99 Volvo 5.0GL

Lou C

Supreme Mariner
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Nov 10, 2002
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13,899
If you have a carb the proper fuel pressure will be on the low end, the 3-8 psi spec you cited.
A 99 Volvo for sure won't have points, they used the Prestolite BID system on early models with electronic ignition and later they switched to the Delco EST IIRC.
You have an electric fuel pump, check the connections carefully, I think they are in the area where the raw water pump is (belt driven or in the crank pulley area?)
 

Bhuie

Seaman Apprentice
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May 7, 2021
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34
Ok,
So far the fuel line is clear from tank to engine. Fuel pump and filter have now been replaced. Same problem exists where full throttle is fine at start and then after a few seconds starts bogging down. Pull back on throttle and runs fine but top end is gone without bogging down and sputtering. So there are some electric components on the fuel filter and some type of large fuse like box you would see in a car fuse box. Wonder if it could be that or should I move to the holly carburetor? Coil?
 

kenny nunez

Captain
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Jun 20, 2017
Messages
3,487
Try to unscrew the fuel suction pipe out of the tank. There is a fine mesh screen in the tube that may be partially plugged. Pitch the screen, put it back together then take the boat for a ride. Make sure all the fuel connections are tight and leak free.
You do not need a high pressure fuel pump with a carburetor.
 

Bhuie

Seaman Apprentice
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May 7, 2021
Messages
34
Try to unscrew the fuel suction pipe out of the tank. There is a fine mesh screen in the tube that may be partially plugged. Pitch the screen, put it back together then take the boat for a ride. Make sure all the fuel connections are tight and leak free.
You do not need a high pressure fuel pump with a carburetor.
I have done all of that as well. All fuel lines are clean.
 

Lou C

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Nov 10, 2002
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You have a fuel pick up tube and an anti siphon valve. That’s the barbed fitting your fuel line attaches to. There is a spring loaded ball inside that valve. It’s there to shut off fuel flow if the fuel line between the tank & fuel pump leaks so you don’t get a bilge full of gasoline. Make sure that valve isn’t clogged and the ball moves freely. I have tested them with a vacuum pump and found that they open at about 1-2” Hg (inches of Mercury). Low pressure fuel pumps should develop about 9-10” Hg.
Fuel tank vent definitely not clogged?
Ever try running it on a separate outboard tank? That isolates the boat fuel system from the engine fuel system
 

Lou C

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IMG_1450.jpegIMG_1474.jpeg
First pic shows the pick up tube & anti siphon valve second pic is testing them for vacuum leaks….
Vacuum leaks in the pick up tube, anti siphon valve or fuel line can cause this problem as can vacuum leaks at your fuel filter. If you run the boat on a seperate outboard tank you can isolate these factors..
 

Bhuie

Seaman Apprentice
Joined
May 7, 2021
Messages
34
View attachment 413266View attachment 413267
First pic shows the pick up tube & anti siphon valve second pic is testing them for vacuum leaks….
Vacuum leaks in the pick up tube, anti siphon valve or fuel line can cause this problem as can vacuum leaks at your fuel filter. If you run the boat on a seperate outboard tank you can isolate these factors..
Anti siphon ball has been removed. The fuel lines are clean from tank to carb. Fuel pump has been replaced. Fuel filter has been replaced.
It still does the exact same thing. Cold run full throttle then in less than like 30 seconds I loose top end power. She just starts sputtering. You can back off the throttle to scoot 3/4 and you can tell it’s trying to run right. Like a loose wire is twitching. I thought about replacing plugs and wires but at cold start she gets right up there then bogs. I have not pulled the carb yet.
 

Lou C

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Nov 10, 2002
Messages
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Did you pull out the fuel pick up tube and see if there's a clogged screen on the end of it? What can happen is this: some of these pick up tubes have a screen on the end and some don't (if you look closely at mine above you can see it doesn't have the screen). If you don't pull out the pick up tube you'll never know.
 
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