280c wont sit still

Hey, I'm new to the forum and after spending the morning searching old threads I decided to just ask the question- My 110 automatic has trouble starting at less than 40 deg F. It usually takes a jump to get it started. The odd thing that is happening is this: When the starter is engaged the car seems to want to move. Then when the engine fires a little (remember hard starting) it actually lurches forward a bit, but when it starts it actually starts trying to go down the road. When it is revved up the brake has to be on to keep it from moving. I can tell that the tranny is not disengaging with the brake. I have tried this scenario in park and neutral, it doesn't seem to care what I do , it just wants to lurch off down the street. The problem goes away when it gets warmed up. The fluid is full. I read about checking the vac. modulator and will do that first thing. I am a lifelong car restorer/buff (I learned to drive at 13 yo on a 1930 Model A chassis with a coffee can gravity feed gas setup) but this is the first Benz that I have had the pleasure to work on. Before I go out there and start trying things I was wondering if anyone had any suggestions for this/these problems. I don't get any satisfaction reinventing the wheel. thanks

[oxymoron]

By no means an expert, but try searching "neutral safety switch".

Just a guess

[ctaylor738]

I would check the linkage adjustment to make sure you are in the gear you think you are in. You might also need shift rod bushings.

I think the adjustment is described in some posts, Basically, with new bushings, put the trans in N and stick a large nail through the holes in the center of the linkage, then adjust the screw end on the linkage arm.

If if ain't that, then you probably need to find a transmission shop. I'd suspect the valve body.

[Tristar1959]

For starting probs, suggest back-to-basics re: choke and choke pull-offs - sounds as though you're either not getting choking or maybe too much - when you crank and it's not starting - can you smell fumes or not...

Some potential related areas:
My "Service Manual, Engine 110" has a large section on the USA 75-76 choke cover-stepped heater and the switchover valve for the automatic choke - the entire nightmare mechanism would do anyone at EPA proud! - your switchover valve (white body) itself shows to be on the back of the mounting plate next to the 8 ohm ballast resistor; but you also have a nasty little relay box on the vacuum controls distributor's back plate - involving just about everything emissions-controlling the carb - and the procedure addresses any of its switching problems by "renew relay box".
You also, in the 76, have a "Thermo Delay Valve" inline in the pulldown's vacuum line, which is supposed to govern the pulldown, depending on OAT.
You also have a 17C temp sensor at the oil filter's housing, which governs the relative strength of the choke heater's juice. Also, whatever's "dragging" in the tranny doesn't zactly help you to spin up starting rpm's...

Given all the carb/emissions/controls/versions variants and the complexity - I recommend getting a copy of this manual - MBNA reprinted in 1994 - "Order No. S-6510-1914-13." Not just for this, but everything.

Tranny/Start.
My 114-115 Service Manual, procedure 27-4, Troubleshooting Hints for Automatic Transmission, under "Vehicle starts to move when starter is actuated", states, "1. Selector Sleeve (28) detached, or 2. Short circuit in starter lock-up switch" (believe that would be the neutral safety switch). These presume, however, that the shifter was indicating and selecting correctly when you were starting in P and N.

Someone more knowledgeable in these automatics is going to have to evaluate and expand on the selector sleeve - I don't think it would be running/shifting at all if the sleeve were in fact detached.

Stan Braisted

OK, I guess its time to get real with the manuals. I appreciate the info and I will follow through asap. Its an extra pressure problem since my wife (she is a garden designer and is going to call on clients in it) is looking to me to make it "go" soon. Also, even though its a '76 people are constantly asking what year in the 60's is it?. Its a very unique model with the older looking front and the hard top. Thanks again and I'll let you know how I get it to sit still and start when I want it to.

[250 Coupe]

I'm wondering if it's a band mis-adjusted? Or correct fluid level. Since it wants to move forward in both park and neutral, I don't think it's linkage related.

My 280C and 250C both kind of move forward when you rev them in park, They don't actually move but sort of rock back and forth. Are you seeing actual movment or just a slight lunge?

As for hard starting, is it spinning slow and thus the jump or are you needing to crank so long that it kills the battery?


Michael

[dkveuro]

As fluid gets older it thickens up a little..someone my also have used an addative to improve shift quality or stop leaks...this will def' increase the thickness of the ATF.

Some slight forward movement is normal when revving a cold engine but dragging you down the street is not. The forward clutch pack assembly acts like a badly slipping clutch when cold in N or P, but it should not affect the cranking speed of the starter by more than 10 rpm.

Remember, the old R/R Silver Ghost would start by just a 1/4 turn of the handle.

You need to make sure the carb/s squirt a little fuel when pressing the throttle to set the choke. At this point, choke flap should be fully closed.

.

It was running the battery down crankin' it and when I would hook it up to the Dakota it would kick off pretty quick-So I started hooking it up to the truck when I would begin and it started right on up. When the starter engages it does put a kind of torque on the car, but when it fires it starts moving and when it starts if you don't have your foot on the brake it will go. The first time it happened I started revving it as soon as it fired and it leaped forward- I came to my senses and hit the brake just inches before it hit the truck that was about three feet away. My wife was standing next to the car and she thought I was trying to hit her. Yeah, it wants to go, from then on ( about 7 or 8 times) I have done nothing without my foot on the brake.
I think I will start with fresh fluid and a check on the neutral switch and linkage tomorrow in the AM. thx

[MunichTaxi]

Next to the end of the transmission shift linkage (passenger side), for the K4C 025 transmission there is an adjustment for the B3 brake band. The spec is "after loosing counternut, tighten adjustment screw to 0.5 MKP (43 inch-pounds), then back off 1-3/4 turns".

The first time I did this I forgot to back off the 1-3/4 turns.
I started the W108, and in Park, was going backwards very, very quickly.
Since my transmission is very old I found that backing off 1-5/8 turns gave me neither forward or backward motion. Caveat: Your mileage may vary

[Tristar1959]

After you try the band adjustment, there is likely nothing wrong with a good fresh filter and fluid, just in case you are also gummed up - may free up something, and in any case not going to hurt anything. (Unless you have really good, clear red fluid which absolutely neither smells sour nor 'caramel' sweetish-burned.)
Levels are important - too low can cause foaming, too high can not only cause blowover out the filler, but excessive heat and possible damage. Normal cold levels MAY be just below lower dipstick mark; but in operating temp range, after cycling through gears, should be between marks, near upper.
If you do decide to do filter/fluid - don't omit draining the "fluid coupling" (predecessor to 'torque convertor') which holds a high percentage of the fluid - you have to rotate crank (27mm deep socket-also useful while adjusting valves and zeroing timing, etc) until its drain plug appears over that round opening in the lower vent screens. Refill, with new filter, should take a total of 4.6L - suggest filling with about 4 qts, running up warm and cycling thru gears, letting settle, rechecking, then gradually topping up.

Plenty of parts advice and sources available here for correct filter & gasket kit - I believe the number on this tranny also on R side of bottom of main casing - right, fellas?