Fuel delivery problem? Fuel injection w111 220SE - PeachParts Mercedes-Benz Forum

Scutch · #1 06-19-2015, 11:03 PM

Hi all, I have begun fixing all the new issues the 1965 220SE sedan that I recently bought. Lately when I have been driving on the highway and the fuel is nearing half full the car starts to sputter like it is being starved of fuel.
This has happened twice. I then go and fill the tank and the car seems to run fine again. The first time the tank was down 7 gals, the second time only 5.5 gals.
Once it starts then I can be in any gear at high rpms and the lost of power occurs. Let off on the accelerator a bit and the problem stops.

Also, I am having trouble starting the car. It happened twice right after I filled the tank when the loss of power occurred. I am not sure but then the other two times I couldn't start it I was parked on an incline where the front of the car was elevated. Not sure if that is related. But the not starting only began after the loss of power issue popped up. It turns over fine, just doesn't catch.
If I wait a couple minutes, the car has started again, so far. Today it was mid 90’s and the car didn’t start a couple more times. But then started after waiting a minute or two.

Not very familiar with fuel injection yet. Does this sound like maybe the cylinder filter below the main fuel pump may be clogged? I have the two port fuel pump going into 6 injectors. Could the pump be weak? Tonight I checked inside the tank. It was spotless and no debris around the bottom gas screen.

I am also hearing a clicking sound that my mechanic said was the solenoid on the fuel pump. I believe it clicks after about 3 seconds whether the car starts or not. But if I try to start the car too soon I won’t hear the clicking noise unless I wait about 30 seconds before starting it again. Don’t know if that is relevant.

I have not ever had a sucking sound when removing the gas cap either.

Thanks much for any help.
Eddie

ScooterABC · #2 06-20-2015, 03:43 PM

First of all, you might have multiple problems. My first guesses would be:

1) tank screen is clogged and needs to be replaced - that would cause you to only get fuel when the tank is more than part full.

2) fuel filter inside the electric fuel pump itself at the rear of the car - that may well be clogged.

3) Fuel filter in the engine compartment.

Based on the idea that the car works better when the tank is full, I would definitely look at a clogged screen. That means draining (and probably cleaning) the tank. You will read all sorts of opinions on the best way to clean a tank, ranging from using that POR stuff to boiling. I've been quite happy with the three tanks I have cleaned using laquer thinner, a chain and agitation, pressure washing at the self-service car wash, etc. You will need to drain the tank which based on what you are saying will be difficult. If the tank screen is clogged that means that gas isn't getting past it when the tank is on the less full side. That means that removing the lower hose, which is the supply hose to the fuel pump, will only allow some of the gas to drain. Expect to need LOTS of containers to collect the fuel. I used 2 5 gallon boxes that had contained chemical rust remover and almost filled both of them. Use extreme caution in draining fuel and dispose of it responsibly.

Assuming you are going to drain the tank (which I think is pretty much for sure) you will want to disconnect the lower hose from the pump (not the tank) and as best as possible drain it into containers. When stuff stops coming out of it, remove the hose from the tank side (again, the lower hose). You might also want to remove the return hose (the upper hose) carefully and see if more gas drains from that. You want to get the tank as empty as possible as easily as possible.

So at this point I'm guessing you will have a fuel tank that has no hoses connected to it but still contains gasoline. At this point you need a 5 gallon paint bucket (the wide mouth things) under the metal lines into the tank. Take some sort of wire or coat hanger and shove it into the lower metal fitting -- if you have rot in this area it will free up and come flushing out with more gas. But I think that is unlikely since I think your screen is the source of the clog. That leaves you with no good option other than removing the screen (the big plug in the bottom of the tank).

To remove the screen take a spark plug socket and invert it on a 6" socket extension, such that the extension is sticking into the place that you would put over the spark plug. The hexagonal base is the same size (or close enough) to the hex plug on the bottom of the tank to use that as a wrench. You might need a breaker bar to get the plug to start turning, but once it starts turning it gets fairly easy.

YOU WANT THE BUCKET UNDER THIS NOW. As you loosen the plug (which is the tank filter) it will start to drip gasoline. So try to do this such that at some point the dripping is fast enough that you can just leave it for a while, or if you are impatient you can unscrew it until it falls into the bucket and expect lots of gasoline to follow. I'm assuming it will be less than 5 gallons if you have already drained the tank from the return line (which I'm assuming isn't clogged).

After it dumps out the gas, take a look in the bucket and pull out the plug/tank strainer. How does it look? Is it all clogged up on the lower area? I bet it is. At a minimum you will need to replace that AND the rubber O-ring that is petrified in place. They are sold separately, not terribly expensive. You can start with this and IF the screen is clogged as much as I think it is and if the gas that came out looks fairly clean.

Report back when done for next steps if needed...

Scutch · #3 06-20-2015, 04:50 PM

Thanks again Scooter.

I looked in the tank last night when I switched the unswitchable fuel senders and it looked very clean, including the mesh drain plug cylinder. That is so short however that I wonder how that could come into play with only 6 gallons down on fuel, even 7.

I will head to the other filters.

ScooterABC · #4 06-20-2015, 05:35 PM

Quote:

Originally Posted by Scutch

I looked in the tank last night when I switched the unswitchable fuel senders and it looked very clean, including the mesh drain plug cylinder. That is so short however that I wonder how that could come into play with only 6 gallons down on fuel, even 7.

Well, one simple test you can run is when the car is behaving crappy and the tank is at the lower end see if removing the fuel line causes a lot of fuel to come out of the tank. I'm still guessing no. When you looked in the tank was the tank screen covered with gasoline? It's about 4 inches long. I'm not sure you would be able to tell if it were under gasoline as the clogging doesn't really look all that clear if it's submerged. You might try taking a picture of it through the sender opening with a cell phone. Cell phones are great for taking pictures in places where you can't get a camera since the flash and lens are right next to each other.

S.

Scutch · #5 06-20-2015, 10:16 PM

I will know more in a couple days, but I think the problem was a recent bad local shop fix of the fuel line from tank to rear fuel pump resulting in bent fuel line.

ScooterABC · #6 06-20-2015, 10:39 PM

Quote:

Originally Posted by Scutch

I will know more in a couple days, but I think the problem was a recent bad local shop fix of the fuel line from tank to rear fuel pump resulting in bent fuel line.

A bent fuel line could definitely cause low fuel delivery, but it wouldn't explain anything about why the car works when the tank is full and not when it is 1/3 full... Looking forward to your discoveries! Fintails are Fun.

Scutch · #7 06-22-2015, 11:03 PM

I took the car out for a long drive on the highway today and it drove fine again at 85mph with less than a half a tank of gas. It seems it was just a kink in the line from tank to rear fuel pump.

Would like to have a chat with the car shop. But they are clients of mine as well. Will just make a mental note, that in addition to only using them for emergencies, to double-check their work.

Scooter, thanks for the tank draining procedure. I will try and do more homework before next posting. :-)

BTW as we were fixing the kinked fuel line today we checked and observed that fuel was pouring out of the main tank line at great volume. I would bet that the bottom mesh screen is pretty clear.

ScooterABC · #8 06-22-2015, 11:12 PM

Quote:

Originally Posted by Scutch

BTW as we were fixing the kinked fuel line today we checked and observed that fuel was pouring out of the main tank line at great volume. I would bet that the bottom mesh screen is pretty clear.

Glad you car is working right now! Yes, fuel should just POUR out of that pipe. Unless the car has sat for a while there isn't a great reason for the screen to be clogged. It's just the "at less than half a tank" thing that makes it all strange...