Front fuel issue

[rmorris]

Interesting issue just started happening, and was wondering if anyone else has seen something similar. Looking for either actual experience, or suggestions based on theory (but please denote which one applies when responding).

Normal start on mr front engine is to engage hi boost pump, wait 7 seconds, engage starter, and after the engine fires off remove the boost pump.

Last few flights it has worked ok for starting, but when I remove the boost pump it dies. I played with some combinations and it now stays 'alive' if I leave in the low boost pump.

Once the engine is warmed up, I can remove the low boost pump and it seems to be fine.

-Robert Morris
rmorris@agsi.us
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[Ernie Martin]

Sounds like a problem I had and fixed. But before I cover that, let me raise another point.

My starting procedure, per the book, is different from yours. I don't know for Turbos or other years, but the procedure for my two 337s (a '69 and a '73) differs in two ways. First, I don't wait 7 seconds and instead I wait until it reaches max flow on the guage and then go 1 more second, but second and far more important is that I turn off the boost pump before engaging the starter. This second point goes along with one step you probably do but didn't mention, which is to bring the throttle down from full throttle to idle before engaging the starter (a step I do after turning off the boost pump).

Now to the problem. One day the rear engine started giving me trouble after it started, wanting to shut-off. Only by hitting the boost pump every few seconds, as the rpm were dropping on the way to shut-off, could I keep it running. After a few minutes (somewhere between 2 and 5) it would run OK without help from the boost pump. It turned out to be the fuel manifold/divider (P/N 631351..., often called the "spyder") which had a busted diaphragm and was leaking. As soon as we replaced that, the problem went away.

Ernie