Hi Brett,

I’m very glad to hear that you’re up and running again, and thanks for following through on your thread by posting the results. I use the archives of this forum all the time to help me figure things out and it’s always a lot more rewarding to read through threads that have some kind of conclusion.

I tried to look up your part numbers, but didn’t have much luck. They look close enough to me that one might have just superseded the other. My guess is that whether a 300 SEL or a 420 SEL, the relay simply energizes the fuel pump, or pumps, when necessary and it shouldn’t much care what engine it’s working for. I’m not certain though, so maybe somebody else can tell for sure.

Kind Regards,

outofspec