Geico266

Geico266

Well Known Member
Should the electric fuel pump be on or off? That is the question.

My normal hot start is open the fuel bypass, open throttle & mixture control, turn on pump for 45 seconds to push hot fuel into left tank.
Turn off fuel pump, set throttle to half, mixture to cut off.
Crank til she pops then open mixture, close down throttle to idle.

Another forum talking about the procedure to hot start a FI Aztec said leave the fuel pump on... use the mixture control to shut the fuel off. They do not have the fuel bypass like AFP.
Open throttle 1/3rd and open the mixture full for 2 seconds, then close mixture.
Start till she pops and open mixture.

While both would work, it seems to me having the pump on and opening the mixture 2 seconds would add fuel to the cylinders faster than relying on the mechanical pump that is now heat soaked.

Any thoughts?
 
Your procedure is correct.. a few things to keep in mind:

Shut down of the AFP system should be with the purge valve.

When hot starting, wait till the engine fires then move the purge valve to "run".

A hot engine will be flooded with fuel from the spyder and lines draining into the cylinders after shutdown, always treat a hot engine re-start as flooded.

If you add more fuel to this by running the pump with the purge valve closed, you will just agravate the situation. The FM200 is not like the Bendix, with the mixture in idle cut-off some fuel will still get by and will flood the motor with the pump running.
 
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Use purge valve

Another successful method to hot start is using the purge valve in the following manner:
Purge the system as you have described but now leave the boost pump
On, Set throttle, mixture rich, start cranking and close the purge valve
While you crank. The engine will start.
Just another way to do it but somehow the starting procedure with mixture. cut off is more widely used .
 
Purge, then.....

Mixture rich, throttle position suitable for 900~1000 RPM, purge valve in bypass position.

Start cranking. Let a few blades go by, then slowly ease the purge valve closed.
 
DanH said:
Purge, then.....

Mixture rich, throttle position suitable for 900~1000 RPM, purge valve in bypass position.

Start cranking. Let a few blades go by, then slowly ease the purge valve closed.
Click to expand...

Furl pump on or off? :confused:
 
N427EF said:
Another successful method to hot start is using the purge valve in the following manner:
Purge the system as you have described but now leave the boost pump
On, Set throttle, mixture rich, start cranking and close the purge valve
While you crank. The engine will start.
Just another way to do it but somehow the starting procedure with mixture. cut off is more widely used .
Click to expand...

My deal with purge valve is about the same and simple. First thing while strapping and getting ATIS, turn boost pump on and let it circulate fuel. When ready to start, hit the starter and push the purge valve in at the same time (fuel to divider). Engine goes VAROOM.

When the engine was cold, it gets 3-4 seconds of prime (purge valve in) after circulate, hit the starter and purge valve in at the same time. It works quite well.

Boost pump stays on until after take off except for a check to make sure the engine pump was working. Always shut down with purge valve. I like it, it's a much cleaner, quicker shut down than pulling the mixture.
 
From Don...

5-5. The following instructions are recommended procedures for operating engines with engine driven fuel pumps.

COLD STARTS
* Purge valve off (?ICO? position).
* Mixture control "FULL RICH".
* Throttle open ? or more.
* Turn on boost pump. Run for 30-45 seconds
* Put purge valve to run (?R? position), count to five then return purge valve to off position. Actual prime time may be different from installation to installation. If the engine tends to flood, reduce the throttle to off idle then prime the engine.
* Reduce throttle to 1/8 or off idle.
* Leave the Mixture control in the full rich position.
* With mags "HOT?, crank engine, when engine fires, put the purge valve in the run position and the throttle to idle. After the engine stablizes idle, the boost pump can be shut off.

ENGINE SHUT DOWN
* Bring engine to idle speed.
* Leave mixture control "FULL RICH".
* Turn boost pump off.
* Put purge valve control to "OFF" position.
* Turn off the ignition.

