Diesel cap question
 

I have this 84 300D and
I am wondering what could be causing diesel to be leaking from the gas cap (or diesel cap). There is a small amount of diesel showing it self on the paint around the door to cap and a some diesel sitting in the compartment. Not a lot but I don't think that this is right.
Is the cap bad or is it some kink of pressure issue in the system?

Jimmy

You probably just need a new seal. Or you can replace the cap.

Thanks , I'll try that . It makes sense to me.

check your tank vent

Answer
 

The engine oil fill cap is identical = you can swap them. :)

Another possible answer = The fuel tank vent may be plugged.



.

Thanks, where is the vent for the fuel tank?

Here is a link to the oil cap seal

http://www.allpartsexpress.com/ShopByVehicle.epc?q=1984-MERCEDES--BENZ-300dt--/--L5--998cc--3.0l--Diesel--Fi--Turbo-Engine--Seals--Gaskets--Sets&yearid=1984%40%401984&makeid=MERCEDES+BENZ%40%40MERCEDES+BENZ%40%40X&engineid=1193789%40%40300D T++%2F+L5%2D2998cc+3%2E0L+DIESEL+FI++Turbo%40%40300DT&catid=Engine+Seals%2C+Gaskets+%26+Sets%40%40En gine+Seals%2C+Gaskets+%26+Sets&subcatid=Oil+Filler+Cap+Gasket@@Oil+Filler+Cap+Gasket&mode=PA

here is the fuel cap seal

http://www.allpartsexpress.com/ShopByVehicle.epc?q=1984-MERCEDES--BENZ-300dt--/--L5--998cc--3.0l--Diesel--Fi--Turbo-Exhaust--Fuel--Tank&yearid=1984%40%401984&makeid=MERCEDES+BENZ%40%40MERCEDES+BENZ%40%40X&engineid=1193789%40%40300D T++%2F+L5%2D2998cc+3%2E0L+DIESEL+FI++Turbo%40%40300DT&catid=Exhaust+%26+Fuel+Tank%40%40Exhaust+%26+F uel+Tank&subcatid=Fuel+Filler+Cap+Seal@@Fuel+Filler+Cap+Seal&mode=PA

Much cheaper than this

http://www.allpartsexpress.com/ShopByVehicle.epc?q=1984-MERCEDES--BENZ-300dt--/--L5--998cc--3.0l--Diesel--Fi--Turbo-Exhaust--Fuel--Tank&yearid=1984%40%401984&makeid=MERCEDES+BENZ%40%40MERCEDES+BENZ%40%40X&engineid=1193789%40%40300D T++%2F+L5%2D2998cc+3%2E0L+DIESEL+FI++Turbo%40%40300DT&catid=Exhaust+%26+Fuel+Tank%40%40Exhaust+%26+F uel+Tank&subcatid=Fuel+Filler+Cap@@Fuel+Filler+Cap&mode=PA

The vent is under the car on the drivers side. It is sort of forward of the L/R wheel but behind it. It has a bell shaped end pointing down.
Charlie

Thanks Charlie! I'll check that out. Maybe I can keep that diesel off my paint.

BTW My heater is now working the way it was designed. It is really nice. Changed the thermostat and cut a hole in the dash mat so the sensor would work and got a piece of pipe insulation from Lowes and put it where the old foam hose was missing behind the glove box. :)

Is this also true with the plastic cap? Just lost my original fuel cap. Fortunately i have an extra plastic oil filler cap. It looks smaller but it went in.

Yes
 

yes.

You need to clean the drain hole out at the bottom of the door pocket, running the plastic coated steel cable down thru is good for that.

actually, the oil and fuel caps are not exactly identical.
put the oil cap on your valve cover, and the handle aligns with the valve cover, the fuel cap sits kittywonkous.
also, the gasket is smaller on the gas cap.
they are indeed interchangeable thought and both will function well in either location.

Thanks for the replies. Going on a long trip with the wife and doter tomorrow with a full tank of fuel. I dont want them complaining of diesel smell. Will go to the dealer to get the right part on monday.

This is true. My oil cap wasn`t inline with the VC like I had seen on other engines. I thought the two pieces of the cap had twisted around.

It wasn`t till i was at PNP (of all places) that I noticed that the oil cap has OEL stamped on them (the metal one`s), and it was in line with the VC.

definately don`t want a plastic cap, the one I had leaked and made a mess. and the metal caps look better and will polish up nice. :D.

They aren`t available, so grap them when you see them.

Charlie

Really? Does the oil cap have the pressure relief vent like the fuel cap?

"Fit" is one thing; "Function" is another.

Failure to engage both lugs on the cap is one possible cause.