# Losing Prime



## GatorBait

Greetings my friends I'm looking for a little help with my outboard. I purchases my boat back two years ago. After realizing I had a scorn cylinder and picking up another engine I realized an issue I have going on. My primer bulb seems to prime well but at idle it will lose prime. I replaced my primer bulb with a quick silver hoping it would correct the issue but no luck. I can run the boat and never have any issue until I idle down. At that point I will lose prime almost to where there is no gas at all in my bulb. Once I hear the engine start to sputter if I run back and prime it up I can keep it idling. Again under load I an fine. My primer bulb is a 3/8 and so are my lines that I replaced last year. Does this sound like a fuel pump issue or fittings or what?? I have looked over my lines and see no gas leaks where air could be getting in but I know air has to be. My primer ball is located right before my fuel separator by my engine arrow to the sky. just don't know at the moment if it's something simple like fuel pump, fittings etc or if I need a good carb cleaning if it might be carbs. I have a 1987 Suzuki DT75. I also have a 27 gallon plastic moeller fuel tank i put in last year. I have noticed the fitting piece that has the tube that drops down into my tank spins freely around. Enough to get my attention and question. I don't know if it is supposed to spin or not kind of makes sense so you can spin it to the direction of your gas line for connection. I just heard too much air flow in your tank could be bad. Any and all help is appreciated. Thanks, Jason


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## FishWalton

Recently I had a similar problem with a 25 hp Yamaha. It turned out to be the connector on the plastic gas tank was loose so the line was sucking air. The fuel system apparently doesn't like air. The loose connected was repaired so it did not move around and the problem was solved.


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## GatorBait

Thanks fishwalton. I guess I'll go over my fittings once more and if I can't solve it that way I guess I'll have to pick up a small tank somewhere and see if I can't rule out the tank issue then on to the fuel pump etc. Thanks for the help!


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## sealark

Do you have the primer bulb in a vertical position with the arrow pointing up? That's the way it should be so the weight of the fuel is pushing down on the check ball. :thumbup:


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## GatorBait

Thanks for the reply sealark, yes my arrow is pointing vertical toward the sky.


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## jross31455

I would try to use a spare tank to see if that will work and it will elimnate your main tank. If you still are having problems I would get a could carb cleaning done on it.


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## lastcast

Probably not a whole lot of help but, if the bulb looses prime and isn't sucked flat, doesn't that usually mean the air leak is below the bulb?


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## Ocean Master

There is an air leak between the tank and engine.


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## Murphy's Law

Ocean Master said:


> There is an air leak between the tank and engine.


+1 If you can reprime it and it runs fine I'd rule out the carbs. As ocean master said your sucking air. Get some new fuel line and replace.

Sent from my HTC EVO 4G using Forum Runner


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## The Maintenance Shoppe

I leaking fitting anywhere in the fuel system between the tank and fuel pump will cause this. Also if the fuel pump check valves aren't perfectly sealing can cause this as well.


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## GatorBait

Thanks for all the info. I cut back my fuel lines and re clamped my hoses today. I really don't think it's my carbs about 5 minutes worth of idling it starts sputtering out. It runs like a charm under load. If I prime it right back up it don't miss a beat for another 5 minutes of idling. I did here some sort of sucking air noise at my gas tank fittings today. I ran to Wallyworld today to pick up new fittings but they were out of the omc line fitting so I could only get the tank fitting. Replaced it and it still made the slurping noise. I think it may be my line fitting that connects to my tank fitting it looks to have a lot of age. Never fails when you need something you can't find it and any other day they would have two pegs of stock just my luck


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## The Maintenance Shoppe

Forget using those quick connect fittings, for diagnosis purposes install a hose barb and connect fuel line to it. If that doesn't fix it and all of your fittings are secure, Then I would be checking to see if air bubbles are present in the fuel coming out of the fuel pump. If bubbles are present then replace the pump. I pump can make an engine run fine and still create air in fuel system.


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## GatorBait

Before spending more money I did in fact pull my fuel pump apart and take a look at it. The diaphragms look very good with no signs of wear. Also the two little plastic circle pieces whatever they are called looked great as well. No signs of cracks whatsoever. The one who I purchased the engine from said before it was set up in the garage that the fuel pump was rebuilt and carbs cleaned out. After taking his word I now do strongly believe him. I have another spare fuel pump I took off of my spare 95 model and compared the two because I freshly rebuilt that pump before realizing the major issue of that engine. It was as in as good of shape as that fuel pump. From the carbs down to the tank all fittings are tight with no signs of leakage. I did however prime it back up once I put the pump back on since when I pulled the pump off initially there was no gas in the fuel pump or in the lines. It drained all back out over the last day or so. While priming I still heard the sucking type air noise at my tank fittings. Does this sound like the line fitting that connects to my tank fitting? I would do as you advised Mechanic Shop and go straight in and bypass the fittings whatsoever but I replaced my original tank with a aftermarket on my Boston whaler and the gas cap is located more towards the middle of the tank and now I have to unhook my gas line and slide my tank out from under my seat a little bit to get to the gas cap to fill up.


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## GatorBait

Update, I replaced the fuel hose fitting to my gas tank. No more air sucking noise at the tank and it primed up nice and firm quick. Usually it takes 20 or so squeezes this time it took about 5 and then a few extra to make sure. I may have over primed because I could not get it to start which is very unusual. Usually when cold it fires right off. Does this sound like I have flooded it which I think? I don't know much about vapor lock just curious if I got too much air in the system when I pulled the fuel pump off. Thanks, Jason


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## FishWalton

It's possible to over pump I suppose but I never have. I just pump until firm, maybe 4 or 5 times, then maybe one more and that's it
. If you think it is flooded cut the throttle back to zero and don't choke, let it sit a while, maybe 5 minutes, Then crank it several good times and that should clear the flood. It might even attempt to start with everything cut back. If that doesn't work pull the plugs and crank a few times to blow out the cylinders. 

That's what I would do with an older motor that did flood now and then. Not sure if this will work with modern motors or not but worth a try. 

Glad you found a simple fix with the gas tank connector. That's where my air leak problem was with just a loose fiting.


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## FishWalton

Clarification: When you try to start leave the throttle and choke in the off or zero position. Then after hitting the start a few times put throttle into normal position and start. If it's normal to choke try that but not until you see if it starts without choke. 

If all this does not work pull the plugs and blow out the cylinders.


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## GatorBait

Ok here's the new dilemma.... Apparently is wasn't flooded. It's priming up hard and quick but I'm having to squeeze the he'll out of the primer bulb more after it's already hard until my forearms feel like popeye to get enough gas in my carbs to crank it. When I thought it was flooded it wasn't I just didn't have enough gas in my carbs yet. I dropped it in the bay today got it running and took off got about 300 yards and made a u-turn back for the docks. It never got full power when I pushed it to full throttle. It was bogging down, got back to the docks and it died once I put it in neutral. Played with for about an hour and it doesn't want to start unless I prime it up hard then squeeze the life out of the primer until I physically can't do it anymore to get enough gas in then it idles fine until finally it loses prime. Any suggestions on this issue I'm having is greatly appreciated. Thanks, Jason


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