Lean Popping on Accleration

[whitehills5093]

Hi, I have a 2005 Volvo Penta GXI-E. My motor recently started popping on acceleration. about 3000 rpms it pops or misfires, and I lose speed. After about a half an hour the popping stops and the boat runs perfect for the rest of the day. I had the injectors cleaned, fuel rail cleaned. Changed the fuel pump, pressure regulator, ECT, MAP, IAC, Rotor and cap, and coil, anti-syphon valve. I don't know what else to do. I can't travel as fast as everyone I'm with until the popping stops. Any ideas? This has me confused as to why the boat runs fine after the popping stops.

 

[Scott Danforth]

welcome aboard

measure your fuel pressure and compare it to the specs in the service manual.

 

[kenny nunez]

Sometimes spark plugs will act like that. You may have an exhaust manifold that is leaking internally. Before you start the engine after it has sat for some time remove the spark plugs and look for moisture.

 

[whitehills5093]

Sometimes spark plugs will act like that. You may have an exhaust manifold that is leaking internally. Before you start the engine after it has sat for some time remove the spark plugs and look for moisture.

I just replaced the exhaust manifold and risers last year. All my spark plugs look great. The spark plugs don't tell the story of a lean or rich condition. I noticed my temp gauge reading about 150-155 which I believe is cold. I am going to pull the thermostat and make sure it's seated correctly.

 

[alldodge]

Most Temp gauges are not that accurate. If you have a 160 thermostat then your good

 

[whitehills5093]

I have a volvo penta 5.0 GXI-E 2005. My engine keeps popping on acceleration about 3200 RPM's. Immediately after accelerating it runs great then 5 seconds later it will pop and sputter and I lose speed. Testing fuel pressure at the rail is 44 psi, down to 42 or so when the poping starts. My pressure should be between 50 and 60psi. I replaced the fuel pump, same issue. I replaced the injectors, cleaned the rail ect, put in a new fuel line to the pump. Any other ideas? Could it be the ECM is calling for enough fuel?

 

[alldodge]

Shouldn't start a new thread with the same question, just repeat the question and might get more answers.

With your fuel pressure not up to spec look at the fuel pressure regulator, item 21 part 3858967

https://www.volvopentastore.com/Fue...on_id.737151055--store_id.366--view_id.769086

 

[dubs283]

Could it be the ECM is calling for enough fuel?

The ecm controls injector pulse width based on engine load and rpm. Fuel pressure is a fixed value the ecm assumes is constant and has been programmed to control pulse width based on the assumption. Some ecms do measure fuel pressure, unsure if volvo uses a fuel pressure sensor though. My guess would be if it did it may set a fault based on value readings

Based on what you've done thus far i would focus on fuel delivery to the pump. Fuel filter(s), anti siphon valve, fuel tank pickup, and fuel quality. May want to inspect the fuel pressure regulator as well

A vacuum test of the fuel system can tell you a lot, you want to see no more than 4 in/hg. If 4 or more there is a restriction somewhere before the fuel pump

 

[Bondo]

Merged threads,..... As AD said, don't keep starting threads about the same problem, as that leads to confusion,....

 

[whitehills5093]

Merged threads,..... As AD said, don't keep starting threads about the same problem, as that leads to confusion,....

Sorry about that. Won't do it again

 

[whitehills5093]

The ecm controls injector pulse width based on engine load and rpm. Fuel pressure is a fixed value the ecm assumes is constant and has been programmed to control pulse width based on the assumption. Some ecms do measure fuel pressure, unsure if volvo uses a fuel pressure sensor though. My guess would be if it did it may set a fault based on value readings

Based on what you've done thus far i would focus on fuel delivery to the pump. Fuel filter(s), anti siphon valve, fuel tank pickup, and fuel quality. May want to inspect the fuel pressure regulator as well

A vacuum test of the fuel system can tell you a lot, you want to see no more than 4 in/hg. If 4 or more there is a restriction somewhere before the fuel pump

Will try that. Thank you. Need to research how to do a vacuum test.

 

[dubs283]

Need to research how to do a vacuum test.

Pretty easy. Vacuum/pressure guage available through amazon/ebay. Some brass barbs and t fittings, 3/8" fuel line and hose clamps. Install the rig between the fuel tank and fuel filter, run the engine at different rpm and load and observe the guage

 

[whitehills5093]

The ecm controls injector pulse width based on engine load and rpm. Fuel pressure is a fixed value the ecm assumes is constant and has been programmed to control pulse width based on the assumption. Some ecms do measure fuel pressure, unsure if volvo uses a fuel pressure sensor though. My guess would be if it did it may set a fault based on value readings

Based on what you've done thus far i would focus on fuel delivery to the pump. Fuel filter(s), anti siphon valve, fuel tank pickup, and fuel quality. May want to inspect the fuel pressure regulator as well

A vacuum test of the fuel system can tell you a lot, you want to see no more than 4 in/hg. If 4 or more there is a restriction somewhere before the fuel pump

I did all that, even used a spare tank. Same issue. When the boat is popping on acceleration, there is a heavy fuel smell likes it's dumping fuel. I don't think the fuel is leaning out properly. I know I started this thread suggesting it was a lean pop, but after researching and trying to diagnose, I now believe the opposite. The fuel pressure is 60psi while the pop is occurring. Another thing, my friend with the same motor, runs at 175 degrees. Mine only runs at 150 and volvo calls for the 150 degree thermostat. The highest I have gotten my motor is 155. Wondering if the operating temp should be higher.

 

[alldodge]

The fuel pressure is 60psi while the pop is occurring. Another thing, my friend with the same motor, runs at 175 degrees. Mine only runs at 150 and volvo calls for the 150 degree thermostat. The highest I have gotten my motor is 155. Wondering if the operating temp should be higher.

44 to 60 psi is a large swing
Temp will not cause a backfire and should have no issue running cooler

If you have not replaced the distributor cap do that