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Fuel Feed Issue

ehlien

ehlien

Regular Contributor
Well a new problem. Running home yesterday my 1994 ..454 Baja was running fine at about 3500 RPM . Approaching home I decided to throttle back to about 1000 RPM and just run back in slow. When I throttled down it died out on me. It sputtered a couple times on cranking at first then nothing and I could not get it started. I did not think it was getting any fuel so I pulled off the fuel filter/water separator and the fuel level in it was down about 1/2 inch from the top. I dumped it to make sure there was no water in it then replaced it. After considerable cranking with nothing I pulled it again and it had minimal fuel in it. I never got it restarted. I suspect the fuel pump crapped out. Any thoughts??
 
First check anti siphon valve at gas tank. Small check valve/ball inside......make sure it is free/rattles air blows in one direction only.

when you change/empty a water separating filter you really need to fill with gas to prime, a typical fuel pump cannot pull enough fuel to fill it.

Only way to properly tell if pump has failed to to put a pressure gauge between pump and carb......
 
I checked for an anti siphon valve at the gas tank and there appears to be none. Will refill the pump and see if it will move any fuel. Is there any filter on a webber carb?
 
Is there another potential failure mode for what I described? Is there a probable connection between the other problem I'm having with fluctuating RPMs, missing and surging between 1500 and 3000 RPM? I also experienced some stuttering and backfire during cold accelerations/hole shots to plane this time out.
 
Well I take it back..after going back into the boat and looking closer what I thought was just a fitting to the gas tank was indeed an anti siphon valve and upon removing it was indeed stuck/NFG . Now I just need to locate a replacement and see if that works.
 
As a TEMPORARY and I mean TEMPORARY test,

Go get a brass barb fitting at a local hardware store and use it to test. same threads and ID or as close as you can get!!

Any marina or marine store should be able to get or have in stock the anti-siphon valve.

If you use a brass fitting to test, remember that the Anti-siphon valve is a coast guard regulation must have installed device in the boat!! SO you must get a new one and install it!!!!!!!!
 
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Hit a few marine stores yesterday and no one had the right sized valve but it was late and several were closed. Will try again today and sure I can find one.
 
Picked up the part today and replaced the old one.. no luck.... it would not pump up fuel on its own..I was finally able to get it started by spraying some fuel directly into the carb and was able to throttle the engine up and down but after about 5 minutes iidleing when i tried to do that again it died and I could not get it restarted even by spraying some fuel in the carb.... next??? Note ..The new valve was definitely better than the the old one but I did notice it was still not really easy to blow through.
 
The Anti siphon valve works off Vacuum not pressure. I said to blow thru it to see if the check ball was stuck..........this happens a lot when boats sit for long periods of time!!!!!

The fuel pump produces vacuum on the gas tank side of the pump.

If I am not mistaken it should be producing ~ 8-10 inches of mercury (in Vacuum terms)

The output of the pump MUST be between 3-8 psi at all times.

You have a can of worms and appear to be looking for the quick fix here..............Not going to happen.

Do you have any idea what the fuel pump pressure is? Are you sure you have gas in the carb?

Either replace the carb, rebuild the carb, or find someone who can assist you IN PERSON with diagnosing your issues.

You seem to be chasing your tail.
 
ehlien said:
Note ..The new valve was definitely better than the the old one but I did notice it was still not really easy to blow through.
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It's not supposed to be. It works by requiring more vacuum from the fuel pump than the vacuum you would get from the "siphon effect" ( via a spring loaded check ball).
 
Yes ..your right its getting to the point where I am just chasing my tail and the boating season is pretty much done. But ..bums me out to give up after all this work but at some point its not worth all the lost water time. I've pulled this boat of out the water for the winter now but want to have it ready to go for the first of next year. Considering its a 22 year old boat and neither the fuel pump or carb have ever been touched it couldn't hurt to replace them both and eliminate those variables. A rebuilt carb is only $288 and the new fuel pump is less than $100. That's pretty cheap by boat maintenance standards. Worst case if it still doesn't solve my problem I know those are new, reliable and not the problem. It won't leave much else that it could be and I can then bring someone on site for the final clean up if necessary.
 
And if it does NOT cure the problem, you at least have some spares.

Shame you couldn't put that behind you before hauling out. Now you have to wonder if the problem will come back next year. Been there, done that.

Jeff
 
Service your fuel tank as well. Pull the suction tube and clean/replace the strainer, it wouldnt hurt to add a antisiphon valve while your at it. All it is is a check valve with a spring it allows fuel to be pulled from the tank but will not siphon off in the case a fuel line comes loose or splits.
 
fastjeff said:
And if it does NOT cure the problem, you at least have some spares.

Shame you couldn't put that behind you before hauling out. Now you have to wonder if the problem will come back next year. Been there, done that.

Jeff
Click to expand...

Ya .no kidding but its that time of year and the weather was looking bad for the upcoming week and I had to tow it to the launch with my wife to get it out so i wanted calm water. Anyway its out and I can still work on it at my leisure now.
 
4 bbl 9772S .. I saw one rebuild sheet where there was an internal inlet filter but you have to take the carb off to get to it.
 
Hey! I had a similar problem with the Quadra-Jet 4 barrel on mine. The cloth basket inlet filer was plugged solid with brown crap.

If you have this carb, remove the fuel line (5/8 wrench and knuckle buster for the big nut) and check the filter.

Jeff

PS: Also loosing the fuel line at the fuel pump end eases this task.
 
Temporarily replacing the fuel delivery system with a 6 gallon outboard tank and hose connected directly to the fuel pump inlet can help to locate and eliminate a lot of guesswork.
 
Update ..well now that I have the boat out of the water and started to winterize I have pulled the carb and fuel pump off the engine.

The carb looks good and there was very little fuel in it. What was in it had a dark yellow color for some reason. I took the fuel feed line off and as I look into the opening I see a small strainer/filter that sticks up into the center of the inlet. It looks good, not dirty or clogged but will have to take the carb apart to check from inside the carb.

The fuel pump might look questionable. It did have fuel in it but when I removed it the cam cavity below the pump was filled with fuel. Not sure if some of that leaked in there as i removed the pump. There is a plastic line that comes from the carb to the lower side of the pump and enters below the diaphragm side of the pump. This tube and the entry port into the pump were plugged solid at the pump. I assume this is a vent tube of some sort but not sure what function it has or how being plugged might effect performance. After taking the pump apart I see the area under the diaphragm is quite dirty. Not sure if replacing it will solve my problems but for the money , about $88.00 its going to happen.
 
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