Shutter and power loss on interstate (W115)

[skis3]

When I am driving my 220 down the interstate at 55-60mph the engine runs smooth and has no problems. However, when I increase the speed to 65mph the engine begins to shutter and loses power after around a minute at 65. Slowing back to 55mph makes the problem go away.

History: After rebuilding the carburetor and installing a new fuel pump, I installed inline fuel filters before and after the fuel pump to protect them from any particles fuel tank particles.

My hypothesis is that I am running the bowl dry due to the inline fuel filters causing restricted fuel flow. Has anyone else had this problem? Opinions are welcome.

Thanks, Bob

[daidnik]

I've never seen a filter used before the fuel pump and those Pierburg pumps last an awful long time; on the order of 20 years without any pre-filter.

The best test of the fuel starvation syndrome you theorize is a hard sustained acceleration, like hitting the freeway onramp and accelerating toward 80 mph. If the float bowl is going dry, the gasping for fuel will happen every time without fail.

You say you rebuilt the carb (a Stromberg I presume). Did you check the float adjustment? It is possible the fuel level in the float bowl is low due to the float valve shutoff being set at too low a level and this would aggravate the fuel starvation syndrome.

But first do the hard acceleration test a few times to get a clear 'feel' for the problem, then get rid of the pre-filter and repeat the test to see if it makes a difference.

Now I assume that the fuel filters are new. If not, that would be the first thing to change. They are cheap and generic.

[skis3]

Your test was perfect. She began to stutter and tried to stall. I removed the prefilter, which was nearly plugged, and now it runs great. Thanks for the advice. Bob

[carnut]

Now remove the fuel tank and clean it!

[skis3]

Good idea. I think I should have used the POR 15 the first time I cleaned it, but I was being lazy. Thanks.