Cummins Repair

The Cummins B-series is the reason a lot of people buy the truck it comes in. It is a straightforward, durable engine, but each generation has a small set of failures that show up repeatedly, and knowing which generation you have changes what we look at first.

We service Cummins engines in RAM and Dodge pickups and in commercial equipment at our East Trent shop.

5.9L 12-valve

The mechanically injected 12-valve is the one with the reputation, and it is largely deserved — there is very little electronics to fail. The known items are the killer dowel pin, a locating pin in the front gear housing that can back out and drop into the timing case, and injection pump and injector wear at high mileage. Both are addressable, and the KDP in particular is cheap to deal with preventively and expensive to deal with afterwards.

5.9L 24-valve

The electronically controlled 24-valve added an injection pump that is the defining weak point of the generation. The symptom pattern is distinctive: a hot no-start that recovers once the truck cools, erratic power, or a truck that dies and restarts. A failing lift pump is very often the underlying cause, because the injection pump relies on it for both fuel supply and cooling, and running it starved will kill it. Checking and maintaining lift pump pressure is the single most useful preventive item on these trucks.

6.7L

The 6.7 brought the emissions equipment, and most of what we see on it lives there. The variable-geometry turbo uses a sliding vane mechanism that sticks with soot buildup, which presents as low power, a check engine light for boost out of range, or an audible change in turbo behaviour — and is frequently cleanable rather than a replacement. EGR valves and coolers foul and fail. The DPF loads up on trucks used for short trips that never complete a regeneration.

On heavily tuned or hard-worked trucks, head gasket failure is a known outcome, because the factory head bolts have a torque limit that raised cylinder pressure exceeds. Head studs are the durable answer if the truck is staying tuned.

Later trucks moved to a higher-pressure injection pump that is far less tolerant of fuel contamination and water than the earlier one. On those, draining the water separator on schedule stops being routine maintenance and becomes genuine insurance — a pump failure of that type sends metal debris through the entire fuel system.

Cold weather

Spokane winters are where most Cummins no-start calls come from, and the cause is usually fuel rather than the engine. Diesel gels as the paraffin in it crystallises and the filter plugs. Treat fuel before the cold arrives rather than after it has already waxed, keep the fuel filter genuinely current, and make sure the block heater element actually works — a surprising number are dead and the owner has no idea until January. Batteries matter too: a cold Cummins needs far more cranking current than a gas engine, and these trucks carry two batteries for a reason.

What we do

We diagnose before quoting. That means scanning fault codes and live data, testing lift pump and rail pressure, checking injector return flow and balance rates, and assessing turbo and EGR condition — because on these engines several very different problems produce the same complaint of low power.

We do not delete or defeat emissions equipment. It is a federal violation, it fails a DOT inspection, and it destroys resale value on a truck that holds value unusually well otherwise.

Call (509) 655-7715 and tell us the year and engine.