Help! See and Hear my incredible groaning 200.

[jamyers]

Most every mechanical fuel pump I've seen doesn't have any bypass, they just build pressure against the diaphragm spring. If there's little to no fuel flow, the pump arm just keeps moving independent of the diaphragm, so there's no need for a bypass.

Looking at the old pump, which was the small non-filter type, it's got a slightly different shaped arm than the one that's in there. Things that make me go hmmmm.....

 

[mustang6]

That is indeed a strange sound- I would have guessed a water pump or distributor too, odd that it would be temperature related, good test was when you removed the fan belt it made no difference. If you have really located it to originate somewhere in front of the distributor and over the oil filter, my guess would be it has something to do with the timing chain/camshaft front timing gear. Almost like the gear is coming loose and vibrating, rubbing on the block or timing chain cover inside....

 

[Mercury Mike]

I'd pull the motor, and look at all the components. If it's making noise, there's gotta be an uneven wear pattern, some shavings, a niche in something... You'll find it.

 

[Anonymous]

my 200 did the same thing for awhile and i nearly never found it----turned out to be a (paper) base gasket for the carb---it didnt leak bad enough to affect its running but GAWD what a racket. it quit when it warmed up becase the metal expanded enough to close it off. think of it the same way reed valves work in a (musical--not car) horn---sucks in air and vibrates making noise. i wont say 100% thats what it is but its worth a look. good luck friend.