Starting Issues - PeachParts Mercedes-Benz Forum

stargazer · #1 03-19-2007, 04:57 PM

I recently bought a 1992 300ce sportline in very very good condition. Obviously I did the initial pre-buy check etc and everything looked fine... also the guy had receipts of all repairs since 1993 when he bought it.

Suddenly the car has developed some trouble with regard to starting.
1) when engine is cold (engine temp <40 C) - one crack for like 1~2 second the car just starts up..- idles 800~1000 for some time and the idle drops (i presume this is normal)

but car seems a little resistive as if lacking fuel when you drive out - especially if push the gas a little more - it kind of catches on and is ready to fly!

2) when engine hot (engine temp 85~90 C) the car will start up in one crank - no problem here

3) PROBLEM - now leave the car for 10 mins or so and come back and crack up it takes like 15 sec of cracking and gas pedal pumping/pushing to start - also it starts rough and then evens out at normal idling...and drives fine after that.

I took it to an independent mechanic (C& H auto, Chicago) - where we changed Sparkplugs to Bosch Platinums - no improvement. {receipts say flue filter was changed like 3 yrs back with fuel pumps}

Also a voltage check across oxygen sensor was at 0.7 -0.8 - idly i guess it should be around 0.5 - but playing around with the fuel air mixture is very very sensitive and we could not get it at 0.5.

So next it seems as the oxygen sensor - but I am not sure if I am on the right path.. The independent mechanic comes highly recommended but he is also trying to figure it out. He suggests - distributor and wire replacement (tune-up) and fuel system cleaning.

I know a tune is something I need to get done since the car was owned by an older gentlemen and sat for 3 months -so far have changed oil/oil filter and topped off all fluids. (transmission and radiator flush need to be done).

Anyone has an ideas or know what could be the issue??

just-n-time · #2 03-20-2007, 12:28 AM

Quote:

Originally Posted by stargazer

I recently bought a 1992 300ce sportline in very very good condition. Obviously I did the initial pre-buy check etc and everything looked fine... also the guy had receipts of all repairs since 1993 when he bought it.

Suddenly the car has developed some trouble with regard to starting.
1) when engine is cold (engine temp <40 C) - one crack for like 1~2 second the car just starts up..- idles 800~1000 for some time and the idle drops (i presume this is normal)

but car seems a little resistive as if lacking fuel when you drive out - especially if push the gas a little more - it kind of catches on and is ready to fly!

2) when engine hot (engine temp 85~90 C) the car will start up in one crank - no problem here

3) PROBLEM - now leave the car for 10 mins or so and come back and crack up it takes like 15 sec of cracking and gas pedal pumping/pushing to start - also it starts rough and then evens out at normal idling...and drives fine after that.

I took it to an independent mechanic (C& H auto, Chicago) - where we changed Sparkplugs to Bosch Platinums - no improvement. {receipts say flue filter was changed like 3 yrs back with fuel pumps}

Also a voltage check across oxygen sensor was at 0.7 -0.8 - idly i guess it should be around 0.5 - but playing around with the fuel air mixture is very very sensitive and we could not get it at 0.5.

So next it seems as the oxygen sensor - but I am not sure if I am on the right path.. The independent mechanic comes highly recommended but he is also trying to figure it out. He suggests - distributor and wire replacement (tune-up) and fuel system cleaning.

I know a tune is something I need to get done since the car was owned by an older gentlemen and sat for 3 months -so far have changed oil/oil filter and topped off all fluids. (transmission and radiator flush need to be done).

Anyone has an ideas or know what could be the issue??

I find it hard to say this but it sounds like you are in the beginning throws of the accumulator going south.Seems like the last week or so this has stood out as a recurring problem.you can find several post on this subject and some good how to info as well.JNT

zcc · #3 03-20-2007, 04:58 AM

Check the fuel pump relay.

david s poole · #4 03-20-2007, 11:29 AM

i agree the fuel pump accumulator sounds like the problem because the fuel pumps were replaced[along with the fuel pump check valves].

ctaylor738 · #5 03-20-2007, 12:18 PM

I agree with the accumulator for the hot start issue.

