Hi all, I have a 20hp 3GMF,NO electrical fuel pump and am having air problems in the fuel system. Am wondering things like; 1) Should the fuel/water seperator be lower t hen the fuel tank but just higher then the fuel inlet on the motor?? My thoughts are gravity will help feed the seperator but air won't go in if higher then the inlet. 2)should the fuel/water seperator be full running???? Mine always seems to have an 1 or so of air. 3) What is the PROPER way to bleed air out completely??? (Low and high pressure sides) I hear open bleed, then pump by hand or by motor. OR start the motor & open the low psi bleed.
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Let's keep it simple
The goal of bleeding is to get the air out of the fuel system. To bleed, you have to move the fuel through the system by some means. And to do that, you have to BLEED the air out of the system. When you move the fuel, keep doing so until all signs of air are gone. You can move your fuel several ways. An electric pump is OK but if you don't have one,,. Another option is a outboard motor hand bulb. I installed one on my 3GM30F and it works great. Or you could use the Yanmar fuel pump priming lever. That's tricky. And last is to just crank the engine with the starter motor and the compression releases open. The relative location of the water separator should not be a major factor. But it should have a means of removing trapped air. Check the top of the housing for a bleed screw. This only works if your method of moving fuel (pump) is prior to the separator. If not, LEAVE IT ALONE! If you still are having trouble, ask a fellow owner. They will in all likely hood, show you how easy it really is. Go get 'em P.S. If you use the last method you listed, your motor might die. Opening an air bleed prior to the low pressure pump will only let in air. The bleed for most purging is the one at the high pressure pump.
The goal of bleeding is to get the air out of the fuel system. To bleed, you have to move the fuel through the system by some means. And to do that, you have to BLEED the air out of the system. When you move the fuel, keep doing so until all signs of air are gone. You can move your fuel several ways. An electric pump is OK but if you don't have one,,. Another option is a outboard motor hand bulb. I installed one on my 3GM30F and it works great. Or you could use the Yanmar fuel pump priming lever. That's tricky. And last is to just crank the engine with the starter motor and the compression releases open. The relative location of the water separator should not be a major factor. But it should have a means of removing trapped air. Check the top of the housing for a bleed screw. This only works if your method of moving fuel (pump) is prior to the separator. If not, LEAVE IT ALONE! If you still are having trouble, ask a fellow owner. They will in all likely hood, show you how easy it really is. Go get 'em P.S. If you use the last method you listed, your motor might die. Opening an air bleed prior to the low pressure pump will only let in air. The bleed for most purging is the one at the high pressure pump.
dies
runs 10-15 mins. caughs, dies, need to bleeed air again. Should the fuel/water seperator have NO air in it? Maybe I could/should take it off the wall, fill it by hand, seal it, then put it back up.
runs 10-15 mins. caughs, dies, need to bleeed air again. Should the fuel/water seperator have NO air in it? Maybe I could/should take it off the wall, fill it by hand, seal it, then put it back up.
it sucks
If your motor runs for a while and then dies and has air in the fuel lines it is sucking air into the fuel system somewhere(obviously). check all fittings on the suction side of your pump. check your fuel pickup tube in the tank. make sure it is not cracked. also check your filter. I have seen spin on type filters that would let air in. hope this helps. Ross
If your motor runs for a while and then dies and has air in the fuel lines it is sucking air into the fuel system somewhere(obviously). check all fittings on the suction side of your pump. check your fuel pickup tube in the tank. make sure it is not cracked. also check your filter. I have seen spin on type filters that would let air in. hope this helps. Ross
OK, once you bleed and it runs, that's it.
You are getting air again because of a path to it. (air) Look for wet spots.
Check things like missing copper washers on the low pressure side and so on. You have fuel in the tank,right?,,,sorry *sry but it happens. I've also heard of a bad diaphragm in the low pressure pump causing this problem. Air is allowed in from the crankcase. (don't know if it's true) But the best clue is air in your separator. But if you can bleed and run as long as you say, then, you are loosing your prime. Bleeding moves fuel a lot faster than the engine will demand when it is operating. A small air leak will then be able to break the siphon. (that's what you are doing prior to the low pressure pump) Again, look for wet spots. P.S. A bad gasket on the separator will give these symptoms.
You are getting air again because of a path to it. (air) Look for wet spots.
