Volvo 5.0GL, fuel pump, feedback to my diagnosis plan of attack

[Waterbyrd]

First, and even if I get no response, thanks for the best boating forum on the Internet.

I own a meticulously maintained Volvo 5.0GL engine installed on a Wellcraft 200SS I/O, driven by an SX outdrive. My kit has less than 500 hours of operation. The kit runs well, with good power and no impairments whatsoever except that on first startup after overnight storage, it requires a pump of the throttle and a few seconds of cranking to pull fuel to start. Once started, the motor pops right off.

Timing is good, valve adjustment and compression good (~170 in each cylinder), normal temperature, no vacuum leaks, spotlessly clean and well maintained -- all is well.

At the end of the season, after a day of pulling skiers and cruising, the motor lost power during a 2900 RPM cruise to the launch. It gradually spooled down. Upon immediate restart it fired up. After a few minutes of cruise, it did it again. With a boat full of worried people, I drove back just off idle. It did not stall at low RPM.

The boat is in my driveway and about to be winterized. Winterized AFTER I diagnose and fix this problem!

THE KNEEJERK DIAGNOSIS: I think it is my fuel cap. I have a Perko cap and a while back the gasket failed. I replaced it with an O-ring. It seals really well. I can recall that if I run the tank down, when I unscrew the cap to fuel up, there is a loud sucking sound. sssssssssssssszzzzzzzzzzzzzzzzzzzzz! I believe the tank is not venting. I believe that I ran the motor so long that day, I pulled vacuum to the point where the fuel pump could not feed the motor. That also correlates to the motor firing after restart (pressure recovers), and that it ran at low RPM without stalling.

Here’s the thing: That can not be verified in my driveway. I can run the motor with the cap off, but unless I’m pulling load and developing vacuum in the tank, the failure mode can not be replicated.

It could be the fuel pump, FP relay, or wiring also. So: here is my plan:

1. Test at the fuel pump relay. Engine on, verify power from alternator to relay. Verify no interruptions. Verify good quality ground.
2. Replace fuel cap/filler assembly (the Perko design appears to be inferior anyway and replacement gaskets are not available)
3. Assuming fuel pump, relay or wiring correction are not indicated (above), run motor 5 minutes in driveway.
4. Figure out a way to connect a fuel pressure gauge – ideally as a permanent engine health monitoring feature.
5. Buy a fuel pump and relay (keep as a spare), failure to do so will guarantee a ruined boating weekend with a campsite full of adults and children – This is the promulgation of Murphy’s Law.

Am I missing anything?

 

[keith2k455]

Is it efi or carbureted? Either way you should be able to check furl pressure in the driveway and if you suspect the pump I would do this first. If your pressure is fine in the driveway, I'd first look for blockage - fuel pickup, carb, filter - or a bad injector. I myself wouldn't jump straight to the pump, but I'm a bit of a shade tree.

 

[alldodge]

First, and even if I get no response, thanks for the best boating forum on the Internet.

I own a meticulously maintained Volvo 5.0GL engine installed on a Wellcraft 200SS I/O, driven by an SX outdrive. My kit has less than 500 hours of operation. The kit runs well, with good power and no impairments whatsoever except that on first startup after overnight storage, it requires a pump of the throttle and a few seconds of cranking to pull fuel to start. Once started, the motor pops right off.

Timing is good, valve adjustment and compression good (~170 in each cylinder), normal temperature, no vacuum leaks, spotlessly clean and well maintained -- all is well.

At the end of the season, after a day of pulling skiers and cruising, the motor lost power during a 2900 RPM cruise to the launch. It gradually spooled down. Upon immediate restart it fired up. After a few minutes of cruise, it did it again. With a boat full of worried people, I drove back just off idle. It did not stall at low RPM.

The boat is in my driveway and about to be winterized. Winterized AFTER I diagnose and fix this problem!

THE KNEEJERK DIAGNOSIS: I think it is my fuel cap. I have a Perko cap and a while back the gasket failed. I replaced it with an O-ring. It seals really well. I can recall that if I run the tank down, when I unscrew the cap to fuel up, there is a loud sucking sound. sssssssssssssszzzzzzzzzzzzzzzzzzzzz! I believe the tank is not venting. I believe that I ran the motor so long that day, I pulled vacuum to the point where the fuel pump could not feed the motor. That also correlates to the motor firing after restart (pressure recovers), and that it ran at low RPM without stalling.

