Zayzaysmith22

Hi! New to the forum and I've jump on here to reach out and get some help! I have a 1997 Mercedes Benz c230k I just picked up drove it about 30/40 miles with no issue! But after it sat for a couple hours it will only crank and takes for every to start! ( About five minutes depending on how long it sits )
but when running and driving it'll start fine right after a drive and when driving no misfires or issues! Some start ups it'll misfire and throw a EGR code random misfires code and fuel level sensor code ( fuel gauge doesn't work) I've done the following work
Fuel pump
Fuel filter
Fuel pressure regulator
Fuel pump relay
Ignition coils and plugs
Maf sensor
Camshaft sensor
Crankshaft sensor
also has a new battery
I've done a fuel pressure test and it all check out
yet it still long/rough starts
I'm at my wits end with this car and it's my first Mercedes any help would be appreciated!
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RollTideW163

Usually, if there is a starts when cold but not when warm issue its a camshaft sensor issue, but you seem to have the opposite problem.

Are there any other codes pertaining to that ?

The other thing is where did you get those parts / who made them. If you are getting cheap parts of ebay or something, it is not uncommon for them to be non-working or not working properly. This often throws people off because they think they changed all the possible parts not knowing one of them isn't even working properly.

You can likely take fuel off the list, so its either a sensor or electrical. Did you change the wires that go from the coils to the plugs too ?

cadman777

I can't tell you what's wrong with your W202, but I can tell you what I found on mine.
Mine is a 1998 C230 4dr sedan 2.3L (no turbo).
It ran OK, but had a slight hesitation before it sat for 3 years.
Last week I wanted to get it running again.
So first thing I checked was the fuel pump and fuel filter.
The fuel pump wasn't working so I cut it open to find it sludged up and totally corroded from separated ethanol.
So that got changed along with the fuel filter.
Then I drained the two sides of the gas tank and dumped into it 2 gallons of non-ethanol with marine Stabil.
It started and ran for about 10 minutes and died.
It wouldn't start again, so I drained the 2 tanks and returned the 2 gallons back into the tank.
It ran good for about 10 minutes and died, and wouldn't start.
When trying to start it both times it tried but wouldn't.
I did that one more time with the same results for verification purposes.
Based on what I learned about the way this gas tank system works, there might be a problem with the tank internals:
www.youtube.com/watch?v=OMEojtNpsrw
Watch the video with the sound off and English subtitles to get the point.
The way I understand this system is, the pump runs almost constantly in a loop, from the right side tank to the engine fuel rails and back to the left side tank.
As the return fuel pumps into the left side tank, it goes through a venturi type pump (mechanical, not electric).
As it passes through that pump, it picks up gas from the left tank and pumps it into a feed well in the right side tank that feeds the pump.
Another line sends fuel to the feed well, and at the base of the feed well is another suction pump that draws gas from the right tank and pushes it into the feed well.
But if there is a leak in any of the left side lines at before or after the venturi pump, the feed well starves of gas.
So the car will run until the feed well is empty.
The fill spout enters the tank right above the feed well, so when you try filling the tank, you pour gas into the feed well.
If you have internal tank hose problems you can have a full tank of gas and the car won't run.
It will happen at any fuel level, depending on when the problem starts.
So I removed the right (passenger) side level sensor but couldn't remove the gland nut on the left (driver) side to check the left side level sensor.
(The guy who tightened that gland nut last time cranked it down REAL HARD...idiot!).
Anyway, there is a pressure sensor on the right level sensor and the o-ring seal on the split body was sticking out on one area so it was getting gas inside.
Also, the 3 wires between the connectors (level sensor flange and pressure sensor connector) had lost their coating (sparks inside the gas tank? nice design mb!).
Also, the plastic hose that connects the pressure sensor to atmospheric pressure (a port in the level sensor flange) was disconnected (due to deteriorating hose), so gas was getting into the sensor that way too.
Also, I'm surprised there was no leak at the flange nipple leading to atmosphere.
Conclusion: The fuel tank pressure sensor wasn't working.
The pressure sensor sends signals to the computer to control the EVAP system.
I suspected an EVAP problem, but didn't expect it to be this kind.
Before removing the level sensor I checked all the EVAP lines for obstructions as well as checking the purge valves.
All was OK (what a PITA!).
Anyway, so far that's what I found on the right side level sensor.
I expect to find deteriorated hoses on the other side level sensor too, IF I can get the gland nut off!
One way or the other I have to fix that bad sensor and gas hose.
So if it's not a simple failed pump or clogged filter, then it's probably a problem with the EVAP or tank internals.
If I can't find a right side level sensor then I'll have to figure out how to add a tank pressure sensor another way.
Maybe I can add it to the EVAP line in the wheel well using a Tee adapter and an external pressure sensor of the same specs?
I'll update this post when I arrive at a conclusion.

W202fan

A lot of fuel draining there... what'd you do with all that old gas?

cadman777

When digging deeper into my runnability problem I had to empty the gas tank totally. There was 5 gallons of very bad gas. The county where I live has a number of chemical recycling houses that this kind of thing can be dumped at. I dumped those 5 gallons at the main recycling center for free.

So I finally got the gland nut off the driver's side level sensor. Had to use a carbide burr to cut through it and then made my own tool that would work with a 3/4" drive breaker bar. Finally it came off. There was nothing wrong w/the lines or float, so I reinstalled it with the good gland nut (a new nut cheapest price @ $50 - extortion!).

Then I removed the passenger's side float again and stuck a bore scope into the tank to look at the back where feedwell is located. Wouldn't you know, the elbow (cheap plastic garbage!) disintegrated. That means the line coming from the driver's side float valve (the one that feeds the passenger's side valve that the elbow is attached to that sucks up gas from the passenger's side tank to feed the feedwell) was dumping its gas directly into the passenger's side tank and not up into the feedwell. So there's NO WAY the feedwell would keep getting gas. Instead, all the gas got distributed into both tanks and when the feedwell ran dry, that was it. No more gas to the fuel pump.

So now I have to cut the tank open and make my own elbow to replace the missing elbow. Gonna have to learn how to do plastic welding on this tank. Anyway, a new tank is over $1000, so there's NO WAY I'm going to spend money on that expense. If that fails, then I'm going to make a gas tank that fits into the spare tire well and run a direct line without all that saddle bag recirculating garbage. I wouldn't mind if Benz designed this tank to allow servicing of the feedwell. What STUPID German ENGINEERING this system is!

I'll make an update when I get the gas tank fixed. To do that, the rear end has to be dropped. HUGE JOB. Another Benz nightmare. STUPID German ENGINEERS!