Engine misses badly when cold

[Gregg Bambo Jr.]

Art,
My cabriolet has an automatic transmission and the injection pump is a two plunger. It has a red cap but I don't know if it is. as you dscribe, a breather as it says "OEL" on the cap (Is this where you would add oil if required?). There is a square indention on the right side of the pump assembly that looks like a provision for an identification plate but there is nothing in that spot. What did you mean when you asked where the "squirter" was located? If the oil is being diluted by fuel and since I will be syphoning the excess fluid volume out, should I completely drain it and replenish it with new oil? If so what kind of oil/weight should I use? There is nothing in my manual that specifies what to use. By the way, when I initially removed the oil dipstick, the amount of oil that overflowed was close to a pint! In the ten years that I have had the car, out of ignorance, I had never checked the IP oil level. That is a lot of fuel oil dilution or does the engine oil system augment the IP pump? Gregg

[Arthur Dalton]

Let me try and answer in sequence

The OEL cap is both the oil fill and the pump Breather
Take this cap off and clean it , as they also get clogged and won't vent, causing oil cavitation [ as does over -fill]

Squirter is the Cold Stat Valve .

The oil has to be changd every 30K in the pump.
It will take 10/30, but if you live in warm climate , straight 30 is fine .. a good quality motor oil, not syn.
The oil in the res is not replenished from the engine crankcase , so if it fills up, it is long time fuel contamination .. bad... [the later pumps went with crankcase integrated lube ]
Get it cleaned up and refilled and we can then see what you have . may be some worn slides and such from lack of adequate lube..

[Gregg Bambo Jr.]

Art,
I couldn't find anything long and thin enough to insert into the IP dipstick hole in order to drain the oil as you suggested. The hole is only 3mm in diameter. Is there a drain plug that isn't obvious? How did you drain the oil? Also, the red "OEL" cap doesn't have a vent hole. Should I drill one in it? Gregg

[Arthur Dalton]

No drain plug [ You would think they would have one , but they don't]

The hose I use on these is plastic and a foot long and it is .150", so that would be a little better than 3mm..it does fit , but tightly..
I got mine at a hobby shop for R/C model supplies, but I have seen that in hardware stores in rolls .. you may also use small copper tubing . Any place that sell refrigeration supplies will have small diam. copper , as they use it for 'Capillary Tubes " on refrigerators... might even see that at the dump...
The trick is to make sure you have it long enough so that it can not drop into the sump. On the other end , I just slip on a piece of vac hose and then slip the other end of that onto a fitting on my vac jar/pump..

The Oel cap does not have a hole , but if you turn it upside-down, it should have little holes around the rim to vent it ...don't drill anything as there may be another vent somewhere I am not aware of.. they has many versions of this pump.

You can also evacuate from the OEL cap hole with a thin straw, but it will not allow full evacuatuon to the bottom of the sump, so you have to get a tube into the dipstick hole , one way or another ..
Let me know how you make out ....
Do you have a vac source ???

[Arthur Dalton]

Another thought came to me

For the plastic tube of the proper size , you may also want to look at the many household cleaners that have a squirter mechanism on the bottle ... take them apart and they all have some sort of dip tube inside... I just looked at a Windex one and it might even work...looked a little fat .. check them all out..
WD-40 has an aiming tube that come on the side of the can are also small , but they are short and might be a little too small
Keep looking around.. you may have something right in the house..

[Gregg Bambo Jr.]

Art,
With your suggestion I was able to come up with an acceptable IP oil evacuation tool. It might not be up to MBZ standards, but although slow, it works. I found an old spay bottle and utilized its 3mm internal siphon extension, glued it to a straw and then glued the straw to a hypo syringe ( a three step graduation in size). It's late, so I'll fill it with new oil tomorrow and see what develops with regard to my engine missing problem. After reading my manual again, an understanding how to remove the " Eccentric Stop bolt" now, I am tempted to looking into: a. Extracting the slide valve and making an adjustment to the "supplementary air control slide valve" adjustment screw to increase its travel in order to cut off the flow of the filter inlet suction. b. If there is still a system vacuum leak, replacing the "electric magnetic cold start valve" rubber seal. The book lists my Injector pump as a ZEB 2 KL75 R13 or R16.

[Arthur Dalton]

Very good..

With refill, start with 6 ounces and then top off slowly while checking the dipstick with each 1/2 ounce addition...
they are easy to over-fill and then you are back to suction again.. which, as you have found, is slow and a pain.

I would not make any pump adjustments until you try running with the proper oil charge. The overfill not only changes mixtures and restricts fly-weights, but creates seal back pressures , so you complaints may need nothing more than oil change..

That is the later style pump, which is good
You may later make sure your squirter valve is not leaking by when the car is running ..common fault

[Gregg Bambo Jr.]

Art,
Unfortunately draining and refilling the IP to the proper level did not solve the missing problem. I guess I'll look into the other items like possible cold start valve leakage. The symptoms are strange in that running the car after a cold start, it will miss badly at low RPM. Even after it is warmed up it will still miss until I start increasing the rpm and letting it run at around 4000-5000. When I let it do that for a while the missing at the lower RPM's and idle disappears, yet it continues to miss in that high RPM range (like something was cleaned out). If I return it to idle, even though it is not missing at idle, the idle will fluctuate between 300-700 rpm and act like it will die! If I turn the key off and restart it, the idle will be smooth and steady? This is my first injection car and carbs seemed a lot simpler. Thank you for all your advice.

[Arthur Dalton]

Change the fuel filter before anything else

Also check the point gap

[Gregg Bambo Jr.]

I don't know if this solution will help others but it sure resolved my frustration trying to discover what was causing my engine to miss. I checked for proper operation of the fuel injector thermostat, drained and renewed the oil in the fuel injection pump (it had been fuel diluted and overfull), changed the seals in the cold start valve, checked the fuel flow volume of the fuel pump, Changed the fuel filter element, removed and had the fuel tank boiled out and cleaned out the fuel tank filter. None of that help until I blew out the injectors and injector manifold. There were very fine elements of rust in the fuel filter and the injector blocks. I was never able to get the Injection pump air filter to eliminate its vacuum function when it was warmed up. It decreased to a very slight vacuum but the book says it should stop sucking vacuum completely when warmed up past 70 degrees. Regardless, it is now purring smoothly at all rpm ranges and stable at idle.

[waybomb]

Hi Gregg
I'm looking at buying a 78 280se that has a problem similar to what you describe in your ordeal. Tell me about blowing out the injectors and lines - how'd you do that?