Question regarding the cold start valve - PeachParts Mercedes-Benz Forum

Litton · #1 12-12-2003, 10:08 AM

I just got my injectors back from the shop after cleaning and reinstalled them. (By the way.....for the "dumb things to do" file, don't put the injector clamps upside down when reassemblying the racks.) The car now just purrs when it's warmed up.

Starting is a bit slow but I attribute some of that to the fact that my timing is not advancing whout vacuum...this will be fixed. Once it starts it runs real rough at about 800 rpm the smooths out in ~1 min and the rpm's pick up to ~1100 - 1200 rpm, slowly decreasing to 800 at 175F temperature.

I also notice a bit of black smoke for the first minute or so then it dissapates. My understanding of the cold start system is that it injects excess fuel directly into the trottle body for awile. At the point of injection, are there orfices of some sort to atomize the fuel, and, if so, should I have cleaned them also.

Subsequent starts after the first minute are about perfect.

In reality, this is something I could easily live with but it just doesn't seem quite correct.

psfred · #2 12-12-2003, 11:47 AM

Litton:

You are way overrich on startup. I'd check the following:

Cold start valve (shouldn't actually operate for more than a couple seconds at start). You may need to pull it and check for leaks, too.

Connections to the air temp sensor in the air intake horn -- if these wires are shorted or open, or the sensor is bad, it will run WAY rich all the time. When running, pull the connector. If you don't get a change in idle, either the wires or the sensor are bad.

Check the temp sensor in the mainfold, too -- bad wires here can also cause trouble.

You also want to check the main mixture sometime -- easy way is to pull a plug after running it warm and check color -- if it's not gray/brown, its either too rich or too lean.

Have you run it enough to get fresh, clean fuel in there? Any old residue will make it smoke and slobber until you get it out.

Should start right up and run up to 1200 or so rpm immediately, then slow down as it heats up.

Peter

Litton · #3 12-12-2003, 05:47 PM

Thanks for the reply Peter. I double checked everything you brought up and all seems OK. It's only for the short period of time after the starting that is a problem which is why I was sorta focused on the point of injection for the cold start valve. Admitidly my gas was a bit old when I picked up the car but I did fill it up with ~14 gallons of hi-test and 2 bottles of Techron.

Maybe, I will just pull those lines off and take a peek at what's down there. If it has dumped a lot of fuel it might take awhile to clean it up after the valve does it's thing. Might also soak the valve in cleaner overnight and see what happens.

psfred · #4 12-12-2003, 09:16 PM

Burn off all the old gas and Techron and you will be fine -- that two bottles of Techron gets up to the limit of what will burn with the engine cold.

Check the condition of the ignition points, too -- mine were badly carboned up when I got the car, and I have to clean them every time I drive it now. I'm going to put a Pertronix full electronic ignition in soon, I've had it with points.

Peter

Litton · #5 12-13-2003, 08:39 AM

Good point on the Tecron. I have burned almost 3/4 of a tank just in the "getting it running" stage. That's without driving it on the road more then 3 miles

. Sure hope that we a result of 3 injectors stuck open.

I have the Pertonix installed but we still have not resolved why my vac retard isn't working. Today I am going to check for interferance between the module and the dust cap. If that isn't it I will send the whole distributer to Pertonix.

I really want it running well enough to go for emmisions check and get it registered.

Tomguy · #6 12-13-2003, 09:21 AM

Litton: That is a good point which you just brought up.

MOST people do NOT have the dust cap installed (and I DO believe I know which one you're reffering to - the black one that seperates the area under the cap and the top of the rotor from the points and the bottom of the distributor). The new style rotors and that cap don't work together (unfortunatley my old rotor was cracked or I wouldn't have chaged it, knowing this - the new rotors have stems too thick to fit into the hole in the dust cap). I would recommend a new rotor and not using the dust cap.

If your rotor is new, then you (or someone else) must have enlarged the hole in it - just take it off and see if it works without it.

Litton · #7 12-13-2003, 11:47 AM

Peter, you were correct in the fit of the new rotor and cap. I pulled the cap off and the marks from the rotor were at the very bottom of the eight little posts. So I removed the dust cover and the rotor went down quite a bit further.

Unfortunetly, this still did not solve my problem with the vac retard......still not advancing when I remove the vacuum. I will go back through the whole thing one more time after it warms up a bit this morning (only 36F in my garage). I need at least 43F to work.

Meantime, I am just runing at -5 on the timing with no advance except the centrifical. Hope this does not screw up the emmision inspection.

Tomguy · #8 12-13-2003, 04:03 PM

It really shouldn't mess anything up - the only time it advances is hot idle (above 95-100°C) or when the AC is on. Other than that it'll be fine. It's true purpose really is just to speed the idle up.
And my name is Tom

Litton · #9 12-13-2003, 05:30 PM

Oops

psfred · #10 12-14-2003, 02:16 PM

Litton:

Sluggish running cold will be at least paritally from late (very late) injection timing. If you leave the vac disconnected, set the timing for 7 degrees BTDC, not 5 degrees ATDC -- otherwise, you will be running 12 degrees late all the time! Gonna slobber cold, will also burn HUGE amounts of gas.

Mine did exactly the same thing when I first got it running. Black plugs, smoke, etc. Setting the timing up properly fixed it.

Peter