Bouncing Timing (1 Viewer)

[Seth_O]

1986 FJ60. I just rebuilt the carb, and redid the manifolds and replaced all the vacuum hoses.

I'm struggling to get the truck to run. I suspect I have some vacuum leaks, but I've found that when its idling the timing bounces around. According to the timing light it idles around 30* advanced. When I back the timing off it swings around 4-5* around either side.

Bad dizzy? Could this be caused by vacuum leaks? Poorly rebuilt carb?

 

[NeverGiveUpYota]

Mine always does that too. I haven’t put a light on it since the redid the bottom end but forever since I’ve owned it it’s done that. I have videos of it. I’ve asked a few but I never got a really clear answer so I’ve let it go.

 

[NeverGiveUpYota]

So your saying tho it won’t idle well unless that advanced? And you’ve never pulled the diz?

 

[Seth_O]

Pulled and reseated the dizzy multiple times. One tooth forward and one tooth back. I am confident its timed correctly. The funny thing is, this much advance is new behavior since I did all the carb and manifold work.

 

[gregnash]

Have you gone by the FSM settings to set the dizzy up... Could have been that because of all those issues that the PO had advanced the timing by turning 180* or something...

 

[Rockymtnreaper]

Have you gone by the FSM settings to set the dizzy up... Could have been that because of all those issues that the PO had advanced the timing by turning 180* or something...

And if you don't have the FSM's, someone has them conveniently located in their Bio... @gregnash

 

[BlackCat]

Keep in mind you’ll have to adjust the idle speed up quite a bit as you’re retarding the timing. That could be your issue.
Mine doesn’t jump around quite that much, but it does jump around 2 or 3 degrees when idling.

 

[Seth_O]

Have you gone by the FSM settings to set the dizzy up... Could have been that because of all those issues that the PO had advanced the timing by turning 180* or something...

Followed the FSM exactly, and that's when I get the result of it running at all. If it's off by a tooth either direction it wont even run.

 

[Seth_O]

Keep in mind you’ll have to adjust the idle speed up quite a bit as you’re retarding the timing. That could be your issue.
Mine doesn’t jump around quite that much, but it does jump around 2 or 3 degrees when idling.

When 'idling' I'm ~1500 rpm's and ~25* advanced. When I retard my timing the idle speed drops but I get the flutter/bounce in timing and it stumbles around and hunts.

 

[BlackCat]

When 'idling' I'm ~1500 rpm's and ~25* advanced. When I retard my timing the idle speed drops but I get the flutter/bounce in timing and it stumbles around and hunts.

What’s your vacuum look like?

 

[Seth_O]

What’s your vacuum look like?

~16" @ 2000rpm's, ~14" @ 1500 rpm's. It was higher, but seems to have declined over the last month or so. All new vacuum hoses.

 

[morganism]

did you check the carb spacer and the J pipe at carb base for leaks w propane or carb cleaner?

Recheck the vac advance lines on distrib, then move the secondary to the primary diaphram, and plug the original primary line?
That will give you 6 deg of advance, instead of 16.

from member @Coolerman

Dizzy FAQ

 

[gregnash]

~16" @ 2000rpm's, ~14" @ 1500 rpm's. It was higher, but seems to have declined over the last month or so. All new vacuum hoses.

What elevation are you at? That seems SUUUUUPPPPERRR low. My guess is there is a massive vacuum leak somewhere... Hell my truck will idle at 0* advanced. So you definitely got something major going on..

 

[Seth_O]

What elevation are you at? That seems SUUUUUPPPPERRR low. My guess is there is a massive vacuum leak somewhere... Hell my truck will idle at 0* advanced. So you definitely got something major going on..

That's been the story of this truck, always something going on. I just redid the manifolds and all new vacuum hoses, and yet my leak has returned.

I'm ~1000ft. So I should be a solid 20" at idle I think.

 

[NeverGiveUpYota]

Or at least 17. Like Morgan said, check the hardline that comes out from the carb insulator... wiggle it. If it moves then it’s leaking. I scraped out mine best I could (some sort of crappy white epoxy) and say it upright w/ a glob of jb weld on it. It’s tight now.
You’ve tried carb spray around the base of the carb and the manifolds too just for who has since rebuild? PCV is free and will slide up and down when shaken too?

 

[Landpimp]

My old fj45 was doing something similar, I know the dizzy are different(points vrs electriconic) but in my case the breaker plate(I think that the right name) was sticking...I lubed it up and timing stays put....after I redid the timing.

 

[Seth_O]

I pulled my carb to take a look at several areas where I suspected vacuum leaks.

Found this:

 

[Seth_O]

It's been addressed as best I can until I can replace it:

 

[Seth_O]

I also snugged down all my manifold bolts and air rail attachments, everything seemed just a little loose. I'm not sure why, I tightened everything to spec when I was last in there, unless the heating cycles in combination with the anti-sieze have caused things to work loose.