12641847
HITACHI 12641847 Pompe Haute Pression pour GM 2.0T LTG Cadillac
12641847, 12639694, 12633492, 12608371, 12634491Integrated Solenoid Fuel Pressure Regulator-150 barPrésentation du produit
The Hitachi 12641847 (GM OE 12639694 / 12633492) is the original equipment high-pressure mechanical fuel pump (HPFP) fitted to General Motors 2.0L Turbo Ecotec (LTG) and 3.6L V6 engines. Driven directly by a specialized intake camshaft tri-lobe via a roller follower, this pump elevates low-pressure tank fuel (5.5 bar / 80 psi) to continuous direct-injection rail pressures up to 150 bar (2175 psi). Widely installed on performance and luxury applications including the Cadillac ATS/ATS-L, CTS, CT6, Buick Regal GS, Envision 28T, and Chevrolet Camaro, it features an ECM-modulated fuel rail pressure regulator valve that delivers on-demand volumetric flow. Failure of this pump results in engine hesitations under wide-open throttle, extended crank times, low rail pressure DTC P0087, and rich fuel trim code P0172 from fuel-contaminated engine oil.
ROLLER FOLLOWER INSPECTION & OIL DILUTION WARNING: Always inspect the camshaft roller follower (GM 12642287) whenever replacing the high-pressure pump. A worn or seizing roller follower scores the camshaft drive lobe, generating fine metal shavings that circulate into the VVT solenoids. Furthermore, an internally leaking pump plunger vents raw gasoline past the shaft seal directly into the cylinder head valvetrain, diluting engine oil, causing elevated oil dipstick levels, and setting false rich codes (P0172) via crankcase fumes.
Compatibilité véhicules et motorisations
| Véhicule | Moteur | Années |
|---|---|---|
| Cadillac ATS / ATS-L 2.0T | GM 2.0L Ecotec Turbo SIDI (LTG / LSY Tripower / LHU) | 2013-2019 |
| Buick Regal GS / Regal 2.0T | GM 2.0L Ecotec Turbo SIDI (LTG / LSY Tripower / LHU) | 2014-2020 |
| Buick Envision 28T AWD | GM 2.0L Ecotec Turbo SIDI (LTG / LSY Tripower / LHU) | 2015-2020 |
| Chevrolet Camaro 2.0T | GM 2.0L Ecotec Turbo SIDI (LTG / LSY Tripower / LHU) | 2016-2020 |
Spécifications techniques
| Spécification | Valeur |
|---|---|
| Pump Generation | Hitachi Radial Plunger High Pressure Mechanical Fuel Pump |
| Operating Rail PressureSpéc. clé | |
| Cam Drive Type | Intake Camshaft Auxiliary Tri-Lobe via Roller Follower |
| Roller Follower Part Number | GM OE 12642287 (Inspect for pitting or flat spots) |
| Solenoid Metering Valve | Pulse-Width Modulated Normally-Open Valve |
| Pump Flange Mounting Torque | 10 N·m (M6 Bolts, alternating two-step torque) |
| High Pressure Line Flare Nut Torque | 30 N·m (18mm flare nut, counter-held body) |
| Tightening Torque | 30 N·m |
| Couple de serrage de bride | 10 N·m |
| Default Safety Pressure Mode | Mechanical bypass ~5.5 bar low pressure feed |
| Pression de serviceSpéc. clé |
Pompe haute pression associée (Ensemble circuit de carburant)
Fonctionne sur le même circuit haute pression Common Rail. En cas de chute de pression (P0087), vérifier le débit de la pompe avant de remplacer les injecteurs.
Conseils de montage
Outils nécessaires : 18mm line wrench and open-end wrench for counter-holding fuel pipe fittings, Torque wrench calibrated for 10-30 N·m range, 10mm socket and ratchet with extension, Clean engine oil or assembly lube for the roller follower and pump O-ring, Shop rags and safety glasses for high-pressure fuel release
- Disconnect the vehicle negative battery cable and pull the fuel pump fuse; crank engine for 5 seconds to depressurize low-pressure lines.
- Wrap the high-pressure fuel line fitting in absorbent shop towels and slowly crack the 18mm flare nut to release residual 150-bar rail pressure.
- Disconnect the wiring harness connector from the pump pressure regulator solenoid.
