TOP END REFINISHING

[Franke]

Look at page 8A-22-10 in electrical diagnosis supplement for a close up schematic of the vac pump ckt. It shows the whole ckt run.

[Franke]

Bummer. Wonder if these can be disassembled for repair? Y-ME on the boards here is disassembling (2) Z's over in Florida. He probably has a couple of used ones.

[Dynomite]

Originally Posted by Schrade

CLIFF!!! Got snappics of this pump broken down?

Best place to buy one? Anyone holding here??????????

Vacuum pump vendor

I guess it is possible to fix a vacuum pump Tom fixed his vacuum pump with WD40

I do not have any photos of a vacuum pump taken apart

Used Ebay 91' vacuum pump

The connectors on the vacuum pump apparently are different between a 90' and 91'-95'
I guess you CAN change the connector

Vacuum Pump Pigtail connector for 1990 application from Jerry

[Schrade]

Any one here given this any thought?

Originally Posted by Schrade

Still thinkin' on this throttle hesitation here...

If [since] 80% throttle opening comes from ONLY [ < 20%, actually] physical Range Of Motion OF THROTTLE LINKAGE ...

then



https://lh6.googleusercontent.com/-D.../HPIM7334c.JPG

then

EVERY operational parameter has almost 0 tolerance for deviation, from 0% Throttle Opening, to 80% Throttle Opening, considering that 80% throttle is reached in such a short span.

There HAS TO be some 'buffer' integrated into all parameters' synchronizing properly; otherwise, every 1 year-old LT5 with even minor hardware degradation is gonna' have some problem...

such as 'Off-Idle Sag'

unless the potentiometer in the TPS has some buffer mechanism built-in, such as logarithmic resistance, and not linear (never mind just now that FSM says that the TPS Voltage response is linear..................... )

This make any sense to anyone?

[Schrade]

Pump is running on the bench.



I manipulated the push-button that opens the internal switch.

Besides that, no clue...........

[mike100]

don't trust a DC motor. it might spin with no load, but it will fail to work as soon as you present it with any kind of load. Maybe the brushes wore out from running continuously due to vacuum leak. That GM HD truck pump seems like the best option unless you can get the orig LT5 unit from somebody else more quickly (and cheaper).

[mike100]

I think the way it works is it connects one side to the other in one state and in the 2nd state connects same side to the vent (3rd port).

same as GM EGR solenoid.

[Schrade]

Originally Posted by mike100

I think the way it works is it connects one side to the other in one state and in the 2nd state connects same side to the vent (3rd port).

same as GM EGR solenoid.

So for a static test, like now, is it supposed to HOLD vacuum? Or is it now in the 'vented' position?

[mike100]

Originally Posted by Schrade

So for a static test, like now, is it supposed to HOLD vacuum? Or is it now in the 'vented' position?

This is a guess, but with no power I think it vents. the vent is supposed to have a foam filter on it, but sometimes they break apart and blow away, but you may be able to cover it with your finger.

[Schrade]

Originally Posted by mike100

This is a guess, but with no power I think it vents. the vent is supposed to have a foam filter on it, but sometimes they break apart and blow away, but you may be able to cover it with your finger.

I'm lost. Again.

If a vacuum solenoid - EGR, ZR1 secondaries, etc., is in the vent position, ...