Hello.

I have a -88 300E which is sometimes hard to start when the engine is cold and the outside temperature is approx zero Celcius (ca 32 F i guess). I have to crank it for ten-20 seconds and puch the accelerator until it starts and then the rmp is very low and the engine takes a couple of seconds to reach correct idle rpm... It runs smoothly as soon it has found the correct idle rmp...

When it is colder outside (approx -10 C or colder) it is easier to start it (strange).

I have checked the cold start valve and it works, the temperature sensor for the CIS-injection also seem to work (the resistance is approx the same as the "Haynes" guide tells), the idle speed actuator works, the EHA seems to work to... The spark distibutor and distributor cap and the spark plugs are new ones (changed this winter)... WHAT could possibly be wrong??
I will try to increase the CO-screw to enrich the mixture since the lambda sensor will force the engine to lean the mixture as soon as the engine is running anyway - right? Is this an good idea? Please help me...

I'm getting sick of not finding what is wrong!!!

Can it possibly be the OVP-relay. I've read on som www-page that this could cause cold start problems....

/Ola, Sweden.

I had the same problem (and I am still working it). However I did manage to rig a temporary fix that works well for now. I ran a wire from the battery to a push type switch which I installed under the dash and then to the cold start valve. When I engage the starter I just push the switch for a moment and I get instant start. When the Temp is over 60 (f) I don't need this. But it sure saved my butt in January. If I ever figure out why it doesent work on its own I will let you know.

Monitor your Idle Control Valve voltage. I suspect the valve is gummed up and not responding well until engine heat loosens the internal lubricant. If, however, voltage to the valve is low or null during warmup, the problem is elsewhere. If it is the valve, clean it or replace it.

Steve

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'91 MB 190E 2.3
'08 RAV4 Ltd 3.5
'83 Lazy Daze m'home 5.7

Mine had no voltage during start or warmup. I had bought a new valve but decided to check the current one before actually replacing it. Now I have a spare.

How did you test the cold start valve?

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Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe

I was using a 10 kohm resistor (between the temperature sensor cable and ground) to emulate cold engine (minus 15 C approx (guess that is ca 0 F). Then I removed the cold start valve and refitted it in such a way that it sprayed out in the open air, then it was obvios that it was working... A fine spray of gasoline in the air (yes I know this i very dangerous....)

The voltage changes depenging on engine temperature and the idle rmp seems constant... if I, however, remove the power from the engine (at cold temperature) it lowers the rpm and at warm engine temperature the rpm increases.... So it SEEMS to work fine, but you never know, right?? ;-) ... But you guys think that cleaning the idle contorl valve will fix this? That might be a good idea... I will try it. What kind of lubricant do you need to put in there after cleaning???

*lol* Funny, I had that idea myself ;-)
Actually I was thinking about doing that, however, I never came to actually doing it, since my "test" of the cold start valve showed me that it was working.
On the other hand, there might be an idea doing such an arrangement, since the problem seems to come and go. Therefore one might think that the problen IS the cold start valve not being actuated due to bad connectrions somewhere....

I recently went thru the same scenario, on a 1993 300E. Would require 2 cranks to get her going when temp. below 40. OVP was replaced, & fuel pressure was good internally, everything else perfect. Donnie from MB Autowerks got a second look at it, overnight, went thru it, and traced it to the battery . I said no way, it is good. Was about 2 years old, tested fine...until under load. Then it would crap out. Dropped a new 850 CCA Interstate in, and all problems went away.

Simple.
Good luck
Q

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FAQ

W124
Sportline Swaybars
Bilstein HD Struts
16" E420 wheels

No, probably not the cause based on your tests. Could be an air leak, though. Sounds like the ECU is trying to reduce airflow when warm, so it might be coming through elsewhere. Probably unmetered, too, which would lean out the mixture - a real problem when cold.

Also, Q-ball's idea about the battery is worth investigating. If voltage drops too low while cranking, it could upset initial conditions set by the ECU.

Steve

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'91 MB 190E 2.3
'08 RAV4 Ltd 3.5
'83 Lazy Daze m'home 5.7

I have been searching for an air leak, but I haven't found any (using start gas), but this was never done properly - I will test it again.

The battery is a 88Ah battery (made for the diesel engine cars)and its only one year old so I think that it is almost over powered and ok (it sounds like the starter engine runs at high power), but I can of cource measure the voltage ot the battery while cranking... I've had that idea myself, but never tested it though - or actually I never really believed that that was the problem... but I will try.


Thanks guys! :-) :-) At least I have som ideas now :-)

What resistance do you get across the connectors of the start valve? The spec is 10-25 ohms.

Also, what engine model do you have - digits 4-6 in your engine serial number - 103.xxx? The CD shows at least two modesl for Sweden.

Do you have EGR?

A catalytic converter?

An O2 sensor?

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Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe

Yes, I have lambda sensor and catlytic converter, but not any EGR-valve... after the weekend i will have the six digit number of the engine... Ok? (also, my car is originally sold in and importef a few years later from Germany)... I will check the resistance...

The engine is called 103.983 and the start valve resistance vas within specs.

I think you should run some basic checks on your warm-up enrichment by measuring the current at the EHA. There is special harness that you can use to do this, although you may be able to rig something up.

Here is what the CD says you should be seeing for a KAT engine as of 09-1987:

KOEO: 20 mA

20 seconds after start: 4 - 8 mA

60 seconds after start: 0 to -4 mA. At +20 degrees, the coolant sensor's resistance should be 2.3 - 2.8 kOhms

Temp at +80, fluctuating currrent reading, 230 - 290 Ohms resistance from sensor

My guess at this point is that your coolant temp sensor may be bad and is telling the brain not to enrich.

Good luck. Many posts on measuring EHA current.

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Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe