Fuel check valve?
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Cargo Master
Joined: May 2011
Posts: 2,388
Likes: 138
From: Northern California
Fuel check valve?
Trying to determine if I need a check valve or if maybe something else isnt working quite right... This is in regards to my marine 302.
It appears that the fuel lines are drained after the boat sits a while (a week or so). The symptoms include about 10 seconds of cranking on the initial start and an empty fuel filter that I can see filling back up as I crank. Once its 'primed' it will restart with a bump of the key.
I tried to research this on my own before posting... Theories include fuel boiling out of the bowls in the carb; I doubt this is the issue as the boat engine runs cool at 160°. It could also be evaporating out of the bowls; this is plausible but its a brand new/rebuilt carb (holley 2bbl). Havent tested this but its seems less likely. And lastly, the fuel pump (mechanical) is failing to hold the prime; this seems most plausible but I am not sure how to test or if this is in fact a function of the fuel pump.
There is about 2 ft of line and a water separator between the pump and the carb; no visible leaks. Since pumps seem to be cheaper than check valves, maybe the only way to know for sure is to replace it... Aside from a bit of cranking, this doesnt seem to be the worse issue I could have but I do like my stuff to work right.
Thoughts? Thanks!
It appears that the fuel lines are drained after the boat sits a while (a week or so). The symptoms include about 10 seconds of cranking on the initial start and an empty fuel filter that I can see filling back up as I crank. Once its 'primed' it will restart with a bump of the key.
I tried to research this on my own before posting... Theories include fuel boiling out of the bowls in the carb; I doubt this is the issue as the boat engine runs cool at 160°. It could also be evaporating out of the bowls; this is plausible but its a brand new/rebuilt carb (holley 2bbl). Havent tested this but its seems less likely. And lastly, the fuel pump (mechanical) is failing to hold the prime; this seems most plausible but I am not sure how to test or if this is in fact a function of the fuel pump.
There is about 2 ft of line and a water separator between the pump and the carb; no visible leaks. Since pumps seem to be cheaper than check valves, maybe the only way to know for sure is to replace it... Aside from a bit of cranking, this doesnt seem to be the worse issue I could have but I do like my stuff to work right.
Thoughts? Thanks!
Posting Guru
Joined: Jul 2013
Posts: 1,685
Likes: 2
From: Oregon
Crazy, have you checked your oil to be sure the fuel isn't leaking into your crankcase?
Also there is this I found searching a bit, for what its worth, sorry couldn't be more help, good luck.
Mechanical Fuel Pump Drain Back - IH PARTS AMERICA
Also there is this I found searching a bit, for what its worth, sorry couldn't be more help, good luck.
Mechanical Fuel Pump Drain Back - IH PARTS AMERICA
Thread Starter
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Cargo Master
Joined: May 2011
Posts: 2,388
Likes: 138
From: Northern California
I have not specifically checked for fuel in the oil so I will do so... Its easy enough. Right now the oil is brand new (as is the engine); any idea how much fuel it would take to be noticeable doing the sniff check? I have been checking the oil level religiously and it hasn't risen. The engine bay still has a bit of that stale fuel/oil smell from some spillage that occurred during the install & troubleshooting... Not sure if the smell would be strong enough to differentiate from what already is lingering.
That thread you linked was really useful and the primer bulb is an interesting consideration however as someone went on to point out, it shouldn't be necessary. So adding it is really a band-aid over an issue rather than fixing the issue.
The fuel pump is the original motorcraft and its a 74... I priced a carter pump and they seem to be in the $20-$30 range for stock replacements so perhaps its worth changing just for safe measure.
Is it safe to assume that a negligible amount of fuel in the oil (if there is any) will simply evaporate off?
That thread you linked was really useful and the primer bulb is an interesting consideration however as someone went on to point out, it shouldn't be necessary. So adding it is really a band-aid over an issue rather than fixing the issue.
The fuel pump is the original motorcraft and its a 74... I priced a carter pump and they seem to be in the $20-$30 range for stock replacements so perhaps its worth changing just for safe measure.
Is it safe to assume that a negligible amount of fuel in the oil (if there is any) will simply evaporate off?
Posting Guru
Joined: Jul 2013
Posts: 1,685
Likes: 2
From: Oregon
I agree on the primer bulb being a band aid crazy. As far as the fuel in oil evaporating, it would be a guess on my part, but I would think ingredients in the fuel would evaporate, but not all and it would change the viscosity of your oil no matter what. A negligible amount probably wouldn't have catastrophic effects.
Modern fuel may have been the downfall of your fuel pump, but again that would just be a guess on my part. I hope your fix is an easy one.
Modern fuel may have been the downfall of your fuel pump, but again that would just be a guess on my part. I hope your fix is an easy one.
Posting Guru
Joined: Jul 2013
Posts: 1,685
Likes: 2
From: Oregon
Found some more information, you may have also already found this, but post #8 seems like good diagnostics and may be worth a try.
Fuel pump drain back? - ClassicBroncos.com Forums
Fuel pump drain back? - ClassicBroncos.com Forums
Thread Starter
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Cargo Master
Joined: May 2011
Posts: 2,388
Likes: 138
From: Northern California
Thanks... I didn't find that thread... I was reading on some of the Mustang sites.
The guy with the bronco makes me wonder if I am looking into a bunch of nothing. Still if there is a little room for improvement then I would like to consider it.
Gonna take some pics of what I have going on...
The guy with the bronco makes me wonder if I am looking into a bunch of nothing. Still if there is a little room for improvement then I would like to consider it.
Gonna take some pics of what I have going on...
Thread Starter
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Cargo Master
Joined: May 2011
Posts: 2,388
Likes: 138
From: Northern California
No gas in the oil... Smells nice and oily; nothing else. This might not be definitive considering a couple ounces of fuel vs 5 quarts of fuel; there may not be enough fuel in the oil, if its getting in the oil, to be able to smell it. On this point I think I can only continue to watch... Er smell it.
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Cargo Master
Joined: May 2011
Posts: 2,388
Likes: 138
From: Northern California
Thought I would post a few picks of the fuel system. Most of this should be familiar looking but remember its on a boat so thats why there are some other things in there.
Here is a pic of the fuel lines coming in from the tanks. This had a tank selector valve but it failed and the previous owner decided to go with this cheaper t-fitting. I will restore this to the original configuration eventually.
Here we can see the fuel line running through the water separator prior to the fuel pump. The filter is empty again and I had this running about 22 hours prior to taking the picture. From the pump to the filter then onto the carb.
This seems pretty straight forward as far as how this is setup. Anyone see any issues with the configuration?
Here is a pic of the fuel lines coming in from the tanks. This had a tank selector valve but it failed and the previous owner decided to go with this cheaper t-fitting. I will restore this to the original configuration eventually.
Here we can see the fuel line running through the water separator prior to the fuel pump. The filter is empty again and I had this running about 22 hours prior to taking the picture. From the pump to the filter then onto the carb.
This seems pretty straight forward as far as how this is setup. Anyone see any issues with the configuration?
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Thread Starter
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Cargo Master
Joined: May 2011
Posts: 2,388
Likes: 138
From: Northern California
Also looking at the fuel pump, I thought it was a motorcraft but I couldnt find any of the expected markings on it; I am not gonna take it off just to check. It does look old though so probably a good place to start.
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