Have you Mastered the Hot Start of your big bore TCM
Do you dread refueling in the summer and then
having to get the engine started with everything in the engine bay heat soaked?
Well the thing that is really heat soaked that
is the cause of the difficulties is the engine driven fuel pump! Yup, that puppy
is really hot and guess what happens when it starts "pumping" the fuel? Yup, the
fuel gets massive hot and vaporizes and there you go cranking 'till your battery
is nearly dead. Been there - done that!
Here is a procedure adopted from Beech List
experts, that has worked for me 99% of the time:
1. Front of throttle lever to the second white line (above the letter
"T" in Baron, in Bonanzas about 1/4 throttle)
2. Mixture to ICO (Idle Cut Off)
3. Boost Pump to HIGH for 45 seconds or more. The
hotter it is outside the longer you should run the boost pump. Put your seat
belt on, get your frequencies out and stuff like that while the boost pump is
running. The first time you do this have
someone outside to be sure you are not throwing fuel out one of your vent lines.
Your fuel flow gauge should remain at zero or very close to zero. A climbing
pressure reading indicates that your mixture control cable or servo is not
completely shutting off the fuel flow. (If fuel spews out onto the ground, your fuel system is in need of service,
because the fuel servo is not remaining completely closed! Maybe you need to
TCM SB 01-1 and check for a seal leak in
your fuel pump? See additional details below)
4. Shut off Boost Pump
5. Mixture to Full Rich
6. Give a Boost Pump shot to bring fuel pressure up on the gage
7. Shut Boost Off and go to Mixture ICO
8. Crank engine
9. At first couple of "pops" move mixture to full rich in a smooth
medium speed motion
10. Release Starter as you get the mixture to Full Rich and the engine begins
to fire on it's own.
This works for me the first time on 99% of the hot starts that I have
encountered. If you get a balked start, that is, couple o pops and mixture to
full but no start, Boost again at full rich, then take mixture to ICO and crank
again at Step #8.
If one engine is just being a crank and you balk a second
time, go to the other engine (Bonanza drivers do not have this option, sorry)
and do the same thing, increasing Step #3 Boost to about a minute at ICO.
My personal preference is to have the alternator off
line until the engine starts, then bring that alternator on line.
If you are in ICO (Idle cut off) and 3-4 GPH is
showing on your FF Gauge, read these comments from
If you are seeing 3-4 GPH fuel flow with the mixture in ICO and the boost
pump on, the problem cannot possibly be with the engine-driven fuel pump (what
you're calling the injection pump, although that's not really correct
terminology) or with the flow divider valve (what you're calling the fuel
manifold). The problem can only be one place: in the fuel control unit. From
your description, it sounds like that is the only component in the system that
HASN'T been repaired!
The engine-driven fuel pump contains a bypass valve that allows fuel pressure
from the boost pump to go to the fuel control unit even if the engine-driven
pump fails completely. (If it didn't, you couldn't prime the engine.)
The fuel control unit contains two valves, one operated by the mixture control
and the other operated by the throttle. The mixture control valve is a
proportioning valve that determines how much of the fuel from the fuel pump goes
to the cylinders (via the flow divider valve), and how much is returned to the
fuel pump vapor tower (and then returned to the tank). If the mixture is
full-rich, 100% of the fuel goes to the flow divider and 0% is returned. If the
mixture is at ICO, very nearly 0% of the fuel goes to the flow divider and very
nearly 100% is returned.
The flow divider contains a valve that shuts off the fuel flow cleanly and
completely when the fuel pressure coming from the fuel control unit drops below
a preset threshold (either 2.5 PSI or 4.5 PSI depending on the part number of
the flow divider). So even if the fuel control unit doesn't totally shut off the
fuel flow at ICO, fuel flow stops as long as the fuel control unit mixture valve
reduces pressure below the flow divider cutoff threshold.
It sure sounds to me like the fuel control unit mixture control valve is not
shutting off the flow properly. If you were seeing just 1 GPH or so at ICO, then
I'd believe that the mixture control valve was good enough and that the fault
was in the flow divider. But if you're seeing 3-4 GPH at ICO, then that's almost
certainly above the flow divider cutoff threshold so the fault has to be with
the fuel control unit.
The fuel control unit should pass almost no fuel to the flow divider if the
mixture valve is at ICO and the throttle valve is at the idle stop (closed).
Obviously, yours is passing lots of fuel. I'd be astonished if that's not where
the fault lies here.