Fuel issues 88 spl

[1986 Newport]

Need some help, Im out of ideas. I am having low fuel issue that can be seen by huge air pocket in fuel filter. Will run dry when taking off. I have put all new 3/8 lines from tank to primer bulb and new 5/16 all the way to the fuel pump, a new primer bulb, a new fuel pump and gasket. I also setup an aux tank and it still has the same issue. Compression is good, new spark plugs, and new elthanal free gas. No leaks on pressure side when running on the hose.

What is next? Do I need to run it on lake to be sure after all the new parts?

[Joe Reeves]

The picture is slightly too large to fit the screen but I did manage to fit it in, graphic & type. I see what you're talking about pertaining to the filter, however.........

This same identical scenario also pertains to the fuel primer bulb, and many boaters question it. Usually the primer bulb is laying horizontally somewhere on the deck or motor well (not so in your case, but still!), for this example I am using the horizontal mention.

It is a case that when you pump the fuel primer bulb up hard, it is completely full... BUT... as the engine runs, the fuel level drops down to the halfway mark due to some scientific code/rule/whatever. I asked a factory rep about that occurrence back around 1968 or so... the answer was "It's the nature of the beast" meaning I a$$ume that it is a normal happening and has no effect on the engine's performance.

I have noticed this effect on various fuel filters that are included in the manufacture of outboards etc with the primer bulb being hard and the engine NOT yet started.

Taking this into consideration, I can only a$$ume that the filters I have observed elsewhere... and yours as pictured above are subject to the same code/rule/whatever.

You have posted no engine performance problem so I a$$ume that your entry is a question to avoid wasted time more-so than anything else. We shall see.

Bottom line... next stop... the lake!

[1986 Newport]

Water test

So it ran great at the lake with 50% air in filter until I parked for an hour or so on an island. Did a one squeaze prime and started, went to takeoff and the filter went dry, happend once more at the next bridge I accelerated from. I plugged in my aux tank and it did the same thing. So I am able to stay on the water but still not good.....

[Joe Reeves]

Originally posted by 1986 Newport View Post

So it ran great at the lake with 50% air in filter until I parked for an hour or so on an island. Did a one squeaze prime and started, went to takeoff and the filter went dry, happend once more at the next bridge I accelerated from. I plugged in my aux tank and it did the same thing. So I am able to stay on the water but still not good.....

That proves that your setup has the engine running normally as long as it stays running... BUT... when you shut it down to fish, whatever, for some length of time... in all probability the fuel is siphoning backwards into the fuel tank. The following is taken from my database and best explains the issue.

********************
(Fuel Anti Siphon Valve)
(J. Reeves)

Many of the later OMC V/6 engines incorporate a fuel restriction warning via a vacuum device attached to the powerhead. If the engine overheats, or if you have a fuel restriction, the warning is the same.... a steady constant beep.

NOTE... Only the V/6 & V/8 engines have the above "Fuel Restriction Warning". The warning horn will not sound on the other models.

The fact that a engine is not overheating, but the warning horn sounds off with a constant steady beep, and that the rpms drop drastically would indicate that the engine is starving for fuel due to a fuel restriction. Check the built in fuel tank where the rubber fuel line attaches to the tank fitting. That fitting is in all probability a "Anti Siphon" valve which is notorious for sticking in a semi closed position. It will be aluminum, about 2" long, and the insides of it will consist of a spring, a ball, and a ball seat. If this valve exists, remove it, knock out those inner components which will convert it to a straight through fitting, then re-install it. Hopefully that cures the problem.

The above procedure will cure a restriction problem with the anti siphon valve as stated. BUT, it may also allow fuel to drain backwards to the fuel tank when the engine is not running (siphoning backwards) due to the fact that the carburetors/fuel pump etc are higher than the fuel tank. This condition is not an absolute as the valves in the fuel primer bulb usually prevent this backwards siphoning problem. However.... if this does take place, the cure would be to install a new anti siphon valve.

NOTE: There has been cases when the output valve in the fuel primer bulb would come apart, and the inner portion of the valve would actually reverse itself and be drawn back into the primer bulb's output valve body. This in effect would create a shut off valve and result in a fuel restriction. If this is the case, you should be able to feel something laying in the bottom of the primer bulb when held horizontally.
***************

Let us know what you find.

[1986 Newport]

Still hunting

So my primary tank (20 gallon plastic) has no antisiphon mechanism but my aux tank does. Pulled the siphon tube from main tank to be sure no cracks or lose tube. Because they both had this issue im still hunting. Anyway something on the presure side is able to do this? Niether tank has a vent but I tried main tank without cap on and that did not work.


How do I test the pump? Can I tee in a pressure gage? What pressure should I look for? I'm thinking my pump vaccum port ( engine side) might be restricted.

I have new quick disconnects on the fuel lines, any issues with male parts on engine cowl?

[Joe Reeves]

Originally posted by 1986 Newport View Post

Both tanks had this issue im still hunting. Anyway something on the presure side is able to do this? Niether tank has a vent but I tried main tank without cap on and that did not work.

How do I test the pump? Can I tee in a pressure gage? What pressure should I look for? I'm thinking my pump vaccum port ( engine side) might be restricted.

I have new quick disconnects on the fuel lines, any issues with male parts on engine cowl?

Quick disconnects create no issue unless there is an obvious leak which would cause the pump to draw air.

All tanks must have a vent... somewhere. If air can't get in, fuel can't get out.

I a$$ume that the "anti siphon valve" was indeed a valve and NOT just a clear fitting? Also a$$uming that you checked the Fuel Primer Bulb valves?

I'm not knowlwdgeable on testing the fuel pump but I do believe that other members, friends of mine on the Evinrude/Johnson forums at www.MarineEngine.com and www.iBoats.com could advise you on that.

[1986 Newport]

So the main tank had a vented gage cap but the gauge is broken and Im guessing the vent is rusted shut. Ill grab a vented cap and see if it improves.

[1986 Newport]

Fixed it!!!!!!!!!!!!!!!

So was not a vent issue, the quick disconnect was leaking air. Ran the fuel line through the unused oil line boss ( cowl is from a 90) and filter stayed full and no starvation on acceleration.

Either its the male part on the cowl or the two atwood disconnects I have both suck.