🔧 Step-by-Step: Installing a Lift Pump on Your LML Duramax

(2011–2016 Trucks — Full Guide to FASS, AirDog, or PPE Kits)

If you own a 2011–2016 LML Duramax, installing a lift pump is one of the smartest upgrades you can make.

Why?
Because GM never gave the LML a factory lift pump — and without one, your fragile CP4 injection pump is running dry under load. A lift pump ensures proper fuel pressure, filters out water and debris, and helps prevent the infamous CP4 failure that can cost $8,000–$12,000 to fix.

Here’s your step-by-step guide to install a FASS, AirDog, or PPE lift pump on your LML the right way.

🧰 Tools & Supplies You’ll Need

Full lift pump kit (FASS, AirDog II-4G, or PPE)
Drill & drill bits
Hose cutter or utility knife
Wrenches (standard & metric)
Thread sealer (Loctite 545 or Teflon paste)
Zip ties or loom
Fuel-safe grease (for o-rings)
Ramps or jack stands

⚙️ What the Lift Pump Does

✅ Supplies constant fuel pressure (8–12 PSI) to the CP4
✅ Filters fuel to 2 microns (depending on kit)
✅ Removes air/vapor from the fuel
✅ Prevents low rail pressure codes (P0087, P0191)
✅ Reduces injector and pump wear
✅ Improves throttle response and power delivery

🧭 Installation Overview

Time: 3–5 hours
Skill level: Intermediate DIY
Location: Frame-mounted, near fuel tank

🔧 Step-by-Step Instructions

✅ Step 1: Disconnect Batteries

Safety first. Disconnect both negative terminals before touching any electrical or fuel system.

✅ Step 2: Raise the Truck & Locate Mounting Area

Get the rear of the truck on jack stands or ramps
Most LML kits mount to the driver-side frame rail, just in front of the fuel tank
Clean the area and test fit the bracket

✅ Step 3: Mount the Pump Bracket

Mark and drill holes (if required)
Use included bolts & spacers to secure the bracket
Make sure there’s enough clearance from driveshaft, exhaust, and suspension

✅ Step 4: Run Fuel Lines

Suction Line:

Connect from the tank pickup (or draw straw/sump) to the "IN" side of the pump
Use hose clamps or quick-connects as supplied
Avoid sharp bends or kinks

Pressure Line:

Run from the "OUT" side of the pump to the factory fuel line leading to the engine
Most kits include a T-fitting or quick-disconnect to tap into the factory line
Secure with clamps and check routing away from heat or moving parts

🧼 Apply fuel-safe grease to all o-rings and barbs before connecting

✅ Step 5: Install the Electrical Harness

Connect the positive/negative leads to the battery
Route the harness to the rear frame
Use the provided relay and fuse
Plug into the pump connector
Use a key-on power source (ignition signal) for the relay trigger

Many kits include an “add-a-fuse” for this — tap into the fuse box under the hood

✅ Step 6: Prime the Pump & Check for Leaks

Turn key to the ON position (don’t start)
Let the pump run for 15–30 seconds
Check all fittings for leaks
Tighten any connections as needed
Repeat 2–3 times until you hear the pump running smoothly

✅ Step 7: Start the Truck

Let it idle for 5–10 minutes
Watch fuel pressure (if monitored)
Listen for any leaks, whines, or unusual sounds
Go for a short test drive and monitor for codes

🧯 Pro Tips

Zip tie lines away from the exhaust and driveshaft
Use fuel-rated loom if routing near heat
Replace filters every 15,000 miles (or sooner if poor fuel quality)
Bleed air out with the Schrader valve (if equipped) after install
Never run below 1/4 tank — lift pumps hate sucking air

💬 Real Shop Example

“Installed a FASS on an LML that had been surging and throwing low rail pressure codes. After install, smoother idle, no more codes, and better throttle response towing uphill. Owner added a disaster prevention kit later and hasn't looked back.”

💯 Final Thoughts

A lift pump on an LML is more than a mod — it’s preventative maintenance. Whether you're towing, daily driving, or tuned for performance, a quality lift pump protects your injectors, CP4, and wallet.

Ready to upgrade?
👉 Order a proven FASS, AirDog, or PPE kit at PistonTwistin.org and get the parts, support, and performance you need.

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