SC Distributor Vacuum Module Problem
 

I think the vacuum advance/retard module on my distributor (83 SC) is not working. When I check the timing with the retard line connected, it does not change. And when I put the manifold vacuum line on the advance port (per the factory manual test method) it also does not change.

I'm pretty sure my centrifugal advance is working because when I put the timing light on it and rev the engine, I can see it advancing. I didn't have a helper to maintain a constant RPM for me. So I still have to verify there is no issue there.

Pelican doesn't seem to have these anymore. (It says temporarily unavailable.) I saw there is one company Philbin Rebuilt Products - Distributors that rebuilds these which one person here recommended (which i have sent an email to).

Any other ideas?

I think I'm past the sourcing issue. Next question.

Can the vacuum unit be removed with the distributor installed, or does it have to be removed from the engine first?

i have experience w/this issue. forget philbin grp- i sent mine to them, they painted it grey and sent it back. so, first make sure its bad. get a length of hose and test both sides- take off the cap, suck on the hose and see if the advance mech moves- if u dont have a vacuum tester this is the next best thing. so if it moves, thats good. then suck on the hose again then stick ur tounge on the end of the hose after uve applied vacuum and see if it holds that vacuum. if it fails one of these tests u still have options. u can buy one for a 82-89 930, itll fit and work. what i did is find one at pickurpart for a mercedes 280e and modified the tube locations and it works great.
the retard side works at idle and the advance side wrks off idle and part throttle

The removal of the unit has to be on the table. the pin the unit hooks points down so you rotate CCW to remove.
'Bruce

Hi Matt,

It is much easier to remove the distributor and do it on a bench.

Be careful when sourcing another vac advance from another car as they usually have twice the advance the SC requires.

A good deal of the vac advance units are damaged by water because of it's position in the car.

Aaron,

My source for the vacuum unit fell through. Any ideas of what I should do?

I currently do not have any good replacement pods, but I do get them in from time to time.

1. You can get a good used dizzy to solve your immediate problem. It's hit or miss as far as condition and longevity. Keeping a spare may start to make sense as they are getting harder to find.

2. Re-curve your dizzy to use a more common pod. I have a decent supply of them. Downside is less mechanical advance under load. This may or may not be a problem depending on how you drive.

3. Keep looking for a replacement pod.


Either way you choose, oil the upper bearing and shims and keep water away from the distributor or you will be sending your dizzy to someone like me to correct it.

Hope this helps!

Thanks Aaron. I think what I am going to do first is remove the distributor and go through it. Maybe the unit is just seized or something. When I tried to suck into it I could not (on either side).

Hopefully I can clean the distributor and free up the vacuum unit. If not, then I'll have to go searching for a new unit or distributor.

Actually, look at the pulse generator and check if the movement is free. If it is locked up odds are the rest of the dizzy needs help.

The pulse generator is the piece with the white coil attached to it? If so, unless I'm doing something wrong, I couldn't move it at all.

The part on top of that (which looks like a spider) move counter clockwise to some degree. I'm guess that is what is attached to the centrifigual advance.

Yes,

coil is attached to the pulse generator. The "spider" is the reluctor.

The outer prongs should move easily when the vac pod is removed.

I tired to move pulse generator while installed in the car and couldn't move it at all.

So I need to take the distributor out, remove the vac pod, and then check the pulse generator for free play? Is this correct?

I'm only just starting to learn about the mechanics of the distributor, so pardon my ignorance. Thanks.

Yes.

Ok. I don't want to remove it yet because we're planning a drive for this week, and I don't have any space to work in garage right now because of all the xmas gifts for the kids.

However, I bought one of those Mityvac vacuum pumps today. I applied vacuum to the advance port. It held 15" of vacuum and did not leak (I wasn't sure how much to apply). I did not see anything move in the distributor when I did this though. Then I applied vacuum to the retard port and it would not hold vacuum at all.

Does this tell you anything?

You really need the dist on the table. Remove the pod and apply vacuum and you should get movement. Thants the advance above the counterbalancers. If your pod is good then the distributor may well be frozen. With the pod off the outer fingers pointed up should rotate about 30 degrees freely.
If the fingers are frozen I drop the dist in a bath of WD40 overnight then put it in a vise and tap the outer base til it frees up.
Clean and lube, ready to go.
Bruce

I agree. I'll dive in after the holidays. I have a new distributor o ring on the way.