Calling Distributor Gurus... (SOLVED)

[bnam]

I faced the following problem on both my cars recently (71 vert with original 1600DP and DVDA, and 65KG with 1600DP and DVDA) -- I could idle it at 780rpm with all hoses connected. If I tried to increase it to 800, just as it hit 800ish, it would shoot up to 1050. Then I would need to turn the screw a lot to get it back down. and when it came down it would be at 650. So turn the screws back out to get it to 780. While driving, it would occasionally rev up to 1050 again.

I spent so much time chasing this one down. Solved finally. I had three lines of approach --
(a) air leak -- majority of inputs were around that
(b) carb - float level etc
(c) I also wondered about the distributor - though I got no inputs in this one

Carb:
I had checked float level, all ok. I stripped the carb and cleaned in ultrasonic cleaner. Blew out all passages. New rings. Screws all good. new gasket. -- NO IMPACT

AIR LEAK:
This took me the most time. Even though I was not really getting a raise when I sprayed carb cleaner (at least not a statistically significant or repeatable rise in revs) - I tore down the manifold and redid all the gaskets with sealant. Even put a bit of sealant under the boots. Throttle shaft showed no air leak.

The one place I did get a repeatable increase in revs was when I sprayed near the idle/bleed screws. So removed those and put thread sealant and then a bit of RTV over the it. Then sprayed again -- and I still got a rise. Then I realized this location was close to the air filter base and probably a bit was getting sucked in there, but that's not an air leak. Crap. I was running out of ideas.

I came back to my thought that this was a distributor problem. Luckily, I had just received a known good distributor to try. We had bought a rebuilt distributor from Bill for a friend whose 71 bus engine I was rebuilding (really reassembling). So I put in that distributor. VOILA!!! Problem gone. Easily tuned and set to 850. No revving up. Drives like it had done before!!

I spent some time this morning tearing down rebuilding the old distributor. I repolished the trackway on the advance plate to make sure it was moving properly. Tried it back on the car -- and back to same issues. Then I removed and measured the shaft vertical play -- I measured 0.43mm. I think the spec is closer to 0.1mm (based on an older posting by Glenn - but I could use some confirmation on this).

So, my theory is that perhaps at 800ish rpm, the shaft is moving (up or down) and consequently advancing (as the gear is spiral cut). This advance in timing is enough to increase the revs. Is 0.43mm of play enough to cause this behavior? Or is there something else wrong with the distributor? I'm planning to rebuild my distributor with new washers and shims. But wondering if I'm missing another issue.

Byas
_________________
1971 1302LS Convertible (RHD) owned since '74
Click to view image
1965 Karmann Ghia Coupe - under restoration
1966 Fiat 1500 Cabrio (with 1600 Twin cam)
1952 Citroen TA 11BL

[Bugsy61]

[Glenn]

The shaft moves down when the engine is running or being turned clockwise. That's why there are 2 steel washers under to protect the soft magnesium. There should also be a anti chatter spring between the driveshaft and the distributor. Endplay on the drive dog and body should be as little as 0.05mm. the steel shims come in 0.2, 0.1 and 0.005mm thickness.

If you need some, email me.
_________________
Glenn
74 Beetle Specs | 74 Beetle Restoration | 2180cc Engine
"You may not get what you pay for, but you always pay for what you get"

Member #1009

#BlueSquare

[modok]

You should have checked the ignition timing with a timing light when you were having the unstable idle. I bet the advance was "hanging up" when revved and not letting it fall back down.
I don't know what happens if the end play is wrong, but, probably not a lot.
i see them running with 1mm end play all the time because the washer exploded, and they don't know the difference, god bless em

[wcfvw69]

I'm wondering if your used distributors are mechanically advancing early or 800rpm. I recently restored a 205Q distributor. When I ran it on my Sun distributor machine post restoration, I was shocked to see it start to mechanically advance at 800 RPM. The primary spring looked fine and correct. I changed it to another 205Q primary and it started advancing at 1100 RPM.

Most Bosch aluminum distributors (except the 009) from the 70's don't start to mechanically advance until 1100 RPM.

So, the spring was either wrong or weak. I'd never experienced that before and this distributor had never been apart since new. Weird.
_________________
Contact me at [email protected]
Follow me on instagram @sparxwerksllc

Decades of VW and VW parts restoration experience.
The Samba member since 2004.

**Now rebuilding throttle bodies for VW's and Porsche's**
**Restored German Bosch distributors for sale or I can restore yours**
**Restored German Pierburg fuel pumps for sale or I can restore yours**
**Restored Porsche fuel pumps or I can restore yours**
**Restored Porsche distributors or I can restore yours**

[modok]

Yeah I think something like that.
I've seen distributors that survived an engine fire and still worked.....but they didn't work right

[bnam]

[bnam]

[modok]

[bnam]

[bnam]

[wcfvw69]

When you're timing this, are you leaving both the vacuum advance and retard hoses on? If so, try it again with the vacuum advance hose removed and plugged with a pencil. It could be possible that you're getting a bit of ported vacuum from the carb and it's vacuum advancing at 800 RPM. You should see NO ported vacuum at idle.

You can also do this- Remove both vacuum hoses from the vacuum canister and plug them. Set your static timing to 7.5 BTDC. You're setting it like it's a mechanical only distributor like an 009.

