Air in the Fuel Line

RoyS

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Jun 3, 2012
1,204
Hunter 33 Steamboat Wharf, Hull, MA
Another possibility: If your return line simply empties into the top of the fuel tank air can enter there overnight and the fuel siphons back through the fuel pick up and associated parts. Even though there are usually check valves present they often leak back. If that is the case you can install a pick-up tube fitting on the return line. As a simple test try this: After running the engine, shut off the fuel line at the tank. The next day open that valve and try starting. If it starts right up your problem may be the siphon back described here. Good luck. Please report results.
 
Jan 22, 2008
32
Ericson 29 tall rig old orchard beach, maine
Hello Every one!
I am happy to say I have cured my issue with Air in the fuel line. All of a sudden I went over to the starter and it started right up no Bleeding. I has done so for the last 4 days. Although I know nothing about how this came about I have a thought about it. I think that my bleeding the system for 4 weeks every time I went sailing that finally all the air is out of the lines and it is now working correctly. Yahoo!

Steven
 
Mar 10, 2015
62
Catalina 30 Moss Landing, CA
Hello Every one!
I am happy to say I have cured my issue with Air in the fuel line. All of a sudden I went over to the starter and it started right up no Bleeding. I has done so for the last 4 days. Although I know nothing about how this came about I have a thought about it. I think that my bleeding the system for 4 weeks every time I went sailing that finally all the air is out of the lines and it is now working correctly. Yahoo!

Steven
Did you ever open the engine fuel pump bleed screw with feed line pressurized with elec. fuel pump? If not, still worthwhile doing it to be sure all the air is out. In the future, this should be the first thing to do if it won't start!
Pete
 
Aug 3, 2014
68
CATALINA, BENETEAU OCEANIS 36, 400 Grosse Ile, Mi and Fajardo, PR
My 2 cents worth. Electronic fuel pumps are designed to push fuel through the primary fuel filter, mechanical fuel pumps are designed to pull fuel through the primary fuel filter. My Catalina 36 w/ M25 is organized as follows; fuel tank, Facet Purolator Gold Flo solid state electronic fuel pump– 476459E, Dahl Model 101 Primary fuel filter, Wix 33390 secondary fuel filter. Your electronic fuel pump is after the Racor (pull). Electronic fuel pumps are designed to push. Racors are designed for a pull system (mechanical pump between primary and secondary fuel filters) The Dahl filter is designed for a push system. My guess is that you do not have a factory installation. The electronic pump should be in front of a fuel filter designed for a push system. It is possible this is the cause of your problems.

Fuel issues are usually on the suction side ( between the fuel tank and the fuel pump. If your primary fuel filter has a transparent bowl you should see bubbles in the bowl if the pump is sucking air between the primary fuel filter and the tank. If you continue to experience problems I suggest you post to Main Sail's forum.

Nick
 
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Jops

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Sep 19, 2020
12
Catalina Catalina 36 San Diego
Steven, I am happy for you but disappoint that you didn't solve the issue as it is my issue. Nick, my setup is the same as Steven's in regard to the electric pump being after the water/fuel separator. Many forums say that setup is better as you have a filter protecting your pump but I understand your logic. I upgraded my pump from the little cube type to the cylinder type and it actually has a filter so I might try your suggestion as I am up for anything now.
I don't see bubbles coming up from the primary filter or mechanical fuel pump, I only see bubbles collecting between the injectors when I try turning the engine over. Could they somehow be entering at the injectors? I have down the soapy water test at the base of the injectors. This is a frustrating issue as I have been at it since January, this is a repowered engine and all new fuel lines, new ball valve on the tank, new electric fuel pump, everything double clamped.
 

RitSim

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Jan 29, 2018
246
Beneteau 411 Branford
Try temporarily adding a section of clear PVC tubing in a low pressure side of the line close to the engine. you will be able to see the air bubbles and be able to troubleshoot the leak. remove the tubing after you are done.
 
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Jops

.
Sep 19, 2020
12
Catalina Catalina 36 San Diego
I have clear tubing at from the mechanical fuel pump to the injectors and out for 4 inches to the excess fuel return line. Is this what you mean or do you mean add some leading up the the fuel filter on the engine? I never see bubbles from the fuel pump up to the injectors, always accumulating in the tubes between the injectors. But I wonder if that is because the bubbles are micro and I just don't see them if not then the air has to be coming in at the injectors.
 
May 20, 2016
2,992
Catalina 36 MK1 94 Everett, WA
My 2 cents worth. Electronic fuel pumps are designed to push fuel through the primary fuel filter, mechanical fuel pumps are designed to pull fuel through the primary fuel filter. My Catalina 36 w/ M25 is organized as follows; fuel tank, Facet Purolator Gold Flo solid state electronic fuel pump– 476459E, Dahl Model 101 Primary fuel filter, Wix 33390 secondary fuel filter. Your electronic fuel pump is after the Racor (pull). Electronic fuel pumps are designed to push. Racors are designed for a pull system (mechanical pump between primary and secondary fuel filters) The Dahl filter is designed for a push system. My guess is that you do not have a factory installation. The electronic pump should be in front of a fuel filter designed for a push system. It is possible this is the cause of your problems.

Fuel issues are usually on the suction side ( between the fuel tank and the fuel pump. If your primary fuel filter has a transparent bowl you should see bubbles in the bowl if the pump is sucking air between the primary fuel filter and the tank. If you continue to experience problems I suggest you post to Main Sail's forum.

Nick
nope - sorry your C36 came with the fuel pump between the primary and secondary filters - just the way it should be. I originally had the Dahl and the pump was the same as the Racor I replaced it with.
 
May 20, 2016
2,992
Catalina 36 MK1 94 Everett, WA
I leave my Knurled Knob open 1/4 turn while running - gets rid of any stray air before it hits the injectors -- the electric pump can pushe 30+ gal/hr but the engine only uses 1/2 gal - so a little running always to the tank keeps the pumps cooler and air out.
 
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