John2189 536 #1 Posted May 4, 2023 Does the plastic rectangle vacuum fuel pumps go bad all at once, or can they be intermittent? 1 Share this post Link to post Share on other sites
953 nut 59,805 #2 Posted May 4, 2023 There are three moving parts on a vacuum fuel pump. The diaphragm pulses in response to changing crankcase pressure. If it develops a leak it will quit working immediately if you are lucky. If it only reduces its flow there is a good possibility that gas is being pumped into your crankcase oil diluting it. Check the oil to see if it smells like gas or has thinned out. The other parts are check valves on the inlet and outlet which can cause poor operation of the pump, primarily when it is being started after sitting for a while. I run low pressure electric fuel pumps on most of my herd rather than taking a chance of a bad diaphragm ruin an engine. 3 Share this post Link to post Share on other sites
John2189 536 #3 Posted May 5, 2023 Thanks, no gas in oil 2 Share this post Link to post Share on other sites
