Silca pump gauge failed after reassembly?

On Sat, 15 Mar 2003 19:12:29 -0800, Michael wrote:

[snip]

Quoted message said:

On the push stroke the needle goes to approximately the right pressure reading, but immediately
falls back to 0. The pump works fine - I can verify the pressure with a separate guauge I've got -
but previously the needle would hold at the current pressure as I pumped. It's pretty hard to read
the value now in the split second the needle peaks at a number, especially considering how close
together the gauge ticks are.

This sounds to me like a problem with a one way valve someplace. Since the pump works, I'd have to
guess that the guage is just on the "wrong side" of the valve, or if it's set up to "pass through",
then that one of two valves is missing. Greg

Michael said:

When I needed to replace the rubber gasket in the pump head of my Silca Super Pista, I took the
opportunity to take the pump completely apart and re-lube everything. But after I put it all back
together, the gauge stopped working.

On the push stroke the needle goes to approximately the right pressure reading, but immediately
falls back to 0. The pump works fine - I can verify the pressure with a separate guauge I've got -
but previously the needle would hold at the current pressure as I pumped. It's pretty hard to read
the value now in the split second the needle peaks at a number, especially considering how close
together the gauge ticks are.

I can't believe I broke the gauge just by taking it off and putting it back on. There's no magic
to how it attaches - it's compressed between the foot pedal and the pump body via 2 bolts, and the
intake hole lines up with a hole at the bottom center of the pump body.

Any ideas?

Yep. You didn't get the check valve back in there properly. The gauge is between the check valve and
the tire's valve. If the tube uses a presta valve, that alos acts a check valve that keeps the air
in the tire from coming out when you release the pressure in the pump barrel. Normally the check
valve at the bottom of the pump barrel keeps the air in the gauge and hose from flowing back into
the pump so that the gauge holds its reading between pump strokes.

Think about the burst of air you hear when you remove the chuck from the stem. That is the air
between the pump's check valve and the tire's "check valve" rushing out. That is also the air whose
pressure is read by the pump's gauge. When the check valve in the pump isn't working, that air flows
back into the pump each time you complete a pump stroke. You can still pump a presta valved tire up,
but the gauge will behave as you have described.

Mark <www.cs.unca.edu/~boyd/bicycling.html

In article <[email hidden]>, [email hidden]

(Michael) said:

When I needed to replace the rubber gasket in the pump head of my Silca Super Pista, I took the
opportunity to take the pump completely apart and re-lube everything. But after I put it all back
together, the gauge stopped working.

On the push stroke the needle goes to approximately the right pressure reading, but immediately
falls back to 0. The pump works fine - I can verify the pressure with a separate guauge I've got -
but previously the needle would hold at the current pressure as I pumped. It's pretty hard to read
the value now in the split second the needle peaks at a number, especially considering how close
together the gauge ticks are.

I can't believe I broke the gauge just by taking it off and putting it back on. There's no magic
to how it attaches - it's compressed between the foot pedal and the pump body via 2 bolts, and the
intake hole lines up with a hole at the bottom center of the pump body.

No, you've just got a pressure leak somewhere. Check all the connections- the valve chuck, the
connections to the hose, and the connection between the gauge and the pump body. You could submerge
the bottom 1/3 of the pump and try pumping a tire- that would rule
in/out most of the possibilities. If it passes this check, then recheck the chuck, hose connection,
and leather piston.

"Michael" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

When I needed to replace the rubber gasket in the pump head of my Silca Super Pista, I took the
opportunity to take the pump completely apart and re-lube everything. But after I put it all back
together, the gauge stopped working.

On the push stroke the needle goes to approximately the right pressure reading, but immediately
falls back to 0. The pump works fine - I can verify the pressure with a separate guauge I've got -
but previously the needle would hold at the current pressure as I pumped. It's pretty hard to read
the value now in the split second the needle peaks at a number, especially considering how close
together the gauge ticks are.

I can't believe I broke the gauge just by taking it off and putting it back on. There's no magic
to how it attaches - it's compressed between the foot pedal and the pump body via 2 bolts, and the
intake hole lines up with a hole at the bottom center of the pump body.

Any ideas?

Since your gauge reads, albeit briefly, we'll assume you haven't broken the gauge itself.

Silca's gauge reads the pressurized area between the check valve of your pump and the bicycle's
valve. Air is escaping that area, most likely at the check valve but possibly at any one of the
threads - check valve cover, gauge to body, etc. Ensure the check valve's rubber seal is smooth and
doesn't have a bit of swarf stuck in it. Assembling with a drop of paint, pipe joint compound or
teflon tape would seal the threads. (Since the threaded bits are bronze, you needn't lean on the
wrench). It could also be something so simple as a worn washer at your tube's valve.

If you cannot spot the leak right away, a bit of soapy water can be brushed over the joints looking
for bubbles.

--
Andrew Muzi yellowjersey.orgyellowjersey.orgOpen ↗ Open every day since 1 April 1971

Update: the problem turned out to be excess grease (from re-greasing the main pump tube) that had
gotten squished down into the brass cylinder around the check valve. That gunk caused the check
valve to get stuck in the open position. I just cleaned the whole check valve assembly and it's back
to normal.

"A Muzi" <[email hidden]> wrote in message news:<[email hidden]>...

Quoted message said:

"Michael" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

When I needed to replace the rubber gasket in the pump head of my Silca Super Pista, I took the
opportunity to take the pump completely apart and re-lube everything. But after I put it all
back together, the gauge stopped working.

On the push stroke the needle goes to approximately the right pressure reading, but immediately
falls back to 0. The pump works fine - I can verify the pressure with a separate guauge I've got
- but previously the needle would hold at the current pressure as I pumped. It's pretty hard to
read the value now in the split second the needle peaks at a number, especially considering how
close together the gauge ticks are.

I can't believe I broke the gauge just by taking it off and putting it back on. There's no magic
to how it attaches - it's compressed between the foot pedal and the pump body via 2 bolts, and
the intake hole lines up with a hole at the bottom center of the pump body.

Any ideas?

Since your gauge reads, albeit briefly, we'll assume you haven't broken the gauge itself.

Silca's gauge reads the pressurized area between the check valve of your pump and the bicycle's
valve. Air is escaping that area, most likely at the check valve but possibly at any one of the
threads - check valve cover, gauge to body, etc. Ensure the check valve's rubber seal is smooth
and doesn't have a bit of swarf stuck in it. Assembling with a drop of paint, pipe joint compound
or teflon tape would seal the threads. (Since the threaded bits are bronze, you needn't lean on
the wrench). It could also be something so simple as a worn washer at your tube's valve.

If you cannot spot the leak right away, a bit of soapy water can be brushed over the joints
looking for bubbles.