Hi Guys,
OK, I try not to post questions on here and can usually figure out most of my issues by just researching the archives but I'm stumped. I'm fishing in Alaska and being 50 miles from port and losing fuel flow is pretty stressful.
So, here's a quick synopsis of my current problem. I have a '95 Volvo Penta 7.4 GL that is "losing prime" at the electric fuel pump. This is carbureted, so its a single electric fuel pump pulling from a fuel filter. The boat runs flawlessly as long as I don't shut it off once its warmed up. Our fishing is a lot of running and then stopping and drifting. Once we are done with a drift and start the motor back up the engine dies due to no output from the fuel pump. At this point we have to pull the pump discharge line off and turn it over until we start getting flow back again, sometimes its as simple as that and sometimes I have to dump fuel down the feed line to get it to start pumping again. It has been an intermittent issue for about a year now. The next part is all of the parts changing troubleshooting stuff. Sorry, its really long.
Now,
This is a long spiel on what I have done since the start of this issue, a caveat being that most of these items I now believe were unrelated to the issue with the pump. Initially the first time this happened I was running at cruising speed and just lost fuel flow, I have a flow meter so I could watch when it happened. At first glance I had thought that there was a blockage on the tank I was pulling from or potentially a clogged vent. I transferred fuel to the opposite tank and swapped tank but continued to have the same issue. After removing the fuel filter and water fuel separator and refilling the issue basically went away on the return to port. The boat then got pulled for the winter and while it was out I decided to completely redo the fuel system since when the issue happened it "fixed itself" and I found no smoking gun, I started by checking the pickup tubes which where completely clear of any debris, I replaced the anti-siphon valves, replaced all fuel lines throughout, verified that the fuel tank vents were clear, replaced the water fuel separator filter (racor), fuel filter and checked through the fuel pump/filter block, replaced the fuel pump and went through the three way valve from main tanks.
Initially when I put the boat back in the water this year I felt pretty confident that whatever the problem was it had to have been fixed since the entire fuel system was basically new. The first trip out wen fairly well for about the first 5 miles, then the engine started to miss once in a while, after a few hours the engine performance started to degrade and the miss started becoming a significant issue. and at one point lost fuel flow from the fuel pump which again after pulling the discharge line and cranking started to pump fuel again. I limped back to port. Once I got to port I had convinced myself that I had multiple issues going on, one of which I believed was an ignition problem and not sure of the either. I decided to completely go through the ignition system and give it a tune up. I replaced all plugs, plug wires, cap, rotor and coil, the coil was a rusted mess on the bottom and the positive side ignition wire was severely degraded so I was convinced this was the issue. Took it out for a spin and it fell flat on its face, it was running terribly and now was backfiring under a load above 1500rpm. Ok, next step, rebuild the carb. Pulled the carb and found the bowls had a fair amount of corrosion gunk in the bowls as well as some plugged jets and an accelerator pump that was a mess. After I rebuilt the carb and put it back on the boat ran flawlessly. No issues at all at any RPM range. FIXED! or so I thought. It ran without issue on the first trip which was an overnight trip. Now fast forward to this past weekend. The boat ran fine on day one, then day two after the first or second stop while trying to get back on step the engine started to lug and within 10 seconds or so died. It seemed obvious to me at that point it was the same fuel pump issue as I had initially, so I decided to check the alternator output by shutting the battery mains off while the engine was idling and it didn't miss a beat which would rule out the alternator losing power, which I also already kind of knew because it wouldn't immediately start pumping when I was cranking the engine over either. Throughout the day it just started becoming more common so we decided to just head in after the last time rather than getting stuck out there if it failed completely. I got the boat up on step and ran roughly 50 miles at 3700 rpm and it ran great the whole way back we even stopped and pulled shrimp pots and the motor idled for 15 minutes or so then got back on step and made it the remaining 20 miles or so to port.
I'm lost, the only thing I can come up with is heat from the motor being hot and sitting without running is creating an issue somewhere but I cant think of what. Its really hard to troubleshoot since it doesn't happen consistently. I'm more than open to any ideas. Thanks for reading all of this, Jess
OK, I try not to post questions on here and can usually figure out most of my issues by just researching the archives but I'm stumped. I'm fishing in Alaska and being 50 miles from port and losing fuel flow is pretty stressful.
