Jump to content

Non return valve in fuel line


GR002
 Share

Recommended Posts

I was thinking of fitting a decent non return valve in fuel line . I know the priming bulb has two non return valves but they after time allow the petrol to return to tank and make pull starting in flight difficult. I was thinking of fitting a non return with viton seal and doing away with primer and pressurising tank to prime. Has any body done this or can any body see a problem with this idea?

Link to comment
Share on other sites

Basically the fuel evaporates.. you can add a heat sink on the manifold or something like a remote system enabling you to use the primer bulb inflight to push fuel back into the carb may be better.  A simple level to push the diaphragm you can reach inflight works a treat.. 

  • Upvote 1
Link to comment
Share on other sites

I remove primer bulb because one way valves in this make very big fuel flow resistor (try blow by mouth) and difficulties for walbro fuel pump ,insted of that I pressurise tank blowing by tube.I use also one way valve wich no need very big pressure (like those from prime bulb)

tmp_26324-img20170226_2210161743176100.jpg

And other reason was to prevent fuel flow back to tank when I spiral dive with engine on

Modification prevent stall engine

Edited by Dariuszk24
Link to comment
Share on other sites

I had this system of pressurised tank by air for years..

There are a lot of issues with it. 

First of all, fuel spills from the air intake tube. Secondly, when you start the motor with pressurised fuel tank it is easy to get too much fuel to your carb and then it is hard to understand is is too much fuel already so the motor is not starting or it is not enough fuel. After changing the fuel sysyem to standard one with primer it is much easier to start the motor.

And thirdly, when the motor is working with fuel coming under pressure from the tanks air you do knot know what is going to happen with idle rpm during the flight when the tank is not under pressure anymore. 

One more minus. If you got poor mixture carb setting (too much air, not enough fuel) you would not be able to understand it strait away. Because the fuel will come under pressure. But later on when the pressure goes down the quality of the mixture goes down as well (less fuel, poorer mixture) and the engine temperature will go up. And you will not be able to start the motor in the air, as the mixture is too poor (in the worst scenario)....

The only one plus I can see is there is no primer as potential failure point. But how often primer fails? Most of us would use Polini primer, I have not heard a lot of negative feedback. To my opinion, the pump of the carburator copes absolutely fine with primers resistance..

 

  • Upvote 1
Link to comment
Share on other sites

  • 2 weeks later...

I bought a decent quality non return valve http://www.ebay.co.uk/itm/VW-T3-T25-Golf-6mm-1-4-Fuel-Check-Valve-Non-Return-Petrol-Diesel-3A0201542-A7-/162414528435?hash=item25d0a907b3:g:ZKMAAOxyVLNS-RJ8

 to my Moster, I fitted it Just as fuel pipe leaves tank, I drilled out the non return valve on bottom side of the primer bulb (as not needed ). Now the fuel pipe stays full of petrol, even after a week lying the pipe is still full. I set up the lever height and the pop off pressure to 14 psi. Blocked middle low jet and filed a notch in butter fly flap in carb in line of low jets and tuned the hi and low screws. I can now confidently start the paramotor on my back now and idle is smooth also can start in the air after being off for a while. Any start after first start is just half a pull on starter. The low screw takes a bit of setting up and less than an eight of a turn will knock it out of tune.

Link to comment
Share on other sites

On 26/02/2017 at 11:37, morgy said:

If you have a walbro carb these can suffer from vapour lock making it hard to re-start in flight.. 

I find dislocating my right shoulder and reaching behind for the priming bulb works well. The problem is my arm then won't work any more!

Has anyone got the priming bulb where you can reach it?

As an alternative I have considered fitting a very small electric pump that can be run for 5 seconds to do the priming. Anyone done this?

Link to comment
Share on other sites

On 10/03/2017 at 21:37, GR002 said:

I bought a decent quality non return valve http://www.ebay.co.uk/itm/VW-T3-T25-Golf-6mm-1-4-Fuel-Check-Valve-Non-Return-Petrol-Diesel-3A0201542-A7-/162414528435?hash=item25d0a907b3:g:ZKMAAOxyVLNS-RJ8

 to my Moster, I fitted it Just as fuel pipe leaves tank, I drilled out the non return valve on bottom side of the primer bulb (as not needed ). Now the fuel pipe stays full of petrol, even after a week lying the pipe is still full. I set up the lever height and the pop off pressure to 14 psi. Blocked middle low jet and filed a notch in butter fly flap in carb in line of low jets and tuned the hi and low screws. I can now confidently start the paramotor on my back now and idle is smooth also can start in the air after being off for a while. Any start after first start is just half a pull on starter. The low screw takes a bit of setting up and less than an eight of a turn will knock it out of tune.

Will an NRV for diesel last long with petrol?

Link to comment
Share on other sites

14 hours ago, AndyB said:

I find dislocating my right shoulder and reaching behind for the priming bulb works well. The problem is my arm then won't work any more!

Has anyone got the priming bulb where you can reach it?

As an alternative I have considered fitting a very small electric pump that can be run for 5 seconds to do the priming. Anyone done this?

I guess you have Parajet? Not sure why they still put it in a place you can not reach!!! On my Mac Fly it is right by my hip when standing attached to the chassis. Very easy to reach pre and during flight..

 

Link to comment
Share on other sites

43 minutes ago, admin (Simon W) said:

That's a bit harsh dude? 

How do you depress the pin on top of the carb in flight or while on your back? (also required for priming) 

SW :D

Not harsh at all as they still supply Polini engines and bailey engines with float bowl style carbs.. If you do need to prime a Walbro style carb it is easy to adapt/Make a remote system..   For pilots who do thermal/ridge soar little things like this are normally overlooked.. ;-)

Link to comment
Share on other sites

7 hours ago, morgy said:

Not harsh at all as they still supply Polini engines and bailey engines with float bowl style carbs.. If you do need to prime a Walbro style carb it is easy to adapt/Make a remote system..   For pilots who do thermal/ridge soar little things like this are normally overlooked.. ;-)

Yes, Thor 190, elec start. I find that after the engine is off for a few mins it won't re-start. This even means that after warming up engine before flight, it needs a quick re-prime before strapping in and going - failure to do so is rather annoying....especially when on my own. However, I have found that that just pressurising the fuel line with the bulb, whilst turning over the engine also works. Thus, if I move the priming bulb, should be problem solved. :)

Has anyone moved the primer somewhere better? If so where? I am not familiar with other makes as learned on Parajet etc.

Link to comment
Share on other sites

On 14/03/2017 at 16:25, AndyB said:

Yes, Thor 190, elec start. I find that after the engine is off for a few mins it won't re-start. This even means that after warming up engine before flight, it needs a quick re-prime before strapping in and going - failure to do so is rather annoying....especially when on my own. However, I have found that that just pressurising the fuel line with the bulb, whilst turning over the engine also works. Thus, if I move the priming bulb, should be problem solved. :)

Has anyone moved the primer somewhere better? If so where? I am not familiar with other makes as learned on Parajet etc.

Just put it where you can reach it... ;-) Bailey Mac Fly and other brands have them on the side by your hip.. 

  • Upvote 1
Link to comment
Share on other sites

  • 1 year later...

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share



  • Upcoming Events

    No upcoming events found
×
×
  • Create New...