Volvo 5.0 GLPEFS idles fine, dies under load

[SV Escapade]

Hi All,
Continuing on with the troubleshooting on this engine (I apologize, I can read the shop manual, follow instructions, but just don't know enough to troubleshoot!). Let's start with the basics. It is a 5.0 GLPEFS serial number 4012021733, outdrive SX-M 4111665406. The boat now starts easily every time. The engine idles smoothly at about 500 rpm on what I believe is an unreliable tach. At the dock, no load, the engine accelerates nicely. I live about 30 minutes down the canals here from open water. All of it no wake/ idle zone. So, I took the boat out, idling (maybe 600-650 RPM) down the canal. After about 20 minutes, the engine seemed to start, lack of better way to describe it, chugging. When I tried to open the throttle a little more, the engine backfired and died. I did smell some fuel in the exhaust.I vented the engine compartment, and restarted the engine. Idled fine in neutral and in gear. Sounded and felt smooth. As soon as I advanced the throttle, same chugging, backfire, and shutdown. I idled the boat back to the dock. Troubleshooting so far includes checking for good spark at the coil, good spark on all the plugs, and 2 good jets of fuel entering the carb. I do not have a compression guage, but will buy one if needed. Any suggestions for my next step?
Thanks,
Bill

 

[Don S]

Re: Volvo 5.0 GLPEFS idles fine, dies under load

Sounds more like a lean condition causing it to backfire. Carb problems, or fuel deliver problems from the carb to the pump. I would run a fuel pump pressure gauge under load and see what you get. Also do these fuel system tests. HOW TO: Testing your boats fuel system. - Page 1 - 283269 . Have you checked the fuel filter for water contamination?
If you can't do the tests, you might try hooking up a remote fuel tank (outboard tank) directly to the fuel filter/pump housing and doing a test run. That will isolate the boats fuel system.

 

[SV Escapade]

Re: Volvo 5.0 GLPEFS idles fine, dies under load

Hi All.... Well, after a couple of day break for Thanksgiving, I am back at it. Don, I have checked the fuel delivery system. Plenty of pressure under load, vacuum good, about 1/4 teaspoon of water in contents of filter (maybe a pint?), Screen on fuel line inlet on carb clean. I rechecked the plugs. Before I knew the engine I actually had, I told the mechanic that changed the oil and plugs that I had a 5.0GL-B. He got plugs for that engine. Turns out that the GL-B and my engine take the same plugs anyway, so that wasn't the issue. However, in looking at the plugs, 4 of them were gapped wrong (40 instead of 35). Fixing that has let the engine now run up to about 2000 rpm under load before backfiring and dieing. Thoughts about next step for me? Is it time for the dreaded carb rebuild? I have not yet done the seperate outboard tank test yet. Going to the sailboat on Saturday and will get the fuel tank from the dinghy then.

And Don......Thanks for the link to the much better shop manual!

 

[skydiveD30571]

Re: Volvo 5.0 GLPEFS idles fine, dies under load

Since you checked the things Don mentioned, I would go ahead and start on the carb after you run with the outboard tank. Rebuilding these carbs really isn't too hard if you take your time. And it's pretty cheap to do. If not for anything, it would atleast eliminate the entire carb from the equation (which contains a majority of the possible culprits).