Check things like missing copper washers on the low pressure side and so on. You have fuel in the tank,right?,,,sorry *sry but it happens. I've also heard of a bad diaphragm in the low pressure pump causing this problem. Air is allowed in from the crankcase. (don't know if it's true) But the best clue is air in your separator. But if you can bleed and run as long as you say, then, you are loosing your prime. Bleeding moves fuel a lot faster than the engine will demand when it is operating. A small air leak will then be able to break the siphon. (that's what you are doing prior to the low pressure pump) Again, look for wet spots. P.S. A bad gasket on the separator will give these symptoms.
The only way I can answer that is
by saying I've never seen one with air in it after bleeding. Maybe yours is made that way but I doubt it. What kind do you have?
by saying I've never seen one with air in it after bleeding. Maybe yours is made that way but I doubt it. What kind do you have?
Fuel Filter / Water Separator
Sounds like air is getting back into the fuel filter/ water separator. Check the gasket between the filter and the filter body and between the filter body and the transparent bowl (if applicable) at the bottom of the separator. Check it's drain fitting and gasket (if aplicable) Remove the fuel line comming from the fuel tank at it's fitting on the fuel filter/separator; attach a small hand vacuum pump to this end of the fuel line and pump a couple quarts or more out of the tank to see that the fuel supply is consistant. (I used the same pump Hunter supplied for oil changes with the small diameter hose that fits down the dip stick) Check the condition of the fuel line for cracking or brittleness, replace if necessary and reattach the full fuel hose to the filter housing. Remove the bleed screw from the filter and check to see that the threads are not stripped and it's plastic or copper washer is in good condition (or just replace it). Using the same small suction pump, remove all air from the top of the filter thru the open bleed screw hole and reinsert the bleed screw with it's new washer. Now do your normal bleeding proceedure from the low pressure pump to the primary fuel filter by cracking the bleed screw on the primary (on Engine) filter and using the manual lever on the low pressure fuel pump (on the side of the crankcase) untill there are no more bubbles. If you didn't get any air into the high pressure side, this would be as far as you should need to go to get the engine running. No air should show up in the fuel filter/ separator if all connections and gaskets are tight and the fuel pick up in the tank has sufficient fuel.
Sounds like air is getting back into the fuel filter/ water separator. Check the gasket between the filter and the filter body and between the filter body and the transparent bowl (if applicable) at the bottom of the separator. Check it's drain fitting and gasket (if aplicable) Remove the fuel line comming from the fuel tank at it's fitting on the fuel filter/separator; attach a small hand vacuum pump to this end of the fuel line and pump a couple quarts or more out of the tank to see that the fuel supply is consistant. (I used the same pump Hunter supplied for oil changes with the small diameter hose that fits down the dip stick) Check the condition of the fuel line for cracking or brittleness, replace if necessary and reattach the full fuel hose to the filter housing. Remove the bleed screw from the filter and check to see that the threads are not stripped and it's plastic or copper washer is in good condition (or just replace it). Using the same small suction pump, remove all air from the top of the filter thru the open bleed screw hole and reinsert the bleed screw with it's new washer. Now do your normal bleeding proceedure from the low pressure pump to the primary fuel filter by cracking the bleed screw on the primary (on Engine) filter and using the manual lever on the low pressure fuel pump (on the side of the crankcase) untill there are no more bubbles. If you didn't get any air into the high pressure side, this would be as far as you should need to go to get the engine running. No air should show up in the fuel filter/ separator if all connections and gaskets are tight and the fuel pick up in the tank has sufficient fuel.
There you have it NewB
Diesels are dependable and simple. You shouldn't see air in a Racor. Follow Stus' guidelines and you will solve the problem. Don't try to over think the solution. Think 'suction' and look for anything that will let the 'pop in your soda straw' drain back into your glass. (best metaphor I know)That's all there is to it.
