need help on 66 230 sl popping and won't idle

[merrill]

when driving , accelerating it pops and misses
it will die at idle

dwell at 39.3 degrees
timing 30 deg btdc at 3000 rpm with vacuum, about tdc at idle
bosch WR7DC+ plugs  (MB part # 002-159-24-03)
distributor 0231 185 0009

new bosch red coil and 1.8 ballast
new battery, rebuilt alternator, starter
rebuit metric motor, 200 km on it
rebuilt injection pump from hans at H&R with tested and verified good R1 injectors.

I have not been able to put my gastester on it to check the exhaust at idle because it dies.  hans said the inj pump is set so it should not be touched.

I have made small ajustments to the idle ajuster on the intake, have put it back where it was each time.  now,  I do not know if it is correct or not as I had the entire car or not.

Ideas?  Is there a base setting for the idle adjust screw, maybe that is off ?

thanks
matt



Matt
Austin Tx
66 230 sl - "white"
78 300 D - Blue
98 C230

[merrill]

so,
while laying awake last night, I figure my next step is to

1. verify inj pump timing to motor.
2. do the valves.  the motor only has 230 km on it. did the valves before installing the motor.

Matt
Austin Tx
66 230 sl - "white"
78 300 D - Blue
98 C230

[Naj ✝︎]

quote:Originally posted by merrill

so,
while laying awake last night, I figure my next step is to

1. verify inj pump timing to motor.
2. do the valves.  the motor only has 230 km on it. did the valves before installing the motor.

Matt
Austin Tx
66 230 sl - "white"
78 300 D - Blue
98 C230

3. look for air leaks - manifold, brake vacuum, cold start aid...

naj

68 280SL

[mcama]

Matt,

What color are your spark plugs?

If they are white or very light, you likely have a lean condition which can cause what you describe.

If this is the case, after verifying for intake leaks and the other suggested checks lengthen the throttle rod that runs to the IP and see if there is any sign of improvement. Came across a 6.3 with these symptoms recently and that was the issue. It was running way too lean, popping through the intake under load. Set it to give a bit more fuel in relation to the throttle butterfly, and all came back into order. NOTE: A little adjustment goes a long way.

Best regards,

Mathieu J. Cama
Lawrenceville, GA
1970 280sl 4 speed w/ 56k miles

Old World Automotive

High Caliber Repair and Mechanical Restoration of Vintage Mercedes Benz
www.oldworldauto.com

1961 404s, 1965 190c, 1967 250s, 1970 280se, 1971 280se (5 speed), 1978 280slc, 1982 280te, 1983 409d, 1983 R80RT, 1985 500sel, 1986 2.3-16

[merrill]

Mathieu ,Naj,
thanks for the replies,

funny, both repies are what hans at h&r suggested.

1. at idle spray some carb cleaner etc  around throttle body, intake manifold, CSV etc looking for a change.

2. the plugs are really really clean, and the car idles at 8 - 850 rpm. so he said If I do not find an air leak to adjust the mixture nob x3 clicks clockwise to richen.

If these do not work I am going to check the valves and pump timing.

Matt
Austin Tx
66 230 sl - "white"
78 300 D - Blue
98 C230

[merrill]

update:

so, I went home and took the easy route.  increased the fuel mixture x3 clicks clockwise.  started the car, it ran but still idled up and down and up an down then died.

I took out the gages, put one on the dwell, started the car, noticed the dwell would go from 39 deg to less than 20 then back up and each time the idle would do the same.

I thought this was strange, put a volt meter on the output of the ballast resistor and noticed the voltage would go from mid 11's to mid 9's.  and yet still the idle would roll then the car would die.

jumped the ballast, started the car and it idled, did not die.
from there I walked around the motor and sprayed carb cleaner trying to find a leak, no luck.  

turned off the car, disconnected the ballast and but an ohm meter on it.  it read 2 ohms on one meter and 2.1 on another.  

looks like the ballast is bad.  Strange because it was new 6 months ago.

the only  real change is I installed a new bosch rebuilt starter with the extra terminal to add extra boost to the start.  this was connected to the coil side of the ballast.

would this cause the ballast to go bad?   I will order a new ballast.

matt

Matt
Austin Tx
66 230 sl - "white"
78 300 D - Blue
98 C230

[hands_aus]

matt,
I notice you are using Resistance plugs.
Generally the plugs used on the Pagoda are NON resistance.
Is the red coil 'hotter' with a higher output and hence the 1.8 ohms ballast?
Have you checked the plug leads for resistance consistency?

Have you done the test for richness or leanness?

diconnect the rod that goes down to the injection pump.
increase the air supply... if engine revs increases more than 100RPM the car is running too rich.
increase the fuel supply... if engine revs increase more than 100RPM the car is running too lean.

