78 Johnson 15 HP Fuel Problem

[Tom6345]

78 Johnson 15 hp. So far I have rebuilt fuel pump,rebuilt carb,replaced fuel lines on engine,replaced primer bulb and fuel line connectors from tank,replaced gasket on gas tank.It will start but runs itself out of fuel.It does not seem to be able to draw fuel from the tank.Ive done everything but replaced the fuel tank.Any suggestions would be appreciated. Thanks Tom

 

[corm]

Re: 78 Johnson 15 HP Fuel Problem

Hi Tom,<br />Will the motor stay running if you keep pumping the primer bulb?<br />corm

 

[Tom6345]

Re: 78 Johnson 15 HP Fuel Problem

Yes,I can keep it running by squeezing the primer bulb or if I elevate the fuel tank so it is higher than the motor it runs fine.

 

[corm]

Re: 78 Johnson 15 HP Fuel Problem

Hi Tom,<br />If the gasket between the block and pump is on correct and sealing good, and the hose between the pump and gas connector is on tight it leaves two choices. 1st,are the gas hose connectors made by OMC so they fit tight.(the rubber o-ring around the male connector. 2nd,and most likely the dreaded fuel pump is drawing air or is just plain bad<br />needing to be replaced.Asumming it was put together in the correct order and position.<br />Hope this helps.<br />...have fun...corm

 

[Tom6345]

Re: 78 Johnson 15 HP Fuel Problem

Hi corm.The gas hose connectors are new but they are not OMC brand.They are the same brand that I used to replace the gas line connectors 2 years ago,which worked good until now.As for the fuel pump,It should be right,I put it together the same as it came apart.One interesting note,Ive been consulting an OMC repair manual,and they say there are no servicable parts on the fuel pump.The complete pump should be replaced.But I bought the rebuild kit from the local authorized OMC dealer.Figure that one out.Well Ill keep trying to figure it out. Tom

 

[corm]

Re: 78 Johnson 15 HP Fuel Problem

The manual is right.I have seen kits for some<br />but the small square one we only sell as a<br />unit. Beats me, good luck.<br />...corm...

 

[Tom6345]

Re: 78 Johnson 15 HP Fuel Problem

Took the motor to an authorized repair shop today.He figured there was an air leak somewhere in the fuel line.He retightened all fuel lines and took the fuel pump apart and looked at it.He thought the outlet should be facing towards the bottom.Put it back on and it didnt work.Its has him stumped too.

 

[Capt DHD]

Re: 78 Johnson 15 HP Fuel Problem

Tom:<br />Has your dealer put a vacuume gauge on this engine yet. This test should be able to narrow your problem. With what I have read here, Two things, <br />1) Try a new fuel pump.<br />2) is there a restriction in your pulse line, the vac***e test will show this. You should develop aprox 1 Lb of vac***e at idle, 2.5-4 LBs at mid to upper rpm's.<br />Good luck, Rob.QUOTE]Originally posted by Tom:<br />78 Johnson 15 hp. So far I have rebuilt fuel pump,rebuilt carb,replaced fuel lines on engine,replaced primer bulb and fuel line connectors from tank,replaced gasket on gas tank.It will start but runs itself out of fuel.It does not seem to be able to draw fuel from the tank.Ive done everything but replaced the fuel tank.Any suggestions would be appreciated. Thanks Tom[/quote]

 

[Tom6345]

Re: 78 Johnson 15 HP Fuel Problem

Were up and running.They put a new complete fuel pump on.They still do not understand why it would not run with the rebuilt pump,since they rebuild them all the time.Thank you for all your suggestions and help.Im going fishing. Tom

 

[gregs]

Re: 78 Johnson 15 HP Fuel Problem

dont know if you will read this. was it difficult to rebuild you carb. i think yours is similar to mine. did the instructions come with the kit. i think my s/s valve has been damaged i'v been told about thirty turns and it will come out. did it come with a new float.

 

[biloxi]

Re: 78 Johnson 15 HP Fuel Problem

I HAVE THE ANSWER for your fuel delivery problem. Past experience has taught me that your fuel tank/cell must have an air vent and this vent must be open during times of the engine running. Otherwise the vacuum created in the gas tank from the fuel pump sucking fuel will put to great of a strain on the pump and it can no longer pick up fuel. Basically think of this situation as putting gas in your car from a gas can. When you tip the can to empty the gas it pour fine for the first couple of seconds and then slows to a small trickle (assuming the vent is closed). Now as the gas flow slows down, open the vent and watch how the fuel dumps out of the can! Be sure that your tank has an open vent hole. Hope this helps!!

 

[biloxi]

Re: 78 Johnson 15 HP Fuel Problem

I HAVE THE ANSWER for your fuel delivery problem. Past experience has taught me that your fuel tank/cell must have an air vent and this vent must be open during times of the engine running. Otherwise the vacuum created in the gas tank from the fuel pump sucking fuel will put to great of a strain on the pump and it can no longer pick up fuel. Basically think of this situation as putting gas in your car from a gas can. When you tip the can to empty the gas it pour fine for the first couple of seconds and then slows to a small trickle (assuming the vent is closed). Now as the gas flow slows down, open the vent and watch how the fuel dumps out of the can! Be sure that your tank has an open vent hole. Hope this helps!!

 

[rudeafrican]

Re: 78 Johnson 15 HP Fuel Problem

Hi Biloxi,<br /><br />Although I am greatful that you are willing and keen to offer suggestions and advice freely, the original problem was posted 3 years ago and the original poster told us that he had fixed the problem. Unfortunately the board carries such heavy traffic that bringing up old posts like this one, only clogs it further.<br /><br />Please take this as a friendly pointer and not as an attack.<br /><br />Regards<br /><br />John<br />

 

[rsmitty]

Re: 78 Johnson 15 HP Fuel Problem

I too have a 15 hp Johnson outboard that I recently bought. It scoots across the lake fine but when I try to troll I have to pump the bulb every few minutes or it dies. I have changed the tank and the line with no success. How much was the new carb.<br /> rsmitty