Hook up your timing light and a tach. If you can set the idle at 700 RPM, do that. Then slowly start revving the engine with the timing light pointing at the pulley. At what RPM does it start to mechanically advance?
_________________
Contact me at [email protected]
Follow me on instagram @sparxwerksllc

Decades of VW and VW parts restoration experience.
The Samba member since 2004.

**Now rebuilding throttle bodies for VW's and Porsche's**
**Restored German Bosch distributors for sale or I can restore yours**
**Restored German Pierburg fuel pumps for sale or I can restore yours**
**Restored Porsche fuel pumps or I can restore yours**
**Restored Porsche distributors or I can restore yours**

[bnam]

I've done it a couple of different ways. I've done it with both hoses on. Then pulled off the advance and capped it with thumb. There was no change in rpm.

I've done it with both hoses off/capped and set to 7.5mm. But, then I added back the advance hose.

I will try adjusting rpm like you suggest with both hoses off and set to 7.5 and report back.
_________________
1971 1302LS Convertible (RHD) owned since '74
Click to view image
1965 Karmann Ghia Coupe - under restoration
1966 Fiat 1500 Cabrio (with 1600 Twin cam)
1952 Citroen TA 11BL

[bnam]

What exactly is the purpose of the ball bearing under the "cup" on the contact plate? Well, I found out the purpose... but let me not jump ahead.

I tore down two of my distributors and found I had enough good washers to build one distributor up. So I did that. When I got to reinstalling the points, I noticed that the new points I had on there were not Bosch so I compared with a Bosch one and this is what I found

The tip that sits in the hole to locate the point is longer on the aftermarket part. And not only does it not sit straight, but when tightened down, it drags on the lower plate.

So I fitted a new Bosch one, gapped it correctly and installed it on the car.

The car did now idle at 850 -- but there was still something wrong -- while it never died, occasionally it seemed no cylinders were firing for a cycle. I checked dwell -- it was 87 degrees. I stopped and checked -- the gap was correct. What the heck was going on???


So I pulled the distributor off and put it on my bench. I had noticed earlier that when I put vacuum on the retard side, before the plate started rotating, there was a bit of lateral play. I assumed that was the result of a worn plate.


Link


It wasn't -- it was just my incompetence -- a couple of my contact plates had worn grooves in the ramp under the ball. So on this unworn one, I had set the ball a bit more loosely so it wouldn't cause a groove over time. Bad idea -- the role of the ball on that ramp, is to take away that lateral play and leave only a pure rotational motion.

So, I tightened that up. The contact gap which I had adjusted to what I thought was 0.016" before -- was barely touching the cam -- that's why I was seeing the 87de dwell.

dropped it back in the car -- perfect -- got it idling nicely at 850, revving up and down smoothly. Took it for a test drive -- no issues at all.

So, between aftermarket quality and my own incompetence, I spent a lot of time on this damn issue. I did learn a lot about the distributors and with new shims and washers on order along with Standard SL2 grease, plus 2 distributors that I've bought over the past week - I think I will have 5 decent distributors shortly (need 1-2 unworn plates still).
_________________
1971 1302LS Convertible (RHD) owned since '74
Click to view image
1965 Karmann Ghia Coupe - under restoration
1966 Fiat 1500 Cabrio (with 1600 Twin cam)
1952 Citroen TA 11BL

[74 Thing]

You can use a rotary tool and a bit like the dremel 462 to smooth out the burr in the plate caused by the bearing so you can use it again. I think I picked up that tip from Ray Greenwood-previously I would file and sand out the burr/groove in the plate.

[bnam]

[hazetguy]

pic from bnam:

wow, that ground "wire" makes me wanna

_________________
thebucket: I invested in hoodride, now DBD won't return my call?
hazetguy: invested?
thebucket: Yeah Haze, its where people put money into a company in hopes of a return on their money

[nextgen]

Your story sounds like what I am going through with my Backfiring problem.

I have been playing with VW since 69 and I can't count the times I had problem that drove me crazy.

OK the good side, most of the time like you start with a basic Tune Up.

After I figured it out I had all new or rebuilt parts in my bug.

You rebuilt your carb, fixed air leaks got a better distributor.

Basically you were forced to do some maintenance .

Sound like my Doctor, he asked me if I was retired, I said no. He said " great keep moving , your body will tell you when to retire".
_________________
email: [email protected]
The TYPE IV UPRIGHT CONVERSION MANUAL
BEETLE MAGNETIC DEFLECTOR SHIELDS
LETS TALK DUBS https://www.youtube.com/results?search_query=joe+cali+ghia https://letstalkdubs.libsyn.com/ep-200-joe-cali-ty...qI3xJTCzjs

[wcfvw69]

[bnam]

Yep, that was the wire that came on one of the distributors -- obviously a repair with regular wire somewhere along the way. Works ok though. Do have desoldering wire to repair/replace it.

Will it solder with a regular 30w soldering iron or needs something more?
_________________
1971 1302LS Convertible (RHD) owned since '74
Click to view image
1965 Karmann Ghia Coupe - under restoration
1966 Fiat 1500 Cabrio (with 1600 Twin cam)
1952 Citroen TA 11BL