Distributor Breaker Plate Movement (1 Viewer)

[Gretsch]

'84 desmogged FJ60. I am replacing my non-functioning vacuum advancer with a working one I got from @4Cruisers. Got the old one out but before I put the new one in, I wanted to make sure the breaker plate assembly moved properly. To test this I was just pulling back on the pin the advancer arm connects to connects to to make sure it moves as it should before I put this nice clean advancer can in this vehicle. Mine does not move every much so I am trying to figure out if there is something wrong with its movement (which may explain why the advancer pot went bad in the first place), or if the way its moving is normal movement with the truck off. Attached is a video I took of its movement:



Not the greatest vid but I think shows basically the movement. I am not sure if the breaker plate can only move when the distributor is spinning, if they simply don't need to move very much, or there is something wrong with mine. I know a proper rebuild/recurve is in order most likely to get this right but just am right now trying to determine if my distributor is moving properly. How much is the breaker plate supposed to rotate? Based on testing the new vacuum advance can, which moves quite a bit, it seems like the plate should move more than can be seen in the video.

FSM has this to say regarding the plate movement:

Thanks in advance for any guidance here.

 

[OSS]

The FSM only suggests checking for smooth rotation - not length of travel. Likely because length of travel isn't something that can get out of spec. I'd just follow the inspection steps in the FSM and not try to second guess it. It's probably fine if it rotates smoothly

 

[4Cruisers]

The maximum lateral displacement of the pin tangent to the radius of the stationary plate only needs to be 4mm or so - that yields about 10 distributor degrees maximum vacuum advance. IIRC the advancer arm pulls in more than that when you apply vacuum to the inner port. Like OSS said, as long as the rotation is smooth (no binding or sticking) you should be OK. BTW, with the signal generator removed, that plate can spin completely around, kind of like this (stolen from Chit-Chat):

 

[Gretsch]

The maximum lateral displacement of the pin tangent to the radius of the stationary plate only needs to be 4mm or so - that yields about 10 distributor degrees maximum vacuum advance. IIRC the advancer arm pulls in more than that when you apply vacuum to the inner port. Like OSS said, as long as the rotation is smooth (no binding or sticking) you should be OK.

OK thanks fellas. So 4MM seems to be about what I am seeing. The new advancer pot pulls in much more than that which is why I was worried something was not right. Just did not have a good feel for how small the movements of the plate were to effect a change in timing. I am not one to second guess the FSM, but was just not sure here what normal movement should look like, or if movement could be impeded by a broken spring or something underneath the plate. It would probably help to have my distributor recurved for the desmog, so if I had to start getting into figuring out why this thing does not move properly, I would more than likely just send it off to Jim or someone to do that rather than getting into taking it apart myself and seeing what the deal is. If the movement looks normal than I'll just carry on. This helps very much. Thanks again to you both.

 

[4Cruisers]

The rotating part of the stationary plate sits on a bunch of small ball bearings in a race, captured in the fixed part of the plate. Corrosion or gummy old grease can keep it from rotating smoothly.

 

[Gretsch]

OK thanks. Advancer is in. Checked movement and it works like you said with the advancer pot hooked up. About 4MM. Works smooth. Appreciate the help.

 

[Rockiemosley]

It doesn’t look right to me. With the advancer pot off, there should be nothing to inhibit the rotation in either direction. Length of stroke is dictated by length of advancer pull. Nothing associated with the advancer plate should inhibit rotation. I would take that thing off and soak it in mineral spirits, it’s probably gummed up with old gunk.

 

[Gretsch]

With the advancer pot off, there should be nothing to inhibit the rotation in either direction. Length of stroke is dictated by length of advancer pull.

So you are saying it should keep moving past 4mm? It moves freely, just not very far. But its moving the 4mm @4Cruisers mentions previous.

 

[Rockiemosley]

So you are saying it should keep moving past 4mm? It moves freely, just not very far. But its moving the 4mm @4Cruisers mentions previous.

Ive had several FJ 60 distributors apart recently and without the advancer attached, the only other thing preventing the advancer plate from spinning all the way around is the wire going to the electronic pickup. Yes the advancer doesn’t move it much but every millimeter matters. I think it is binding due to rust or caked grease. There are 2 screws holding the advancer plate down. It is a small assembly with ball bearings with a top and bottom race held together with small metal clips. I rebuilt a rusty one recently with new ball bearings from a bike shop. The one I worked on had gotten rusty. I cleaned the parts and used grease to hold the bearings into place while I reassembled.

 

[Gretsch]

So would you say then it needs to move more than what's in the video to get the advance I need or can I get away with it as is? Maybe its gummed up and could use a cleaning but I am not sure how much I want to get into taking this all apart to do that at this point. I think if I had to go that far I would just send it off and have it repaired by a pro while a recurve is done to it for the desmog. Maybe its not that big a deal to get this plate out but looks like lots of small parts to get at while the distributor is in the truck. Really wanted to avoid having to pull it out to get at intricate stuff.

