2008 Volvo Penta 5.0GL Carb Problems

[CLi87]

Hey all, I'm working on my 2008 Starcraft with a Volvo Penta 5.0GL with the 2 barrel holley carb. When I got it it had some issues running, when I looked down the carbs I saw one side was dripping fuel fine while the other was only letting out a few drops, so I figured a carb rebuild was in order. I took the carb completely apart and ran it in my ultrasonic cleaner for 30 minutes, then used compressed air @ 175psi to blow out all the passages. After I put it all back together I put it back on the engine and it ran better but the one side still wasn't providing as much fuel as the other side and then after giving it a rev up to 3000 rpms, suddenly the slow side completely stopped dripping fuel. I took the carbs off the engine again and checked for blockages and blew more compressed air through all the passages but didn't see anything come out. I put the carb back on, once again, it would start up and idle fine but I saw one side drip slightly more fuel than the other, and then once again once I gave it a rev up to 3000 rpms and dropped it back down to idle, the one side of the carb stopped dripping fuel. Any idea what would cause this? I was thinking the AF adjustment might be off but on this carb hole on each side of the carb where the AF screws should be is blocked off, so I'm guessing there's no adjustment? Also I know it's not a fuel supply issue as I checked to make sure the fuel pump was pumping plenty of fuel and also when I took the carb off and turned it upside down a lot of fuel came out, so the bowl must be full.

 

[jimmbo]

I know Holley used to put a Plastic, easy to remove, Cover over the Idle Mix Screws on the Metering Block.
As for One Side Dripping Fuel, as they share a Common Fuel Bowl, is the Carb/Boat/Trailer Level?

 

[Scott Danforth]

Hey all, I'm working on my 2008 Starcraft with a Volvo Penta 5.0GL with the 2 barrel holley carb.

you have to run either soft copper wire or fishing line thru each passage to ensure they are clean. I have had some carbs with so much crud in the passages I have had to use my pin drills to open them up.

from what you describe you have blockage in at least two circuits.

at idle there should be nearly zero drips coming from the boosters, or just a minor one that forms periodically. Idle is supposed to run solely off the transfer slots and the idle needle




first, after the carb has been pulled apart, and all the passages verified clear with a bit of fishing line and a spray can of carb cleaner, make sure the power valve is not blown, and the emulsion tube orifices are clear

second, on the squirter assembly, make sure the check valve (its a carb float needle) is loose and properly working.

next, assemble the carb, make sure if your accelerator pump is the orange rubber umbrella, you nip off the pull tab or it will hang up your float. if you have the older dual check ball version, this isnt an issue.

with the carb assembled and upside down, where is the transfer slot adjustment? it should be a nice square

idle adjustment is started at 3/4 turn out from seated.

install carb.

since you have an electric fuel pump, you can adjust the float without the motor running. pull the site glass, fuel should be at the bottom of the sight glass opening. not any higher, not any lower. it should be at the bottom, and not running out the hole

too high a float setting and you will have dribbles at idle. too low and you have other issues

Now set the choke. the choke should be nearly closed, about 1/8" open from closed when ambient temperature is about 50 degrees. you can adjust this a bit later if needed

Now make sure your on the muffs, fire up the motor. now adjust the idle screws evenly. from the 3/4 turn out from seated position, using an unlit propane torch, wave it over the motor. if the RPMs increase, back out the screws just a bit. if the motor RPM's drop a bit, turn them in a bit.
if you are more than 1 turn out or further in than 1/2 turn out, then there is something not right.

there should be no drips from the boosters until you get the motor off the idle circuit and into the transition circuit or the high speed circuit. then you should see fuel almost spraying as you crack the throttle, along with the squirt from the accelerator pump nozzles.

 

[CLi87]

I know Holley used to put a Plastic, easy to remove, Cover over the Idle Mix Screws on the Metering Block.
As for One Side Dripping Fuel, as they share a Common Fuel Bowl, is the Carb/Boat/Trailer Level?

Yes the boat is level, I do see the cover, it seems to be a brass cover, it's pretty in there that I can't pry it off with a screwdriver, any suggestions how to remove it? Maybe drill a small hole and pry it off with a pick tool?

