No fuel passing spider

[pazmanyflyer]

So I'm prepping for first engine start and working through the last of the fuel flow checks. When I have mixture rich, throttle 1\8 open and turn on the Boost pump I see 10 PSI on the Dynon and no fuel flow. Disconnected the supply line from the spider "in" port and try again and I then have FF of 2 gph and still 10 PSI pressure. Reconnected to spider and back to 0 and 0. Okay, next I disconnected the FI lines from the spider and tried again. Nothing. No flow through the spider. Fuel stops at the spider. I've read about the spring pressure needing to be passed before it opens. I think the 10 PSI I'm seeing is enough to do that. But fuel will not pass the spider on boost pump alone. So, am I missing something in the manual that says the servo provides addition pressure to the spider when starting? I'm new to FI and I'm scratching my head about this. I have an IO360M1B with Bendix servo and spider both overhauled by AFP. I sent an email to AFP and waiting for Don's response. Until then please educate me.

 

[rocketbob]

Pull the cap off the divider and carefully pull the diaphragm off the body of the divider. With a pair of pliers pull the plunger out by the cap screw. Not uncommon for them to get stuck after sitting for a prolonged period. Clean with carb cleaner and reassemble.

 

[Skysailor]

Try actual boost pump pressure

The boost pump for a fuel injected engine should be putting out over double that pressure. Mine runs at 26 PSI. Try running your actual boost pump to it. I do not think 10 PSI is enough to open the spider.

 

[rleffler]

As Mark said, you should have quite a bit more pressure. Have you tested fuel flow from your tanks yet? What was the measurement coming out of your electric pump? Just validating that you don’t have any construction debris in the line. It wasn’t clear how much testing you’ve down before troubleshooting the spider issue.

 

[lr172]

Pull the cap off the divider and carefully pull the diaphragm off the body of the divider. With a pair of pliers pull the plunger out by the cap screw. Not uncommon for them to get stuck after sitting for a prolonged period. Clean with carb cleaner and reassemble.

+1

follow this advice! The std spring needs 2 PSI at idle. The pressure you are reading (servo input) has nothing to do with the pressure coming out of the servo. Suspect there is an issue with your sender or picked the wrong one in the dynon configuration.

 

[rocketbob]

The boost pump for a fuel injected engine should be putting out over double that pressure. Mine runs at 26 PSI. Try running your actual boost pump to it. I do not think 10 PSI is enough to open the spider.

The fuel pressure in the metered fuel line and divider is typically less than 4 psi. 10psi should be able to get some fuel flowing but if your electric pump isnt putting out 25 psi something is wrong there. Blockage or electric pump not working.

 

[PaulvS]

Step back

Does it make any difference if you switch tanks?

See post #4 above, it could be something basic (no offence intended!)

 

[Avanza]

Fuel pressure sender

If the pressure sender is placed before the fuel servo it should read 20-25 psi.
If the pressure sender is placed after the fuel servo it should read 1-7 psi.
Check the RANGE of the pressure sender and compare with your G3X settings.

Good luck

 

[pazmanyflyer]

Issues resolved!

Pull the cap off the divider and carefully pull the diaphragm off the body of the divider. With a pair of pliers pull the plunger out by the cap screw. Not uncommon for them to get stuck after sitting for a prolonged period. Clean with carb cleaner and reassemble.

Thank you, Bob. I did as you advised and sure enough the diaphragm was gummed closed. It took me a minute to actually get it out. Once cleaned up it slides around and up/down smoothly. FF now shows 4.8 gph with the pump on.

The boost pump for a fuel injected engine should be putting out over double that pressure. Mine runs at 26 PSI. Try running your actual boost pump to it. I do not think 10 PSI is enough to open the spider.

As Mark said, you should have quite a bit more pressure. Have you tested fuel flow from your tanks yet? What was the measurement coming out of your electric pump? Just validating that you don’t have any construction debris in the line. It wasn’t clear how much testing you’ve down before troubleshooting the spider issue.

The fuel pressure in the metered fuel line and divider is typically less than 4 psi. 10psi should be able to get some fuel flowing but if your electric pump isn’t putting out 25 psi something is wrong there. Blockage or electric pump not working.

If the pressure sender is placed before the fuel servo it should read 20-25 psi. If the pressure sender is placed after the fuel servo it should read 1-7 psi. Check the RANGE of the pressure sender and compare with your G3X settings.
Good luck

+1
follow this advice! The std spring needs 2 PSI at idle. The pressure you are reading (servo input) has nothing to do with the pressure coming out of the servo. Suspect there is an issue with your sender or picked the wrong one in the dynon configuration.

Further investigation I found I had the wrong fuel sensor selected in the Dynon EMS map setting. Once the correct one was chosen, the psi now reads correctly and showing 30 psi when the boost pump is on.

Does it make any difference if you switch tanks? See post #4 above, it could be something basic (no offence intended!)

No it did not at the time of testing yesterday. You were correct in that is was something basic. Both corrections were simple. No offense taken at all. I appreciate you mentioning it.

Thanks all!

 

[PCHunt]

Very nice feedback, Carlos!
Great way to close the loop for everyone. Wish more would do that!