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Measuring internal pressure
by
anto
on 08 Dec, 2009 02:31
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Bought myself an oil pressure gauge and fitting kit (copper pipe with compression fittings) to measure my internal pressure.
Ive drilled and tapped the little pedestal that comes with some na vw pump. Comes standard on 406/306/xantia etc that we get over here so id a few spare to use.
The gauge is rated 0-100psi.
I know the internal pressure of our pumps goes higher than that but my worry is that the gauge will leak above say 150psi?
Would this be the case or have i nothing to worry about?
Measuring above 100psi isnt a concern for me so i dont mind seeing the gauge pegged when at high rpms i just dont want the thing leaking in the dashboard.
Thanks,
Anton
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#1
by
RadoTD
on 08 Dec, 2009 08:37
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It probably won't leak, but it could bend the tube inside the gauge, or if there's a physical stop for the needle, it might skip a few teeth and actually move where the needle sits, both of those rendering the gauge inaccurate.
It's probably a Bourdon Gauge, as shown here
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#2
by
anto
on 08 Dec, 2009 09:17
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#3
by
55eta
on 08 Dec, 2009 10:17
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{www. rs components} dose a wide range of pressure gauges at a reasonable price and a wide range of pressures
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#4
by
rabbitman
on 08 Dec, 2009 11:04
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So you're planning to mount the gauge inside and always be able to look at it?
That's not really necessary though it would be fun to watch.
The internal pressure "should" always have the same curve once it's set. Until parts start wearing.
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#5
by
anto
on 09 Dec, 2009 00:11
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{www. rs components} dose a wide range of pressure gauges at a reasonable price and a wide range of pressures
I dont intend to buy another one 55eta, i got this one cheap from a friend so if i dont mount it in the car (if it cant stand the pressure) then i wil just use it once to set the pressure and remove it.
Would having the gauge permanently in the car be of any benefit?
It would surely show up any problems that may arise with the pump?
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#6
by
Mark(The Miser)UK
on 09 Dec, 2009 07:58
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{www. rs components} dose a wide range of pressure gauges at a reasonable price and a wide range of pressures
I dont intend to buy another one 55eta, i got this one cheap from a friend so if i dont mount it in the car (if it cant stand the pressure) then i wil just use it once to set the pressure and remove it.
Would having the gauge permanently in the car be of any benefit?
It would surely show up any problems that may arise with the pump?
As Rabbit man says; Put it on, do some tests and then take it off.
All it will show is a few psi or 10's of psi over several 10's of years... Unless something catastrophic happens ... in which case... 
Put it back on in a few years... 
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#7
by
anto
on 09 Dec, 2009 08:22
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Il do that, no chance of it exploding in a cloud of diesel while im driving along then....
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#8
by
Op-Ivy
on 09 Dec, 2009 12:13
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Il do that, no chance of it exploding in a cloud of diesel while im driving along then....
That's what I would be concerned about as well. I don't know about Ireland but it's actually illegal here to have a a fuel source from the engine or from the fuel tank to the engine running through the interior!
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#9
by
anto
on 10 Dec, 2009 04:08
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No need to be concerned about that i just hooked it up last night, set it to 43.5psi at 1k engine rpm (give or take 0.1/2 psi) and took it off again once i was satisfied it was ok.
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#10
by
anto
on 10 Dec, 2009 08:39
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Il do that, no chance of it exploding in a cloud of diesel while im driving along then....
That's what I would be concerned about as well. I don't know about Ireland but it's actually illegal here to have a a fuel source from the engine or from the fuel tank to the engine running through the interior!
Just on that point op ivy the gauge i am using is an oil pressure gauge which would normally be mounted in the dashboard i assume. That would bring oil into the car, where would you stand with that where you are? Essentially that oil would be a fuel source....
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#11
by
Op-Ivy
on 10 Dec, 2009 11:49
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Il do that, no chance of it exploding in a cloud of diesel while im driving along then....
That's what I would be concerned about as well. I don't know about Ireland but it's actually illegal here to have a a fuel source from the engine or from the fuel tank to the engine running through the interior!
Just on that point op ivy the gauge i am using is an oil pressure gauge which would normally be mounted in the dashboard i assume. That would bring oil into the car, where would you stand with that where you are? Essentially that oil would be a fuel source....
It depends on how the gauge works. If it consists of a tube that runs from the pump to the cockpit that would still be illegal. If it has a sensor on the pump with a sender that relays the pressure to the cockpit that would be ok. I think the idea is considering that if it is hooked up directly and something happens to the line or the gauge, fuel is going to start gushing out.
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#12
by
92EcoDiesel Jetta
on 10 Dec, 2009 21:11
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Bought myself an oil pressure gauge and fitting kit (copper pipe with compression fittings) to measure my internal pressure.
Ive drilled and tapped the little pedestal that comes with some na vw pump. Comes standard on 406/306/xantia etc that we get over here so id a few spare to use.
The gauge is rated 0-100psi.
I know the internal pressure of our pumps goes higher than that but my worry is that the gauge will leak above say 150psi?
Would this be the case or have i nothing to worry about?
Measuring above 100psi isnt a concern for me so i dont mind seeing the gauge pegged when at high rpms i just dont want the thing leaking in the dashboard.
Thanks,
Anton
The internal pressure measured on the fuel return side? Is so, why not use a vacuum tee fitting 0n the injector return line instead of drilling and tapping a fitting into the pedestal? Seems like a lot less work.
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#13
by
Vincent Waldon
on 10 Dec, 2009 21:25
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It's measured *before* the out bolt, so unfortunately tapping into the return line won't work.
My approach is to use a standard VDO electric oil pressure gauge with a 10 bar sensor for fuel pressure... switch on the dash lets me select a 5 bar oil pressure sensor to measure oil pressure most of the time.
No oil *or* diesel my lap this way.
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#14
by
rabbitman
on 11 Dec, 2009 00:06
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Has anyone thought about the fact that the threads of the 'out' bolt are not sealed to the return lines and so fuel can flow up the threads and into the banjo? The path up the threads is probably as large as the orifice in the bolt. Any wear in the threads would affect the pressure as well.
You got a point there.....but wouldn't that remain constant enough?