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  #1  
Old 11-06-2010, 09:07 PM
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Fintail Ignition Timing

Before I figure out what's wrong with my carburetors, I want to be sure the ignition is up to snuff. 1966 230 with the 180.945 engine. I see the timing spec in the owners manual says "approx. 2 degrees UDC." However, the service manual has an assembly setting stating "Stroboscope check at starter speed and with spark plugs installed 3 degrees BTDC". Then there is also a table for "Ignition setting and stroboscope values at engine speed" and lists a range of degrees at various RPMs. The text says to check it at 4500 RPM without vacuum. That setting is listed as 37 degrees.

First of all, is UDC the same as BTDC?

Secondly, is there really 37 degrees of advance at 4500 PRM? Seems like a lot. What do you guys recommend? Just set it at 2-3 degrees BTDC at starter speed and then check it at 4500 RPM?

Also, is the table with "Closure angle" the same as dwell?

Forgive me, I am more familiar with diesels and it's been many years since I tuned up a gasser. What's more important, dwell or gap? Doesn't one affect the other?

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1981 300TD 310k miles
1970 280sel 172k miles
1966 230 Fintail 162k miles

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  #2  
Old 11-07-2010, 06:39 AM
t walgamuth's Avatar
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The 37 degrees sounds about right to me. I think dwell is more accurate for setting timing than point gap but I always just used point gap and that worked for me. I did not have the tools to do dwell.
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  #3  
Old 11-08-2010, 10:42 PM
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This may not be at all relevant... When I was waking my Fintail from a 10-year slumber, I rebuilt the carburetors but still was not getting power beyond 3000 rpm, then discovered that the vacuum tube from the carburetor to the distributor was blocked. The advance was not working correctly until I cleared the line. Now the engine has a nice smooth acceleration and torque curve.
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Old 11-09-2010, 12:07 AM
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Thanks for the replies, everyone. Spent the day working on the ignition and it starts and runs well, now. I pulled the plugs and checked the gaps. Disassembled the distributor and cleaned and oiled everything. Checked the vacuum advance diaphram. Made a little grommet to ensure the terminal through bolt would not touch the distributor body. Set the dwell. Advanced the timing which was way retarded by the PO. Now sits at 3 degree BTDC at idle.

On the carb, I found that the vacuum fitting was loose, so I turned it around so it fit tightly into the body. I adjusted the choke linkage so that each plate position was identical. I tested the idle switch and adjusted it so it actuated correctly. Reset the idle speed and mixture. Lastly, I balanced the carbs using the 3 and 4 plug wire pull-off method.

The car starts right up but I still get a stall when putting in gear. I'm thinking there must be a faulty solenoid on the transmission, although it shifts well enough when you get going.

I'm relieved that it looks like I won't have to tear into the carbs. I have not been able to find an exploded diagram for my particular carb (Solex 38PDSI).

The Ponton site was a real godsend in doing this work.

http://www.mbzponton.org/valueadded/maintenance/workshop.htm#fuel
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1981 300TD 310k miles
1970 280sel 172k miles
1966 230 Fintail 162k miles

"Where are we going? And why am I in this hand basket?"
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  #5  
Old 11-09-2010, 08:43 PM
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WRONG. Today I tried to start the car and it was as hard to start as usual. Starts great when warm, but is a bear when cold.

Any ideas?
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1981 300TD 310k miles
1970 280sel 172k miles
1966 230 Fintail 162k miles

"Where are we going? And why am I in this hand basket?"
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  #6  
Old 11-11-2010, 12:38 AM
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Quote:
Originally Posted by Carpenterman View Post
WRONG. Today I tried to start the car and it was as hard to start as usual. Starts great when warm, but is a bear when cold.

Any ideas?
Just exactly what is it doing when you are trying to start it?
Hard starting can be any of a hundred things but without knowing what the engine is doing when you are trying to start it,it's impossible to give an answer. i would start off though by getting the battery checked and replace it with the correct type . These cars use a Big battery . Next clean ALL the terminals on the battery AND the starter motor . While you are at it,remove the starter and rebuild it.
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Old 11-11-2010, 02:44 AM
mak mak is offline
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if you have not, worthwhile to check
rotor resistance and for tracking .same would be true for cap.

if the carbs are fueling correctly then the last item to check would be valve clearance ;should be .10 intake and .20 mm exhaust. cold engine

mak
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  #8  
Old 11-11-2010, 08:57 AM
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Do you have a choke? My car starts much better on cold mornings with choke on. (You did say "any" ideas... Hope it is not too obvious a suggestion/thought/idea
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  #9  
Old 11-11-2010, 09:30 AM
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The battery is new and the correct type. Terminals good. The starter turns and sounds fine, although it never hurts to rebuild something at this age.

The points, rotor, cap, wires and plugs are new. No sign of tracking. Dwell and timing set to spec.

I have not checked the the valve clearances. PO said he just did them, but you know how that goes. I'll check them again, soon. I tore the heater cores out and need to get them boiled and pressure tested. I had to resolder the intake pipes where the fitting was separated from the body of the core.

Yesterday, I sprayed carb cleaner around the leak points on the carbs looking for a vacuum leak--couldn't find one.

What works best is to pull choke all the way out, turn over, car catches then dies. Push choke in to half way, turn over, car catches and dies. Try again, slightly pump pedal. Car catches and dies. Try again at half choke, car catches and if I give it more pedal, car will stay running. I then let it run until the engine warms and will stay running without choke (about 5 minutes). When warmed-up, the car sounds like a well-running sewing machine and will re-start without any problems.

Sounds like a fuel problem, doesn't it? Should the choke butterflies be all the way closed at full choke? I left about a 1 mm gap. Is there a spec for this?
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1981 300TD 310k miles
1970 280sel 172k miles
1966 230 Fintail 162k miles

"Where are we going? And why am I in this hand basket?"
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  #10  
Old 11-12-2010, 04:36 AM
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No specs for the choke butterfly and only practice makes perfect when dealing with a manual choke , but it sounds like the old mercedes bug bear , the fuel pump.
Check all connections from the tank to the pump to make sure there are NO Vacuum leaks . not a fuel leak , but somewhere the air is being sucked into the line ciasing a loss of vacuum so that when you go to start the car,the fuel has run from the pump back to the tank. All rubber hoses are suspects .
I have seen this cured by fitting a facet pump at the rear ,close to the tank outlet and connected to the ignition coil so it gets 12 volts when the ignition is on .
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  #11  
Old 11-12-2010, 08:37 AM
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I finally got hold of a 38 PDSI carb adjustment procedure. It states that the choke butterflies should be completely closed with the choke pulled all the way out. However, your suggestion of a vacuum leak in the fuel line is very likely. I'll check the lines as soon as I get a chance.

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1981 300TD 310k miles
1970 280sel 172k miles
1966 230 Fintail 162k miles

"Where are we going? And why am I in this hand basket?"
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