Browse Prior Art Database

# Automobile Diagnosis

IP.com Disclosure Number: IPCOM000073361D
Original Publication Date: 1970-Dec-01
Included in the Prior Art Database: 2005-Feb-22
Document File: 1 page(s) / 11K

IBM

## Related People

Briney, LS: AUTHOR [+6]

## Abstract

A cylinder with weak compression will reduce the load on the starter motor during cranking for the compression stroke. This is shown by a momentary increase in engine speed accompanied by a decrease in cranking current. One measures the cylinder firing time and cranking current during cranking and compares the firing time (from points open to points open) of each cylinder to average firing time and compares current values read during each firing to average current. If either the firing time or the current varies from average value by about 20%, the following speed drop test is performed at a selected fixed throttle setting, such as 1500 rpm. Then one measures the firing time/cylinder and calculates engine speeds while sequentially grounding each spark plug wire.

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Automobile Diagnosis

A cylinder with weak compression will reduce the load on the starter motor during cranking for the compression stroke. This is shown by a momentary increase in engine speed accompanied by a decrease in cranking current. One measures the cylinder firing time and cranking current during cranking and compares the firing time (from points open to points open) of each cylinder to average firing time and compares current values read during each firing to average current. If either the firing time or the current varies from average value by about 20%, the following speed drop test is performed at a selected fixed throttle setting, such as 1500 rpm. Then one measures the firing time/cylinder and calculates engine speeds while sequentially grounding each spark plug wire. At 1500 rpm, a cylinder with weak compression will not contribute the proper power on its power stroke as manifested by a decrease in engine speed during firing of the weak cylinder. Average speed is calculated and then the speed drop per grounded spark plug is calculated and a determination of weakness is made and is indicated if the speed drop is excessive, e.g. greater than 20%. A computer is used to store and calculate the above values.

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