I think your oxygen sensor may be TU. If you can't get it below .7, then the lambda system or EHA (not sure what a '92 CE has) is going to lean the mixture as much as possible based on a false reading. So get the proper (3 wire?) generic Bosch sensor from Phil for $35 or so, then adjust your on/off ratio as described in many posts.

stargazer · #6 03-20-2007, 01:00 PM

Quote:

Originally Posted by david s poole

i agree the fuel pump accumulator sounds like the problem because the fuel pumps were replaced[along with the fuel pump check valves].

when u say fuel pump accumulator - is this what u are talking about ??

http://cgi.ebay.com/ebaymotors/Mercedes-fuel-accumulator-300SEL-300E-W201-W124-W126_W0QQitemZ320092563566QQcategoryZ33553QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

Also where in the engine bay is it located??

david s poole · #7 03-20-2007, 03:33 PM

yes but it's not in engine bay,it's above fuel pump[s] by right rear axle.

lkchris · #8 03-20-2007, 06:48 PM

Hot start issue is symptom of leaking injectors flooding the engine.

Try starting with accel pedal down some to verify.

loubapache · #9 03-27-2007, 10:14 AM

Cold start -> OK
Hot Start -> OK

Warm start -> problematic.

I agree with one previous post. This is a typical symptom of slightly leaky fuel injectors.

When they leak a little, hot start is not affected because there is not enough fuel to leak out. Cold start is also not affected because there is enough time for the leaked fuel to evaporate.

Warm start is affected because there is leaked fuel (flood). Enough fuel has leaked and not enough time for it to evaporate. You can further confirm by doing a double start. Start it (it may not start). Stop and wait for a few seconds. Start it again (it should start now). The first (failed) start will burn off the leaked fuel and the second start will be successful.

Before you try to replace the injectors, try to clean using an approved fuel injector cleaner. Contrary to what have said by many, MB does approve two injector cleaners in their 2006 approved service products for all engines. On page 15, one is an MB product that you can buy from the dealer. Another is Chevron Techron.

You can get a 20 oz bottle and put in the tank and filled it up. Do a mixed driving and preferably over a few days. Let the car sit after driving (Let it leak so the cleaner can clean the injectors to simulate the leaky situation). Or you can go to Advance Auto Parts and get two 12 oz bottle (buy one get one free before the end of this month).

You should notice some improvement after one application (a few successful warm starts). You may need a second application. Change the oil after the applications.

This should cure deposit related leaks. If it is an internal (parts related), then this cleaning will not fix.

glenmore · #10 03-27-2007, 09:13 PM

Quote:

Originally Posted by loubapache

Cold start -> OK
Hot Start -> OK

Warm start -> problematic.

I agree with one previous post. This is a typical symptom of slightly leaky fuel injectors.

When they leak a little, hot start is not affected because there is not enough fuel to leak out. Cold start is also not affected because there is enough time for the leaked fuel to evaporate.

Warm start is affected because there is leaked fuel (flood). Enough fuel has leaked and not enough time for it to evaporate. You can further confirm by doing a double start. Start it (it may not start). Stop and wait for a few seconds. Start it again (it should start now). The first (failed) start will burn off the leaked fuel and the second start will be successful.

-snip-

This is helping me zero in on my situation, although I am guilty of what stevebl scolds us not to do, namely throwing parts at a problem.

My car, 1991 300CE at 143m, bought it at 111m. It has always had a slightly sluggish start. I occasionally get a quick cold start so that must be the cold start valve working? But for most cold starts, it doesn't catch for a couple of seconds, but it will catch. If I let go too soon and it does not start, and then I restart, it catches immediately. A hot start is fine also. But anything less than a hot start, it stumbles. The car otherwise drives and idles perfectly. I decided to change the fuel filter and since I was going to be rooting around there, I decided to change the accumulator. I only have history back to about 87m and no record of these changes. It's been a few days, and absolutely nothing has changed.

