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

[bolomiester]

Originally Posted by Ivanerrol

An often overlooked cuase for stalling.
Hall effect sensor on the back of the speedo. It can cause intemittant havoc.
It seems that once you take your foot off the throttle and you are slowing down, this sensor's signal tells the software in the EFI module to prepare for idle mode, without it the computer thinks you actually want the fuel supply to stop all together and as such, shuts down because that is what it thinks you want it to do. Something so small can cause so much grief .

Its start/stall/start/chug-chug/run behavior is only at startup. It never does it when driving. It runs and drives extremely well. If not for this one little thing, it would be as perfect a runner as you could imagine.

I have a new throttle microswitch on the way. I decided to try it as you can sidestep the "start/stall/start/chug-chug/run" thing by holding the throttle open during cranking, then holding it open a little for a few seconds. Usually you can then take your foot off and the car will be idling perfectly. However, there are times that it will stall as soon as you take your foot off the pedal when you've held it down during cranking. When this happens if you let it go through its "start/stall/start/chug-chug/run" thing it will be fine.

It's seems to need the "start/stall/start/chug-chug/run" thing to happen before it will idle properly.

Replacing the throttle microswitch is probably a crazy idea, but Phil sells them for only $28, so "hope springs eternal."

[bolomiester]

Originally Posted by bolomiester

Its start/stall/start/chug-chug/run behavior is only at startup. It never does it when driving. It runs and drives extremely well. If not for this one little thing, it would be as perfect a runner as you could imagine.

I have a new throttle microswitch on the way. I decided to try it as you can sidestep the "start/stall/start/chug-chug/run" thing by holding the throttle open during cranking, then holding it open a little for a few seconds. Usually you can then take your foot off and the car will be idling perfectly. However, there are times that it will stall as soon as you take your foot off the pedal when you've held it down during cranking. When this happens if you let it go through its "start/stall/start/chug-chug/run" thing it will be fine.

It's seems to need the "start/stall/start/chug-chug/run" thing to happen before it will idle properly.

Replacing the throttle microswitch is probably a crazy idea, but Phil sells them for only $28, so "hope springs eternal."

Well . . . the throttle microswitch did not solve the problem, nor did the new fuel pressure regulator I installed next. I wouldn't have replaced the FPR if I hadn't found a brand new one sitting on a Volvo specialist shelf, it was the only MB part he had, and was cheap enough that I couldn't pass it up.

The injectors all look as though they haven't been touched since the car left Germany, so they are next. I ordered them today, so by the weekend they should be in place.

Is there anything in paticular I should be aware of for the RR?

[MrsSudz]

I have the same car with the same issue. I've done everything on this thread.

[bolomiester]

Originally Posted by MrsSudz

I have the same car with the same issue. I've done everything on this thread.

Me too, and none of it has had any effect, except a slight improvement when I turned the EHA adjustment 3/4 turn CW!

This was a very nice car when I bought it in March. Rust free body, nice original paint, great interior, ran & idled perfect and everything works! The only thing that gave me pause was that it came without records. It's got 'em now!

The problem showed up about 2 weeks after I bought it, so it made sense that it was one of the parts I've replaced that had failed or was failing. Since none of the replaced parts has made any difference, it appears that the culprit is still waiting to be discovered.

The new injectors arrived today and I'll start replacing them this evening. I have high hopes that this will be it! If it sits overnight it takes several seconds of cranking before it fires. The longer it sits the more likely it is to start after the extended crank time and not do its start/stall/start/chug-chug/run thing. If it's started within a few minutes of shut down, it fires up perfectly without a hint of anything being wrong. Where the problem really shows up is after it sits for anything from about 30 minutes to an hour.

My latest theory is that I have one or more leaking injectors that are both bleeding off the system pressure, and flooding the engine by leaking raw fuel into the cylinders.

[Noelelectrique]

Damn, i have a 300SE 1989 in pristine condition, only i have the SAME EXACT PROBLEM than you, when i bought it it wasnt running, it turned out to be the spark plugs, cap, rotor, wires that were no good, now it runs fine, exept for the start chug chug start, when i throtle it is seems like its clearing up its throat , after its al fine. Ha, and i hear a faint clack clack clack from engine , and sometimes, 20 secs out of every 2 hours , the engine stutter at 500 rpm without any power even if i have full throtle, then suddently in comes back to life.

I love this car! PanzerWagen!!!!

