Mercedes-Benz Forum banner
1 - 11 of 11 Posts

·
Registered
1989 560sel
Joined
·
10 Posts
Discussion Starter · #1 ·
morning everyone,

1989 560sel, bought about a month ago and put about 5000km on it
so when I first got it, the cold and warm start were both fantastic, started on the first crank every time

since then my cold start has deteriorated to the point where it takes 4 - 6 cranks, and feels sometimes like there is a miss or something before the idle kicks in.

warm start, or even the second start after the cold start if I turn it right off and start again is fine.
1 or 2 cranks

so, I also noticed the other day a strong fuel smell in the cabin, right after I filled up
and thereafter noticed a puddle near the right wheel well, where my fuel pump and lines are located.

however, the fuel is not coming from pump or anything, its coming from the black rubber hose that is connected to the little hole just below my gas cap.

whats going on?
are these two issues related?
do I just need a new gas cap?
do I just need to not fill the tank full?

this only happens when I fill the tank right full.

thanks everyone!
 

·
SuperModerator
1986/1990 W126
Joined
·
17,216 Posts
Oh, it's coming down that drain tube then.
I would check the archives for the information about the little check valve that controls pressure in the tank, for starters. Very easy fix but it can cause a lot of hassle if not sorted.
This could be affecting your starting too, fuel tank damage can happen after a time.
 

·
Registered
1989 560sel
Joined
·
10 Posts
Discussion Starter · #3 ·
thanks!

how does it get into that drain tube?
just from looking at it, it would seem the only way would be if it was leaking out of the gas cap
 

·
Registered
1985 500sel and 500sec 2012 E63 1989 Porsche 911
Joined
·
5,941 Posts
show us a picture of where you speak of
 

·
SuperModerator
1986/1990 W126
Joined
·
17,216 Posts
Yes getting squeezed out of the gas cap.

The gas cap is MB specific with a vent pressure. So seems like it may be exceeding that.

They're cheap from MB, so I would suggest a new one of those. But so is that check valve and its important. So maybe both.
 

·
Registered
Too many to list
Joined
·
10,455 Posts
It’s the check valve
Never fill your tank all the way full you will flood excess fuel into the vapor canister
 

·
Outstanding Contributor
1989 560SEC, 1989 560SEL, 1995 E420
Joined
·
5,204 Posts
It’s the check valve
Never fill your tank all the way full you will flood excess fuel into the vapor canister
Tell me more about this. I've been filling tank very full for 11 years and over 100k miles. I've never heard of this and now I wonder if I've just gotten lucky or if I may have ruined the vapor canister.
 

·
Outstanding Contributor
'17 GLS450, '14 GLK250 "Grandpa's Roadster" Project Car, 350SDL (Sold)
Joined
·
4,034 Posts
The tank and fill plumbing is designed to prevent overfillling. As long as you don't spend 5 minutes trying to squeeze in that last gallon, the auto shutoff on the pump will not allow you to fill the designated air space with fuel. As long as that air space has air in it, the vapor canister won't get liquid fuel in it.
 

·
Registered
1989 560sel
Joined
·
10 Posts
Discussion Starter · #10 ·
thanks everyone

would a bad check valve not cause issues with warm start too since its not holding pressure?

thanks
 

·
SuperModerator
1986/1990 W126
Joined
·
17,216 Posts
thanks everyone

would a bad check valve not cause issues with warm start too since its not holding pressure?

thanks
If the vent valve is blocked, it will increase vacuum or pressure in the tank. You might be thinking of the check valve on the fuel pumps or the accumulator.

Sometimes starting problems due to this vent valve. But those pumps are extremely strong, so in my case the car ran perfectly until I realised the tank had begun to rupture.
 
1 - 11 of 11 Posts
Top