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380SL Fuel Injector Replacement

15K views 10 replies 7 participants last post by  JS5D 
#1 ·
I have a 1984 380SL. When I first got it last year, it sufferred from an intermittent problem characterized by almost a complete loss of power when going up a hill, especially from a stop. After a few seconds of sputtering and shaking and feeling like it was going to stall (misfiring cylinders?), I'd get a sudden punch of power and everything would be fine until the next time I needed to get moving again from a slow speed (like the next stop sign at the base of a hill).

I took it to a mechanic for a completely unrelated problem, and despite getting ripped off real bad, he did replace a bad fuel injector as a small courtesy for cheating me on the other thing. He said it wasn't misting the gas at all and that it's likely there is still another bad one, which he didn't replace. With the one new injector, the car ran MUCH better.

However, I still intermittently lose power under similar conditions, although to a much lesser degree than before. I'd like to solve this problem once and for all, so I figure I'll just replace all 8 fuel injectors with new ones. I haven't been able to find any detailed enough information on how to replace an injector on a 380SL, so I figured I'd just start taking things off and try to figure it out as I went. I got as far as removing the fuel line and a little metal bracket from the injector, but there still seems to be something else holding it in. I think there's some sort of black plastic or rubber thing holding it in. I've posted photographs of the area in question here:

380SL Fuel Injectors

If anyone could give me some hints, clues, advice, or a step by step, I'd greatly appreciate it.

Thanks!

Max Rogovy
Seattle, WA
 
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#2 ·
Each have their own way and the way I go about it is to remove the air tube that feeds all 4 injectors on the bank (your #4 picture unknown bar/tub). Then clean with vacuum around each injector. We do not want contaminants fall into engine. Remove fuel line from top of Distributor and remove the Injector holding bracket (#2 picture 5 mm). Take hold of the connection of the injector/fuel line and the inlet pipe from air tube - pull out with force complete assembly. I will post picks after work from my parts layer across garage from head removal.
 
#4 ·
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Whereas the Manual is a necessity it certainly is not 'The End' as it fails to address the infernal difficulties one encounters in gaining access to these tight spaces.

'Maxr' does raise a valid point ..and politely too, ..has taken the time to post well indicated photos and should not be discouraged from further enquiry, or utilising the 'Search this Forum' function here or on the W126 section.


Some injectors are so inaccessible they refuse to 'leap' from the block when issued a formally written invitation. Further ...we could all benefit from a learned response to his genuine request.

Say it isn't so ...'knob' ! ;)


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#5 · (Edited)
BNZ said:
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Whereas the Manual is a necessity it certainly is not 'The End' as it fails to address the infernal difficulties one encounters in gaining access to these tight spaces.

'Maxr' does raise a valid point ..and politely too, ..has taken the time to post well indicated photos and should not be discouraged from further enquiry, or utilising the 'Search this Forum' function here or on the W126 section.


Some injectors are so inaccessible they refuse to 'leap' from the block when issued a formally written invitation. Further ...we could all benefit from a learned response to his genuine request.

Say it isn't so ...'knob' ! ;)


.
All good points, BNZ.
Let me formally apologize to MAXR if I seemed abrupt...that was not really my intention.
The way I see things (maybe somewhat narrow), if you want to "do it yourself" you need tools. Agreed? First tool, in my opinion, is information..i.e. a manual.
I have had a manual for all my cars. In fact, I drove mid seventies Chevy Malibus exclusively for years partially because I had the manual!
 
#6 ·
No apology necessary. Getting a manual is good advice. I got the Chilton book a while back only to discover it is completely worthless. It tries to cover too many different models, and as a result, covers none of them well. I'm sure the topic of good manuals has been discussed before, so I'll look around for some recommendations.

As for the injectors, I ordered a new set that should be arriving tomorrow. I also ordered new fuel injector insulators, o-rings, and seals. Again, I'm not sure how all those pieces fit together, but I'll try to follow Stinger's advice and disconnect the injector from the air tube. If I can get one out, I should be able to see how the new ones go in. The tight wrench spaces could be frustrating though.

Depending on how it goes, I may be back for more help. If I'm successful, I'll try to document the process as clearly as possible for anyone else who might be struggling with the same repair.
 
#7 ·
maxr said:
Getting a manual is good advice. I got the Chilton book a while back only to discover it is completely worthless. It tries to cover too many different models, and as a result, covers none of them well.
The first manual you should get is the MB shop manuals on CD. It's available from MBUSA for $20 plus shipping. It isn't complete - not all the sections of every manual is in there - but the majority of the things you'll run into are. Second, keep your eye on ebay for a hard copy of the MB shop manuals.
 
#9 ·
Limited Progress

My new parts arrived today so I gave the injector replacement a shot. It took me two hours but I successfully replaced one of the eight injectors. Just 7 more to go!

The biggest challenge was disconnecting the air tube from the plastic thing the injector sits in. It just snaps on so tight. The one I got off was on the end, so I was able to pry it off with a screw driver, but even that took a lot of force. The others look like they're going to be a lot more difficult because there's so much stuff on top of the air tube.

Does anyone have some suggestions on an easier way to get that air tube off?
 
#10 ·
Bump on this. I am doing exactly the same thing and the thing that should be the easiest (plastic air hose removal) is the hardest. Do you need to completely remove all the fuel lines from the distributor to the injectors? Perhaps that would open up more space to yank it out
 
#11 ·
I managed to change out the injectors without removing the air hose. On the right (US passenger) side you need to remove the throttle linkage and some breather hoses but otherwise it is quite easy. The alan bolts can be tight so make sure you have a good socket etc to avoid rounding them.

On the left side it is more congested and not so easy. I recall I had to remove the throttle linkage, fuel return line and the frequency valve thing. I managed to work around the rubber air hose, which I think is for the start injector. The second alan bolt from the front was the most difficult to remove and replace. I typically just nudged the fuel lines maybe removed some support to get more flexibility

Get yourself a very good quality alan socket one straight and one ball type. Also I used one of these open spanner heads with a socket hole, you know for the awkward corners to release some of the unions on the injectors.

Took me about a hour to change all the injectors, bit fiddly but workable. Some of my only injectors were wet indicating they did not close 100% New injectors are particularly beneficial for that: smooth idle. You can clean injectors but at $175 for a full set I decided to avoid playing with nasty cleaning products.
 
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