DT225 Stalling

[fishlaw]

The other day my DT225 started losing RPMs and stalled. It wouldn't turn over until I cleaned the battery terminals, at which point it cranked, started and seemed to run fine. About 10 minutes later it died again, and would only start if I squeezed the fuel ball, at which point it ran fine for about 5 minutes, then again stalled. This time it would turn over, but wouldn't fire until I again squeezed the fuel ball, at which point it ran well enough to put it back to the mooring. (We did have an incident a few months ago where the batteries were close to going under-a friend was using the boat, and I definitely need to address the battery connections, but it has always run and started after that incident.) All systems are well maintained-The internal fuel tank is 2 years old. Racor filter with water separator-I haven't had water issues since the tank was replaced. HP Fuel pump is 2 years old and has about 50 hours on it-all filters replaced at same time. Low pressure pumps were redone a few years ago, as well. We always run on premium fuel from reliable marina. Wondering if running issues can be related to the battery-The charging system has to have sufficient capacity to handle all engine electrical loads plus surplus to the batteries themselves. Is there any scenario where just bad battery connections can cause the engine to lose RPMs and stall. (I once had a stalling problem related to a sticky needle valve in the fuel vapor separator-very tough to figure out, and this is kind of consistent) When this happened the ball did not seem collapsed, so it wasn't a supply issue.

[Solarman]

Having to squeeze the bulb repeatedly sounds like air is getting into the fuel line. Check the fuel filter on the side of the motor under the cowling when this happens to see if it gets filled up with air. Also, does the fuel bulb pump up firmly, as it should?
Do you have a plug connector for fuel line on side of motor? When you pump up the bulb are there any areas between the bulb and fuel pumps showing leaks?

Good luck, post back when able to let us know.

[fishlaw]

I visited the boat today and fixed the electrical issue-corroded cable ends at both batteries. The low pressure fuel filter on the engine was less than 1/2 full I pumped the fuel ball until it was hard-detected no leakage under the cowl and the engine started and ran fine for about 10 minutes. The engine then stalled and would only start if I pumped the ball and even then, it would only run for a minute or two unless I kept pumping the ball. I am suspecting either the low pressure pumps or the needle valve in the fuel vapor separator-which has been a problem in the past.

[artdf175]

this is sounding more like a vacuum problem with your fuel deliverly system
fuel tank vents are often a problem small spiders can plug up the vent to the point no air can get through the engine pumps fuel out until there is a vacuum in the tank and engine cannot pump more

I would start there
Ary

[fishlaw]

If there was a venting issue, I would suspect the fuel ball would collapse, but I can check it. The boat stays on a mooring, and spiders are unlikely. The vent was certainly clear when I fueled it a week ago.

[artdf175]

how old is your boat - motor? fuel lines are know for breaking down internally and causing blockage
have you checked the small inline fuel filter
should remove and check there is no debris inside
one more . observe this when running does it stay full of fuel? or does it fill up with air
if you are getting getting air then you have most likely a hose connection issue

the only other problem I can see would be the low pressure fuel pump
I checked mine by taking the fuel line off the out side and then turning over the engine
should see a fair amount of fuel pumps
put the hose on it and into a container to collect the gasoline
Art

[fishlaw]

Boat is 30+years old-tank and all fuel lines, fill hose, vent hose, racor filter, etc.. new within 3 years. Motor is 16 years old. Recent High Pressure fuel pump-2 years ago, inline filter and HP filter, vapor separator rebuild... About 750 hours total-when it runs, it runs perfectly. Kept well greased, lower unit resealed.... Am I crazy, or wouldn't a low pressure fuel pump failure cause a problem like this? Without them, fuel will not enter the vapor separator from which the HP pump draws fuel.

[artdf175]

check the fuel hose connections - doesn’t take much to get a air leak
and again with engine running observe the inline clear fuel filter
would do the check I suggested on the low pressure pump
the other thing to do a double check on is the float in the high pressure pump
if it is sticking for whatever reason the bowl might not fill properly

[Moonlighter]

If you have a anti-syphon valve on the fuel tank take-off, it could be failing, typical symptoms are starving the engine of fuel at idle speeds when the fuel pump is not moving enough fuel to keep it open. Pumping the bulb sucks fuel through.

If you have one just remove it and replace it with a open fuel barb. Or, remove it and punch out the internal valve parts. (Ball, spring and seat).

[Solarman]

Yes, clean electrical connections are needed for charging battery(ies).

Yes, bad low pressure fuel pumps can cause lack of fuel to vst - causing you to pump bulb. If you had them re-done, possibly the check-valves inside have fractured (clear discs), causing low suction of fuel from tank. (New check-valves are not provided in rebuild kits, usually have to purchase new pumps to get them.)

You can inspect LP pumps by carefully taking them apart. If the check-valves are broken, missing pieces, generally they will get caught in the needle valve seat, restricting fuel flow into vst (yes, the needle valve seat for each - some motors have multiple carbs/floats - float assy would need to be removed to clear the pieces). If the check-valves are intact, but the diaphrams are torn then they can be rebuilt again.

The reason i asked about air into the filter, is because often the fuel connector o'rings may let air into that filter, and may not leak when pumping bulb. Also, if air is leaking in front of the bulb. Another possibility is that the small filter might have a small crack, or the bowl seal may be leaking air, but usually pumping bulb would show signs of leakage there.

And generally, bad LP pumps do not let air back into that small filter unless the diaphragm is damaged allowing positive air pressure to push backwards through diaphragm.

Good luck, post back when able to let us know what you find out.

[fishlaw]

I see all of your points. I will see if I can pull a vacuum from the supply to the LP pumps with the line blocked at the Racor. If I can't get a vacuum there, I can isolate an air leak. If I can pull a vacuum there, i will see if I can pull a vacuum against supply side of the LP pumps, which should let me know if the check valves are working. If not, I will pull and likely replace the LP pumps. The LP filter is always a problem given its location behind the oil tank, which requires removal of the oil tank to access.

[fishlaw]

Was able to pull and hold vacuum on supply side of engine, indicating filter assembly and LP fuel pumps fine-also checked to make sure LP pumps would pass fuel through and confirmed check valve operation. Started working way back to tank, and discovered Racor spin on filter had come slightly loose and seal was bad. (I didn't replace it this year, due to low hours, new tank and generally doesn't come off easily. ) Thanks for focusing me on diagnostics rather than replacement for no good reason.

[Solarman]

It's always best to locate the source of the problem instead of replacing parts to see if problem goes away.

Good luck. Post back when able to let us know how it went.