CP4 to DCR conversion
Replace the CP4 before it fails and takes the fuel system with it. Same-day installs and a 2-year warranty.
SpartanburgDiesel repair & service.
From your grandpa's 12-valve to your dream truck fresh off the lot. Book a multi-point inspection, or a pre-purchase inspection before you buy.
Platforms
Every Duramax, Power Stroke and Cummins.
Find yours by engine code or model year. Not on the list? Call anyway.
Duramax Chevy / GMC 6.6L
- LB7 / LLY2001–2005
- LBZ / LMM2006–2010
- LML2011–2016
- L5P2017–today
Power Stroke Ford Super Duty
- 7.3L1999–2003
- 6.0L2003–2007
- 6.4L2008–2010
- 6.7L2011–today
Cummins Dodge / Ram
- 5.9L 12-valve1989–1998
- 5.9L 24-valve1998.5–2002
- 5.9L common rail2003–2007
- 6.7L2007.5–today
Smaller diesels too: 2.8 Duramax, 3.0 Duramax (LM2, LZ0), 3.0 Power Stroke and 3.0 EcoDiesel. No semis.
Services
Repair, upgrade, maintain.
Transmission repair
Slipping, flaring or stuck in gear. Repaired, rebuilt or replaced, most with a 2-year, unlimited-mile warranty.
Engine repair
Misfires, hard starts, low power or a leak you can't track down. We find the cause before we replace parts.
Maintenance & reseals
Oil, filters and fluids on your truck's schedule, plus reseals for the oil and coolant leaks that keep coming back.
Used truck inspection
Buying a used diesel? A $199 pre-purchase inspection tells you what you're getting before you hand over the money.
Suspension & lifts
Loose steering and worn front ends fixed so the truck drives straight. Lift and leveling kits installed right.
Fuel system
Hard starts, lost power or water in the fuel. We find the failing part and fix it before the damage spreads.
Disaster prevention
Every diesel has a known weak point. We fix yours before it strands you or turns into a bigger repair.
Why us
Why Williams Diesel.
- A real person on the phoneMon–Fri, 8am–5pm, you talk to someone in the shop, not a call center.
- Every generationDuramax, Power Stroke and Cummins, from the 12-valve to the newest trucks.
- Parts availabilityCommon maintenance parts on the shelf. Most repair parts the same day.
- Same-day DCR installsCP4 to DCR conversions can often be scheduled and done the same day.
- 2-year warrantiesDCR pumps and most transmissions carry 2 years, unlimited miles.
- Fleet pricingDiscount pricing on inspections and maintenance for multi-truck fleets.
How it works
How a job goes.
Call us
(864) 415-0808, Mon–Fri, 8am–5pm. Tell us the year, the engine and what the truck is doing, and we'll go from there.
Bring it in
We're at 8693 Fairforest Rd in Spartanburg. Can't drive it in? We can arrange a tow within 100 miles.
$99 inspection
We run a multi-point inspection and tell you what it needs. You get a written estimate before any work.
We do the work
Parts carry the manufacturer's warranty, and DCR pumps and most transmissions get 2 years, unlimited miles.
Pre-purchase inspection
Check it before you buy it.
Buying a used Duramax, Power Stroke or Cummins? For $199 we look the truck over before any money changes hands, so you know what you're buying.
- Weak spotsEvery engine has one, from CP4 pumps to 6.0 oil coolers.
- Leaks & fluidsOil, coolant and transmission fluid, and any leaks found.
- Test driveHow it starts, shifts and pulls once it's warm and working.
- Before you payA confident seller won't mind a second set of eyes on it.
Fleet
Fleet service for work trucks.
Construction crews, lawn care companies, HVAC and plumbing outfits: if your business runs diesel pickups or service-body trucks, keep every one of them at one shop.
- Discount pricing on inspections and maintenance
- Upcoming work flagged, so you can plan it around the schedule
- A written estimate for every truck before any work
- Fords, Chevys and Rams, all at one shop
About
Locally owned in Spartanburg.
Williams Diesel Performance is a locally owned shop that specializes in light-duty diesel. We work on the whole truck: engines, transmissions, fuel systems, CP4 to DCR conversions, suspension, lift and level kits, maintenance and reseals.
Every truck that comes in gets a multi-point inspection. We tell you what needs fixing now, what can wait, and what it'll take to keep it on the road for years. Then it's your call.
Blog
Guides for diesel owners.
What breaks on each engine, what heads it off, and what to ask before you pay for it.
Upgrade · 2 min read
CP4 pump failure, and what a DCR conversion does
Which trucks have the CP4, how often it actually fails, and what a conversion changes. Plus the two things a conversion can't do.
Prevention · 3 min read
The weak spot on every Duramax, Power Stroke and Cummins
Every diesel generation has a part that tends to go first. Here's the one to watch on each engine, and how to get ahead of it.
Repair · 2 min read
5 signs your diesel injectors are going bad
The five symptoms that point at injectors, and the harness and fuel-supply problems that can look exactly the same.
FAQ
Common questions.
What does an inspection cost?
A multi-point inspection is $99. A pre-purchase inspection on a truck you're thinking of buying is $199. Either way, you hear what the truck needs and what can wait before you spend anything else.
Do you work on my truck?
If it's a diesel pickup or a similar light- or medium-duty diesel, yes. Every generation of Duramax, Power Stroke and Cummins, plus the 2.8 and 3.0 Duramax, the 3.0 Power Stroke and the EcoDiesel. No semis. Not sure? Call and tell us the year and engine.
Will you tell me what can wait?
Yes. The inspection sorts it into what needs doing now and what can wait, so you can plan the work instead of getting surprised by it.
Why aren't repair prices online?
Because the price depends on the truck in front of us. Injectors on an LB7 and injectors on a 6.7 Cummins are different jobs. Every repair gets a written estimate first, so you know the number before we start.
How long will it take?
CP4 to DCR conversions can often be scheduled for the same day. For other work it depends on the job and the parts: common maintenance parts are on the shelf, and most repair parts can be had the same day. Once we've looked at the truck, we'll tell you how long it should take.
What warranty comes with the work?
DCR pumps carry the manufacturer's 2-year, unlimited-mile warranty, and most transmissions we install carry a 2-year, unlimited-mile warranty. Other parts carry their manufacturer's warranty.
Do you tow?
Yes. If the truck can't be driven in, we can arrange a tow from anywhere within 100 miles. The tow is billed when the truck arrives.
Do you work on company trucks?
Yes. Construction crews, lawn care companies, HVAC and plumbing outfits: if your business runs diesel pickups or service-body trucks, ask about discount pricing on inspections and maintenance. Call (864) 415-0808.
Can I bring my own parts?
No. We don't install customer-supplied parts. We source the parts for every job ourselves.
Request service
What can we help with?
Pick what you need and leave your number. We'll call you back. Calling is quicker if you can.