I don't know if they are the same, however the relay for my 75 450 SL was really inexpensive from Fastlane. Since I am having similar problems I also replaced the fuel filter and as a new fuel pump is over $600.00 I didn't want to just try it to be trying it. I have to be able to afford the gas also.

Same deal with relay as for pump. Tends to operate or not. May operate for a few tries, than not operate for a few tries, but I have not seen a partial situation here either.

Could be the filter or the fuel accumulator, or an induction problem, or an electrical problem.

If you do replace the fuel pump (only 1 pump for you), get a Bosch. Do not be tempted to get the 'made in Taiwan' pump that many parts stores stock. Will be loud, and will not last long. Been there.

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1986 300E 5-Speed 240k mi.

I like the sound of experience, as it sure helps. I did find a pump at NAPA for about half price and after what you said I'll bet it is not a Bosch but a knockoff.
Thanks

UPDATE:

Well, after changing my fuel pump and filter, the car still ran rough. In fact, after starting it, it ran fine for a few minutes then started hesitating again! I don't mind changing the fuel pump (it was noisy anyway...sign of failure) and the fuel filter (first change in 3 years) but I didn't want to go on a "fishing trip" and start changing parts randomly. I was going to change the fuel pump relay next before taking it to my mechanic, but I decided against it because I figured at approximately $130, I would be better off taking this in to my mechanic and spend that money on a complete diagnostic and just change what needs to be changed.

When I brought the car in, it started fine and ran great for a few minutes. I thought "Great, it'll run fine here, and start messing up later when I get the car home" I was kind of pissed off because I had towed it pretty far. Luckily the problem reproduced itself a few minutes later. The mechanic first checked to make sure I installed the new pump and filter correctly, he then checked the coil (working), then replaced the fuel pump relay (no change in performance). At that point he told me I could leave and he'll run a complete check on the car.

The next day he said my car was ready. He ended up cleaning out the fuel injectors and replacing the temperature sensor. He told me that the fuel pressure was fine. After replacing the temperature sensor, the car seems to run fine. He warned me that this may not have fixed the problem, but after changing the temperature sensor, the car ran good the whole day that he was testing it. He said sometimes the temperature sensor causes the car to run poorly and have a hard start. I paid him $118 for his work (sensor was $60, parts cleaner $2, rest was labor to clean out the fuel injectors and to clean around the coil and the distributor) and went home. I hope this solved the problem. I'll update this post if my car still runs poorly. If you don't see another post by me on this thread, the problem has been solved.

Comments anyone?

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JR
1986 Gold 300E 4Dr automatic