WOT issue 2002 4.3L Merc. MFI 258 hours

[bpetersen5]

engine sn 357510. Idles and runs good but bogs at WOT. fuel, with Sea Foam, and filter are new. I suspect fuel pump and was wondering if I should replace pump relay 1st since it's a LOT easier to do. I suspect not as I assume a relay either works or it doesn't. Thankyou from Austin TX

 

[Bondo]

I suspect fuel pump and was wondering if I should replace pump relay 1st since it's a LOT easier to do.

Ayuh,...... Welcome Aboard,....... Diagnosis comes 1st, then ya buy parts,.......

Test the fuel pressure at the rail,......