84 SEC has hard start smells like gas HELP!!
 

OK here is the issue, my 500 sec sometimes is hard to start, I have to crank it for 3-4 seconds and there can be a gas smell and rough idle for a minute or so. It has new fuel pumps and new plugs. I just bought it and have not changed the cap and rotor. But the fuel smell is only at starting as is the rough start as it chugs to life. After that the car is a rocket

Jake

SEC hard start
 

Do you have a problem with a hard warm start as well?
You can "search" hard cold start. And hard warm start. Take a day to do this and have lunch ready. The info is awesome.
I did with my 84 SEC and decided to replace cold start valve. All injectors with new seats and seals. The vacuum pipes that border each valve cover and dip under the fuel distributor. New fuel filter,pump and accumulator.
New coil,wires,nonresistor sparkplugs. And a new O2 sensor.
I recently removed the idle control valve and cleaned it out with carb cleaner. Starts right up cold or hot and runs smooth as glass now.

for sure
 

I did that with my 420 SEL and it did make a difference. It
The problem occurs warm or cold. A man that has owned a couple said it was the TPS throttle position sensor and that the computer can't figure out where the throttle is positioned and dumps to much gas... what do you think?

TP sensor
 

does anyone know where the TP sensor is located?

Throttle position sensor
 

I did a web search on "throttle position sensor" and they are supposed to be located on the butterfly spindle.
Strange that your 84 500SEC has this and mine does not. I don't even have an EGR valve. But the engine is California Stock.

Are you pushing the gas down about 1/3 on start up? If not try it....and never shut it off hot unless it will have a chance to cool down pretty much completely.

I chased the exact same problem on mine for months and all I accomplished was spend a lot of money.

After doing the above on the advice of an old Mb mechanic, I was able to adapt to the quirks of the car and lived happily ever after.

Tom W

1984 California cars didn't have EGR valves from the factory, that came later, My 1984 Euro 500 SEC has one that was added when it was Federalized in CA in 1988.

With the same symptoms, but in a different car (w202) the problem was the injection pressure regulator.