I know this is like the 5th time I have posted this – get a fuel pressure gauge! I went about insane diagnosing shutdowns until I did so and uncovered things I could never have figured out otherwise.
Joe Della Barba Coquina C&C 35 MK I Kent Island MD USA From: David Knecht via CnC-List <cnc-list@cnc-list.com> Sent: Friday, June 30, 2023 1:18 PM To: CnC CnC discussion list <cnc-list@cnc-list.com> Cc: David Knecht <davidakne...@gmail.com> Subject: Stus-List Re: Engine strangeness As I have thought about this and tried to come up with a cause, another data point occurred to me about the sequence of events. The stall has happened on 3 occasions on three different days in the last few weeks and not on 5-6 other occasions under similar conditions. In each of the cases where the engine stalled, it always happened within the first minute after starting the engine. In each case, the engine started and then stalled several times ( run for about 10 seconds then stall, repeat 2-3 times) and then after waiting a few minutes, it started and ran fine for extended periods. Those symptoms seem like limited fuel getting to the engine causing the stall, but I don’t see how they can be fuel filter related. But I realize that I always left the key switch on and thus the fuel pump running between start attempts. Any way they could be fuel pump related in the sense of it running for a while (warming up or purging air) while waiting to restart? Dave S/V Aries 1990 C&C 34+ New London, CT On Jun 28, 2023, at 8:53 PM, Neil Gallagher via CnC-List <cnc-list@cnc-list.com <mailto:cnc-list@cnc-list.com> > wrote: David, This may be a long shot, but on a Universal M3-20B that I installed on a club launch, and I think all Universals, the fuel pump gets its power under normal running conditions via an oil pressure switch. When starting the engine, the glow plug switch energizes the electric fuel pump in addition to the glow plugs (you can hear it clicking when you press the glow plug switch), but once the oil pressure rises it closes the oil pressure switch and keeps the fuel pump running when you let up on the glow plug switch. Incidentally the reason you hear the pump running after you shut the engine off is that it takes a few seconds for the oil pressure to drop to the point where the switch opens. I ran in to a problem with that engine when sludge got in to the connection to the oil pressure switch and kept it from closing properly, and thus the fuel pump intermittently stopped running and stalled the engine. Until I found the real problem I put a relay powered by the engine on/off key switch that powered the fuel pump directly, but when I flushed the oil switch a few times it cured the problem. Not sure how relevant this may be to your issues, but may be of interest. Neil Gallagher Weatherly, 35-1 Glen Cove, NY On 6/27/2023 12:45 PM, David Knecht via CnC-List wrote: So I am back to my engine problem hoping someone can help clarify things. I have had the engine quit several more times, but with no consistency as to when or why it happens. We were on a cruise recently and used it often and for long periods going in and out of harbors. Mostly it worked fine but had it stall several times: start and run for a few minutes, then stall, restart then stall, restart then stall, then run fine for 20 min or more. This happened in two separate situations a few days apart but no stall several other times. In all cases, it has eventually restarted and ran for extended periods. These intermittent problems are the hardest to diagnose in my experience. This seems most likely to be a fuel related issue so now I am trying to fully understand the fuel system. I installed a Racor 500 unit last summer with a T-handle vacuum gauge on top. Fuel goes from the tank, through the shutoff lever to the Racor, then to the fuel pump, then to the secondary and on to the engine. If I understand this correctly, the gauge on the Racor unit will measure restriction in the fuel flow upstream of the gauge, ie the primary (30 µm in my case). I know the gauge works because if you partially shut off the fuel lever, you see the gauge gradually increase in vacuum reading. But it seems that it will not tell you if the secondary is plugged. 1. I don’t see how the secondary (10 µm in my case) could be plugged if the primary is fine but I guess not impossible. My temptation is to replace the secondary since the primary is not showing any sign of being plugged (from the gauge), but I don’t see how this could lead to an infrequent intermittent stall. 2. Fuel pump problem (loose wire etc.)? You can hear the fuel pump running when the engine is off and I have never heard it stop or pause. Can fuel pumps fail like this? Can that lead to an intermittent stall? 3. Air getting into fuel line- seems possible, but I don’t see how that can be the cause if the engine runs for an hour continuously once restarted. Any ideas welcome! Dave S/V Aries 1990 C&C 34+ New London, CT Please show your appreciation for this list and the Photo Album site and help me pay the associated bills. Make a contribution at: https://www.paypal.me/stumurray Thanks for your help. Stu Please show your appreciation for this list and the Photo Album site and help me pay the associated bills. Make a contribution at: https://www.paypal.me/stumurray Thanks for your help. Stu
Please show your appreciation for this list and the Photo Album site and help me pay the associated bills. Make a contribution at: https://www.paypal.me/stumurray Thanks for your help. Stu
