TheSamba.com :: View topic - Timing Issue

Sun Jun 18, 2023 5:35 am

Hello all, I have an issue with my Type 181 that has me a bit perplexed. Hoping you friendly folk here may be able to help me resolve. Apologies for the long post, but I thought the full picture would be more helpful.

A little background: I inherited this vehicle from my father a couple years ago and it's seen sporadic use since. Knowing my father, I doubt it was really taken care of and I've already corrected a few issues. Even before it came to me, it's always been a hard starter, until this past fall it was driving along and everything died. I diagnosed this as a bad ignition switch. This spring, I replaced the switch, adjusted the valves, and removed a little elbow on the oil filler that I suppose was on there to make filling easier, but was very loose and I believe allowing oil mist to spray into the engine compartment (VERY oily in there, I've been slowly cleaning it up). Battery was also replaced. After this, the engine fired right up and ran decently, but seemed to be missing at low RPM.

That is, until I drove it more than a mile away, at which point it wouldn't start and had to be towed home. I worked with my step-father to diagnose what looked like a spark issue. I replaced the rotor and cap, and the car started, but again seemed to be missing. I've since replaced the plugs, wires, points (set to 0.6mm), and condenser, and gave the "Uh-oh-Nine" one hell of a cleaning, and the hard-start/missing conditions seem to persist.

At this point, I hadn't touched the timing, only checked the current timing (~7-10° ATDC static, 22° BTDC at 3k RPM). My theory was that the timing was set so far retarded, the engine was missing or just otherwise running poorly. I tried setting to 5° BTDC statically, but the motor wouldn't start. So I reset the timing statically to the original timing, started the motor, warmed it, then set the timing dynamically to 30° BTDC at 3k RPM. Seemed to run well, until I turned it off and tried to restart. Now it just cranks and cranks until the garage smells like gasoline, with the occasional fart. Setting the timing back to what it was when it came to me, it will start.

Engine is an AM series, 1600 DP, if I am not mistaken. Dizzy is an 009. TDC was checked and verified to be at the dimple on the crank pully via the straw method on cylinder 1. I have the pully with the dimple and the groove cut at 7.5° ATDC (left of dimple). Carb is a Solex 34PICT3, very dirty on the outside, but jets send a goodly stream into the throttle body (observed with air hose disconnected).

I'm pretty green when it comes to these motors, but what I am observing seems incongruous with what I've read about them. I am currently going through the nls.net "Why Won't My Engine Start" checklist, but I thought I'd start a dialog here in the meantime. Thought? Suggestions? Thanks in Advance![/list]

Sun Jun 18, 2023 7:46 am

Update: did a compression test. Looks good to me:

1: 112 psi
2: 112 psi
3: 120 psi
4: 125 psi

Also checked firing order of plug wires. It is correct.

New plugs which had been turned over quite a bit and run for a short period were black, wet, and sooty... Does this indicate rich fuel mixture? Or just from unsuccessful starts?

Sun Jun 18, 2023 8:28 am

Double check the wires. Cause it does sound like the spark plug wires are in the
wrong order.

Sun Jun 18, 2023 10:42 am

Thanks for the suggestion. Checked again, plug wires are definitely in the right order.

Sun Jun 18, 2023 12:43 pm

What distributor are you using?

Post a photo of your engine.

Sun Jun 18, 2023 2:07 pm

Distributor is a 009, Engine code AMO25145

Sun Jun 18, 2023 5:51 pm

Time the 009 at 7.5 or max advance 28 to 32 degrees.

Your engine will run better without the 009. Get a 113 905 205 AN (stock unless California model) or a 043 905 205 (034). That will get rid of the hesitation at low RPM.

Sun Jun 18, 2023 8:32 pm

Hi, thanks for the advice. When tuned to 30° BTDC at 3k RPM and then shut off, the motor will not restart. The motor will only start when tuned statically to ~5° ATDC. That's the problem I'm trying to solve. I could be wrong, but I don't think a different distributor will solve that issue.

Sun Jun 18, 2023 11:39 pm

I think it will. Check out the link. If you need to retard timing it can mean too lean for the setup it dosn't mean you should make the carburattion richer it could, but is most likely the timing curve dosn't follow the richness curve of that carburettor. 009 give poor performance as there maxi advance is only 30° at best but usually around 25° (poorly designed and made) where a later original (single or double vacuum) dual advance has upto 42° timing variation giving way better performance and fuel economy. 009 the lower the rpm's the worst they run so a staring problem with an 009 isn't at all surprising. https://www.thegoldenbug.com/en/vw_technical_articles/d131/history_of_the_bosch_009_distributor

Mon Jun 19, 2023 6:34 am

You may very well be right, but let me explain why I don't think the current distributor isn't the main issue.

