300E No start on first crank, any ideas?
 

Greetings All,

Just to throw this one out there for responses. My '86 300E will crank and start on the first go around, but immediately will die. I then have to crank it over again to get it to stay running. Any ideas out there what I should be looking at? I changed the plugs out not more than 500 miles ago, but haven't chenged out the fuel filter since I owned it a year ago. Don't really know if the P.O. was real consistance on routine maintenance, but if oil changes are an indication, then it was most likely done sometime within the last 15000 miles. Are there any major items I can look at that may be causing this problem besides the fuel filter? Any input would be great as this is my wifes daily driver, and now it's a mentioning headache to me daily.

Thanks,

Charles

REALLY common problem on this car. Search the boards. There is a pressure accumulator near the fuel pumps that goes bad, check valves in the pumps, misadjusted air plate in the throttle body, bad pressure regulator, and finally the entire fuel distributor can leak down causing this. Best way to check is with a fuel pressure tester, I understand, and a knowledge of troubleshooting this problem. I never completely fixed it on the 87 300e that I had.

Good luck,
Bob Johnston

Anyway to tell if it's check valve vs. accumulator?
 

Greetings,

Thanks for the insight, it gave me direction for better searches on posts related to this problem. Just wondering if there is an easy way of telling if the problem is check valve related or accumulator related. Any Techs out there that can chime in on this? Also kind of curious why an accumulator is used if there is a check valve in line to prevent fuel travel back to the tank? This may also be a dumb question, but if the ignition key is turned on and the fuel pump is operating, don't we have enough constant fuel pressure to keep the engine running with the first crank?

Just Curious,

Charles

My father in laws 300E had a similar problem, but the lazy a... never really looked at it till I had to go and pick him up with a tow at 3:30 in the morning. It turned out to be 2 things, for some time the fuel pumps located under the vehicle or under right rear passenger had started giving a whining noise, had that replaced and it helped but the car still quit on him or was hard to start, so I had the fuel pump relay replaced and that took care of everything for good, the relay is behind the plastic cover behind the battery. I think I should mention that his car as well as mine, are Euro.
Hope this info helps out, good luck.

Oh yeah, one more thing. The fuel injectors can leak down when they get old and cause that symptom too. I you want to "hunt and peck", you might try changing the check valves first as they are cheap and relatively easy. Then, the air flow plate adjustment, but be careful, then the accumulator, then the injectors. I believe the pressure regulator is the next more expensive, and the fuel distributor is the big boy.

Bob Johnston

Kind of wanting to troubleshoot if possible
 

Greetings Bob,

Yeah, I guess I could try one thing after another, but was looking for experience from other members that could guide me one way or the other as to whether this or that happens if the check valve fails, and this happens when the accumulator goes to crap. I know the symptons would most likely be close but there would have to be a reaction type of difference to determine which one has failed. I don't have that fancy special tool fuel pressure gage they mention in the book and probably wouldn't use it but twice in the cars life if I sank the mega bucks they most likely want for it. As far as the air valve is concerned, I remember it being slightly open when changing the air filter less than 1000 miles ago, and can't see it really being out of adjustment unless you bend or lean on it in some manner. I can believe the check valve or accumulator going bad as they are moving parts without adjustment. I think I'll try the check valve first, but like anything else, it will turn out to be the accumulator anyway. Did you Dad's car start up fine if the key was left in the first position for a few seconds before cranking the engine? Just wondering why fuel pump pressure with the pump running wouldn't allow the engine to continue running on the first crank. Is air getting in the system somewhere in the middle of the fuel line travel that can't be overcome by pump pressure?


Just Curious,

Charles