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ROADSIDE TESTS FOR M-SERIES VEHICLESNow we’ll move on to the same roadside tests on M-seriesvehicles with 24-volt waterproof systems. Since both the ignitioncoil and distributor are sealed within the Igniter, which mustbe assembled to function, there aren’t many tests you can makeas simply as with the WWII-style systems where you can checkthings out with the distributor cap removed. Most of the time onM-series systems you will replace components with your sparesuntil your engine starts again.If, after checking for spark at the spark plugs in the same waywe tested the WWII-style system, check to make sure that poweris getting to the Igniter from the ignition switch by removing theprimary wire from the Igniter and testing for power (with the ignitionswitch on) with your test lead or probe tester. If you aregetting power, then turn the ignition switch off and remove thetop of the Igniter.You will usually see a coil capacitor and a resistor in additionto the condenser found in WWII-type distributors. Check tomake sure the rotor isn’t broken or the connector pin on the driveshaft isn’t sheared in the same way we checked the older systemcomponents. If the cap and/or rotor are burned or eroded, replacethem with your spares and try to start your engine. If that was theproblem, then you’re on your way.If the engine won’t start, then turn off the ignition switch,clean and re-gap the points, and also check that the little springin the distributor cap which contacts the coil’s secondary toweris making a good connection. If the engine still won’t start, youshould probably install your spare condenser and coil now. Asmentioned, many 24-volt Igniters also have a resistor and/or coilcapacitor, and while these are usually very long-lived, one shouldstill carry spares.If the engine still won’t start after replacing the condenserand coil, try replacing the resistor and/or capacitor as well. If thisdoesn’t get you going, then try installing your entire spare Igniter...which, of course, you have already tuned-up and tested athome. If that doesn’t work, then at least be consoled by knowingyou have done just about all you can in the field.About your only option is to create a mutant system usingcivilian components as suggested in the illustration. As alreadymentioned, many points and condensers, and sometimes the rotors,in 24-volt Igniters have civilian counterparts and may bematched by appearance at well-stocked auto or truck supplyhouses... though this may not work at many chain stores where,if a part isn’t on their computer, many clerks don’t have the necessaryreal-time experience to help you...and also often lack theinclination.However, the failure of a 24-volt Igniter cap or coil, or the Igniteritself is a more serious matter, and you will seldom find replacementsat any auto store. But, if your vehicle is an M37, M38,M38A1, M715, M211, or Reo-powered M35, you may be ableto locate a civilian type distributor, and certainly a 12-volt coil.It’s simple to install these civilian distributors in place of the24-volt Igniter. Don’t worry about the vacuum advance line onsome of these distributors: you don’t need to hook it up. Likewise,you won’t need to hook up your vehicle’s fording vent lines.Install a 12-volt coil in some convenient place on your engine,and make sure it’s grounded. You can either use your existing 24-volt spark plug cables and waterproof plugs by taping the cablesOne of the first things to check is if the distributor might havecome loose, which could have messed up the timing. Check thedistributor’s mounting to make sure it’s tight.into the civilian distributor cap, or you can use civilian type wiresand tape them into your waterproof plugs.Alternatively, you can replace your waterproof spark plugswith civilian counterparts. You can supply 12 volts to the coil bytaking a lead from your vehicle’s “first” battery. If possible, usea coil that doesn’t require a resistor. If your replacement coil hascome from a scrapped vehicle, be sure to liberate the resistor aswell.If you find yourself in a situation where your 24-volt coil hasfailed, you can usually rig up your Igniter to run with a 12-voltcoil. In fact, a 12-volt coil will fit right in place of the 24-voltcoil in the Igniters of M211s and M35s, though you will haveto shorten the coil’s center tower by sawing or filing some ofthe insulation away. Disconnect the Igniter’s resistor and run theIgniter’s input wire directly to the 12-volt coil’s primary inputterminal. Likewise, disconnect the Igniter’s primary input wire,which comes from the ignition switch, cut the wire, and rig up alead to supply the Igniter with 12 volts from your vehicle’s “first”battery.YOU SHOULD BE READY TO ROLL!By now one should surely realize the importance of carryingtools and spare parts aboard their vehicle; and while not allHMVers take their vehicles into the bush or even on long roadtrips, one should still consider the inconvenience if driving theirjeep or M37 down to the local Quickie-Mart and finding it won’tstart again.Even if you have towing service, you can usually do sometrouble-shooting and replace a coil or condenser in the time ittakes for a tow truck to arrive. You may also discover that manytow companies with smaller trucks designed for today’s carswon’t even want to handle your M37 or M715... and definitelynot your Chevy G506 or White Scout Car! If your HMV is largerthan a jeep, always make sure the dispatcher understands howlarge—or at least at large-appearing—it is.Once again, with a good basic tool set, on-board spare parts—and a little ingenuity—you can almost always get your militaryvehicle going again when you are stranded “in the field.” ✪Military Vehicles Magazine June 2013 45