuum advance. I just can't seem to get it to run right using vacuum advance at any timing setting. I'll try an aftermarket distributor as a test at some point to see if that points to my oem distributor as the culprit.

However, with my vacuum advance plugged, I buttoned up my old project, fired it up and drove it around the block to check out the running gear. No smoke, plenty of power, albeit still a little rough, shifts fine and stops ok. All of that were question marks up to this point.

I've owned two later model landcruisers (80 & 100 series) as daily drivers for the last 25 years but have never driven a FJ40. Even in its current state, it did not disappoint. Still smiling as I write this post.

Way early in the project with lots yet to do, but I am re-energized!

 

[CruiserInProgress]

There was a flange with two pipes here, the smaller one was for the PCV and the larger one was EGR.View attachment 3690878

A belated thanks for pointing out how the PCV line should attach to the intake manifold on my desmogged 79 FJ40. I have since installed a egr delete plate from Redline that provides what you suggested. One step at a time. Thanks again.

 

[dazerb]

FWIW...
74 1.5F desmogged, headers, HEI dizzy, 38/38 Weber. I know it's a different set up but... Everything else is pretty original, LOL>

I had been constantly tweaking timing, checking plugs/wires, adjusting carb UNTIL...

I just adjusted the valves and I am embarrassed that I put it off so long! NOW those mixture screws really are sensitve and so is my timing!! Some were tight, some were really loose. Was burning some oil, not burning all the fuel... AND I did it with the engine running cuz I couldn't figure out a reason not to. Watched v adjust videos on ANY solid lifter vehicle for weeks!!

Saw others already mentioned advance the timing and look at throttle plates. The Weber diagrams show how the throttle plate being alittle open pull fuel from the main jets so I had to make sure it was flat closed.

And that vacuum!

I really enjoy learning and relearning this stuff. Now that I've broken my valve cherry, I'm like the man with a hammer and everything is a nail, LOL. VALVES!!!

 

[charliemeyer007]

My PO was my favorite gunsmith among other things. "If you have a hammer and torch it has to fit" "You have pants on where is your knife?" Thanks Jack.