 

[Rockiemosley]

Well it would probably run well enough...im not sure if the amount of pull is 4mm, or 8mm, I know its not big. Since you have the vacuum advancer off, pull a vacuum on it and see if you can measure the stroke. With the advancer plate giving at least some movement, it will probably work OK... hard to say if you’re getting the whole amount of intended advance...you could be missing out on a little, maybe not. If taking that apart is beyond something you want to do the put it together and see how she runs. Put a dial back timing light in it and see how much advance you get with vacuum applied.

 

[4Cruisers]

This is a handy little calculator:

Right Triangle Calculator

Plug in 4 for "a" and 22 for "c" and see what you get for "∠α" (advance in distributor degrees).

 

[Gretsch]

Nice here. I get ∠α = 10.476° = 10°28'32" = 0.18284 rad. So advance of 10 degrees using 4mm movement? What is the total advance one would expect to get out of the primary and secondary advance on these trucks? What was the intended advance from the factory for this dual advancer can setup? I don't want to cut corners with this but will have to mull over what to do here in terms of taking this apart to see what's going on if anything. Based on the calculations above however, it seems like it might be working as designed if 10 degrees is what you can expect out of the stock setup.

This would be in addition to the mechanical advance being applied correct? Is it possible that the mechanical advance doesn't work because of a potential breaker plate restriction or is that a separate mechanism for advancing the timing? I thought it was two different advancing mechanisms but maybe I am mistaken. Thanks for the help everyone.

 

[Rockiemosley]

Yes, mechanical and vacuum advance are separate and work independently of each other. If you can grab your rotor and twist it and get a little bit of play, then your mechanical is probably doing something. Dont discount the value of a proper recurve, especially if you are desmogged.

 

[4Cruisers]

Separate mechanism. Factory advance specs are usually found at the back of the appropriate FSM, in some cases Toyota even included the distributor part numbers, which is helpful. I got the 19100-61102 specs from a Gregory's publication, and I put together the following table:

 

[4Cruisers]

From what I've read here and on the Internet, 10 to 11 distributor degrees vacuum advance is about the maximum you want.

 

[Gretsch]

Dont discount the value of a proper recurve, especially if you are desmogged.

Yeah understood here. I think I might let this ride for now and get the distributor looked at by someone who can do the recurve while fixing anything else wrong with it. The original advancer can on here was not working at all. Wouldn't develop vacuum. The way the PO hooked this up I don't see how I didn't have a massive vacuum leak but maybe the old can wouldn't develop vacuum but was sealed enough to seal the system. Not sure. Questions like these are really why I want to try and get this thing normalized as much as possible. Since a proper recurve seems pretty paramount for a successful desmog, I think the best thing I can do here is have a pro do everything at once.

Separate mechanism. Factory advance specs are usually found at the back of the appropriate FSM, in some cases Toyota even included the distributor part numbers, which is helpful. I got the 19100-61102 specs from a Gregory's publication, and I put together the following table:

From what I've read here and on the Internet, 10 to 11 distributor degrees vacuum advance is about the maximum you want.

OK thanks for the clarification on the mechanisms. Great chart. From what I am getting I should be right at 10-11 then. Amazing how little the plate needs to move to get that. Again I think I'll let this go for now and plan for a recurve from someone who knows what they are doing.

So sorry for over-thinking this a bit, but if there was a restriction in the movement of the breaker plate, the only side effect here would be I wouldn't get as much advance as I could. There is no chance that a restriction would damage this new advancer can right? As in pulling normal vacuum and having the arm stopped prematurely wouldn't tear up the diaphragm inside the can? Seems these are not the easiest thing to find so want to avoid damaging it. I know the answer is probably take out the plate and see if its restricted. If there was any chance of damaging the can then I would be willing to do that before I go any further. But if there is no chance of it getting damaged then I'll let it ride until I can get a proper recurve done.

 

[Rockiemosley]

No a restriction in the advancer plate will not tear up your new vacuum advance. If your old vacuum advance was not advancing, then it was probably responsible for a vacuum leak.

 

[4Cruisers]

Earlier Land Cruiser and similar Toyota/NipponDenso advancers (pre-81) with a straight actuator shaft/arm have a pair of lock nuts that limit the travel and therefore vacuum advance, no problem with those damaging the advancer diaphragm(s). I adjusted the one below to 4mm maximum travel, or ~10.5 distributor degrees vacuum advance.

 

[Gretsch]

OK thanks to you both. I'll roll with this and see where it goes. Any movement is better than the 0 movement I was getting with the old advancer. If 4mm is what it takes to get to 10.5 then I am pretty sure I will get that. Really appreciate the time here. Learning a lot about the details of the advance setup on these. I'll probably try sourcing a used large cap distributor so I can get a properly recurved one in this truck to handle the desmog. Thanks again for the time. Very informative.