Roadside Diesel Repair

Economy and reliability are great reasons to own a heavy-duty diesel 4x4, so even when the conditions are bad it's easy to feel a bit over-confident when driving an old reliable diesel-powered truck. Compared to a computer-controlled gasoline engine with its electronic spark ignition system, a mechanically injected diesel is downright simple. The lack of a distributor, wires, spark plugs and some sort of electronic control means that you have considerably fewer parts to fail. Then what makes a diesel decide not to run?

Suffer the Fuel
Fuel. Ninety-nine percent of the time a diesel engine stops running or runs badly without any previous warning is due to a problem with the fuel itself or its delivery. Air bubbles in the fuel, water in the fuel, gasoline in the fuel, clogged fuel filters, fuel that is too cold or a faulty fuel shut-off valve are all good reasons for a diesel to shut itself off. Fortunately, all of these problems can be remedied on the side of the road if you have the knowledge and some simple tools.


The first tool you need is either a good manual for your vehicle or a long intimate acquaintance with all the workings of your truck. Other tools that you should carry with you are whatever wrenches and screwdrivers will allow you to access and disconnect your fuel lines. You should also carry a new set of fuel filters and the tools you need to change them, some duct tape, a bottle of water-dispersion chemical additive, and maybe a piece of wire for hot-wiring that pesky fuel shut-off valve. The only special tool that we suggest carrying is a hand-operated vacuum pump. It is the same kind you may have used to bleed brake fluid. They're also great for bleeding air or flushing contaminates out of a diesel fuel system when you're on your own.

Shut-Off Solenoid
One of the first things to check is the fuel shut-off solenoid. This little valve opens when you turn on the ignition to allow fuel to flow through the injector pump. Its primary job is to turn off the fuel when you turn off the truck, so if this valve were to lose power while running it would shut the engine off in less than a second.


When the ignition is turned on you should hear a little click in the vicinity of the injector pump. If in doubt, just run a wire from the battery to the valve and try to restart. Make sure you know in advance which wire is which! Obviously the wires and terminals differ from one brand to another and even from one truck to another.