GLOWPLUGS

Harold Brochmann

 

Cleaning all the electrical contacts in GYPSY's engine compartment certainly made a difference to starting, but I still felt she could be more enthusiastic about it.. A friend, Alan Kirk, was consulted. "Let's check the voltage on your glowplugs", he suggested.

 

Sure enough, the readings were a hair less than 9 volts. Presumably they ought to read close to 12. Voltage drops in any electrical circuit means lost power. In this case the lower voltage results in less heat in the glow plugs and hence more sluggish starts.

 

The diagram shows the original circuit which supplied the glow plugs. The complete wire path from the battery to the engine compartment, on to the cockpit and back again, is around 35 feet, most of it in a wiring harness that has multi-plug connectors similar to what you see in trailerhitches at either end. These are notorious for corrosion, impossible to clean and a nuisance to replace. There were about 40 unsoldered metal-to-metal contacts altogether along the way; every one of which likely added some fraction of a volt drop under the approximately 15 Ampere load.

 

Solution: install a solenoid. Such a thing is readily available from any auto-supply store. The least expensive one available will do fine. I bolted it to the engine block and did some re-wiring as shown in the smaller illustration. I used crimp-on connectors, but soldered all of them to the size 10 wire.

 

 

Result: 11.3 volts on the glowplugs. Approximately 25% increase in voltage resulting in 25% increase in current, which means around 60% increase in heat in the glowplugs.

 

Did it work as anticipated? You bet!