Bob Smith (Brisbane,Australia)
RHD,1967 early 250 SL, auto

[merrill]

Bob,
you must have been reading my mind.
yes I am running WR7DC+ which is what K&K sold me and gernold recommends.

my ignition is the bosch red coil with 1.8 ohm ballast.
shoud I use different plugs with the red coil set up?

when I ordered the ballast I also ordered ngk BP6ES  and bosch 7500's
I will try both (they are supposidly similar) to see how the car runs.

Matt
Austin Tx
66 230 sl - "white"
78 300 D - Blue
98 C230

[hands_aus]

Matt,
I would try adjusting the timing before spending more money.

The 30 degrees at 3000rpm might not be 'correct' for your particular car.
Is TDC correct for idle for a 230sl?
Have you tried adjusting the timing the other way ie., at idle first then checking the timing at 3000rpm?

When I installed my Pertronix unit the engine popped while accelerating and slowing down.

I adjusted the timing to be exactly on spec for my 250sl.

All of a sudden the popping disappeared.
The next thing I had to do was adjust the air/ fuel mixture. I used the method I described earlier and have not needed to make any changes in nearly 3.5 years.

Bob Smith (Brisbane,Australia)
RHD,1967 early 250 SL, auto

[merrill]

Well,
I think I have figured out the oscillation of my motor at idle.
I think either the red coil or condenser is bad as well as the ballast resister (measures 2.1 ohm vs 1/8) .  the tech talk below discusses the funtion of the coil, condenser etc .

Technical Talk – Ignition Condensors
Basically the function of a condenser in a coil ignition circuit is to reduce the spark at the contact points as they open in the distributor and thus minimise burning and pitting of the points. Arcing is caused by the effect of self induction in the coil as the points interrupt the flow of current. The resultant collapse of the magnetic field produces a high voltage to be generated in the primary winding which then tends to flow across the points, thus causing burning or pitting. This current flows into the condenser and charges it as the points open the rapid collapse of the magnetic field produces this high voltage in the primary windings, which can be as high as 250 volts. This further charges the condenser and the consequent collapse of the field causes a high voltage to be induced in every turn of both primary and secondary windings. As the secondary winding has about 100 times the number of turns of the primary, the voltage can reach as high as 25000 volts. Normally this voltage is not reached as it is limited by various factors such as point gap, compression, engine revs. Etc. so only sufficient voltage is produced to produce a spark at the plug. As the spark is produced at the plug gap the energy in the coil, stored in the form of magnetic flux, begins to drain from the coil through the secondary circuit thus sustaining the spark for a fraction of a second or several degrees of crankshaft revolution. During this interval the condenser discharges back through the primary winding producing an oscillation of the current flow in the primary circuit for the brief interval that is required for the primary circuit to return to a state of equilibrium. The condenser DOES NOT DISCHARGE UNTIL AFTER the spark has occurred at the spark plug.

Matt
Austin Tx
66 230 sl - "white"
78 300 D - Blue
98 C230

[enochbell]

Matt,

Thanks for the tech talk and update.  I hope you have solved the puzzle, but I still don't get how the the coil, condenser or ballast resister could make your dwell fluctuate like it does.  I would think that symptom was related to a mechanical issue, like a worn distributor shaft or lobes or some such.  But I have to admit, I did not follow all of the tech discussion.

Hope you are fixed,

g

'64 230sl, fully sorted out...ooops, spoke too soon

[merrill]

so, back to the drawing board.
installed new, coil, points, condenser and NGK spark plugs.

old points were burnt, bad, old plugs were fouled.
 
so, set the dwell at 38.8 and then the timing. car ran sweet
started the car and all was great, no problem idled smooth.


then took it for a drive, ran good, then once it warmed up it ran rough, took it home and it started to idle low and almost died.

I now think the injection pump thermostat is causing the car to lean out too much when the car gets warm.

I will call hans at H$R tomorrow to see what he thinks.  thoughts?

the cold start selenoid and thermo time switch are new and hand checked the selenoid on the back of the inj pump when it was rebuilt.

Matt
Austin Tx
66 230 sl - "white"
78 300 D - Blue
98 C230

[waqas]

Hey Matt,
If you want to change the mixture during warm running, then you could adjust the shims underneath the IP thermostat. You can remove them and see if the engine runs better while warm.

WAQAS in Austin, Texas

[merrill]

so, here is additional information,

waited till this morning, put test lights on the inj pump seleniod and cold start seleniod.

started the car it was 50 deg C,
both selenoids just came for a second.
the car idled perfectly, about 880 rpms (a little high)
dwell was spot on.

Waited for the car to warm up, at 68 deg c the car started to stumble
I could hold the idle open just a little and it would smooth out.

called hans,  he said it was vapor lock in the return line between the inj pump and the dampner.  he claims the vapor builds up and cannot escape.  

the solution is to either change the routing of the return line so it
does not come out of the pump and go straight down. instead route the line horozontal so the vapor can be pushed to the dampner.

or

once the car gets hot and it acts funny again, turn off car, turn pump on, then bleed system at the 19mm banjo bolt at the dampner.
the only catch is, there is a chance the vacuum can buld up again.

i guess I wil try the second on first.