 

[CLi87]

you have to run either soft copper wire or fishing line thru each passage to ensure they are clean. I have had some carbs with so much crud in the passages I have had to use my pin drills to open them up.

from what you describe you have blockage in at least two circuits.

at idle there should be nearly zero drips coming from the boosters, or just a minor one that forms periodically. Idle is supposed to run solely off the transfer slots and the idle needle

View attachment 402090


first, after the carb has been pulled apart, and all the passages verified clear with a bit of fishing line and a spray can of carb cleaner, make sure the power valve is not blown, and the emulsion tube orifices are clear

second, on the squirter assembly, make sure the check valve (its a carb float needle) is loose and properly working.

next, assemble the carb, make sure if your accelerator pump is the orange rubber umbrella, you nip off the pull tab or it will hang up your float. if you have the older dual check ball version, this isnt an issue.

with the carb assembled and upside down, where is the transfer slot adjustment? it should be a nice square

idle adjustment is started at 3/4 turn out from seated.

install carb.

since you have an electric fuel pump, you can adjust the float without the motor running. pull the site glass, fuel should be at the bottom of the sight glass opening. not any higher, not any lower. it should be at the bottom, and not running out the hole

too high a float setting and you will have dribbles at idle. too low and you have other issues

Now set the choke. the choke should be nearly closed, about 1/8" open from closed when ambient temperature is about 50 degrees. you can adjust this a bit later if needed

Now make sure your on the muffs, fire up the motor. now adjust the idle screws evenly. from the 3/4 turn out from seated position, using an unlit propane torch, wave it over the motor. if the RPMs increase, back out the screws just a bit. if the motor RPM's drop a bit, turn them in a bit.
if you are more than 1 turn out or further in than 1/2 turn out, then there is something not right.

there should be no drips from the boosters until you get the motor off the idle circuit and into the transition circuit or the high speed circuit. then you should see fuel almost spraying as you crack the throttle, along with the squirt from the accelerator pump nozzles.

How do I know if the power valve is blown? It seems to work fine, I'll post detailed pictures of all the parts of the carb later today but it seems to spring open and close just fine. Looking at the diagram it seems the idle jet is hidden behind the main jet and not removable? Where is the squirter assembly? I don't see it on the diagram? My accelerator pump seems to work fine, it squirts a good amount of fuel each time I pump the throttle lever. By transfer slot adjustment are you referring to the idle mixture screw?

 

[jimmbo]

You really need a Book that describes and shows what the Holley Fuel Circuits look like. I have searched Online for the Holley Idle Circuit Diagram, but can only find one, but is was for an International Harvester Tractor and had an adjustable Air Bleed(which permits fully closed Throttle Plates and thereby no problems with throttle plate Transfer Slot issues), which yours won't. It is also shown as a 4bbl, but the 2300 is the front half of a 4150/4160 carb


If the Power Valve is damaged, fuel will pass through the Diaphragm directly into the Intake Manifold.
The Accelerator Pump Discharge Nozzles(Squirters) are above and to the front of the Venturies, and there are a few varieties,

 

[CLi87]

I took the carb off again and took some pictures, the idle air corrector was definitely clogged on one side, cleaned that with carb cleaner and blew through with compressed air, tried to get a fishing line through it but couldn't get it through. I also found the idle jets on the other side of the middle plate and those are clean but I ran a wire brush through them again anyway. After re-assembling everything the carbs seem to run *more* correctly, there's no more fuel dripping from the boosters at low RPM, as I rev it I see the accelerator pump shooting some fuel then once I get high enough RPM I see a nice fine spray shooting from the boosters, now my only issue is the engine won't idle now, I'm guessing I need to adjust the A/F screws but those covers are a pain to get off and I don't want to damage the needle below them, I'm gonna try hammer them some more with a screwdriver to get something to grab onto so I can pry them out with a pick tool.

 

[jimmbo]

Post a pic of the Covers you are trying to remove.

Edit: you were posting as I was typing

 

[Scott Danforth]

dont try to remove the welsh plugs from the metering plates you will destroy the metering plate. dont try to remove the air bleeds unless you want to machine for adjustable air bleeds.

you test a power valve with a vacuum pump. however with that amount of corrosion, the power valve in the pic is junk replace it with the new one in the kit.

the air bleads are plugged based on the picture. the accelerator nozzle never was taken off and cleaned.

the paint between the metering plate and the main body appears to have not been broken, so the metering plate may not have been removed.

the accelerator pump appears to not have been removed.

