hard starting (always miss the first try)
 

I have a weird problem with my 1987 260E (2.6L engine). Anyway,
everytime I go to start it, it would seem to have start, but I settle the
key to run position and it would shuts off. On the next try
its ok. What i mean is, suppose I walk to the car in the morninng
I put the key in, then turn it to the start position. The c
car would make that cranking noise and I can hear the engine
revved up and sounds like it has started. So? I turn the key
away from the start position to the run position. Let my hand
go off the key. And the engines shuts off. I have to start
it once more before the engine stays on. Or I would have
to step on the gas just when the engine is about to shut off
and by doing this the engine would continue running and
everything is fine. What kind of problem am I looking at?
Fuel pump relay has been replaced. In fact I have 3 or four spare
fuel pump relay and it does it to everyone of those. Is it
the fuel distributor unit? or maybe its idle control valve? any idea?

i had same problem with my 87 420sel.finally broke down and replaced fuel distrib and now starts first time every time.

What is involve in replacing this unit? Take off the air filter unit? Its right underneath right? I don't suppose you bought a new unit did u? Those thing cost a thousand bucks each.

no they're available rebuilt for less than $500.

So do they have a website where you can pick up a rebuilt
fuel distributor? I might actually attempt this to see if it
will fix the problem. I intend to keep the car and drive
it so I don't mind putting in more money into it. I checked
ebay and these fuel distributor things (used) go for quite a sum.

specialtauto.com-----will be about $450 exchange.

Is it so bad that you cant live with it ?

Replacing the fuel distributor is an expensive thing to do and there could be other parts such as the cold start valve that may be the culprit. Does it also happen when you try to start the car after it has warmed up ?

Yes it happens all the time now. Several months ago, only happens
early in the morning when car is cold. Now a day it happens
even at the shopping plaza. I park the car, go get milk.
Comes out, and it happens. Have to crank more than once
to get it started. I don't personally mind, but whenever
the girlfriend is along for the ride, it always made her
tell me to get rid of teh car. I told no!

Before I spend that money I would have a fuel pressure leak down test performed.

It does look like a leak type situation. If you open the hood, and start it in the morning, if there is a leak, you should smell gas.

Also check the cold start valve. You can remove this valve from the engine and see if there is fuel coming out when you crank, there should be a spray.

If you dont see a spray:
you can check the voltage at the cold start valve's connector. You should get about 10-11V when you try to start the car.
If you do get this voltage:
then check the resistance across the cold start valve's pins (connector removed). It should be between 10-20 ohms. If you dont have resistance, replace valve
If you dont get this voltage:
then there is an electrical problem somewhere else.
If all electrical tests are normal but you dont see a spray, replace valve.

I thought the cold start valve only activates when engine temp is below 40C. Anyway, if your fuel pressure test turns out positive, you can work your way up from cheapest to costliest. Start with the fuel filter, pump check valve, accumulator, regulator and last is the dist. If you get to the distributor, at least you won't have to worry about your fuel system for a while assuming all your injectors are working fine.

Thats correct, it may not just be the cold start valve since you are having both cold start and warm start problem now. Check the fuel injection temperature sensor also. It is also called coolant temperature sensor. This sensor informs the computer about the temperature of the engine and based on the signal the computer adjusts the air/fuel artio. On my 87, 260E, this is the last sensor on the engine, towards the windshield. You can measure resistance on the sensor, when the engine is cold (20 deg-C), it should be between 2.5 and 3.5K and when it is at 80 deg-C, it should drop to between 250-350 ohms. The exact values may be different but when engine temp changes from 20 to 80 deg-c, the resistance should drop by a factor of 8 to 10.

OK, now for some updates (2k7_07_04)
I know a local guy who is selling a fuel distributor assembly from his 300E with the 3.0L M103 engine. He says he will swap mine out and put his in to see if it works. If it does then I buy it off him. Sounds good, cause I am always disturbed when trying to start this car (260E). My concern is compatibility. My 260E has a 2.6L engine instead of the 3.0L, I know they are both M103. But can I assume that the fuel distributor assembly is compatible?

Yes, they should be the same distributor, but no guarantee that it will be adjusted the same. If you plan to pull out your distributor, there is one user serviceable part in it and that is a rubber gasket at the shaft. HOWEVER, you have to be careful when you open this, you will have to measure the height of the shaft with respect to the outer frame and then adjust the height to the same level when you put it back. Will need a special Vernier tool to do this measurement.

And I believe, a special tool to open the screw as well, like a split screw driver. The screw that holds the gasket passes thru the shaft.