[anthonywclark]

Hello everyone.
My daughter has a 1989 300sel(gasoline) straight 6. She purchased this car last year and it ran fine. We had a few minor repairs that needed done. power steering hose leak and had to grease linkage for the acceleration issues.
Recently, she has been having issues on startup. First she had to pump the gas. Then, she had to hold down the gas pedal. Now, this doesn't seem to work half the time. Once the car does start, it idles rough for a second then its fine and drives great after this.
What I need to know is if this is definitely the Idle Control Valve(which I'm replacing) or is there something else I need to look at.
I do plan on replacing the fuel pump, fuel filter, and distributor cap and rotor this month.
Please help.

 

[luckymike]

Hello everyone.
My daughter has a 1989 300sel(gasoline) straight 6. She purchased this car last year and it ran fine. We had a few minor repairs that needed done. power steering hose leak and had to grease linkage for the acceleration issues.
Recently, she has been having issues on startup. First she had to pump the gas. Then, she had to hold down the gas pedal. Now, this doesn't seem to work half the time. Once the car does start, it idles rough for a second then its fine and drives great after this.
What I need to know is if this is definitely the Idle Control Valve(which I'm replacing) or is there something else I need to look at.
I do plan on replacing the fuel pump, fuel filter, and distributor cap and rotor this month.
Please help.

If you know that list of parts is bad or ready for replacement, I'd certainly install them. But if the problem persists, I'd follow the troubleshooting section in the manual: 15-540. If that all checks out okay, then you look at 07.3-121.

 

[GreenT]

Do the sixes have a fuel accumulator?

 

[anthonywclark]

I don't recall seeing a fuel accumulator. Wouldn't that be inline with the fuel pump and filter under the tank?

 

[GreenT]

I'm not familiar with the I6s but a lot a members here have them. Someone will jump in.

 

[anthonywclark]

I looked online and found several different designs. Some have it in plan sight and some have it hidden behind the fuel filter and pump. I looked and could see anything, but this may change once I start replacing it. I also saw pics of the accumulator being under the air filter. I will check this tomorrow.
IMPORTANT: I have noticed that when I put fuel in the car, I smell gas for a few days. No leaks. Tank is sealed. Gas cap makes a chssshhh noise when opening. The smell goes away after a few days. I did find a hose under the car that has the gas smell coming out. WHAT IS THIS?????

 

[McGavin]

The fuel smell can be the diaphragm in the fuel regulator, I replaced the one in my M117 with one from a M103 as they shared the same part number, this got rid of my fuel smell. The hard start sounds like a dodgy accumulator, but like GreenT I am unsure of the existence on a six, but I would assume so.

 

[GreenT]

I found the service manual for the M103.

Mercedes Benz Model 124 - M103 Maintenance Manuals

 

[Vizezeul]

I looked online and found several different designs. Some have it in plan sight and some have it hidden behind the fuel filter and pump. I looked and could see anything, but this may change once I start replacing it. I also saw pics of the accumulator being under the air filter. I will check this tomorrow.
IMPORTANT: I have noticed that when I put fuel in the car, I smell gas for a few days. No leaks. Tank is sealed. Gas cap makes a chssshhh noise when opening. The smell goes away after a few days. I did find a hose under the car that has the gas smell coming out. WHAT IS THIS?????

The hose that just cuts off next to the fuel filter is a draining hose. It's connected to the little hole on the bottom-left side of the gas tank. It's meant to drain any fuel that may have dripped out of the nozzle during a fill-up to the ground rather than letting it accumulate in the gas cap area.

I actually discovered it on my 560SEL while I was pouring a fuel additive in the gas tank and it spilt out. I saw that the spilt fluid drained down the hole and exited from the hose.

 

[anthonywclark]

Thank you for that update. That makes sense. It appears I will be adding an accumulator and pressure regulator to my list. The repairs are adding up, but a car for $1300, I can't complain.

 

[wooky_chew_bacca]

My former '91 300SE had an accumulator on it. Anthony, 1300 bucks for a car that I/many still consider to be one of the safest in the world 25 years out is well worth the price

 

[anthonywclark]

Yeah, its a great car for a decent price.
UPDATE: I tried a few test yesterday. I turned the ignition switch to the on position (not cranking). Let the pump motor "prime". Then turn it back off. I did this about six times before cranking the engine. When I did this procedure, the car started up great with no idle issues or pumping the pedal. I feel its the accumulator that some have mentioned in the post. I did find it. Its hidden behind the Fuel pump and filter. Here are a few pics I took.

