Diesel Engine Repair and Service in Upland

A diesel that acts up makes you nervous, because the parts cost more and the truck usually has a job to do. The good news is that most complaints trace back to a short list of systems. This table matches what you notice to the usual causes and tells you how soon to act. If the truck will not start or runs away on its own, do not keep cranking. Call (909) 608-7699. We accept tow-ins.

We work on light and medium-duty diesels: half-ton, three-quarter-ton and one-ton pickups, diesel SUVs, and diesel cargo and passenger vans that contractors and delivery crews run up and down Foothill Blvd every day. If you drive something larger, a cab-over box truck or a dually with a heavy service body, call before you drive over so we can tell you honestly whether it fits our bay and our equipment.

Diesels are welcome for routine work too, not just breakdowns. Oil and filter changes, fuel filters, air filters and valve lash checks keep a diesel healthy, and they give us a chance to spot a weeping injector seal or a soft coolant hose before it leaves you stranded on the 210. Our diesel truck owners page covers how we set up a maintenance plan around the way you actually use the truck.

A light puff at a cold start or a hard pull is normal on many older diesels. Newer trucks with a particulate filter should show almost nothing from the tailpipe. Smoke that you can see in the mirror, or that hangs behind you at a light, is a symptom worth testing. Here is how we read it:

A diesel has no spark plugs. It lights fuel with the heat of compression, so anything that lowers cylinder heat makes a cold start harder. Weak glow plugs, a failing glow plug controller, low cranking speed from a tired battery, and low compression all show up first on the coldest mornings of the year. Air in the fuel does the same thing at any temperature, often after a filter change or when a line has a pinhole leak. Our diesel glow plug replacement page explains how we test each plug before replacing any.

Reduced power, often called derate or limp mode, is the engine computer protecting itself. It limits fuel when it sees a problem it cannot trust, such as rail pressure that does not match what it asked for, boost that runs high or low, an overheating reading, or an aftertreatment fault. Clearing the code without finding the reason usually brings the message back within a few miles. We read the stored and pending codes, then compare live sensor data against the values the engine is asking for. That comparison is what points us to the right system instead of the most expensive one.

Each service below has its own page with symptoms, process and timing. If you are not sure which one you need, start with diesel engine diagnostics and let the testing decide.

We do not remove, bypass or reprogram emissions equipment. That means no particulate filter deletes, no EGR deletes, no DEF system disabling and no aftermarket performance programming. We also do not perform state emissions inspections or sign any emissions certification. Those modifications are illegal on road vehicles in California, and they tend to create new problems for the owner at registration or resale.

What we do is diagnose the fault that sent you looking for a shortcut. A clogged filter often has a cause upstream: a leaking injector, a stuck EGR valve, a bad sensor or a truck that never gets a long enough drive to clean itself. We find that cause, explain it in plain words, and put the repair on a written estimate that keeps the truck in factory form. You can check open recalls on your truck with the NHTSA recall lookup (opens in a new tab) before your visit.

Sometimes the tests point inside the engine: low compression on several cylinders, coolant in the oil, or heavy blow-by. That is when owners worry most, and it is when a clear plan matters most. We show you the test numbers, explain the options, which can include a gasket job, a head repair, an overhaul or a replacement engine, and tell you honestly when the truck's value makes a big repair a hard sell.

Your written estimate shows every step of the job, including any parts that need inspection or reconditioning, so nothing surprises you on the invoice. Our diesel engine overhaul page walks through how that decision usually goes.

Yes. Contractors, delivery operators and small fleets use us for diesel pickups and vans. We put unit numbers on invoices, set up A, B and C preventive maintenance intervals around your mileage and hours, and give fleet vehicles priority when the board allows. Payment is by card or cash at pickup, the same as any customer. Our fleet managers page explains how we keep a running history for each unit.

Diesel parts cost more than most gas engine parts, and some jobs take longer because components sit under turbos, intake plumbing or cab structure. The price depends on the engine, the part brand you choose, how much has to come apart to reach it, and whether seized parts such as glow plugs or exhaust bolts need extra time. Phone quotes are ranges until we inspect the truck. Once we do, you get a written estimate, and if the job grows we stop and ask again.

Simple maintenance often fits into the same day when the board allows. Diagnosis of an intermittent problem can take longer, and some parts need to be ordered. We tell you the look window we can hold and text you if it will slip. If a second technician is needed on a heavy job, we explain that before the clock starts. AAA members save 10% on parts and labor, up to $75, with the card at time of service.

After fuel system work, the engine may idle a little rough for the first few starts while any remaining air works out. After a turbo or intercooler repair, listen for any new whistle and watch for oil at the charge pipe joints. Keep an eye on coolant and oil levels for the first week after any gasket job.

Declined items stay on your repair order, so you have a record of what can wait and why. If a problem comes back, bring the truck in. Comebacks go to the front of the line, and we write the root cause on the repair order. Warranty coverage depends on the part and the repair and is printed on your invoice.