1999 F100 Tapping Noise (top end?)...

Having a tapping noise, sounds like a stuck lifter. When first startup, something taps for about 5-10 secs then quits.

After running down lake, fish awhile, start engine, same tapping for about 5-10 sec then it quits.

Pulled the cowl, it sounds like it's coming from the top end. Am I on the right track.... Valve adjustment, stuck lifter??????

Which service manual would you recommend?

[boats.net]

Remove valve cover and check valve clearance.

sometimes the clicking comes from the fuel pumps.make sure the system is holding a prime.

Check valve clearances. The exhaust side seems a little tight. All of the exhaust clearances measured 0.011. The Yamaha manual says "0.013 +/- 0.001". Is this too tight, is it a bad thing?

It seems to tap at different times. It doesn't always start tapping when first started, maybe 5 sec after. Then will tap for different lengths of time. I tried decarbing the piston/valves through the spark plug hole, didn't help.

Somewhat sure the tap is comming from # 1 exhaust valves (steth-a-scope trick). I'm beginning to think its a weak valve spring. Any advice an this, the chances of a weak spring, how hard to change out?

[boats.net]

The valve may be sticking due to carbon.

[mokaction]

run a can of ring free.. or techcron..

Larry

After many, I mean many trial and errors, I found the problem. The simplest things are often overlooked.

If I squeeze the primer bulb every time before start up, the tap is gone. If I forget the bulb, the tap reappears.

Amazing how the simplest things seem to be the hardest to find?????????

[mokaction]

so it was the fuel pump ticking..