Vacuum in Fuel Tank and common intermittent problem on 1992 190e 2.0

[webcentre]

Hi all, im new to the Mercedes shop forum, i tried the mercedesclub forum, but alas no luck with my problem.

Although it seems a common fault, i have been unable to find any diffenitive answers, or places to look. As said, i have a merc 190e, which up until about 5 months ago, was a cracking car. Then this mysterious problem crept in.

As im sure uve read time and time again, it stalls usually when approaching a junction, when u slow to a stop and idle whilst still in Drive. If u leave it idleing, it sounds as though it misses a beat every so often, and once it has missed that beat, if u try and pull away, it will stutter and jerk when accelerating.

Typically enough, when taken to a garage, it will not display these faults, then 5 minutes after i get it back, it does it again, only to work fine once i go back to the garage.

Such an annoying problem, becuase it is guarenteed to happen at least once every journey, which leads not only to an uncomfortable ride, but also i fear i might be damaging the engine.

Also i have noticed a rather strong vacuum in the fuel tank, i.e when i take of the cap to fill up, there is a strong intake of air into the filler neck (if u see what i mean). Now, am i right in thinking this might be a blockage in some sort of vapour recycler in the fuel tank (if such a thing exists on mercs of this age? i dont particulally want to drill a hole in the cap to release the pressure, rather than fix the fault)


I apologise for the very long post, but i hope it explains my predicament well enough. The enfuriating thing is that when it is running, the old 190 is a joy to drive (although possibly slightly high revving on the motorway, due to the 3 gears on the auto box?)

yours

Matthew.

[Duke2.6]

Modern fuel systems with evaporative emission controls are designed to hold pressure or vacuum up to about 2 psi. The relief valves are usually built into the cap.

It's not uncommon for me to here a "whoshing" noise when I remove the fuel filler cap on my 190.

Duke

Some things come to mind :

Plugs
Cables
Distributor
Rotor
Ignition coil

Does the problem come when the engine is warm and stays that way; or does it come and go intermittently?

By the way, the fuel system in our cars are pressurised so when you take off the gas cap, you will get the whoosh from the release of pressure in the fuel system.

I get the same thing with my car, too.

Cheers.

[xp190]

My car had a problem like that when the O2 sensor connector was seeping voltage to the heater connections. Don't ask me how this happened, but I fixed it up and the problem has yet to come back. It happened once the car was all warmed up since that's when the O2 kicks in.

Also check the fuel pump, is it buzzing really loud? Does your car give codes? Try monitoring the EHA current to see what it does when the problem occurs.

xp

[psfred]

Check the condition of the idle control valve hoses. If they are hard instead of flexible, replace them and clean the idle control valve with carb cleaner or brake parts cleaner.

Check the condition of all the rest of the rubber bits on the vac lines, too, replace any that are at all not perfect.

If you indeed have a strong vac in the tank -- do you have to pull the filler cap off, or does it vent as soon as you turn it? -- you have a plugged evapration control system vent line. It's under the car someplace near the tank, rubber hose ending in a valve assembly of some sort. Nice place for spiders or etc to build nests.

Peter

[webcentre]

thanks for the replies. After finding another thread on the matter, i whipped the spark plugs out, and found something quite strange. 3 plugs were in good condition (the threads were coated in oil, not sure if that is bad or not) but the last one (nearest the bulkhead) was covered in black soot, which i beleive is a sign of overfueling?

The question is, how can 1 cylinder be over fueling, and would this cause this strange stutter?

[psfred]

Bad fuel injector is the cheap cause, bad fuel distributor is the expensive one.

I would replace at least that one injector and all the injector seals for a start. This may fix the problem completely, as a leaking injector can cause #1 to foul at idle. If the plug stays black, chances are you have a fuel distributor problem.

Lean running due to injector seal leaks on the other cylinders, or clogged internal filters resulting in low fuel delivery will also make #1 run over rich, so a complete set of injectors isn't a bad idea either. Cannot usually clean them once plugged.

Peter

[haasman]

I would also try bleeding the injector lines at the fuel distributor.

I had never heard of this, a Mercedes tech friend suggested it.

Worked successfully on the 190e, rather amazing. A lot of crud came out and then the car ran and idled quite well.

Haasman

[webcentre]

thanks for the reply. hmm, is there anyway to check the injector, aside from replacing it? also, ive never heard of a fuel distrubtor, im used to old peugeots, which i dont think have them?

also, i presume the oil on the threads is not a problem then?

[haasman]

Your fuel distributor is under your air cleaner. It is the device that all the individual fuel injector lines run to/from.

Bleeding fuel lines is dangerous in that raw fuel will come out. If you don't know how or feel it is something over your head, have someone else do it.

Injectors can be removed and checked with a proper injector testing stand. It supplies the proper amount of pressure and also allows one to observe correct spray pattern.

Have you tried the old two bottles of Techron Fuel Injector Cleaner in less than a full tank of fuel? This is a simple and cheap way to try cleaning them out.

Old on spark plug threads? That unto itself isn't a problem. It probably indicates your valve cover gasket is leaking.

Haasman

[webcentre]

right, update

ok, changed spark plugs and leads, and changed the injector (not the main single point one) on the cylinder that was fouling the spark plug, and i now have another problem, as well as the still unsolved misfire.

the car is permantly running rich, its fouling all four plugs now. Its flooding the engine, so that it wont restart. when it does restart, it idles at about 1200rpm (its cold) then drops to around 1000rpm. It still misses occasionally, but what i have discovered is that if you feed the throttle in very very very lightly, it coughs and splutters, but it clears itself. If you apply anymore than slight throttle, it overfuels and floods itself, after which it will not restart!

Now other things ive noticed. the idle control doodaa(underneath the air filter) was not connected. reconnected that and now it idles high to start, then drops once it warms up (as it should) also the air filter is very dirty (getting changed tomorrow)


But does anyone have an idea what would cause this dramatic overfuelling/stalling?


sorry for the long post.

[manny]

Just a shot in the dark.
Have you checked the fuel pressure?

[webcentre]

how? i saw a fuel pressure tester kit in my local trade place, but it was 300 pounds!

[webcentre]

well, it now seems that its just chucking too much fuel in below 2k rpm. after that, it clears up, and revs nicely. this is all at idle by the way, becuase the minute u put the transmission into drive, it stalls. Very annoying

[Jim Anderson]

No, Peugeot's don't have a fuel distributator, they use a common rail with solonoid type fuel injectors run by a computer.