I have used Techron every so often since I bought the car. Some new injectors are on the way, so I'll give them a shot.

Thoughts?

Thanks,

glenmore
1991 300CE
2000 C280
1990 LS400

stargazer · #11 03-28-2007, 09:17 AM

Quote:

Originally Posted by glenmore

This is helping me zero in on my situation, although I am guilty of what stevebl scolds us not to do, namely throwing parts at a problem.

My car, 1991 300CE at 143m, bought it at 111m. It has always had a slightly sluggish start. I occasionally get a quick cold start so that must be the cold start valve working? But for most cold starts, it doesn't catch for a couple of seconds, but it will catch. If I let go too soon and it does not start, and then I restart, it catches immediately. A hot start is fine also. But anything less than a hot start, it stumbles. The car otherwise drives and idles perfectly. I decided to change the fuel filter and since I was going to be rooting around there, I decided to change the accumulator. I only have history back to about 87m and no record of these changes. It's been a few days, and absolutely nothing has changed.

I have used Techron every so often since I bought the car. Some new injectors are on the way, so I'll give them a shot.

Thoughts?

Thanks,

glenmore
1991 300CE
2000 C280
1990 LS400

give a try replacing the injectors and see what happens

just-n-time · #12 03-31-2007, 04:45 PM

Quote:

Originally Posted by stargazer

give a try replacing the injectors and see what happens

I was under the impression that the cold start injector,only operates when it is very cold out,That it dose not work just any time you start the car! Temp must be low enough for it to get the signal to inject!JNT

glenmore · #13 04-01-2007, 08:06 PM

On to the injectors! On removing the air filter, I had a eureka moment, when I saw that one of the injectors had an obvious leak. Luckily it was one of the easy ones to get to. The pairs of injectors on either end have great access but the two in the middle look difficult. I changed the leaky one and one other and am waiting some more in the mail. The injectors themselves look fine, the delicate tips look just like the new ones. The fit of the new Oring and new insulator in the head is tight. I had to tap them in with a 15mm socket. The old ones came right out. The old seals were very brittle and mashed. It was nice to freshen up the seals but after a couple of starts, I don't think this is the cause of my stumbling start.

glenmore
1991 300CE
2000 C280
1990 LS400

stargazer · #14 03-28-2007, 09:18 AM

Quote:

Originally Posted by loubapache

Cold start -> OK
Hot Start -> OK

Warm start -> problematic.

I agree with one previous post. This is a typical symptom of slightly leaky fuel injectors.

When they leak a little, hot start is not affected because there is not enough fuel to leak out. Cold start is also not affected because there is enough time for the leaked fuel to evaporate.

Warm start is affected because there is leaked fuel (flood). Enough fuel has leaked and not enough time for it to evaporate. You can further confirm by doing a double start. Start it (it may not start). Stop and wait for a few seconds. Start it again (it should start now). The first (failed) start will burn off the leaked fuel and the second start will be successful.

Before you try to replace the injectors, try to clean using an approved fuel injector cleaner. Contrary to what have said by many, MB does approve two injector cleaners in their 2006 approved service products for all engines. On page 15, one is an MB product that you can buy from the dealer. Another is Chevron Techron.

You can get a 20 oz bottle and put in the tank and filled it up. Do a mixed driving and preferably over a few days. Let the car sit after driving (Let it leak so the cleaner can clean the injectors to simulate the leaky situation). Or you can go to Advance Auto Parts and get two 12 oz bottle (buy one get one free before the end of this month).

You should notice some improvement after one application (a few successful warm starts). You may need a second application. Change the oil after the applications.

This should cure deposit related leaks. If it is an internal (parts related), then this cleaning will not fix.

Thanks loubapache -- will do as suggested and keep you posted!!