Replacing fuel injectors on an '86 300E - DIY job?
 

My wife owns a neglected '86 300E that has developed a chronic case of cold starting difficulty. It's often necessary to crank the starter for 30 sec. before the engine fires. Once started, the engine runs fine. Two mechanics have told me, independently, that leaking fuel injectors are the likely culprit. I'm going to try a tune-up first, but if that doesn't work, I may try to replace the fuel injectors.
Is this a task that I can do at home with simple tools and limited experience, or is this a job best left to prfessionals? What's involved?
Thanks for the input!
Mika

cold start, warm start
 

Is it also hard to (re)-start once warmed-up? If you stop the car and start it again, how does it go?

I'm not familiar wtih your car but could the cold start valve be part of the problem?

If you warm the car up, turn it OFF, then immediately turn it back ON, it starts easily the 2nd time. However, if the car sits for more than about 30 minutes, it becomes difficult to start. I don't get it!
Mika

Is your anti-lock brake light also on?

It has come on and off on occasion... once every few weeks. why do you ask?
Mika

Sorry I did not read closely enough. There are an OVP relay and cold start relay that can cause hard start but it would not run fine when cold.

Replacing injectors is a pretty easy job on a 103 motor. And injectors are fairly inexpensive on a 103 - used to be under $20 each (but everything has gone up so much lately). But it doesn't sound to me like bad injectors. When injectors leak down it is usually only one or two of them. And then when you start it up it runs quite rough for a few seconds - because some cylinders have fuel at start up and others don't. It doesn't smooth out for a few seconds when all cylinders get the same fuel pressure.

Oh...
Well, it does run rough until you give it gas. It often won't take unless you pump the gas pedal while cranking. Once you rev it, everything smooths out. Not sure it that helps narrow anything down...
Mika

Does anyone know where I can find a shop manual or instructions that would show me how to replace an injector? It looks like many of the service manuals are out of print...
Thanks,
Mika

Read this first.
http://www.peachparts.com/shopforum/tech-help/55115-m103-hard-start-rough-idle-hesitation-solved.html?highlight=replace+injectors+m103

Mika:

Fuel injectors don't cause hard start problems unless they also cause rough running problems. If they leak into the manifold, it should do just hte opposite of what you describe -- hot starts would be a problem from flooding, accompanied by black smoke for a second, while cold starts would be slow from lack of fuel until the accumulator pumps up.

I suspect (in spite of the advice of your mechanics) that you have a bad accumulator (leaking down) and/or a bad cold start valve.

Pumping the gas does nothing but open the throttle up more, it's not activating enrichment on that car while starting.

I would have a shop check the accumulator leakdown before putting in new injectors, since new ones won't fix the problem in my opinion. Note that leaking injectors can cause a loss of pressure too, but they will dribble with the engine off.

Another thing to check is the air meter flap under the air filter -- if it' dirty, clean it out, it will stick closed cold and cause a no start condition due to no fuel delivery. You can test that by pressing down gently on it while you wife tries to start the car -- if it starts right up, thats the problem.

I would also check for vacuum leaks -- the idle control hoses are a common culprit (and the cold start valve plugs into one of them). If they are hard, replace them, it may cure the hard start.

ABS light coming on means the overvoltage protection relay is bad, replace it (I'd do that anywhat, as it is probably bad unless replaced already). If the fuel pump relay gets hot, replace that, too! -- you don't have an intermittant stalling problem do you?

Peter

I can think of 3 sources - the search function herein, seems to me like there has been some good posts on changing 103 motor injectors, 2) the Haynes 124 manual, about $35 @ 303-237-0911, and the 124 service CD, available from the dealer or sometimes on Ebay for less. I don't it's a bad idea to replace the injectors - they're not that expensive on that car and they're easy to replace. That may not be the principal problem - but you'll have new injectors. If original they're probably on their last legs anyway.

Thanks, everyone, for the great info!
Mika