injected non turbo Arrow hard to start, please help

jasper7821

In need of assistance please,
for the last month or so my 1976 Lycoming 200hp Arrow has been hard to start and I'm not sure if this means anything or not.
When following the starting procedure, I open the throttle 1/2", turn the fuel pump on for a few seconds and I see the GPH needle move up to about 4-5gph and then I ritchen the mixture for a few seconds and when I go to idle cutoff the GPH needle moves back to zero. If I remember correctly, I thought it stayed at 4-5gph when I closed the mixture.
Anyways, with the mixture rich and pump on, I got out and fuel was coming out of the copper drain or whatever it is on the bottom of the motor. IS THIS NORMAL?
With idle cutoff, no fuel leaks, only with the mixture rich.
I'm confused, can someone please tell me if this is normal or not. Also any suggestions what is wrong if anything

flyguydon

It should not leak fuel unless over primed.

COLD: Throttle up half an inch. Fuel pump on. Mixture up to full rich until GPH shows flow for 5 seconds then idle cut off. Crank. At first sign of ignition go full rich.

HOT: Throttle up half an inch. Fuel pump on. Mixture at idle cut off. Crank. At first sign of ignition go full rich. If you do not get any ignition after a few seconds, go about halfway up on the mixture for a brief moment while continuing to crank. Go full rich at first sign of ignition.

jasper7821

Thanks,
Should the GPH needle go to zero when moving the mixture back to idle cutoff before starting the motor/

Big Dog

jasper7821 wrote:

Anyways, with the mixture rich and pump on, I got out and fuel was coming out of the copper drain or whatever it is on the bottom of the motor. IS THIS NORMAL?

Yes, completely normal. This is how it should work.

It sounds like you are doing everything correctly. It's a matter of priming enough. That is a question of how long you leave the mixture rich before bringing it back to idle. With summer temps, five seconds should be good. It could be as long as 10-15 seconds in cold weather. The fuel pump must be on the entire time during the start, until the engine is running smoothly. Should you see gas coming out stop priming, it is overprimed and the flooded start should be used.

jasper7821

Thanks,
So if I'm understanding this correctly, when coming in for landing with the fuel pump on and low RPM, does that mean that fuel would be leaking out of the copper drain tube on the bottom of the motor?

Big Dog

Negative, it will not. The Bendix fuel "injector is based on the principle of differential pressure, which balances air pressure against fuel pressure. The regualted fuel pressure established by the servo valve when applied across a fuel control (jetting system) makes the fuel flow proportional to airflow." (From the POH) This all happens just fine while the engine is running. This is also why the starting procedure is written as is. You must have fuel pressure for the system to operate properly. The electric fuel pump must be on during cold and hot starts, until the engine driven pump can supply enough fuel pressure to keep the system running. Once the engine is running and airflow (which is why it may run rough for the first 4 seconds or so) is established, the servo does it's thing and sends the proper amount of fuel to the cylinders based on airflow (throttle position). I'm also pretty sure in that engine that pressure from combustion closes the valve (or valves) that allow the fuel to drain out, although I'd have to look at the engine to be sure.

jasper7821

WOW, great details. Thanks you very much.
I just though that the GPH gauge stayed at 4-5 GPH when I moved the mixture to idle cutoff before start up. But I must have been wrong.
So I guess it's totally normal to go back to zero when moving the mixture to idle cutoff with the pump still on before start up.
Thanks again for the help, I really appreciate it.

Big Dog

Correct.

If you are still having trouble, vary the priming time. Try 7 seconds. If that isn't doing it, try 3. Most people will tend to underprime in fear of overpriming. Start counting not when you put the mixture rich, but from when you first see the fuel flow gauge increase. You must get a fuel flow reading on the gauge for the engine to actually prime. If your fuel flow doesn't come up after a few seconds with the pump on and mixture full rich, open the throttle a bit more until the full flow increases, then reduce the throttle to 4-5 gph. Make sure to quickly go full rich at the first cough of ignition. And keep the electric fuel pump on until the engine is running smoothing. Watch the fuel pressure and fuel flow when you turn it off,it should not change much. This is a good check that the engine driven pump and fuel servo are working properly.

Let us know how it goes...

jasper7821

Awesome,
that's the exact directions I was looking for. Thank you very much.
It usually only takes a second or so til I see the GPH needle move. I'll start it after work today and see if everything goes ok. And see if after shutdown, the needle still registers for a few.
Thanks Again

Big Dog

Fuel flow or fuel pressure shouldn't change much after you turn the electric fuel pump off with the engine running, as opposed to shutting down the engine. Shutting down the engine should make everything go to zero within a few seconds.

jasper7821

WOW,
I don't know what's been wrong the last month but I just went out to the plane on my lunch break and it started right up. I think I may have been possibly not giving it enough throttle while cranking. maybe 1/2" isnt enough on my plane. I had it about an inch open and it fired up within a few seconds.
The GPH needle stayed at 4GPH when I turned off the pump and at 1000rpm's. And when shutting down the needle went back to zero.
Thanks again everyone, I guess it was pilot error all along.

Big Dog

Good Deal!