Fuel Flow at Start

[Kent Gillen]

On my 1967 260B I used to be able to start the engine cold with about 4 seconds of running the mixture in with the fuel pump on then mixture off and cranking. Start usually happened quickly. Now it won't start with out running the mixture all the way in and cranking with the mixture full rich. When checking the pressure of the electric fuel pump on a guage we are showing about 10 PSI. The fuel flow (pressure) gauge on the dash shows zero even after the engine starts until around 15 inches of MP.

Should there be fuel pressure indications with the electric pump on in the cockpit? Any other suggestions where to look? Pump seems to be running but not sure if output is enough.

[N3322G]

Kent,

I see this is your first post on this Forum. Welcome.

Does the fuel pressure always increase when the electric fuel pump is turned on?

My IO230 in the twin had a similar set of symptoms awhile back - for me, the fix was overhauling the electric fuel pump. Since the electric fuel pump is a big safety feature, we got it fixed right away. It has saved us an engine out more than once.

I have to say the lack of fuel pressure after starting makes me think the engine driven fuel pump may also need attention. The engines on the twin, even at idle show some fuel pressure on the Shadin fuel fuel gauge - I haven't had this circumstance so that is just speculation on my part.

Hopefully others will chime in because I'm a learn-by-checkbook owner as opposed to a trained mechanic.

[Kent Gillen]

I don't get any pressure on the FF gauge with or without the pump. We put a pressure gauge on the output side of the electric pump and read 20 psi. We put the same gauge in line while the engine was idleing and read 4 psi. The electric pump did not make any increase in pressure on either the in-line gauge or the FF gauge in the cockpit.

[N3322G]

Kent, our fuel pumps always make a difference in fuel flow ... I take this as another finger pointing at the fuel pump - operating under the assumption that yours used to make a difference in fuel flow

[Kent Gillen]

After starting at the electric pump with good pressure and then the motor driven pump with good pressure, we disconnect the injector nozzles and flow was good. Then we checked the vent lines and found the motor driven pump line was clogged with mud dobber stuff. Blew out the line and now have 11 p/hr on the gauge for start. Could this also be the reason for rough running at altitude do to pressure difference in the motor driven pump?

[9089P]

Hi Kent,

I have a 260B as well. Any idea how the contamination got into what I assume is a closed system?

Thanks, Don

[Kent Gillen]

Hey Don, it is the engine pump cavity vent that has a line run out the belly about parallel the wing leading edge.

That did not fix my problem. Reconnected all the lines and back to no pressure on the FF gauge. Showing 20 psi out all the way to divider. With #2 line off and blocked closed we get 13 gph on gauge with electric pump and mixture rich. No pressure on gauge with it unplugged. Anyone have any ideas?

[Kent Gillen]

Just had my FF overhauled by Air Parts because of fuel inside the bellows. Hope this fixes the "no flow at start" problem.

[N3322G]

Kent, hope it does too - please post on result so we can all learn. Thanks.

[Kent Gillen]

Sent FF indicator off to Air Parts and they found fuel leaking through the bellows in the gauge. Back in and everything is running fine again. I don't know if that was my problem that caused rough runner but putting everything back together seemed to fix what ever the problem was.