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  #1  
Old 01-25-2001, 08:03 AM
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Location: Calgary, Alberta, Canada
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I have an 1988 300e that has a rough idle at initil cold startup that lasts for about 3 seconds and then it is fine. I have replaced wires, cap, rotor, plugs and it is still there. The car uses no oil or antifreeze as that was my first thought that might be causing an idling problem (fluid in one cylinder). Also, occasionally I will feel a very slight miss at idle. Car runs and drives perfect except for at idle. Any ideas?

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  #2  
Old 01-25-2001, 09:18 AM
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'88 300E

I have the same situation with my '88 300E. This appears to be a fairly common problem. I replaced the plugs and have used some fuel injector cleaner which did seem to help for a while. In my case the problem seems to be worse at times, and then almost go away at other times.
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  #3  
Old 01-25-2001, 11:11 AM
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Same here...I am seriously considering changing the injectors seeing as they are cheap and its a pretty simple DIY job.

ps I hope its not unique to 1988
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  #4  
Old 01-25-2001, 09:06 PM
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This definitely sounds like bad injectors to me. Had a few cars with the same problem. Putting in new injector should take care of the problem.

However, new injectors have to be pressurized. You wouldn't belive how many people just put in the new injectors. Sometimes it's fine, but most of the time you end up with the same problem or make it even worse.

CIS injectors have a certain pressure at which they open and close. In order to get them to work right (when brand new) you need to put a lot of pressure on them to open them up. The car fuel system pressure doesn't go this high. You need to take it to someone that has a pump or you can take it to your dealer. I don't think they charge that much to change injectors.

Vin
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  #5  
Old 01-25-2001, 11:07 PM
terryloh
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Hi Vinamg,
I'm just curious bout the new injectors needed to be pressurized stuff. Is it in the mB manual or is it thru experience. I've just replaced my injectors and never heard of this from my mech???
1987 300E
Thnks
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  #6  
Old 01-25-2001, 11:29 PM
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I'm pretty sure it's somewhere in the manual.
I didn't know about pressurizing the injectors either.
Anyway, I was working on a 88 560SEL about a year ago. The car was in real bad shape. I changed the plugs, wires, distributor, rotor and injectors. The car ran perfectly except for a slight hesitation from a dead stop. I knew the problem was fuel related. I checked the whole fuel system, checked for vacuum leaks etc. The car was driving me crazy.

Finally, I decided to ask my friend about it at the local Mercedes dealership. I told him about the problem and about the parts I changed. Without hesitation he asked me if I pressurized the fuel injectors. To make a long story short. He pressurized (opened) them, I installed them and my problem was gone just like that.

I am pretty sure the techs on the forum know about this.
ALL NEW MECHANICAL INJECTORS HAVE TO BE PRESSURIZED (OPENED) AND CHECKED FOR CORRECT OPEN/CLOSE PRESSURE AS WELL AS SPRAY PATTERN.

Vin
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  #7  
Old 01-25-2001, 11:38 PM
terryloh
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Hi Vinamg,
thnks for your reply. As for pressurizing the injectors, would using an air gun work? Or how do the experts do that?
Thnks again
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  #8  
Old 01-26-2001, 01:28 AM
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They have a small Bosch pump with a fuel container. It's the same pump that they use to test the injectors. I think the pump can go all the way up to 10 bar. Normally you don't have to go over 5 bar to open them up and have a nice spray pattern.

Vin
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  #9  
Old 02-03-2001, 09:04 PM
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pressurizing injectors

I want to change my injectors and the sleeves soon. I believe you about pressurizing the injectors(which just made it a NON-DIY for me). If at all possible could any of the moderators or more experinced techs go more into detail about this? Vinamg, if you are a more experienced tech I do apologize for the oversight.
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1986 300E
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  #10  
Old 02-04-2001, 06:45 AM
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I was hoping that one of the techs from the forum would confirm the info. However, my friend that told me about it has been a certified Mercedes tech for 8 years.

I've changed injectors in a few "CIS" cars and never had a problem. Once I found out about it I always do it. With the proper pump it can be done in 5 minutes. I'm not sure what they would charge for it. I just take it down to my friend at the dealership and he does it for me.

If done and you still have a problem, at least you can eliminate the injectors. I just don't want anybody repeating my mistake. I eliminated the injectors because they were brand new. The car drove me crazy until I talked to my friend about it.

Vin
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  #11  
Old 02-05-2001, 02:07 PM
Bigshot
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Have the same problem with 89 560. The dealer found a antifreeze leak and had to remove intake or some ****. I have a bag of black plastic tubes that were replaced then too. Since then the car shutters at start up most of the time. Do used injectors have to be pressurized as well or just reinstalled?
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  #12  
Old 02-05-2001, 06:54 PM
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Re:pressurizing injectors

You take your injectors to have them pressurized before you install them yourself? Or,does the shop do this as a favor to you? Larry, Jeff, Benzmac, Donald, Stevebfl, M.B.D.O.C is anyone there to confirm this? We need to know before I go to a shop and make a fool out of myself.
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  #13  
Old 02-05-2001, 07:18 PM
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hmmmmm, I have never heard of

doing anything other than turning the ignition to "on" for a couple of seconds and not starting the car. May have to do it a couple of times. It is my opinion that the system will then be pressurized.
Jim
'95 E320
'97 CRV
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  #14  
Old 02-05-2001, 07:24 PM
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The largest problem from my point of view, with K-jet and KE injection is leaking injectors. This has been a problem with these systems since they were introduced in the mid 70's. The rough start is caused by excess fuel leaking out of the injector and causing an rich cylinder, another problem is that it takes a second or two for that fuel circuit to refill and acheive opening pressure. As far as presurizing new injectors prior to installation, I don't. I have probably installed a thousand or more. However there certainly would be no harm in testing a new injector with the proper solvent. The most important thing to keep in mind is cleanliness. Take the time to blow the dirt from around the injector fittings and leave the caps on until you are ready to screw on the lines. The pressurizing is cleaning out contamination. It would have no effect on the mechanical operation of the injector.
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  #15  
Old 02-05-2001, 09:08 PM
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Would it make any difference taking them out and having them cleaned to see if they are leaking or anything or are they just bad injectors (quality) to start with.

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