 

[anthonywclark]

I hope this purge valve is the fix. I am ordering online, today. Its only about $20. Unfortunately, no one carries these parts locally. I double checked the fuel lines and hoses. The hoses do need replaced. But nothing is leaking (liquid or fumes) I let it run while doing this and checked again after shut down. It appears the fumes are coming from the tank area through the trunk, which then seeps into the car.

 

[KRH]

If the 6 is the same as the 8 with fuel accumulator to hold pressure in the fuel system ready for next start up -then it will be the problem - especially knowing the engine runs fine once fired up.
Also when underneath where the pumps & filter are check all the rubber hoses thoroughly and look for signs of fuel leakage.
The rubber hoses go brittle and hard with age and even where they clamp to metal they can have a poor seal.
Any loss of fuel pressure in the system after the car has been parked up will cause hard starting at next start up with the main culprit being the fuel accumulator not holding pressure

 

[wooky_chew_bacca]

Yup, that's the accumulator back up in the nether region. Although the rubber back there isn't leaking now, when I went to change the filter the lines all cracked and two started leaking. This is one of those "while you're back there/in there" go ahead and replace all the rubber lines and at least look at the tank strainer. The smaller line can be replaced on the cheap with local obtained fuel injection rated 5/16 hose and clamps, the main tank feed can be gotten from most any online parts house. I can't remember the size of the rubber between the accumulator and the "F" fitting

Oh, let me add, mashing the gas with the engine not running does nothing, no carb or priming device on these

 

[John350]

In 1975 there was a problem with fuel pressure leaking back through the pump's check valve. As far as I know, it was fixed in later pumps and I don't recall seeing the problem at all in subsequent years. Not that this helps...

 

[anthonywclark]

Update

So I have replaced all the hoses, accumulator, filter, and pump. The car starts and runs great. No idle issues. I also replaced the purge valve from the charcoal filter. I have NO gas smell in the car.
She was driving it for several weeks and it appears we DID NOT fix all the problems.
When the car has been driven a while (warm engine), she stops the engine and then tries to restart and it will not start up. You can crank it and fuel IS getting to it. Crank it enough, you smell it. Now once the engine cools down an hour or so, it starts up with no problems. She has had it stall once while cruising through town with her friends. I'm wondering if it the engine temp sensor or pressure regulator. I am waiting on a few parts to come in and wondering if there is anything I need to look at besides these 2 items.

 

[luckymike]

So I have replaced all the hoses, accumulator, filter, and pump. The car starts and runs great. No idle issues. I also replaced the purge valve from the charcoal filter. I have NO gas smell in the car.
She was driving it for several weeks and it appears we DID NOT fix all the problems.
When the car has been driven a while (warm engine), she stops the engine and then tries to restart and it will not start up. You can crank it and fuel IS getting to it. Crank it enough, you smell it. Now once the engine cools down an hour or so, it starts up with no problems. She has had it stall once while cruising through town with her friends. I'm wondering if it the engine temp sensor or pressure regulator. I am waiting on a few parts to come in and wondering if there is anything I need to look at besides these 2 items.

I would urge you to go methodically through the troubleshooting sections in the manual.

That said, you didn't mention replacing the cap and rotor. If that is the case, I would be looking closely at both of those before continuing. My Dad's 300TE (same engine as your daughter's) had the same symptoms you describe. The center electrode had disappeared from the cap! Started great cold, wouldn't restart hot.

 

[John350]

Temperature related stalling is often caused by flaky electronics. Look at all the electronic components under the hood related to ignition and fuel.

 

[anthonywclark]

I plan on replacing the Cap, rotor, wires, and plugs next weekend. It will cost around $250.
I just finished replacing all vacuum lines, elbows, etc... The overload relay and air filter are fairly new. Checked all electrical connections for wear and damage. The appear to be ok.
I just hope its none of the real pricey stuff, like the EHA($280), Idle control valve($150) or the Fuel regulator valve($250).