I think my dissy isn't working properly (1 Viewer)

[Random Dan]

A couple days ago I did a valve adjustment and set my timing. Only problem is I was really down on top end power* when I took it for a drive. So I played with the timing a little and after a few test drives I got the power improved. Then I put the timing light on it and my baseline timing was set at 15 degrees, and that's in addition to the 7 degrees accounted for the the ball-bearing. I have no pinging at any RPM/any throttle.
This leads me to believe that my dissy is not advancing like it should.

My question for you guys is: what should I do?


*I have operationally defined "top end power" by my cruising speed with the first barrel wide open.

 

[cwwfj60]

So did it go down on power after you adjusted valves and adjusted timing? or were you just adjusting timing to get more power? Unless something happened when you messed with it before it sounds like the advance is stuck/not working, I had this issue come up with mine. After countless attempts to figure it out I pulled the distributor out and the shaft was almost frozen, it would barely spin and was getting progressively worse as I was working on it. Replaced it with a good used unit ($250) and it worked better than ever before, had no idea how bad the advance was.

 

[Random Dan]

Well I have another dissy on a low-mileage 2F that I could probably pilfer. Is there a way to check the advance before putting it in?

 

[Random Dan]

On a related note, how well would a 3FE dissy work on a 2F?

:EDIT: Nevermind, found the answer.

 

[klinetime574]

Test the advance, remove the cap, pull vacuum on the advance and see if it pulls the arm.

I have been running my distributor on the BB since forever. I never mess around with timing.

How is the carb? Secondary diaphragm functioning? Paperclip test (however that is done) to confirm that, I think it involves placing a paperclip around the arm and seeing if it moves after a test drive.

Pretty sure a 3FE dizzy will not work, different animal.

I have some distributor tech in this post: ROTM- klinetime574

 

[2mbb]

I would also check to make sure your secondary diaphragm is working properly. I'm not sure about your definition of "top end power". It implies the secondary is either closed or at the same position when your primary is at WOT.

There are procedures in the emissions manual to check the vacuum advance parts. I suppose you could also check the centrifugal advance by disconnecting the vacuum advance and watching with a timing light as you increase engine RPM. These tests won't necessarily tell you if the parts are so worn your advance curve is off, but it will tell you whether they are working at all.

 

[Random Dan]

Okay, maybe I'm not sure how exactly the secondary works. The throttle pedal was not depressed enough to open the secondary.

In any case, it took noticeable less throttle to cruise at 100 when I had it set at 27 degrees baseline advance.

 

[Random Dan]

What exactly does the secondary diaphragm do?

 

[klinetime574]

What exactly does the secondary diaphragm do?

My understanding... More load on the engine = secondary opens to allow more fuel into the engine.

You can't control when the secondary opens unless you're at idle, off the pedal. That is a low load scenario. Acceleration would be a higher load, therefore opening the secondary.

 

[Random Dan]

My understanding... More load on the engine = secondary opens to allow more fuel into the engine.

You can't control when the secondary opens unless you're at idle, off the pedal. That is a low load scenario. Acceleration would be a higher load, therefore opening the secondary.

Hmm, I didn't know that. I thought it only opened when the throttle linkage moved far enough to open it.

 

[cwwfj60]

throttle linkage has nothing to do with it, technically, you have the primary centrifugal advance which is purely based off rpm, or rate of rpm, and your secondary is based off vacuum/load. Just clarifying what klinetime said, or maybe I just made it worse, good luck

 

[cwwfj60]

'83 fj61? I'm not familiar with this one, is it 2f - carb? Where are you/truck from? please explain?

 

[Random Dan]

When the throttle pedal is fully depressed it opens the secondary.

 

[Random Dan]

Truck is from Japan originally. From the factory it had a points dissy but I swapped in the USA big cap last year. Other than that just a regular 2F. It has EGR but no other smog stuff.

Is there a way to test the centrifugal advance? I think it must be stuck because I don't know how else I could run 27 degree baseline without getting any pinging.

 

[cruisertom]

First of all what is your base timing? Are you following the instructions for checking the base timing? Some you have to pull the vaccuum advance and plug it first. If you have a timing light that has is able to check advance you can rev the engine and read what the total advance is. My digital Snap On light has this ability I am sure others have it as well, then you can see if the timing is advancing or staying in one position. There is probably a spec in the factory manual that will tell you how much it should advance. Also what elevation are you at? We used to advance our base timing because we lived at 6000ft and wheeled all the way up to 12k. For example a carb'd small block chevy has a base of 8 degrees BTDC but that spec is for sea level. In denver (6000ish ft)we would set the base at 12-13 and made a big difference.

 

[Random Dan]

Ok, I checked the timing at higher RPM (2500-28000ish I think, not sure since I don't have a tacho) and... it's exactly the same as idle.

 

[cruisertom]

Does the vacuum line have vacuum? And is it at the right time? Meaning is it hooked up to the right source? If so check the diaphram on the distributor with a vacuum guage and see if it holds vacuum. Repair or replace it don't start sticking BB's a crap everywhere it will just cause other issues and make it hard to diagnose.

 

[Output Shaft]

Ok, I checked the timing at higher RPM (2500-28000ish I think, not sure since I don't have a tacho) and... it's exactly the same as idle.

Distributor mechanical advance has seized.

 

[Spike Strip]

Send to FJ40Jim for rebuild/recurve.

 

[Random Dan]

I have not checked vac advance yet. It is definitely hooked up to the right places. Hopefully tomorrow I'll have time to pull and inspect another dissy that I can use as a replacement.