Diesels are dependable and simple. You shouldn't see air in a Racor. Follow Stus' guidelines and you will solve the problem. Don't try to over think the solution. Think 'suction' and look for anything that will let the 'pop in your soda straw' drain back into your glass. (best metaphor I know
)That's all there is to it.There Should Not Be Air In The Filter
I sounds like you have a Racor 500. It has a T handle on top that you loosen to change the filter. Those filters come as a filter with a new 'O' ring for the lid. From all the posts I am guessing that the ring on the removable top is not seated. IF the filter is made like the oil filter on a car, then it may be that it is not seating properly. In the end there should not be any air in the filter, line, injection pump, or any place in between. If there is a problem in the line or the pickup that is allowing air to get into the fuel line (which is under a vacuum because the fuel pump on the engine is sucking) you will never be able to fully bleed the engine. Start at the fuel tank and check all the connections. It may be that you will find a leak. If there is any fuel seepage, there will also be an air leak. As already mentioned, I recommend an electric fuel pump between the tank and the filter. You can go through and change filters, do any other fuel system maintanance, and once you have all buttoned up, turn on the electric fuel pump for 20 minutes and the diesel system is compltely bled and the diesel will start and run....everytime.
I sounds like you have a Racor 500. It has a T handle on top that you loosen to change the filter. Those filters come as a filter with a new 'O' ring for the lid. From all the posts I am guessing that the ring on the removable top is not seated. IF the filter is made like the oil filter on a car, then it may be that it is not seating properly. In the end there should not be any air in the filter, line, injection pump, or any place in between. If there is a problem in the line or the pickup that is allowing air to get into the fuel line (which is under a vacuum because the fuel pump on the engine is sucking) you will never be able to fully bleed the engine. Start at the fuel tank and check all the connections. It may be that you will find a leak. If there is any fuel seepage, there will also be an air leak. As already mentioned, I recommend an electric fuel pump between the tank and the filter. You can go through and change filters, do any other fuel system maintanance, and once you have all buttoned up, turn on the electric fuel pump for 20 minutes and the diesel system is compltely bled and the diesel will start and run....everytime.
Stu raises a good point
The cannister with the primary filter has a ring gasket that needs to be replaced when replacing the filter. The ring is usually jammed in tight and requires a pick to remove. Make sure there's one there in the first place, or that's where the air leak could be coming from.
The cannister with the primary filter has a ring gasket that needs to be replaced when replacing the filter. The ring is usually jammed in tight and requires a pick to remove. Make sure there's one there in the first place, or that's where the air leak could be coming from.
Fuel tank vent/overflow
From the diesel fill hose there should be a small hose that runs to the outside of the hull. People generally refer to this as the overflow. It really is the tank vent and allows air to escape as you fill the tank. If the hose has a droop in it and you filled the tank right to the top fuel could actually be sitting in this hose and preventing the tank from breathing and creating an ait lock. This will restrict the flow of fuel through the engine and will cause the engine to cut out and die. Check to see if anything is blocking this hose by blowing through it. This could cause the symptoms you have described.
From the diesel fill hose there should be a small hose that runs to the outside of the hull. People generally refer to this as the overflow. It really is the tank vent and allows air to escape as you fill the tank. If the hose has a droop in it and you filled the tank right to the top fuel could actually be sitting in this hose and preventing the tank from breathing and creating an ait lock. This will restrict the flow of fuel through the engine and will cause the engine to cut out and die. Check to see if anything is blocking this hose by blowing through it. This could cause the symptoms you have described.
air lock
That is a new one to think about when all else fails I suppose. However sence there is no fuel gauge, I often take the fill hose off
That is a new one to think about when all else fails I suppose. However sence there is no fuel gauge, I often take the fill hose off
Water/algee in fuel
Is there a chance that the fuel could be contaminated and algee is blocking the fuel pick up line in the tank ?
Is there a chance that the fuel could be contaminated and algee is blocking the fuel pick up line in the tank ?
Have just had the same problem
I am a new owner of a 1984 34 foot hunter with the same engine. Three weeks ago I had to be towed in because engine would not start after close check of the lines the line from the primary filter to the pump was lose at the pump. That was where the air was getting in. Solve the air inlet problem and all will be okay. I am also in Texas at Kemah Boardwalk My boat is the "III Sheets II The Wind" and sail every weekend weather permitting. Where is your port? Jerry
I am a new owner of a 1984 34 foot hunter with the same engine. Three weeks ago I had to be towed in because engine would not start after close check of the lines the line from the primary filter to the pump was lose at the pump. That was where the air was getting in. Solve the air inlet problem and all will be okay. I am also in Texas at Kemah Boardwalk My boat is the "III Sheets II The Wind" and sail every weekend weather permitting. Where is your port? Jerry
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