Here?€™s the thing: That can not be verified in my driveway. I can run the motor with the cap off, but unless I?€™m pulling load and developing vacuum in the tank, the failure mode can not be replicated.

It could be the fuel pump, FP relay, or wiring also. So: here is my plan:

1. Test at the fuel pump relay. Engine on, verify power from alternator to relay. Verify no interruptions. Verify good quality ground.
2. Replace fuel cap/filler assembly (the Perko design appears to be inferior anyway and replacement gaskets are not available)
3. Assuming fuel pump, relay or wiring correction are not indicated (above), run motor 5 minutes in driveway.
4. Figure out a way to connect a fuel pressure gauge ?€“ ideally as a permanent engine health monitoring feature.
5. Buy a fuel pump and relay (keep as a spare), failure to do so will guarantee a ruined boating weekend with a campsite full of adults and children ?€“ This is the promulgation of Murphy?€™s Law.

Am I missing anything?

:welcome: to iboats

Your on the right track but more then likely it is that your tank is not venting, Check the cap and see where the vent line connects to it or does it come out at another location? You can not pull fuel fast enough to create a vacuum sitting on the trailer. The boat needs to be under load so it will burn a lot of fuel. If it happens most often when the tank is full then it is a vacuum issue. This would go along if it did not do it when the tank is less the half full.

 

[Waterbyrd]

Thanks fellow iBoaters. The GL motor is carbureted. I replaced the carb a few seasons ago and I tend to discount the filter or pickup because I change the filter at least once a season, the engine failure occurred with lots of fuel remaining, and the last chance screen in the carb has less than 40 hours on it. If there was an issue, I'd expect to see some impairment during the hours when running under high fuel flow rate (pulling skiers or donuting the kids in tubes).

I think the biggest issue will be finding a good fuel pressure guage kit and finding a replacement fill assembly. Wellcraft stopped supporting these boats years ago and accordingly everything is custom.

 

[alldodge]

Thanks fellow iBoaters. The GL motor is carbureted. I replaced the carb a few seasons ago and I tend to discount the filter or pickup because I change the filter at least once a season, the engine failure occurred with lots of fuel remaining, and the last chance screen in the carb has less than 40 hours on it. If there was an issue, I'd expect to see some impairment during the hours when running under high fuel flow rate (pulling skiers or donuting the kids in tubes).

I think the biggest issue will be finding a good fuel pressure guage kit and finding a replacement fill assembly. Wellcraft stopped supporting these boats years ago and accordingly everything is custom.

Your fuel pressure should be between 4 to 7 psi. No need for a real good one, anyone like these or similar will work. Just put a tee fitting between pump and carb.

http://www.harborfreight.com/fuel-pu...ter-93547.html
http://www.amazon.com/Actron-CP7803-.../dp/B0006V2BS2

If you want to put one inline and leave it there you can use one like this with some fittings in the same place
http://www.autozone.com/gauges-and-g...et/153654_0_0/

 

[dypcdiver]

All you need do is to find a suitable container and run the outlet from the pump into it and observe the flow if it stars to drop off, remove the tank cap and see if the flow returns, if it does then you need to sort out the tank vent. No need to run the engine just power the pump.

 

[Waterbyrd]

Thanks, people. I'm definitely going to set up a permanent inline gauge. I'm a strong believer in engine health monitoring. It would be nice to bring the gauge up to the dash area, but at minimum, I will take AllDodge's suggestion. Good idea to bench test the fuel pump also. Boating is funny sometimes. If i were alone, I would have stayed on the water and run the diagnostics (including loosening the fuel cap, and checking voltages) right there on the water. But, it was the last day of the Labor Day weekend, getting late and with a boat full of men women and children and a long drive ahead to get home, it would have been inappropriate to do the checks. Now, I have this monkey on my back, thinking about making SURE this problem is fixed before the next trip and doing the diagnostics with the boat on trailer seemed very "suboptimal." Suboptimal, as in, i was kicking myself for not doing diagnostics on the water. Thanks to this forum for confirming the approach. eace: