Reply to thread

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

Message: <blockquote data-quote="MrGiggles" data-source="post: 507713" data-attributes="member: 22613">I had a heck of a time troubleshooting the electric pumps in the FSM on my 90hp Merc. It would run to the first spot fine, then quit once you tried to leave. If I filled up the FSM with the primer it would run only until it was empty again. Vesselview showed a generic float switch code, but was not descriptive at all.I fiddled around with different pumps, cleaned and bench tested the float switch many times and never got anywhere.I eventually had to back-probe the low pressure pump wires, hook up an led test light in parallel on that circuit, and put my voltmeter on the float switch signal wire. Once I did, it was clear that the float switch was not opening when the FSM was empty, so the ECM was not commanding the low pressure pump. New float switch fixed it. No idea why the float switch passed bench testing in a jar of gas a dozen times but would not work in operating conditions, that was kind of a head scratcher.If I had the Merc software, troubleshooting it would've taken about 30 seconds once I got it to act up and saved a lot of hassle. Even just being able to read the code with a full description of the conditions that trigger it would've been a huge help.</blockquote>