Engine problems

[Bertus]

I have a Hunter 33, I've recently started to encounter my engine starving/cutting out under load at highish revs. The puzzling thing is, if I leave it fir 10-15mins, the engine will start but will only operate under load at idle speed. First I thought it was a dirty filter, so I replaced the primary filter. It still happened, then I thought it might have been dirty fuel lines, so I replaced all the piping and again a new filter, no improvement. Has someone encountered a similar problem? Can anyone give advice as to how to diagnose the problem? Many thanks Bertus

 

[kloudie1]

Does sound like fuel starvation.. another couple of places to check are the tank vent.. make sure it is clear of bug stuff at the outlet, and another place is a possible plugged screen at the tip of the fuel outlet dip tube in the fuel tank.. The tank vent thing can be checked by loosening the fuel fill cap and venting the tank that way. If the vent is plugged, loosening the cap will make things operate normally.. The fuel pickup plugging can be checked by blowing back into the tank to clear it. blow from the primary filter inlet line back toward the tank .. If that clears it, it will run normally for a while then plug again..Good luck.

 

[Bertus]

Does sound like fuel starvation.. another couple of places to check are the tank vent.. make sure it is clear of bug stuff at the outlet, and another place is a possible plugged screen at the tip of the fuel outlet dip tube in the fuel tank.. The tank vent thing can be checked by loosening the fuel fill cap and venting the tank that way. If the vent is plugged, loosening the cap will make things operate normally.. The fuel pickup plugging can be checked by blowing back into the tank to clear it. blow from the primary filter inlet line back toward the tank .. If that clears it, it will run normally for a while then plug again..Good luck.

Thanks. I've syphoned the primary line and it seems to flow freely this baffles me. Can it be the fuel pump or injectors?

 

[Sailm8]

I had a similar problem that turned out to be a failing fuel pump. Mechanic replaced it with an electric and I have had no problems since. My engine was a 2gm.

 

[kloudie1]

Sailm8 is right on .. A failing "lift" pump can do this too.. If there is no black smoke when this is happening, then you most likely have a problem with fuel getting to the engine.. could be an air leak in the line or the connections previous to the lift pump as well..

 

[Bertus]

I've also been told that if it happens under load, it could be the injectors. What is your take on this?

 

[JoeWhite]

Check the exhaust manifold - they clog up and restrict exhaust.

 

[Benny17441]

Many folks get their terminology crossed when talking about primary and secondary filters. Since a clogged water separator/primary filter is the usual culprit for the symptoms you describe it is important to comfirm that the filter you replaced was indeed the primary filter which is located between the fuel tank and the lift pump. If that is correct then it would not be a bad idea to replace the secondary one mounted in the engine cannister. There are many possibilities and they need to narrowed down. We can concentrate on or eliminate the fuel tank as the source with a rather simple substitution. Take a small portable tank with a squeeze bulb on the line and attach it to the boat's fuel line before the two filters. Fill it up with a couple of gallons of diesel fuel and fire the engine up. If the engine runs good then the problem is likely on the tank or the condition of the fuel in it. If it still runs bad then you have isolated the problem to the engine side, pumps and filters. The bleed screw on top of the secondary filter is famous for stripping the threads and allowing air to leak into the system. I may hold at idle but as the flow of fuel increases so do the chances of getting air. Those are my two suggestions based on previous experience with those symptoms. 1) Primary filter 2) bleed screw. It could be the lift pump, but if there is no visible leak of fuel and the oil level is not rising (internal leak) it is not likely a cause for your problem. It could also be a clogged exhaust mixing elbow but if you are not getting black smoke at higher RPM then it is not likely the source either.

 

[Bertus]

Many folks get their terminology crossed when talking about primary and secondary filters. Since a clogged water separator/primary filter is the usual culprit for the symptoms you describe it is important to comfirm that the filter you replaced was indeed the primary filter which is located between the fuel tank and the lift pump. If that is correct then it would not be a bad idea to replace the secondary one mounted in the engine cannister. There are many possibilities and they need to narrowed down. We can concentrate on or eliminate the fuel tank as the source with a rather simple substitution. Take a small portable tank with a squeeze bulb on the line and attach it to the boat's fuel line before the two filters. Fill it up with a couple of gallons of diesel fuel and fire the engine up. If the engine runs good then the problem is likely on the tank or the condition of the fuel in it. If it still runs bad then you have isolated the problem to the engine side, pumps and filters. The bleed screw on top of the secondary filter is famous for stripping the threads and allowing air to leak into the system. I may hold at idle but as the flow of fuel increases so do the chances of getting air. Those are my two suggestions based on previous experience with those symptoms. 1) Primary filter 2) bleed screw. It could be the lift pump, but if there is no visible leak of fuel and the oil level is not rising (internal leak) it is not likely a cause for your problem. It could also be a clogged exhaust mixing elbow but if you are not getting black smoke at higher RPM then it is not likely the source either.

Thank you I'll try the fuel tank substitution and work my way from there,

 

[Paul F]

It's a fairly easy step to add an electric fuel pump. Buy an inexpensive one at an auto parts store. By-pass the mechanical pump and there will be plenty of fuel.