77 Johnson 115 rich on WOT. Needles?

[mudweiser]

I'm etting a 77 johnson 115 v-4 up and running on a 1977 Ranger 1750. The ignition system has been checked and necessary repairs made. It's timed and syncd properly. Carbs were rebuild last season along with the fuel pump. The engine cranks right up but does show some fouling at idle. If i flip the warm up lever, the RPM slowly climb and clean out the engine. When i mash the throttle, the engine pulls but hessitates, sounds like a miss. I verfied it's not missing due to ignition. Keep the throttle pinned and the engine cleans out pulling about 5,000-5,500 RPM's. You can hear it surging a bit, ok surging alot when running at WOT. If i squeze the primer at WOT, the bulb is hard and squeezing more does not change things at all. If i hit the choke for a split second, it falls on it's face. spark Plugs do show a rich condition. Compression is good and engine has been decarboned. The longer i run it, the better it gets. It does use a ton of fuel which you can smell and see on the fuel gauge. However the problem retruns when i let off the throttle. If the engine sits shut off while i'm fishing, i can hit the key, mash the throttle as soon as it starts and it's fine (pulls RPM's right away but still surges) when i let off and hit it again the problem returns. The fuel pump was just removed and cleaned the other day, everything looked fine, it was rebuilt last season. I moved back to the carbs, removed them, checked to see that all the jets were correct for the engine. The carbs were cleaned, jets removed and cleaned. Floats are plastic and were set so they are level / parallel with the carb body. Needles and seat were new last season and look to be in good condition. Once assmebled, i flip the carbs upside down and using a vacuum tester i can pump it to 10 psi and the gauge drops fast. Are the needles leaking? With the carbs back on and hooked up, i can prime the fuel system and if i keep squeezing the primer bulb i can flood the carbs and get fuel to flow out the venturi. Guessing bad needles, bad floats? Needles are cheap money (Sierra) so i'm going to replace again with Sierra. How do i know the floats are good?

 

[mudweiser]

Re: 77 Johnson 115 rich on WOT. Needles?

Ordered floats and inlet needle and seats. Hate to trouble shoot with parts, but i'm out of ideas with this motor.

 

[ezeke]

Re: 77 Johnson 115 rich on WOT. Needles?

Why pull a vacuum on a float valve?

If you can flood the carburetors with the primer bulb, your float valves are not closing, but they stop fuel flow when the float is up so you need a pressure test.

Testing a float is a matter of function. I suppose you could weigh them.

 

[mudweiser]

Re: 77 Johnson 115 rich on WOT. Needles?

no, i was trying to test the needles with vacuum. Is that the correct way to test them?

 

[CharlieB]

Re: 77 Johnson 115 rich on WOT. Needles?

I'm assuming that your pump like mine is both a press/vac and that when you said 10 PSSI you meant 10 PSI and NOT 10 inchs vac. Right?

You're on the right path, carbs should NOT flood using the primer bulb unless you're the 'Hulk' and seriously over pressuring the fuel line.

Also check the crankcase hose to the fuel pump, is it wet or dry inside? Wet indicates a pinhole in the diaphragm leaking excess fuel into that cylinder fouling that plug and making the engine very sluggish until you rev and get it cleaned out. It will get worse and take out the rings in that hole if left very long.

 

[mudweiser]

Re: 77 Johnson 115 rich on WOT. Needles?

I'm assuming that your pump like mine is both a press/vac and that when you said 10 PSSI you meant 10 PSI and NOT 10 inchs vac. Right?

You're on the right path, carbs should NOT flood using the primer bulb unless you're the 'Hulk' and seriously over pressuring the fuel line.

Also check the crankcase hose to the fuel pump, is it wet or dry inside? Wet indicates a pinhole in the diaphragm leaking excess fuel into that cylinder fouling that plug and making the engine very sluggish until you rev and get it cleaned out. It will get worse and take out the rings in that hole if left very long.

Correct, it's 10 inch vac. The fuel pump bolts directly to the block, so there is no pulse connection that is made with a hose. Too bad, that would be a little bit easier. I'm just going to have to wait to test until Tuesday when the needles and floats arrive. I'll post results. Thanks.

 

[ezeke]

Re: 77 Johnson 115 rich on WOT. Needles?

A lift type fuel pump is only a few pounds of pressure at most. The float valve rises with the float arm until the float valve needle closes off the incoming fuel so that you don't flood the carburetors.

The needle doesn't drop and open until the engine pulls some of the fuel out of the float bowl.

You test the valve's functionality with pressure. If the pump is upside down, you can blow in the hose and tell if it is closing the valve or not.

 

[mudweiser]

Re: 77 Johnson 115 rich on WOT. Needles?

Got the needles put in today and ran the boat. Still no improvement. It does run a little better, but i still have the same problem. Could the fuel pump be dumping fuel in the pulse end of the fuel pump?

 

[mudweiser]

Re: 77 Johnson 115 rich on WOT. Needles?

Found out today it was not fuel related. Brought a timing light with and cylinders 1 and 3 are both miss-firing, sometimes not firing at all. Looks like im back at ignition issues.