Engine misses badly when cold

[Gregg Bambo Jr.]

Lately my 1963 six cylinder engine (m127.984) has developed a cold start up problem. It misses badly at all rpm's until it is thorougly warmed up. Initially after a cold start up, it misses so badly that I can hardly increase the rpm above 1500. As it warms up, I can then increase the rpm to max but it still misses slightly. At that time, if I let it idle, it slowly oscilates between 300 and 700 rpm. When it is completely warmed up it runs like a fine watch and doesn't miss a beat at idle or high rpm! I checked the spark plugs and they all have a light brown color without soot. I thought it might be an injector problem, but if that was the case, why would it run perfectly once it is warmed up? Six months ago it had a valve job with new seals and the compression is even across the board. Anyone have an idea as to the cause?

[Arthur Dalton]

Did you ever check the cold temp thermo sensors intake filter on the IP I mentioned to your last post?

[Gregg Bambo Jr.]

Arthur,
Yes, the filter was checked and free flowing.

[Arthur Dalton]

OK
Next quick test is to put you finger over that port with filter removed and see if you have suction there when engine is running cold
if you do, does it stop suction when engine gets to approx 70C

[Gregg Bambo Jr.]

Arthur,
I performed the vacum check as you directed. With the filter off and a cold engine there is maximum suction/vacuum at the port. With the engine fully warmed up, the vacuum is quite a bit less but still present. What does this test indicate? If I plug the port with my finger while the engine is warming up the engine stalls. At normal operating temperature the engine idle fluctuates between 300 and 800 rpm.

[wbain5280]

Vacuum leaks cause the idle to fluxuate as you describe. Check the plunger under the IP thermostat, the one with the two hoses. Also check the IP oil level. Too much oil causes the govenor weights to slosh in the oil.

[Arthur Dalton]

The vac has to completely close off at that port when coolant is at 65C.. if not , that is the vac leak.. you have to take that tower off and clean it.. they get stuck and full of crap..
don't let any anti-freeze get in the pump..
Also , after you get that running right , block off the booster hose and see how she runs..

[Gregg Bambo Jr.]

Arthur,
I removed the IP thermostat. It didn't look too bad inside but I have a question regarding what looks like a small plunger tip on the end of the brass tube insert. Is it supposed to move in and out? I tried compressing it and it doesn't move. How does this component work? From looking at it, if the gasketed end is sandwiched between the housing and the mounting, it doesn't appear to have any moving parts! Picture attached. It also has two gaskets, one brass washer and one rubber. Gregg

[Arthur Dalton]

The pin moves in/out with temp on the bulb of the cylinder
At room temp [20c] it is about 6 mm , At 80C , it should extend to about 9 mm..
You can test it in some hot water..
When the car reaches about 70c , the pin should push the air slide under the pi assem closed , so no air is sucked in the port.. check that slide for clean and oiled ...put all spacers back where you found them, as they are the adjustments.

[Gregg Bambo Jr.]

Art,
Took close measurements and the thermostat tip, in the cold condition, was 3mm and, after boiling it in water, it extended to 5 1/2mm, resulting in 2 1/2mm of travel. Since it no way matched your specifications of 6mm & 9mm and 3mm of extension, does that mean that the brass bulb needs replacement? Checked with a discount parts provider and the cost of replacement for the thermostat unit is $787!! Checked the underlying plunger and it is free. Couldn't remove the underlying shaft, as suggested, as I couldn't figure out how to remove the adjusment bolt on the side of the thermostat base. It just kept turning and an I observed an internal tip adjusting the plunger to a lower position. According to my manual, a half turn clockwise would depress the plunger enough to eliminate the IP thermostat function.. Even with the adjustment pushing the plunger to what I would assume to be full depression, there was still a slight bit of suction coming from the air filter inlet. Isn't that plunger in full depression supposed to cut off the vacuum completely? Looking down into the hole I see a mushroom like pin with a nut at its base. Is that pin adjustable so that it can be extended and create additional travel? Gregg

[Arthur Dalton]

Is the coolant getting up to 180F ???

There should be no air suction at temp.
Do you have a pump # ?
The last "R" number will do [ like R11]

[WANT '71 280SEL]

There is a member here parting out a 220SE coupe. Try PM'ing him with a request. I'll go find out his name right now for you...
Thanks
David

[WANT '71 280SEL]

wdba123190

-David

EDIT:
Sorry, I guess his is a 280SE coupe. Would they happen to be the same thermostats? maybe, but I wouldn't know the answer to that.
Thanks
David

[Gregg Bambo Jr.]

Art, To answer your question, I looked all over the Fuel injection pump with mirrors but couldn't find a model number . Where would I find it? To answer the question about the water temp, I had the thermostat in boiling water for at least 5 minutes, which I assume is over 100C and should have caused the pin to fully extend. I did check the pump oil level and discovered it to be over filled as the oil came lowing out when I removed the dipstick. I siphoned as much as I could to bring the level down with the smallest pipe (the dipstick hole is very tiny) that I had but, according to the dipstick marking, it is still overfull. I'll have to locate a syringe I guess from a local junky to get the level down further. I am still curious as to why, with the maual adjustment bolt turned down why I continue to get suction from the air filter inlet. Gregg

[Arthur Dalton]

You are correct that with the manual bolt you should have no intake of air.
I don't know what happened to your pump ID plate , but it should have one.
I will assume it to be an R11 or 14 , but there were 6 different ones on the 127.984.. 220Seb ??.. I can narrow it down if I know auto or stick..
It should be the 2 plunger .. does it have a red air vent cap?
these will help ID it..

Anyway, you have to get all that oil out .
The reason it overflows is they get gas diluted and fill up.. so that breaks the sealing of the plungers.
I just did one this week on a six plunger and the easiest way is to go get a long ,skinny air tube at a parts place [ the kind they use on small air actuators- plastic line that comes with the separate ferrels] and hook it to a vac pump . there is about 10 ounces in there when the dip-stick shows Normal.. and you have to go in through the dip hole in order to get it all out ... takes some time
I have a clear , sealed jar I use that allows for vac to be pullled on the jar and let the fluid drop in , but the air to come through ..
Anyway , you MUST do this first..
I also remember seeing a modification on the early pump thermo adjustment and will look that up.
Where is the squirter on your model?