Side-Mount Tank. Cap at Eye Level
NPR • NPR-HD • NPR-XD • NQR • NRR • FTR • FVR
Isuzu N-Series and F-Series cab-overs carry side-mounted tanks with an exposed cap right at eye level — an easy target on any jobsite or delivery route. The Work Truck Fuel Vault puts an armored, locking door over it.
Founders Edition pricing — starting at $159.95 (Save up to $110 on the 3-Pack) · Security screws included
Isuzu Builds the Truck — Not the Fuel Lock
Isuzu commercial trucks leave the factory as incomplete chassis. The body builder finishes the truck, and nobody adds a lock to the fuel filler.
- Side-mount tanks put the fuel cap at eye level and easy reach
- Box trucks and landscape bodies park loaded overnight
- NQR, NRR, FTR and FVR builds add an exposed DEF filler
- Locking gas caps come off with pliers
- Contaminated fuel or DEF puts a delivery truck out of service
- Fleet fuel loss hides inside fuel card totals
The Locking Fuel Door for Your Isuzu Truck
The Work Truck Fuel Vault is an armored, locking fuel door that bolts on at the filler. It covers the whole fill area, not just the cap.
- Armored locking door over the filler on the side-mount tank
- Small door for NPR, NPR-HD, NPR-XD and NQR
- Large door for NRR, FTR and FVR
- Second door option for the DEF filler on dual-filler builds
- Bolt-on install in 8–15 minutes; security screws included
- Limited Lifetime Warranty and 30-day money-back guarantee
The Part The Factory Forgot
The Work Truck Fuel Vault is an armored, locking fuel door that covers the entire fuel access area on your work truck. No more exposed caps. No more easy targets.
Why Didn't This Exist Before?
Despite billions lost to fuel theft every year, nobody built a real solution for commercial work trucks. Here's why.
"Good Enough" Thinking
The industry defaulted to cheap aftermarket locking gas caps. A $15 key-locked cap was considered good enough — until thieves proved otherwise with a pair of pliers.
Upfitters Focus on the Body, Not the Cap
Manufacturers like Knapheide and Reading engineer every compartment lock on the service body — but the chassis fuel pocket belongs to Ford or Ram. Nobody owned the gap.
The Zero-Drill Engineering Problem
Consumer billet doors are made for flat pickup beds. The recessed fuel pocket on a commercial chassis is a completely different geometry — and drilling risks voiding the chassis warranty.
The Cost Was Just "Absorbed"
Fleets treated fuel theft like weather damage. A $500 siphoning hit got buried in operating expenses. Without a purpose-built product available, the problem was simply accepted.
The Work Truck Fuel Vault is the industry's first drop-in armored fuel door that uses existing factory mounting points. No drilling. No cutting. No warranty risk.
Isuzu Owners Who Need This
Delivery & Box Trucks
NPR box trucks run routes all day and park in open lots all night.
Landscapers
Landscape dump bodies on NPR-HD sit at yards and jobsites.
Municipal Fleets
Public-works cab-overs park in open yards — lock the fuel.
Isuzu Dealers & Upfitters
Add it at upfit for box, dump and stake builds.
Utility & Service
Service bodies on NQR and NRR need DEF locked too.
Rental Fleets
Protect fuel on cab-overs that change hands every week.
Chassis Compatibility
Purpose-built for the most popular commercial chassis platforms in the industry.
Ford
Super Duty & Commercial Chassis
- F-350 Chassis Cab
- F-450 Chassis Cab
- F-550 Chassis Cab
- F-600 Chassis Cab
- E-350 / E-450
- F53 Workhorse
Ram
Chassis Cab Heavy Duty
- Ram 3500 Chassis Cab
- Ram 4500 Chassis Cab
- Ram 5500 Chassis Cab
Locking Fuel Cap vs. Fuel Vault
See how The Work Truck Fuel Vault compares to the alternatives.
| Feature | Locking Fuel Cap | The Work Truck Fuel Vault |
|---|---|---|
| Protection Type | Cap only | Full armored door over the fuel fill area |
| Tamper Resistance | Low — pliers remove in seconds | High — armored composite, security screws |
| Prevents Siphoning | Partial — hose can bypass | Yes — locked door blocks access |
| DEF Protection | Not included | Second door locks the DEF filler |
| Install Time | 1 minute screw-on | 8–15 min bolt-on (one time) |
| Warranty | None or 90 days | Limited Lifetime Warranty |
Feature comparison between standard locking fuel cap and The Work Truck Fuel Vault
Protection Type
Cap only
Full armored door over the fuel fill area
Tamper Resistance
Low — pliers remove in seconds
High — armored composite, security screws
Prevents Siphoning
Partial — hose can bypass
Yes — locked door blocks access
DEF Protection
Not included
Second door locks the DEF filler
Install Time
1 minute screw-on
8–15 min bolt-on (one time)
Warranty
None or 90 days
Limited Lifetime Warranty
Our Guarantee
Limited Lifetime Warranty
Built to last. Warranted against defects in material and workmanship for the life of the vehicle on which it was originally installed.
30-Day Money Back
Not satisfied? Return within 30 days of receipt for a full refund. No questions asked.
Free Replacements
If your Fuel Vault is defective under normal use within the warranty period, we replace it at no charge.
Frequently Asked Questions
Which Isuzu trucks does it fit?
Our fitment guide lists the NPR, NPR-HD and NPR-XD (one Small door), the NQR (Small door, two recommended for diesel plus DEF on later builds), and the NRR, FTR and FVR (Large door, two recommended).
Which Isuzu fit is most common?
The NPR-HD is our most common Isuzu fit, and the NPR-XD uses the same filler.
Does it fit the Chevrolet Low Cab Forward?
Yes. The Chevrolet Low Cab Forward is an Isuzu-built cab-over. The LCF 4500 and 5500 take one Small door and the LCF 6500XD takes one Large door.
How long does install take?
About 8 to 15 minutes per door with basic hand tools. It bolts on — no welding and no changes to the body or chassis.
How much does it cost?
The Small door (WTFV-1001S) is $159.95 and the Large door (WTFV-1002L) is $169.95. A 2-pack of Small doors (WTFV-2001S) is $309.95. Tamper-resistant security screws are included with every door at no extra cost. UPS shipping is calculated at checkout. Fleet and dealer volume pricing is available.
Is there a warranty?
Yes — a Limited Lifetime Warranty and a 30-day money-back guarantee.
Lock the Fuel on Your Isuzu — Starting at $159.95
Armored locking fuel door. Security screws included. Bolts on in about 15 minutes. UPS shipping calculated at checkout.
Secure checkout • Live UPS shipping • No charge until your order ships
Isuzu Fitment Guide
Door size and how many doors we recommend for each model.
| Model | Years | Door Size | Doors | Notes |
|---|---|---|---|---|
| NPR | 2012–2026 | Small | 1 | Side-mount tank, small door. |
| NPR-HD | 2012–2026 | Small | 1 | Most common Isuzu fit. |
| NPR-XD | 2016–2026 | Small | 1 | Same filler as NPR-HD. |
| NQR | 2012–2026 | Small | 2 | Diesel plus DEF on later builds. |
| NRR | 2012–2026 | Large | 2 | Large door for main fill. |
| FTR | 2018–2026 | Large | 2 | Large door. |
| FVR | 2018–2026 | Large | 2 | Large door. |
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