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Fuel Pressure  


Steevo25
(@steevo25)
Active Member
Joined: 3 years ago
Posts: 5
Topic starter  

A few months ago I purchased a J160 (built in 2009). After a few running problems relating to the selection of jets by a previous owner, I now have one issue remaining.

First off, the aircraft is running fine, but after adding a fuel pressure sensor (UMA 7psi sender), I noticed that I am getting readings that can go as high as 6psi at idle. They tend to go down a bit when power is applied, but are consistently above 4psi.

When not started and I use the Facet electric pump they are showing 3.7psi which sounds about right considering the Facet pump is rated up to 4.5psi.

Thinking it could be the sender, I substituted the electronic sender for a manual 0-10psi sender/gauge and this confirmed that with the engine running and just using the mechanical pump, I am getting fuel pressure close to 6psi at times (averaging around 4.5psi-5psi). The Jabiru manual states it should be max 3psi but it is never this low.

I am not getting any flooding or rough running, but surely the fuel pressure should not be this high and I have no idea why it is running this high. I have confirmed that it has a version 2 mechanical pump on there with the correct size pushrod and the pump is fairly new direct from the UK Jabiru dealer. I have also checked the breather hose and can confirm this is completely clear with no obstructions or restrictions.

I have not carried out a compression check yet, but by feel, all the compressions feel strong and even.

What could be causing this high fuel pressure and is it something I should be worrying about?


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Doug Smith
(@doug-smith)
Member Admin
Joined: 3 years ago
Posts: 82
 

Hi Steevo,

The mechanical pumps can vary a bit, depending how stiff of a diaphragm and spring they have fitted.  5-6psi is certainly getting on a bit but it sounds like your float valve is coping - as I've said elsewhere, the 2200 can tolerate a bit higher supply pressure than the 3300.  There are obviously things to change should you want to lower it - either the mechanical pump overall or just its internal components - but if the engine is otherwise running OK I'd be inclined to leave sleeping dogs lie, especially now you're monitoring it with a gauge.

Regards,

Doug.

 


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Steevo25
(@steevo25)
Active Member
Joined: 3 years ago
Posts: 5
Topic starter  

Thanks Doug, I will just monitor it for now. I do have a V1 pump as well that was overhauled.

 

Just out of interest, what were the changes between the Version 1 fuel pump and the Version 2. I know the pushrod was a slightly different size, but are there any differences in the internals?

Many Thanks
Steve


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