I drive an 87 300e manual, no cat, no lambda.

In my search throguh this forum, I've found there was a change in fuel pump relay in 1987, part number 002 545 27 05 up to engine number A396764 and 003 545 24 05 for engines after that.

I've just checked my new relay and discovered the part number is 003 545 24 05 but the engine number is A351018, which means I should be using the 002 relay.

Now, the engine runs fine apart from the fact that it starts cutting out at 4,000rpm when driving, but not when in neutral or with the clutch in.

The fuel pump relay was replaced as part of a whole series of new bits solving a rough idle/hot start combo, which is now cured. I've also changed the fuel filter, OVP, all injectors and all usual suspects, incluing rotor and cap.

Does anyone know what was changed with the new relay? In particular if there was an introduction or change to the rev limiter element.

I need to know if there's any connection to my problems and whether I can fix or disable the rev limiter before I have to track down the old part and pay for that just to test it out.

Anyone running an old 300e with the new part without problems?

OK, answering my own post here but have identified the Fuel Pump Relay as the cause of the 4000 rpm rev limit. Removed the relay, wired the terminals to activate fuel pump and went out for a test. Engine revved quite happily above 4000 rpm.

My problem is that I can't get the correct old style relay. I ordered one through my local parts shop using the number 002 545 27 05 but when the relay arrived, discovered it was exactly the same as the one I'm using right now. Its not a Bosch part but made in Hungary.

Have tried Parts Shop but there's no photo of the relay listed under the number 002 545 27 05 and I'm afraid I'll only get the same Hungarian relay again. Can anyone help me with finding out how to tell if is the the correct relay or even how to disable the rev limiter in the relay I'm using now?

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1987 300e manual 250,000 km (sold)

Both relays should be available and from the info I just looked at both should work just fine. For the rev limiter to occur at 4000 I would think you have a 4cyl relay. The rpm limit should be on the side of the relay but the relay doesn't wait a minute to count rpms, it looks at the frequency and divides by the number of cylinders.

6000rpms is 18000 firing events in a six; it is 12000 on a 4. 4000 rpms on a six is also 12000 firing events.

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician

Steve, thanks for that. Makes perfect sense to me. Aklthough the pattern relay has 6cyl printed on the side, it doesn't say 6zyl/6350 like the OEM item for an automatic I saw, which also had "Kickdown" written on it, which is why I didn't buy it. I will need to order the genuine item obviously.

Just out of interest, would it be a problem using a relay for the automatic in a manual?

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1987 300e manual 250,000 km (sold)