Hello Frans and thank you too for your input.
> No that is not how it works. It just maintains proper fuel pressure over
> the airbox pressure. It is just a pressure valve, opening the return if
> the pressure gets higher, closing it a bit more when the pressure gets
> lower.
I was unaware of how the regulator works and still am to a large degree.
What you say makes sense and when I get a chance to read some 914
literature, I hope to understand a lot more things about the 914.
> This situation again shows the importance of a differential fuel
> pressure gauge. Why not install one now permanently, and see what is
> going on, now you have to hook up a gauge anyway? It is a must have for
> the 914. Without such a gauge you can't tell whether your regulator is
> working correctly, or that your filters are clogging, or whatever. If a
> differential fuel pressure gauge shows a healthy value you can pretty
> much rule out the majority of the fuel related problems.
After the experience we had and seeing where the fuel pressure is taken from
on this aircraft, I couldn't agree with you more Frans. Subsequent to
viewing the Rotax Owners video on testing the regulator, I had already
decided that a differential fuel pressure gauge is the meaningful way to go.
The fuel pressure readings we are getting on this aircraft are next to
useless on a 914.
> I would place my bets on the carb slides, just like Trev said. It is
> common that after some months out of use the slides get a very small
> layer of oxidation due to lack of fuel, and they get a bit "sticky".
As I said to Trev, this will be thoroughly checked out and now that I have
been made aware of this phenomenon, I am certainly not discounting this as
the cause.
>> I am however convinced the problem IS the
>> fuel pressure regulator
>
> Without a differential gauge you really can't tell.
Well you will be pleased to know I am now not so convinced given the
revelations about the carb slides. I agree that without a differential
gauge I won't be able to tell and this is another test that I will be
carrying out.
>> Now that I have read your full posting, with hindsight and as a result
>> of the steep learning curve I have been on regarding the 914, maybe if I
>> had clamped off the fuel return line somewhat, we may have at least seen
>> some change in the running to confirm we might be on the right track.
>
> It wouldn't tell anything, even if the engine runs better. You might
> overcome the improper mixture due to a stuck slide by changing the fuel
> pressure outside the normal range, but for sure this fix wouldn't be
> airworthy. It would be similar like intentionally clogging the fuel
> filter to keep your engine running with the choke stuck in the activated
> position. . . . . . . .
I wasn't for a moment suggesting that restricting the return line would be a
FIX Frans, rather, I thought that in the middle of nowhere like we were (up
the creek without a paddle so to speak!) it just might have been a method to
help diagnose the problem but as you have pointed out, it might also have
given us a bum steer.
Thanks again Frans.
Kingsley
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