Matt
Austin Tx
66 230 sl - "white"
78 300 D - Blue
98 C230

[merrill]

so, when I got home from work, car started like a champ, idled nice and smooth.
removed the idle adjustment screw entirely, idle went up but was smooth.

Then, once it warmed up, to 70 deg c the stumbling stated.

removed the gas cap, no change
put the idle screw back in, adjusted a little, no change

checked the fuel return line, it already is parrallel to the fuel rail when it comes out of the inj pump.

so I went ahead an cracked the line, till fuel came out, no change.

my inj pump has a nut to "turn off" the inj pump thermostat, I will call hans tomorrow and see if he thinks I should try the car with it off.



Matt
Austin Tx
66 230 sl - "white"
78 300 D - Blue
98 C230

[JimVillers]

Mat ... I just read through the posts and it did not sound like you have correct your ignition issues.  First, set your timing with the distributor vacuum line disconnected.  It sounds like your timing and dwell is not consistent when measured at different times and temperatures. Burning points is also indicates that something is not correct.  

Look at your timing marks with a timing light, if it is not stable at a constant speed, it is time for a rebuilt distributor.

Installing a Pertronix ignition should correct your other problems.

Jim Villers
190SL, 230SL 5-Speed, 190E 2.3-16, MGB 5-Speed

[merrill]

Alas!! all is fixed, I knew being stubborn would work.

called hans at h&r today he said, after all the things I have done
go home and check that the 14mm bolt for the inj pump thermostat trave the o is up.
then try the car, well nothing different.
then he said increase the pump by 2 clicks clockwise.
still nothing,
called hans, we increased by 5 clicks, no avail,
he had me pull the vacuum line for the brake booster no change
he had me pull the entire idle mixture screw mechamism off the intake manifold and make sure that was claer,  all clear.

then called gus at pacific, told hiim everything, he said do the richness test,  the motor rpms would not go up more than 10 rpm.
we increased the pump an additional 4 times clockwise in 2 attempts
still no significant increase doning the richness test.

then got a hold of hans again,  told him we were at 11 to 12 clicks clockwise with out improvement.  He said, wow, that is too much,
IT MUST be your fuel pump pressure.

well, pulled the fuel line off the cold start selenoid and put on the fuel pressure guage, the pressure was over 16 with just the pump on.

then hans had an idea.   There is an atmmospheric pressure guage on the pump that controls the fuel going thru the pump.

(those sneaky germans)  It is the tuna can on the top of the pump forward of the injection pump thermostat.  He said unscrew it and check the spacer washer thickness.

my washer was .5mm thick, we ended up putting in another washer for a combined spacer thickness of 1.9MM.

backed off the inj pump about 10 clicks, started the car and
MAN IT WORKS GREAT.
the idle is about 850 rpm and the motor is responsive to the idle adjustment screw.  did the richness test and the motor went up to 1200 rpm.  Both hans and Gus were ok .

I will probably back off the inj pump a few clicks till the rpms only go up 100 rpm, then set the idle at 850 and check the exhaust
to see what the gas reading is.

yeah!! it works.

thanks everyone for their patience and help.
Special thanks goes out to hans and Gus.  I was probably on the phone for 2 hours between the both of them and they were very patient.

Matt
Austin Tx
66 230 sl - "white"
78 300 D - Blue
98 C230

[J. Huber]

Good job staying with it Matt. Now I have a semi-related question. Here's my scenerio: car is running and idling well after my lessons in points, linkage, timing, etc. However, I'd still bet I am running rich. One clue is my mpg continues to stink -- somewhere in the 12-16 range. And that 16 is highway miles. Having had my car so long I know this is down from my more typical 16-20 range. My question is: would a few clicks to the leaner side with fuel idle screw help -- and can it be accomplished without messing up the idle?

James
63 230SL

[Dick M]

quote: . My question is: would a few clicks to the leaner side with fuel idle screw help -- and can it be accomplished without messing up the idle?

James
63 230SL

Take it to Rick...

Dick M
1970 280SL

[J. Huber]

quote:Originally posted by Dick M
Take it to Rick...

Dick M
1970 280SL

That's very good advice, Dick. Good chance I will -- do you have any plans for a trip out to the Ranch soon?

For those wondering, Dick is referring to Rick -- our resident MB mechanic extrordinaire (SP?). His Father was a career Mercedes Factory tech in the Fatherland for many years. Retired to the country here in Nevada County -- and now his son Rick has carried on the family tradition. I believe they call it the Silver Star Ranch.

While not quite as exciting as the Mustang Ranch, its a neat place.

James
63 230SL