Compression Test

[MarkC]

I need to measure compression to assess if valve damage occurred when my TB broke. Which fuses should I pull to kill the ECM, ignition, and fuel pump?

From my shop manual, it looks like Fuse #28 supplies the fuel pump (but you would never figure that out from the fuse card on the fuse box cover).

From the fuse card, it looks like several fuses supply the engine controls (possibly #10, #29, #34, #43).

I'm concerned that if I don't de-energize the ECM, something bad will happen with the throttle body (since it is disconnected).

Another approach I could take is to remove power from everything except the starter, and apply +12V to the starter solenoid. Unfortunately my manual provides conflicting information in identifying the starter locking relay.

2001 Beetle, 2.0 AVH.

Any help out there?

Mark

[IndyTom]

Originally Posted by MarkC

I need to measure compression to assess if valve damage occurred when my TB broke. Which fuses should I pull to kill the ECM, ignition, and fuel pump?

From my shop manual, it looks like Fuse #28 supplies the fuel pump (but you would never figure that out from the fuse card on the fuse box cover).

From the fuse card, it looks like several fuses supply the engine controls (possibly #10, #29, #34, #43).

I'm concerned that if I don't de-energize the ECM, something bad will happen with the throttle body (since it is disconnected).

Another approach I could take is to remove power from everything except the starter, and apply +12V to the starter solenoid. Unfortunately my manual provides conflicting information in identifying the starter locking relay.

2001 Beetle, 2.0 AVH.

Any help out there?

Mark

HMMM, I think a compression test would be pretty much pointless if your valves and perhaps pistons are damaged unless you want to damage them some more? I think the only way to assess the damage done to the valvetrain is to pull the head.

[Smileybug]

Just pull the head. There is damage. The 2.0 is an interference motor.