When set at 5° ATDC, the Max advance was found to be 20° BTDC, meaning the advance was ~25° between engine off and max advance... within spec for the 009.

At this point, I set the max advance to 32° BTDC. Engine runs fine, idles this way, but when I shut it off, it won't start. I checked the static timing at this point and found it to be at about 7° BTDC. Again, the mechanical advance is 25°

Even though it has been timed correctly with the second scenario, the engine won't start. Doesn't seem to me to be distributor related, but maybe I am misunderstanding? How can this be?

Mon Jun 19, 2023 7:47 am

5 Atdc to 20 Btdc= 25° movement
32Btdc-7Btdc=25°
5Atdc to 32 Btdc= 37° movement
Means you need a distributor with at least 37° variation.??

Mon Jun 19, 2023 7:57 am

Hmm.. interesting.. my hypothesis was that I need to get the motor to start closer to 7.5° BTDC rather than a distributor with more variation..

Is it safe to start the motor with the initial timing so far retarded?

Mon Jun 19, 2023 9:03 am

kecknj13 wrote: Y
When set at 5° ATDC, the Max advance was found to be 20° BTDC, meaning the advance was ~25° between engine off and max advance... within spec for the 009.

At this point, I set the max advance to 32° BTDC. Engine runs fine, idles this way, but when I shut it off, it won't start. I checked the static timing at this point and found it to be at about 7° BTDC. Again, the mechanical advance is 25°

That sounds close to being right. 7 degrees at idle is usual.

Are you able to clean your distributor? It might be sticking.

Mon Jun 19, 2023 3:26 pm

7.5 BTDC would be normal... It will only start and idle at around 5 to 7 ATDC.

Dizzy has been pulled and cleaned, I don't think it's sticking.

Tue Jun 20, 2023 3:35 am

Check this video out. I think it might help. The leads on a 009 distributor should be rotated 90° compared to a standard factory distributor cap .

https://m.youtube.com/watch?v=787INwvir24

Tue Jun 20, 2023 1:19 pm

kecknj13 wrote: Thanks for the suggestion. Checked again, plug wires are definitely in the right order.

With the distributor cap off, put your engine on TDC #1 cylinder. Where is the rotor pointing at in the cap? Is it pointing at where the #1 spark plug wire is in the cap? Are the rest of the wires in the correct firing order 1-4-3-2?

Wed Jun 21, 2023 4:28 am

wcfvw69 wrote: kecknj13 wrote: Thanks for the suggestion. Checked again, plug wires are definitely in the right order.

With the distributor cap off, put your engine on TDC #1 cylinder. Where is the rotor pointing at in the cap? Is it pointing at where the #1 spark plug wire is in the cap? Are the rest of the wires in the correct firing order 1-4-3-2?

Yep, pointing to number 1 wire when at TDC. Wires are definitely in the correct fitting order. Also verified tdc for cylinder 1 with the straw test in spark plug hole for cylinder 1.

Wed Jun 21, 2023 8:10 am

kecknj13 wrote:
Yep, pointing to number 1 wire when at TDC. Wires are definitely in the correct fitting order. Also verified tdc for cylinder 1 with the straw test in spark plug hole for cylinder 1.

Using a straw isn't good enough. You have to look at the valves as well.

Wed Jun 21, 2023 12:14 pm

heimlich wrote: kecknj13 wrote:
Yep, pointing to number 1 wire when at TDC. Wires are definitely in the correct fitting order. Also verified tdc for cylinder 1 with the straw test in spark plug hole for cylinder 1.

Using a straw isn't good enough. You have to look at the valves as well.

Yes that's true. I had just adjusted the valves and they were both closed for cylinder 1 when the dizzy was pointed to the cylinder 1's plug wire. I then found absolute TDC with the straw test, verified it was at the notch on the crank when the dizzy was pointed to the plug wire for 1.

I'm setting the timing correctly. The engine will only start when set statically at ~-5deg ATDC or dynamically at ~20deg BTDC at 3k rpm. Something else is going on here that's not right.

Pulled the plugs today and they were fouled with dry black soot. More and more evidence seems to point to running rich. Thoughts?

Wed Jun 21, 2023 7:12 pm

5 atdc static and 20 btdc@3000 rpm is the same point of explosion in the motion/cycle ie. on the downward side at least 5 degrees minimum but in reality more like 15°+ by the time the spark ignites the mixture and it fully explodes. Way after tdc the only thing stopping it being able to explode before this point of the cycle would have to do with the valves not being fully closed before this point in the cycle. I suggest checking the valves are correctly adjusted both exhaust and intake valves.