Mechanical Diesel Injector Testing & Rebuild Service
A mechanical diesel injector rebuild is one of the highest-return repairs you can make on an older diesel, and Valley Fuel Injection has been testing and rebuilding these injectors the right way for decades. Mechanical, pop-type injectors are the spring-and-nozzle injectors and nozzle holders fitted to virtually every mechanically injected diesel ever built: Yanmar and Kubota tractors, excavators, and boats, older Cummins engines, GM 6.2 and 6.5 pickups, ag tractors of every color, and small marine and industrial power units. There are no wires and no electronics. A spring holds the nozzle closed until pump pressure pops it open, and when the nozzle, seat, and spring wear, atomization falls apart and the engine lets you know about it.
Most shops cannot do anything with a worn injector except sell you a replacement of unknown quality. We do the opposite. We rebuild your own injectors with brand-new nozzles, reset each one to exact factory opening pressure with calibrated shims, and prove the whole set on a calibrated pop tester before it leaves the building. One note so you land on the right page: modern common-rail injectors are electronically controlled and have their own dedicated common-rail injector testing and rebuild service; this page covers mechanical, pop-type injectors only.
The Valley Fuel Injection Difference
We are a rare breed. There are not many shops left in the country with the training, the certification, and the test equipment to rebuild diesel injectors to factory standard, and fewer still that pop-test every unit before and after the work. This is not a box of cheap imported knockoffs and it is not a quick wipe-and-return. It is a genuine, certified, factory-spec rebuild, done by hand and proven on the test stand before it ever leaves the building.
When you send injectors to Valley Fuel Injection, they are rebuilt by licensed, factory-certified diesel technicians, set to the same specification they held the day they left the factory, and returned as a matched, balanced set backed by a real warranty. That is the whole point of what we do.
Applications We Service
Mechanical injectors cover an enormous range of engines and equipment. The most common we see:
| Engine / Equipment | Typical Applications |
|---|---|
| Yanmar & Kubota | Tractor, excavator, and marine diesel injectors with Denso hole-type and pintle nozzles |
| GM 6.2L / 6.5L | Military and civilian 6.2/6.5 diesel pickup injectors |
| Ag tractors | John Deere, Case, Massey, Ford tractor injectors of every era |
| Marine & industrial | Small marine diesels, gensets, and industrial power units |
Common Injector and Nozzle Types We Service
Injector hardware varies by manufacturer, but nearly everything that comes across our bench falls into a few families:
Denso hole-type & pintle nozzles: Yanmar, Kubota, and Japanese diesels (including ND-DN0PD80 family)
Bosch nozzle holders: American and European ag, truck, and industrial diesels
Delphi / Lucas nozzles: Tractor and industrial engines with CAV-pattern injectors
Do not see your engine or injector type? It does not matter. If your diesel is mechanically injected, we can almost certainly test and rebuild the injectors. Call 530-668-0818 with your engine make and model and we will confirm it and quote the job.
Signs Your Injectors Need Testing or Rebuilding
- Hard starting or long cranking, especially on cold mornings
- White or black exhaust smoke that never clears up
- A sharp diesel knock from a nailing injector
- Rough idle, a persistent miss, or a dead cylinder
- Fuel dilution of the engine oil from an injector dribbling instead of atomizing
- Poor power and sluggish response under load
- A failed emissions or smoke test caused by poor atomization
How We Rebuild Your Injectors
Injector work is priced and performed per job, and every job gets the same full treatment. This is not a rinse and a visual check. Every injector is rebuilt and set to specification, one measured step at a time:
- Baseline pop-test. Before anything comes apart, every injector goes on the calibrated pop tester. We document opening pressure, spray pattern, chatter, and leak-off so we know exactly what each unit is doing.
- Complete disassembly and ultrasonic cleaning. Every injector is fully disassembled and ultrasonically cleaned so we are building on bare, spotless metal, not carbon and varnish.
- Brand-new nozzles. Nozzles are replaced with new, hole-type or pintle to your engine’s exact specification, never a close-enough substitute.
- Opening pressure set with calibrated shims. Each injector’s opening pressure is reset to factory specification using calibrated shims, not guesswork.
- New sealing hardware. New crush washers, dust seals, and banjo connector hardware, so the set installs clean and seals the first time.
- Final pop-test as a matched set. Every finished injector is pop-tested again for opening pressure, spray pattern, chatter, and leak-off, and the injectors are matched as a balanced set before they ship back.
That before-and-after testing is what separates a real rebuild from a parts swap. Anyone can screw on a new nozzle. Very few shops can put your injectors on a test stand, prove the whole set against factory specification, and stand behind the result.
Our Warranty
We control every step of the rebuild, so we stand behind it. Every pump and injector we rebuild carries a 1-year warranty. Electrical and electronic components are warrantied for 30 days. Clean, water-free fuel is essential to injector life, so we recommend fresh fuel filters at installation to protect your rebuild.