 

[jimmbo]

That Power Valve looks like it was was exposed to Salt Water, replace it with one of the same Value. Just don't assume if there is one in the Carb Kit it is correct
That carb looks dirty where the Air Bleeds are.
The Accelerator Nozzles are in plain sight, under that Big Philips Screw
When you put it back together, make sure the Gasket between the Metering Block and the Carb Body is oriented correctly, as some Passages are only on one side
My Holley, had plastic Caps over the mix needles. Being sealed, yours might not have an adjustable Needle, but it is just a way of keeping Tinkerers out. If everything else is fine the engine should idle fine.

 

[CLi87]

dont try to remove the welsh plugs from the metering plates you will destroy the metering plate. dont try to remove the air bleeds unless you want to machine for adjustable air bleeds.

you test a power valve with a vacuum pump. however with that amount of corrosion, the power valve in the pic is junk replace it with the new one in the kit.

the air bleads are plugged based on the picture. the accelerator nozzle never was taken off and cleaned.

the paint between the metering plate and the main body appears to have not been broken, so the metering plate may not have been removed.

the accelerator pump appears to not have been removed.

Ok, I'll get a new power valve, would that cause it not to idle at all? I wasn't able to get a fishing line through the air bleeds but let it sit in carb cleaner then blew it out with 175 psi and now I can see through the hole pretty well. The welsh plugs you're talking about are the plugs covering the A/F adjustment screws right? That accelerator nozzle is STUCK on there good, I tried to take it off but couldn't get it to budge at all and was scared of breaking it. I never took off the accelerator pump because I thought it was working properly, it squirts plenty of fuel each time so I didn't bother removing it. Would any of those issues cause it not to idle?

 

[CLi87]

My Holley, had plastic Caps over the mix needles

View attachment 402109

Mine are definitely metal, seems like brass to me.

 

[CLi87]

That Power Valve looks like it was was exposed to Salt Water, replace it with one of the same Value.
That carb looks dirty where the Air Bleeds are.
The Accelerator Nozzles are in plain sight, under that Big Philips Screw
When you put it back together, make sure the Gasket between the Metering Block and the Carb Body is oriented correctly, as some Passages are only on one side
My Holley, had plastic Caps over the mix needles. Being sealed, yours might not have an adjustable Needle, but it is just a way of keeping Tinkerers out. If everything else is fine the engine should idle fine.

View attachment 402109

O I thought the accelerator nozzle is the u shaped metal piece, I did unscrew the big phillips in the middle where the fuel comes out from the accelerator pump and did clean that out.

 

[jimmbo]

That is the Bowl Vent, on a Marine Carb, is shaped like that so any Fuel expelled by it, goes into the Motor, not the Bilge

 

[Scott Danforth]

No, the Welsh plugs over the emulsion tubes.

Cover over the idle screws can be removed with a small screw and prybar if you can't get it with a pick

 

[CLi87]

Any suggestions how to get these tamper proof covers off the A/F screws? I tried drilling and I don't know what it's made of but I can't drill through it, I tried using a small chisel to cut a slit in the side but this is one tough cover.

 

[Scott Danforth]

It's staked. Use a Dremel (or a good pocket knife) and remove the stakes. Then I would use a cut-off wheel in the Dremel and cut a slit in top to get a screw driver in to pry out

 

[CLi87]

It's staked. Use a Dremel (or a good pocket knife) and remove the stakes. Then I would use a cut-off wheel in the Dremel and cut a slit in top to get a screw driver in to pry out

I removed the stakes with a screwdriver and hammer, that's a good idea, I'll use my dremel with a diamond cut blade to cut a slit in the cover and hopefully pry it off with a screwdriver.

 

[CLi87]

Man, those covers were a royal PITA to get off, but I finally got them off after using a cutoff wheel and drill to get a hole large enough to get a big pick in, tuned the A/F screws to 1 full turn out each and now the engine runs great, idles perfectly and revs nicely, now just gotta take it out to the lake to do a full test.