502 MPI hard to start/won't idle
06-20-2011, 04:21 PM
#1
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502 MPI hard to start/won't idle
Changed oil, oil filters and fuel filters prior to M-Day this year. Had the boat out on M-Day weekend ran for about 10 hours with no issues. Both motors always start on first crank.
The problem.....this past weekend backed into the water and the fun began. Both engines would crank but neither would start. Applied some throttle (which I have never had to do) while attempting to start and both would start ONLY with throttle applied. As soon as you would return the throttles to idle position they would hesitate and die. Once running and easing back to idle if I stopped it about 800 RPM both would oscillate between 500-1100 RPM. There is no problem with the engines running above idle and throughout the RPM range. The problem seemed to being fixing itself as I moved away form the no-wake area only to find they kept dying. Everyone once and awhile I could get them to idle as long as I didn't throttle chop to idle. If they were eased back to idle position it was a 50 - 50 chance on whether they were going to stay running.
I dealt with the situation throughout the weekend. Only to keep thinking of why!!!!! Both engines, same time, exact same symptoms. "Fuel" water in the fuel is the only idea I could come up with.
What are your thoughts, any would be great especially with a poker run on LC coming up this weekend.
Thanks
The problem.....this past weekend backed into the water and the fun began. Both engines would crank but neither would start. Applied some throttle (which I have never had to do) while attempting to start and both would start ONLY with throttle applied. As soon as you would return the throttles to idle position they would hesitate and die. Once running and easing back to idle if I stopped it about 800 RPM both would oscillate between 500-1100 RPM. There is no problem with the engines running above idle and throughout the RPM range. The problem seemed to being fixing itself as I moved away form the no-wake area only to find they kept dying. Everyone once and awhile I could get them to idle as long as I didn't throttle chop to idle. If they were eased back to idle position it was a 50 - 50 chance on whether they were going to stay running.
I dealt with the situation throughout the weekend. Only to keep thinking of why!!!!! Both engines, same time, exact same symptoms. "Fuel" water in the fuel is the only idea I could come up with.
What are your thoughts, any would be great especially with a poker run on LC coming up this weekend.
Thanks
06-20-2011, 04:24 PM
#2
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Make sure air tube connections are tight. The weird thing is if it is both engines, it sounds like bad fuel. A loose air tube connection might cause one engine to lean out at idle but not both. Is there one fuel tank?
Wannabe
Wannabe
06-20-2011, 04:27 PM
#3
I think you are on track thinking it is a fuel issue, since it involves both engines. If it was only one, I would also be checking for signs of reversion and hydro lock, but sounds like fuel to me. Put some fuel stabilizer in there, top the tank off with some fresh fuel, and change out fuel water separators.
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