[mak]

after all that work ,replacement of the fuel pump relay and OVP would be the only items left. i replaced these on my 300se and all is well now. the opv and fuel relay had cold solder joints ,temp dependent.
mak
89/300se

[MrsSudz]

I guess I will try the fuel pump relay now. What is the OVP?

Thanks,

Erika

[Cal Learner]

OVP = overvoltage protection relay. Sits right next to the fuel pump relay.

http://catalog.peachparts.com/ShopByVehicle.epc?q=1989-Mercedes--Benz-300se-Engine--Electrical&yearid=1989%40%401989&makeid=63%40%40MERCEDES+BENZ%40%40X&modelid=6215%3AMBC%7C1513%3AED%7C10000012%40%40300SE&catid=240798%40%40Engine+Electrical&mode=SS&yearid=1989%40%401989&makeid=63%40%40MERCEDES+BENZ%40%40X&modelid=6215%3AMBC%7C1513%3AED%7C10000012%40%40300SE&catid=240798%40%40Engine+Electrical

[MrsSudz]

Ahh thank you, mine is missing one of those 10A fuses in it. Could that be my issue? Can I pick them up at Napa?

thanks again,

Erika

[fiat]

bolomiester, Did you installed those new Injectors yet? Does it fix the problem???

[MrsSudz]

Got it FIXED!

Earlier in this thread someone mentioned a hose that looks like it is molded together. Both of mine were worn out. I replaced them and VIOLA! She purrs like a kitten now. No start and stall issue. Tried it this AM and no problems at all.

The hoses are underneath the air filter housing. If you are standing in front of the car they are to the lower left corner of the injectors.

Now I have to figure out how to dismantle my door and put a plastic piece in there to keep the window up and figure out why I don't have heat.

Take Care,

Erika

[bolomiester]

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.

[iamjohnlarkin]

Originally Posted by gschira

Bolomiester,
I've been watching your thread because of a very similar problem with my own car, a beautiful 1988 Triple Black 300SE. I just repaired this similar problem with duct tape. Try not to laugh too hard. This whole past weekend I was on this forum like a duck on a june bug, trying to make sense of all the years of experience these people have here. All the electronic lingo like ohms, potentiometer, cps ,ezl, cis, icv and such is pretty confusing.....But I'm hanging in there and will learn all this stuff. I consider myself pretty dang good at mechanics, and have been all my life, even as a kid. You have to remember and you probably are aware....In a gasser you need ( and this probably sounds pretty crude to the true pro's out there) gas, oxygen, and ignition, in the correct ratio for that all important combustion. Before you spend one more cent, and hours trying to figure out mutimeters and such (and maybe you've already checked, but didn't mention) CHECK the approx. one half inch vacuum line under the throttle body. It is a molded small length of hose, maybe 3" or so, that will split at the seems on both ends. I did not have a new hose, so had to actually repair the hose with duct tape. Put it all back together...She fired right up and is running great for 3 days now. The hose will split a little at first and as time goes by will get worse and so will your hard starts and stalling until the hose will allow too much air , there will be a backfire and that will blow the plum off the throttle body and the other thinga majig it attaches to. I hope some of you pros can tell me what that hose is called so I can order a new one. This all might not make a hoot toya or pertainto your problem, BUT maybe it WILL. Sure was a cheap fix. Maybe it will help someone out there............Good Luck

GSCHIRA

Have been trying to solve this poor running problem for past few weeks. So many different views on different forums in Europe and USA, can lead unless careful to investment in parts well beyond value of this lovely old car.

Mine's a 190 but I believe has the same basic engine and fuel injection setup as the 300SE
Interested in your instant Duck tape fix but cannot identify the hose you refer to. Can't find a hose half inch diameter and three inches long below the throttle body.Could you clarify size/shape location a bit more, and what it connects.
Could you also clarify the effect of a backfire. Some weeks back when car was running fine I was on M1 Motorway alongside a Chrysler MPV, when massive bang, didn't know whether it was backfire from my Merc or the Chrysler. Poor running began a couple of days later. May be connected.

Look forward to your comments.

Thanks for any help

JL

JL

[dhjenkins]

Disconnect the fuel return line at the fuel distributor. Take the air gun from your compressor and blow out the line. You should hear nothing but bubbling in the gas tank. If it builds up any pressure at all, even just for a second, you probably have a bad check valve in the tank.

It's what happened to me...

[dongra]

MrsSudz/Erika
could you kindly posts the pictures of the Engine and the hose etc.Mine is a 94 E200.I have changed OVP,Fuel Pump Relay fuse,Bosch Spark Plugs,Had the wiring harness relooked to no avail.

Am at my wits end
dongra