HOT STARTS
* Mixture control "FULL RICH".
* Throttle ? to wide open.
* Purge valve "OFF" position.
* Turn on boost pump and let run 30 to 45 seconds. This will purge the hot fuel and vapor from the system, and will cool and fill the fuel system components with cool fuel.
* Leave the boost pump on.
* Set Throttle to 1/8 open.
* Give engine a short prime by putting the purge valve to ?run? then back to ?off?. The amount of prime required my vary from installation to installation.
* Leave Mixture control "Full Rich?.
* With mags "HOT?, crank engine, when engine fires, return throttle to idle and purge valve to ?Run".
* Leave the boost pump on during hot, low power, operation.

Another method for starting the engine when hot is to leave the mixture ?rich? after purging the system. With the purge valve in the ICO position and the throttle at idle, crank the engine while slowly moving the purge valve to the Rich position. The engine will start during this movement to the Rich position.
 
HOT STARTS
* Mixture control "FULL RICH".
* Throttle ½ to wide open.
* Purge valve "OFF" position.
* Turn on boost pump and let run 30 to 45 seconds. This will purge the hot fuel and vapor from the system, and will cool and fill the fuel system components with cool fuel.
* Leave the boost pump on.
* Set Throttle to 1/8 open.
* Give engine a short prime by putting the purge valve to “run” then back to “off”. The amount of prime required my vary from installation to installation.
* Leave Mixture control "Full Rich”.
* With mags "HOT”, crank engine, when engine fires, return throttle to idle and purge valve to “Run".
* Leave the boost pump on during hot, low power, operation.
Click to expand...

That is exactly the procedure used on our company RV6 except the bit about using the purge valve (bolded). The 360 engine has Airflow Performance fuel injection, but has had the purge valve removed. I have similar on my RV7 and have also removed the purge valve. We dont have any problems with hot starts and it it can get very hot here. For instance its 44C here today :)
 
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The "New" hot start procedure works great. Leaving the boost pump on and closing the bypass valve just makes more sense, and the engine starts much faster with a lot less cranking.

It was 15F when I tried it so not sure that qualifies as a "hot start" . ;)
 
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I have the AFP system on my rocket and have installed the same on some others as well. I do not have a purge valve installed and the engine starts just fine, for hundreds of starts.
Cold starts as normal
Hot starts, mixture on, 2 to 3 sec of prime, throttle 1/4, mixture full lean, crank to start.
After it fires I usually just move the mixture half way, a taxi setting, and throttle as required.
 
Fuel that is vaporized will turn back into liquid when pressurized. So it makes sense to always have the boost pump on when starting.
 
rocketbob said:
So it makes sense to always have the boost pump on when starting.
Click to expand...

On the other hand, having extra loads turned on during start only serves to tax your electrical system with another load that is not required, pumps & lights are typically heavy current users so its generally best to turn them off before start. IMO

When starting a hot (flooded) engine there is really no need for the boost pump to be running.
 
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I disagree, every airplane I fly with a boost pump I start with it on. Never have had problems doing this.
 
In the past, I always started with the Fuel Pump "on" (both cold and hot starts) ... and it was always a bear to get it started if the engine was hot. One day I forgot to turn the Fuel Pump "on" and it started right up on the second or third blade. I now always start with the Fuel Pump "off" (cold and hot). Each airplane/engine/fuel delivery system is slightly different. If you're having trouble with hot starts, try a different method and see how it works - you might surprise yourself and discover an easier way to get the beast started : )
 
I had quite a bit of difficulty with hot starts my first summer. Then I realized I wasn't really following AFP recommended hot start procedure. Once I carefully read it, and actually followed it, I didn't have any more problems.

But I am curious now...will try turning off the pump and see if that makes a difference.
 
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In the 172 with IO360 (Bendix injection), hot starts are a non-issue (again - each engine is different, this works for me)

Quite simple - no boost pump, no prime, mixture ICO, throttle wide open, crank 2 seconds and the engine will cough. On first cough, shove the mixture full rich and pull the throttle closed, you'll catch it right at 800 rpm like a charm.

Can't wait to crank my IO360 in the 9A for the first time to compare notes!
 
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