Diesel Engine Repair

Diesel engines are built to work, but they are not simply larger gas engines — the fuel system runs at pressures over 25,000 psi, the emissions equipment is a system in its own right, and cold weather affects them in ways gas engines never experience. Spokane winters make that last point a practical reality rather than a theoretical one.

All Motors Center has worked on diesels out of the East Trent shop since 2010, on everything from three-quarter-ton pickups to Class 8 trucks. We service Cummins, Duramax and Power Stroke engines, and the heavy-duty engines behind Freightliner, Peterbilt, Kenworth, Mack and International equipment.

Cold starting and winter fuel

The most common diesel call we get between November and February is a truck that will not start, and the cause is usually fuel rather than the engine. Diesel fuel contains paraffin wax that begins to crystallise as temperatures drop — the fuel clouds, then gels, and the filter plugs. A truck that ran fine at 20°F can refuse to start at -5°F.

What actually helps: winter-blend fuel, a treated anti-gel additive used before the cold arrives rather than after the fuel has already waxed, a fuel filter that is genuinely current rather than nearly due, and a working block heater. We check block heater elements and cords as a matter of course on winter service, because a surprising number of them are simply dead and the owner has no idea.

We also check glow plugs and intake grid heaters, batteries and cables — a diesel needs far more cranking current than a gas engine, and a battery that starts a car in July will not turn a cold diesel in January.

Fuel systems and injectors

Modern common-rail diesels run extremely high injection pressures with very tight tolerances, which makes them sensitive to fuel contamination and water. Symptoms of a fuel system problem include hard starting, a rough or lopey idle, white smoke on startup, loss of power, poor economy, and a knock that changes with load.

We test rather than replace on spec: injector return flow and balance rates, rail pressure against commanded pressure, lift pump and supply pressure, and the water separator. Injectors are expensive enough that diagnosing which one is at fault is worth doing properly.

The water separator deserves a mention on its own. Draining it is a two-minute job that prevents some of the most expensive failures a modern diesel can suffer, and it is one of the most commonly skipped items on the whole vehicle.

Turbochargers

Symptoms of turbo trouble include a whistle or siren that rises with boost, blue or black smoke, loss of power under load, and oil in the intake tract. On variable-geometry turbos, sticking vanes from soot buildup are common and often present as intermittent low power or a check engine light for boost pressure out of range, which is a very different repair from a failed turbo. We check the actual cause before quoting a replacement.

Emissions systems: DPF, EGR and DEF

The emissions equipment on a modern diesel is where a lot of expensive frustration lives. The diesel particulate filter traps soot and periodically burns it off in a regeneration cycle. Trucks used mostly for short trips around town often never reach the conditions needed to complete a regeneration, so soot accumulates, regens become more frequent, and eventually the truck derates into limp mode.

We diagnose regeneration problems, differential pressure sensor faults, EGR valve and cooler failures, and DEF and SCR system faults including quality sensors and injectors. We can perform forced regenerations and clean or replace filters where that is what is needed.

One thing we will not do is delete or defeat emissions equipment. It is a federal violation, it makes the vehicle fail a DOT inspection, and it destroys resale value. We will fix it properly instead.

Fleet and commercial

A truck that is not moving is not earning. We handle scheduled preventive maintenance, DOT inspections, and repairs for local fleets, and we offer mobile diesel service for equipment that cannot easily come to us.

Call (509) 655-7715 to talk to a diesel technician.