So, here's a quick synopsis of my current problem. I have a '95 Volvo Penta 7.4 GL that is "losing prime" at the electric fuel pump. This is carbureted, so its a single electric fuel pump pulling from a fuel filter. The boat runs flawlessly as long as I don't shut it off once its warmed up. Our fishing is a lot of running and then stopping and drifting. Once we are done with a drift and start the motor back up the engine dies due to no output from the fuel pump. At this point we have to pull the pump discharge line off and turn it over until we start getting flow back again, sometimes its as simple as that and sometimes I have to dump fuel down the feed line to get it to start pumping again. It has been an intermittent issue for about a year now. The next part is all of the parts changing troubleshooting stuff. Sorry, its really long.
Now,
This is a long spiel on what I have done since the start of this issue, a caveat being that most of these items I now believe were unrelated to the issue with the pump. Initially the first time this happened I was running at cruising speed and just lost fuel flow, I have a flow meter so I could watch when it happened. At first glance I had thought that there was a blockage on the tank I was pulling from or potentially a clogged vent. I transferred fuel to the opposite tank and swapped tank but continued to have the same issue. After removing the fuel filter and water fuel separator and refilling the issue basically went away on the return to port. The boat then got pulled for the winter and while it was out I decided to completely redo the fuel system since when the issue happened it "fixed itself" and I found no smoking gun, I started by checking the pickup tubes which where completely clear of any debris, I replaced the anti-siphon valves, replaced all fuel lines throughout, verified that the fuel tank vents were clear, replaced the water fuel separator filter (racor), fuel filter and checked through the fuel pump/filter block, replaced the fuel pump and went through the three way valve from main tanks.
Initially when I put the boat back in the water this year I felt pretty confident that whatever the problem was it had to have been fixed since the entire fuel system was basically new. The first trip out wen fairly well for about the first 5 miles, then the engine started to miss once in a while, after a few hours the engine performance started to degrade and the miss started becoming a significant issue. and at one point lost fuel flow from the fuel pump which again after pulling the discharge line and cranking started to pump fuel again. I limped back to port. Once I got to port I had convinced myself that I had multiple issues going on, one of which I believed was an ignition problem and not sure of the either. I decided to completely go through the ignition system and give it a tune up. I replaced all plugs, plug wires, cap, rotor and coil, the coil was a rusted mess on the bottom and the positive side ignition wire was severely degraded so I was convinced this was the issue. Took it out for a spin and it fell flat on its face, it was running terribly and now was backfiring under a load above 1500rpm. Ok, next step, rebuild the carb. Pulled the carb and found the bowls had a fair amount of corrosion gunk in the bowls as well as some plugged jets and an accelerator pump that was a mess. After I rebuilt the carb and put it back on the boat ran flawlessly. No issues at all at any RPM range. FIXED! or so I thought. It ran without issue on the first trip which was an overnight trip. Now fast forward to this past weekend. The boat ran fine on day one, then day two after the first or second stop while trying to get back on step the engine started to lug and within 10 seconds or so died. It seemed obvious to me at that point it was the same fuel pump issue as I had initially, so I decided to check the alternator output by shutting the battery mains off while the engine was idling and it didn't miss a beat which would rule out the alternator losing power, which I also already kind of knew because it wouldn't immediately start pumping when I was cranking the engine over either. Throughout the day it just started becoming more common so we decided to just head in after the last time rather than getting stuck out there if it failed completely. I got the boat up on step and ran roughly 50 miles at 3700 rpm and it ran great the whole way back we even stopped and pulled shrimp pots and the motor idled for 15 minutes or so then got back on step and made it the remaining 20 miles or so to port.
I'm lost, the only thing I can come up with is heat from the motor being hot and sitting without running is creating an issue somewhere but I cant think of what. Its really hard to troubleshoot since it doesn't happen consistently. I'm more than open to any ideas. Thanks for reading all of this, Jess