Fuel check valve
 

I have a bit of trouble starting my 300CE when the engine is either warm or hot. I have changed out all of the injectors as well as the fuel pressure regulator and accumulator. The one thing I haven't done is the check valve which I've heard being talked about. Where is is located in relation of the rest of the fuel delivery components and is it an item likely to go bad over time or are they fairly reliable?

I'm with you. '91 300E. I have done the same and everything seems to improve then it goes back to the same. If I turn the key before starting and prime it 4 times, it will start strong. Have you tried that? Supposedly if it does, you don't have enough residual fuel pressure. I've seen a lot about replacing the EHA valve too. Everyone seems to have this same ongoing issue. I'm perplexed. Wondering if a stronger battery with more cranking amps will help.

mbzman, the check valve should be at the fuel pump (under the car in front of the right rear tire).

Im having the same issue and often prime the pump first. For me it went south after replacing the fuel filter. I must have damaged it.

My EHA was bad too. The case had a crack in it causing fuel to leak. I've done a lot of things to get the car running well. It is now down to just a few small things. If I can get a bit better starting and idling characteristics from the engine then I will be pretty happy. The only thing I may have missed is the oxygen sensor. I keep seeing them be mentioned to be replaced every 60k miles or 100k km. With my mileage that would put me right in line for a replacement, even though the car passes emissions inspection with excellent numbers.

i worked on my buddy's '88 300CE and replaced both of the check valves (two fuel pumps) as part of a big round of service right after he purchased the car. on occasion the car will still die immediately after you start it cold, first start of the day. it will start and run perfectly the second time. it seems a bit random when it happens. i suggested he prime it a few times before starting and report if this cures the immediate stall issue, no report back yet however. but i would have expected the new check valves would prevent this issue from ever happening but it didn't seem to completely eliminate it.