GENE RAL INFORMATION IS I Compression Gauge An engine with low compression cannot be properly tuned and will not develop full power. A compression gauge (Figure 37) and adapter specifically designed for diesel applications is required to measure the high cylin- der compression pressure (390-470psi [2700-3300kPa]). lf these specialized tools are not available, refer compres- sion testing to a qualified technician. Sec Chapter Three. Multimeter or YOM This instrument (Figure 38) is required for electrical system troub leshooting. H attery Hydromet er A hydrometer (Figure 39) is the used to check a bat- tery's state of charge.
A hydrometer measures the weight or density ofthe sulfuric acid in the battery's electrolyte in specific gravity. Screw Pitch Gauge A screw pitch gauge (Fig ure 40) determines the thread pitch of bolts, screws, studs, etc. The gauge is made up of a number of thin plates. Each plate has a thread shape cut on one edge to match one thread pitch. When using a screw pitch gauge to determine a thread pitch size, fit dif- ferent blade sizes onto the bolt thread until both threads match.