What Mechanical Injector Testing and Rebuilding Costs
Typical Job Cost
$350 to $600 typical range per set
Injector service is priced per job, not per part. Most mechanical injector jobs, a complete set tested, rebuilt, and matched, land between $350 and $600, with a typical job around $450. Those are real figures from 50 recent injector jobs over the last 18 months, not markup guesses. Hard-to-source nozzles or badly worn nozzle holders run higher. Because every job is priced on your injectors’ actual condition, we give you a firm quote after inspection, before any work begins.
Prices above cover the service and parts. Any applicable sales tax, plus shipping and small shop fees (such as a hazardous-waste disposal fee), are added at invoicing, so your quote reflects the full out-the-door number before any work begins. Buying tax-exempt? Qualifying diesel repair shops, fleets, farms, and agricultural operations can purchase tax-free. Set up tax-exempt purchasing by submitting your resale or exemption certificate once, and every qualifying order is tax-free going forward.
How It Works · Call for Pricing and Availability
Because every set of injectors is rebuilt on your own cores, pricing depends on their condition and the nozzles they need, so we quote each job individually. Here is the process:
- Call us with your engine make and model and the number of injectors, and talk through your symptoms.
- Ship the injectors to us or drop them off. We pop-test and inspect them, then give you a firm quote before any work begins.
- We rebuild the set, prove it on the test stand, and return it matched, balanced, and ready to install, backed by our warranty.
Call 530-668-0818 for pricing and turnaround, or start your rebuild online → and we will walk you through shipping it in.
Why Valley Fuel Injection
Valley Fuel Injection & Turbo is a full-service, factory-certified diesel fuel injection shop in Woodland, California, serving truck owners, farmers, fleets, boat owners, and other repair shops across the country. We are a Bosch-authorized service center with the tooling, the test equipment, and the certification to test and rebuild mechanical injectors correctly, and we have been doing it long enough to have seen just about every way an injector can fail. When a shop cannot fix it, they send it to us. Ship your injectors from anywhere or visit us at our Woodland shop.
Want a step-by-step walkthrough on pulling, packing, and shipping your injectors before you send them in? Read our mail-in diesel injector testing guide.
Frequently Asked Questions
How much does mechanical diesel injector testing and rebuilding cost?
Most mechanical injector jobs run between $350 and $600 for a complete set, with a typical job around $450. Those figures come from 50 real injector jobs over the last 18 months, not guesses. Hard-to-source nozzles or badly worn nozzle holders can push a job higher. Because every job is priced on the actual condition of your injectors, we give you a firm quote after inspection, before any work begins. Call 530-668-0818 for current pricing.
Can I mail my injectors in from out of state?
Yes. We test and rebuild injectors for customers nationwide. Pull the injectors, cap the fuel connections, wrap each one so the nozzle tips are protected, and ship the set to us. We pop-test and inspect them, quote the job, and return the finished set matched and ready to install. Our mail-in diesel injector testing guide walks you through the whole process step by step.
What warranty comes with the rebuild?
Every pump and injector we rebuild carries a 1-year warranty. Electrical and electronic components are warrantied for 30 days. We control every step of the work in-house, from teardown to final pop-testing, which is why we can stand behind it. Clean, water-free fuel is essential to injector life, so we recommend fresh fuel filters at installation to protect your rebuild.
What is pop-testing and why does it matter?
Pop-testing puts each injector on a calibrated test stand and pressurizes it the same way your engine does. We verify the opening (pop) pressure, watch the spray pattern for proper atomization, listen for healthy chatter, and check the nozzle for leak-off. We test every injector before teardown to document its condition, and again after the rebuild to prove the whole set meets factory specification.
Why rebuild my injectors instead of buying new ones?
For many of these engines, new injectors are either unavailable, generic imports, or surprisingly expensive. A rebuild keeps your original nozzle holders, which were made for your engine, and pairs them with brand-new nozzles set to exact factory opening pressure with calibrated shims. You end up with a matched, balanced set proven on the test stand, usually for less than a set of questionable replacements.
My engine is not on your list. Can you still service my injectors?
Almost certainly. Mechanical injectors were fitted to far more engines than we can list, and we service Denso, Bosch, and Delphi and Lucas CAV-pattern injectors from every era. If your engine is mechanically injected, we can almost always test and rebuild the injectors. Call 530-668-0818 with your engine make and model and we will confirm before you ship anything.
Should I send the whole set or just the bad injector?
Send the whole set. Injectors wear together, so if one is nailing or smoking, its siblings are usually not far behind, and mixing one fresh injector with worn ones leaves the engine unbalanced. We test and rebuild injectors as a complete set, matched on the test stand, so every cylinder gets the same fuel delivery. That balance is what restores a smooth idle and even power.
How long does injector testing and rebuilding take?
Turnaround depends on our current shop schedule and nozzle availability for your specific injectors. Common Denso, Bosch, and Delphi nozzles are usually quick, while unusual pintle nozzles can take longer to source. We give you an honest timeline when we quote the job, and if your truck, tractor, or boat is down, tell us when you call and we will do our best to prioritize it.
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