Fuel issue

jaysurfer · Post by **jaysurfer** » Sat Jan 21, 2017 2:17 pm

1984 trojan international 9 meter. 350 crusaders. brand new fuel lines. all fittings new. new stem in tank. new fuel pump. two new filters. first filter is a fuel/water sep. that is amber in color and see through. the next is a regular fuel filter. i can bleed all of the air out of the system and then connect fuel line to fuel pump. boat will run perfect. bring her up to speed and i can visibly see the fuel level in the first filter drop. eventually it will start sucking air and sputter out... HOW IS AIR GETTING IN THE FILTER????

P-Dogg · Post by **P-Dogg** » Sat Jan 21, 2017 5:16 pm

Dunno, but are you sure your see-through separator is rated for gasoline use?

prowlersfish · Post by **prowlersfish** » Sat Jan 21, 2017 5:41 pm

Check all the lines and fitting from the tank to the filter , if that's ok then look at the tank pick up tube .

On to the fuel filter . There is no see through fuel filter approved for gasoline inboard use . They may only used for outboards or with diesel fuel .They need to go and the air leak could be there too .

Big D · Post by **Big D** » Sat Jan 21, 2017 6:42 pm

++ to all the above.

Also, did you replace the anti-siphon valve at the top of the tank where the fuel line hooks up? Check and make sure there are no kinks in the fuel line. Any restriction on the suction side will increase vacuum which is one of the causes of vapour lock. This happens when fuel changes from a liquid to a gas state due to excessive vacuum which reduces the boiling point, or excessive heat (110* if I recall). Considering how hot it can get in a marine engine compartment, it doesn't take much vacuum to push the requirements over the edge. Anything more than 2" Hg on the suction side increases the chances of vapour lock....a little bend in the fuel line, a sticking anti-siphon valve, more than one fuel filter on the suction side, internally collapsed lines, etc. can all contribute to this. The result can be a engine stall or not being able to restart shortly after a shutdown due to heat soak.

Is there any fuel in the small see through line from the fuel pump to the carb? You could have a bad pump.

How long does it take for this to start happening?

jaysurfer · Post by **jaysurfer** » Sat Jan 21, 2017 6:58 pm

P-Dogg wrote:Dunno, but are you sure your see-through separator is rated for gasoline use?

yes.

jaysurfer · Post by **jaysurfer** » Sat Jan 21, 2017 7:00 pm

prowlersfish wrote:Check all the lines and fitting from the tank to the filter , if that's ok then look at the tank pick up tube .

On to the fuel filter . There is no see through fuel filter approved for gasoline inboard use . They may only used for outboards or with diesel fuel .They need to go and the air leak could be there too .

lol!! good to know. i had no idea. i removed it today to test if that was my problem. i may have fixed my problem. too foggy to really put a good test run on it. tomorrow ill know for sure

jaysurfer · Post by **jaysurfer** » Sat Jan 21, 2017 7:04 pm

Big D wrote:++ to all the above.

Also, did you replace the anti-siphon valve at the top of the tank where the fuel line hooks up? Check and make sure there are no kinks in the fuel line. Any restriction on the suction side will increase vacuum which is one of the causes of vapour lock. This happens when fuel changes from a liquid to a gas state due to excessive vacuum which reduces the boiling point, or excessive heat (110* if I recall). Considering how hot it can get in a marine engine compartment, it doesn't take much vacuum to push the requirements over the edge. Anything more than 2" Hg on the suction side increases the chances of vapour lock....a little bend in the fuel line, a sticking anti-siphon valve, more than one fuel filter on the suction side, internally collapsed lines, etc. can all contribute to this. The result can be a engine stall or not being able to restart shortly after a shutdown due to heat soak.

Is there any fuel in the small see through line from the fuel pump to the carb? You could have a bad pump.

How long does it take for this to start happening?

the anti-siphon valve is brand new. i removed the clear fuel filter and so far so good. i ran it at 3500rpm for about 10 minutes and no issue. it was super foggy today and didnt want to chance an accident. i really think that clear fuel water sep. might have been my problem... ill try a longer test run tomorrow if its not foggy!

jaysurfer · Post by **jaysurfer** » Sat Jan 21, 2017 7:16 pm

jaysurfer wrote:
Big D wrote:++ to all the above.

Also, did you replace the anti-siphon valve at the top of the tank where the fuel line hooks up? Check and make sure there are no kinks in the fuel line. Any restriction on the suction side will increase vacuum which is one of the causes of vapour lock. This happens when fuel changes from a liquid to a gas state due to excessive vacuum which reduces the boiling point, or excessive heat (110* if I recall). Considering how hot it can get in a marine engine compartment, it doesn't take much vacuum to push the requirements over the edge. Anything more than 2" Hg on the suction side increases the chances of vapour lock....a little bend in the fuel line, a sticking anti-siphon valve, more than one fuel filter on the suction side, internally collapsed lines, etc. can all contribute to this. The result can be a engine stall or not being able to restart shortly after a shutdown due to heat soak.

Is there any fuel in the small see through line from the fuel pump to the carb? You could have a bad pump.

How long does it take for this to start happening?
the anti-siphon valve is brand new. i removed the clear fuel filter and so far so good. i ran it at 3500rpm for about 10 minutes and no issue. it was super foggy today and didnt want to chance an accident. i really think that clear fuel water sep. might have been my problem... ill try a longer test run tomorrow if its not foggy!

time for this to happen was actually different every time it happened... ? but because i HAD the clear filter i was always able to keep an eye on it. or at least someone on the boat with me to keep a close eye on it. as soon as the fuel level dropped to the bottom of the filter it would only last about 30 seconds max before sputtering because it most likely was starting to suck air at that point. but like i said before... i removed that filter today nad so far so good. ill take her out tomorrow and give her a good test run.

P-Dogg · Post by **P-Dogg** » Sat Jan 21, 2017 8:27 pm

They may only used for outboards or with diesel fuel .

That's the nuance I was looking for.....Not being around outboards much, I forgot the clear ones were OK for gas sometimes.

OK, now who makes a vacuum gauge rated for gasoline use so that I know when my filter ???

Big D · Post by **Big D** » Sat Jan 21, 2017 9:09 pm

jaysurfer wrote:.....ill take her out tomorrow and give her a good test run.

Fingers crossed.

jaysurfer · Post by **jaysurfer** » Sun Jan 22, 2017 5:06 pm

Big D wrote:
jaysurfer wrote:.....ill take her out tomorrow and give her a good test run.
Fingers crossed.

fixed!

mikeandanne · Post by **mikeandanne** » Sun Jan 22, 2017 5:09 pm

P-Dogg wrote:
They may only used for outboards or with diesel fuel .
That's the nuance I was looking for.....Not being around outboards much, I forgot the clear ones were OK for gas sometimes.

OK, now who makes a vacuum gauge rated for gasoline use so that I know when my filter ???

Cant use that type of filter for gas in an enclosed engine compartment, otherwise ok.

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