Installing new M103 fuel injectors, How sould they be oriented? - PeachParts Mercedes-Benz Forum

bolomiester · #1 09-14-2009, 12:49 PM

This is an extention of this long running thread:

'80 300se start,stall,start,stall,start,stall

I'm finally down to replacing the fuel injectors in an effort to cure a start/stall/start/chug-chug/run behavior that I started working on in June.

I was going to replace them over the weekend but had to make a quick trip 500 mile round trip to St. Louis instead. Anyway, I'm doing it today and will post the results on the original thread for the benefit of everybody that's been following it, looking for a solution to the same problem on their own cars.

However, I have a couple of questions for our MB masters. See the photo below. The first is the "slots or windows" that are in the holder below the O-ring. Do they need to be oriented in any particular direction, say fore and aft or side to side? The second is the O-ring. The new one is not as "fat" as the original, I got all the parts from Fastlane, so I assume they are correct and perfect but I just wanted to be sure. Also, the o-ring is a very tight fit over the holder, so is there a "good" way to get them over the two "ridges" and into their groove without damaging them?

The last question is the seal. Should it go over the injector first and then into the holder, or should the seal go into the holder first and then have the injector pushed into assembly. I'm sorry for what must be dumb questions, but I've never replaced fuel injectors before, and I'd like to be sure I get it right the first time. Unfortunately the CD doesn't say much.

Thanks, for all the help on this process. I have high hopes on the injectors being the problem, as I sprayed the allen bolt and fuel line connections with PB blaster this morning, then took the car for a drive to get it nice and warm, then came back and sprayed everything down again. I then pulled the first injector as soon as I figured out the process, maybe a 15 or 20 minute delay, and when I broke the fuel line loose there was almost no pressure. Seems like a leak to me. I have my fingers crossed.

pawoSD · #2 09-14-2009, 01:58 PM

My 300E has the exact same issue, and I too plan on replacing the injectors in the not too distant future.....I will be waiting for answers to your questions as well....as my questions are the same.

ps2cho · #3 09-14-2009, 04:27 PM

When I did my injectors, I put the seals on first. You will need to use a small flathead screwdriver to pry it up carefully.

When I did mine it cured this rhythmic unhappiness.

I'm not sure about orientation though. I didn't do it with mine....but I'll let somebody with more knowledge pipe in. The FSM does not mention anything about it so I would say its safe to assume it does not make a difference.

bolomiester · #4 09-15-2009, 12:35 PM

Well, the new injectors did the trick! The start/stall/start/chug-chug/run behavior is gone. As best as I can figure, the injectors were leaking fuel into the cylinders, which relieved the pressure in the system. On the first start attempt, the engine would fire on the leaked in fuel, but would stall because there was no pressure in the system to open the injectors, The chug-chug came from the fuel laying in the cylinders causing a "flooded" condition. Eventually, continued cranking would build up enough system pressure to fire the injectors, the extra fuel would go out the exhaust, the plugs would dry out and the engine would operate normally. I don't know if this is right, but it sounds good to me. However, I'm open to alternate therories.

Changing the injectors was easier & cheaper than I thought it would be. It would be even easier if I did it again, as I know a few things about the process. All the parts cost $223 and change from Fastlane, arrived in one day (Atlanta to Northern Illinois) and after 6 months of struggle finally solved my starting problem.

A few tips that made the process easier:

1. Leave the clips that hold the injectors down, in place until your remove the fuel lines. I found it easier to get to the allen head bolts that holds some of the injectors in place by taking the fuel lines loose at both ends. In one case that required removing the EHA valve to allow me to turn the wrench.

2. I was able to slip a 17mm open end over the clip where the hex on the injector is to provide back pressure to loosen the fuel lines.

3. I had to use an allen wrench with a ball end to remove and replace the bolt on injector number 4, and it was tough getting the bolt to line up straight when I put it back in. The rest were pretty easy.

4. I used brake cleaner and an acid brush to clean around where the holders go into engine so that no dirt would drop in when I removed them. I'm glad I did, as though the engine is clean, it wasn't clean enough.

5. After it was all back together, and warmed up I had to reset the duty cycle, the reading had changed from 50% to about 75% and the idle was "hunting" up and down. Setting it back to 50% smoothed it out perfect.

When this happens on my "next" Benz, I'll start with the injectors and work the other way. Some of the old ones fit nice and tight, others slipped out easily. I'm sure there must have been vacuum leaks around the the really loose ones.

Hopefully this will help others struggling with the same behavior.

Wolfe190 · #5 02-04-2010, 09:56 PM

If anyone is still playing with the idea, check this out!

http://190rev.net/forums/showthread.php?t=36419

Good luck! and feel free to ask any questions - I might just have an answer

estmersbenz · #6 02-05-2010, 12:58 AM

wonderful news, my w123 230E 1984 has exactly the same issue. I haven't yet tested the WUR I thought it might be that culprit now based on your post I'm more thinking of buying new injectors instead

and because I'll do that anyway why not do it sooner than initially planned lol.

JamesDean · #7 02-05-2010, 04:06 PM

how many miles were you on your m103 when you changed the injectors?

I'm facing a similar issue with mine, I was able to remedy the start/stall/start-chug-chug/ by using my "cranked up" EHA...

My m103 has around 90k on it now.

I dont recall if when I bought the 3L it came with injectors..so its possible that I have my 2.6 injectors (217k) running my 3L...and your solution might fix the problem..

Wolfe190 · #8 02-08-2010, 02:10 PM

Mine has just over 160,000 miles.

After I replaced the injectors, it made a big difference in start-up, and it idles much better, but didn't actually fix the problem I was going after:

When I drive my car nicely (shift at 3500 or so) my car doesn't idle down and makes shifting a PITA because you have to slip the clutch when going into every gear. When it is cold this problem is non-existant, but as the engine warms up this condition progressively gets worse

However, when I drive it hard (shift at 5500 or so) it revs down normally and shifting is as smooth as it ever was, regardless of engine temp

I'm pretty stumped on this...

Hit Man X · #9 02-08-2010, 09:02 PM

Quote:

Originally Posted by Wolfe190

Mine has just over 160,000 miles.

After I replaced the injectors, it made a big difference in start-up, and it idles much better, but didn't actually fix the problem I was going after:

When I drive my car nicely (shift at 3500 or so) my car doesn't idle down and makes shifting a PITA because you have to slip the clutch when going into every gear. When it is cold this problem is non-existant, but as the engine warms up this condition progressively gets worse

However, when I drive it hard (shift at 5500 or so) it revs down normally and shifting is as smooth as it ever was, regardless of engine temp

I'm pretty stumped on this...

Any vac leaks? The M103 suffers from the big time, but is VERY easy to reseal unlike the M116/7 V8s. I had two leaking three way connectors also.

Oil leaks are vac leaks. All the tubing under the hood can get brittle easily with age. Check the oil pan gasket too.

Also use a meter and check your engine senders on the head.