Volvo Penta 4.3 GL-C Running Rough Trouble Shooting

[sb6bb]

Hey,

I'm new to the forum and a first-time owner to a 2003 Volvo-Penta 43. GL-C inboard outboard. It's in really good condition based on age. I've had an outboard Merc for years, so maintenance on this new engine is an adventure. I'd love for any tips.

Here is a list of the things we have done in the troubleshooting process with no real change.

- Changing of Distributor Cap (#3854331), rotor (OEM ROTOR 3854311), Spark plugs (AC41-993) and ignition wires (OEM 3888325).
- Cleaning out the Carborator
- Fiddling with idling control (which seemed to smooth it out a bit)
- Fiddling with timing light and shunt (Connector Tool 885163)

All of which have not made it run any smoother or worse, aside from the changing of ideal speed.

The timing line was about a 1/4 - 1/2 inch from the notch in the block but when we used the shunt connector, it got even rougher.

The compression of all cylinders are high (over 120 if I recall, but I would be wrong) and equal across the board.

My father and I would love to get to know the engine better before we send it into the shop.

Does anyone have some advice on what to check next?

 

[Augoose]

Can you describe the "running rough" a bit more and what the "fiddling" with the carburetor involved?
Does it idle rough or does it stumble or get better when the throttle is increased?
What is the condition of the fuel? Did you replace the water/fuel separator? Did you completely disassemble the carb and clean/replace jets, seals and gaskets or did you just spray carb cleaner down the throat? What did the old plugs look like? How many turns out on the fuel screws are you?
Consider taking a short video of the engine running rough and post it.

 

[Lou C]

120 is not really normal comp test results for that engine, normal comp test results are 160-170. I’d also check for vacuum leaks at the intake manifold (if there is a removable square plug in the manifold see if you can get a nipple to screw in to do a vacuum test. should be over15-16” inches of mercury at idle. Lastly you can get a leak down tester that will give the most accurate indication of internal engine condition. Have you checked the ohms of each plug wire? Should not be more than 1000 ohms per foot. Might need a full carb rebuild if it’s a carbed engine.

 

[QBhoy]

Fresh fuel ?

 

[sb6bb]

Can you describe the "running rough" a bit more and what the "fiddling" with the carburetor involved?
Does it idle rough or does it stumble or get better when the throttle is increased?
What is the condition of the fuel? Did you replace the water/fuel separator? Did you completely disassemble the carb and clean/replace jets, seals and gaskets or did you just spray carb cleaner down the throat? What did the old plugs look like? How many turns out on the fuel screws are you?
Consider taking a short video of the engine running rough and post it.

Here is a video we took. https://youtu.be/loKhXbDrkwE It just shakes is all. Sorry for the links but it's the only reference I have. It seems very different than something like this https://youtu.be/AWsrafoY5Xc?t=28

For the carb, we sent it out, disassembled and cleaned out and installed new gaskets. No other repairs or modifications. We didn't do this one ourselves. We sent to a place that cleans out Holleys so I hope they did it all well.

The roughness is mainly while idling. When increasing speed, I honestly can't tell as much, but looking at other similar engines.

The fuel is probably 3-4 months old based upon the last time the past owner ran it. We have not added fuel yet.

Water/ fuel separator has never been addressed by us.

The old plugs (see attached images).

As for the fuel mixer screws, we never addressed them until you brought it up. When we looked at them today, they were two "1/2 turns" (360 degrees). We bottomed them out and tested every 1/8 of a turn on both sides until we got to three 1/2 turns + a 1/4 (so 630 degrees from being bottomed out). Throughout that range, it ran even worse. It progressively got better as we backed it out, but we were not sure how far to go. I'm not sure if the fuel mixture screw was the original issue but I'm sure it has a factor in it now.

Thanks for the time and help everyone.

 

[sb6bb]

120 is not really normal comp test results for that engine, normal comp test results are 160-170. I’d also check for vacuum leaks at the intake manifold (if there is a removable square plug in the manifold see if you can get a nipple to screw in to do a vacuum test. should be over15-16” inches of mercury at idle. Lastly you can get a leak down tester that will give the most accurate indication of internal engine condition. Have you checked the ohms of each plug wire? Should not be more than 1000 ohms per foot. Might need a full carb rebuild if it’s a carbed engine.

I may be wrong with 120. Dumbass me, I didn't record it at the time. We just order a vacuum gauge to start down that route next.

Thank you!