Mystery Fuel Problem ?
 

Finally got my 1987 560 SL on the road, and need to take it through New Jersey inspection. Have a few problems, however:

1. Car appears to run out of gas (gauge is broken) but, when filled, only takes about 13 gallons.

2. Engine runs rough at idle (intermittment miss) and also under load. Feels like its surging a little.

3. Exhaust seems abnormally hot. I tried to hold a plastic bag up to it to see if I could hear a miss, and it melted the bag immediately! Makes me think it might be running lean (engine water temp is fine).

I'm wondering if this could be as simple as a clogged fuel filter, or involve the dreaded OVP relay. Anybody have any advice?

Max J. Sandler,

It is hard to say, really, what the problem might be, but I have found some filling stations with relatively high pressure hoses and they can cause the filling procedure to become a challenge. The agitated gas foams a little (nothing compared to Diesel!) and trips the shut off sensor. It also seems to pressurize the air in the tank, and you get air pushing back out as the gas is going in which also makes the little trip device shut off. Have you tried putting the filling nozzle on the lowest flow rate notch and seen how much gas you get to go in?

Seems to me if you are getting expected engine performance (starting, throttle response, mileage) on the 13 gallon load you put in, there is really nothing much else wrong. And exhaust gas temps are higher on cars with active catalytic converters, so melting a plastic bag after it is warmed up is not really alarming.

Hope this helps, Jim

Thanks for the quick reply, Jim.

You may be right about the gas pump shutting off due to trapped air. I'll try putting more gas in it at a self-serve gas station (the ones in NJ are all attended). Now all I have to do is figure out the engine miss/surging problem!