- Disconnect the quick-connect low-pressure fuel supply hose from the pump inlet nipple.
- Remove the two 10mm pump mounting bolts evenly in half-turn increments to relieve spring tension from the camshaft lobe.
- Extract the pump and immediately inspect the roller follower (GM 12642287) in the cylinder head bore. Check for free roller rotation and surface pitting; replace if scored.
- Clean the mounting bore surface and lubricate the new pump O-ring seal with clean engine oil.
- Position the engine camshaft at base circle (lowest lobe lift) so the pump spring does not bind upon installation.
- Seat the pump into the bore and thread the two mounting bolts finger-tight. Tighten bolts alternately in steps until torqued to 10 N·m.
- Thread the high-pressure steel pipe flare nut by hand to prevent cross-threading; counter-hold the pump body adapter with an open-end wrench and torque flare nut to 30 N·m.
- Reconnect low-pressure quick-connect hose and wiring connector; prime fuel system by cycling ignition, and inspect for leaks before starting.
- Camshaft Base Circle Positioning: Before bolting the new pump down, bump the engine so the camshaft lobe is at its lowest position. Attempting to bolt the pump down against peak lobe lift cross-threads aluminum threads in the cylinder head and damages the pump flange.
- Flare Nut Counter-Holding Mandate: Always use a backup wrench on the pump body hex fitting when torquing the 18mm flare line nut to 30 N·m. Failure to counter-hold loosens the factory factory-torqued pump fitting, causing severe fuel leaks.
- Mandatory Oil & Filter Change: If replacing the pump due to an internal seal rupture, you MUST change the engine oil and filter immediately. Gasoline-diluted oil destroys main bearings and turbocharger thrust washers within hundreds of miles.
Questions fréquentes et diagnostic
What diagnostic trouble codes indicate a failing 12641847 HPFP on GM 2.0T LTG engines?
The most frequent DTC is P0087 (Fuel Rail Pressure Too Low), triggering engine limp mode under acceleration. Crucially, a ruptured internal pump seal also triggers P0172 (Fuel Trim System Too Rich) because gasoline seeps into the crankcase, causing PCV vapors to saturate the intake with unmetered fuel vapor.
Why does my engine oil smell strongly like gasoline on my Cadillac ATS or Buick Regal?
On GM 2.0T LTG engines, the high-pressure fuel pump is mounted directly to the cylinder head valvetrain cover. When the internal plunger shaft seal degrades, high-pressure gasoline bleeds directly into the engine oil cavity. If your oil dipstick reads overfilled and smells like gasoline, the HPFP has suffered an internal diaphragm seal failure.
Do I need to replace the camshaft roller follower when installing a new HPFP?
Yes, standard ASE practice dictates inspecting the roller follower (GM 12642287) every time the pump is unbolted. If the internal needle bearings seize or develop flat spots, the roller scores the intake camshaft lobe, requiring expensive camshaft replacement.
Can a bad GM 2.0T HPFP cause a cold-start extended crank of 5 to 8 seconds?
Yes. When the pump internal check valve fails, fuel rail pressure bleeds off completely while parked. Upon cranking, the starter must spin the engine until the mechanical pump rebuilds 40-50 bar of rail pressure before the ECM permits the injectors to fire.
Say this to the shop: How do I confirm the pump is bad instead of the low-pressure tank pump?
Ask the technician: 'Please hook up a scan tool and compare Low Fuel Pressure Desired versus Actual, and High Fuel Pressure Desired versus Actual under full boost. If low pressure stays steady at 5.5 bar (80 psi) while rail pressure drops from desired 150 bar down to 40 bar with P0087, we know the in-tank pump is healthy and the mechanical HPFP has failed.'
Codes de Defaut (DTC) & Protocoles de Diagnostic
Codes de defaut diagnostiques (DTC) courants déclenchés lorsque cet injecteur common rail subit une usure, des pannes de circuit ou une dérive d'étalonnage:
Fuel Rail / System Pressure Too Low
Excessive internal backleak from worn control valve seats drops common rail pressure below target under engine load.
Injector Circuit Malfunction / Open Circuit
Solenoid coil resistance drift (0.2-0.5 Ω) or piezo stack degradation triggers driver stage shutdown on affected cylinders.
Cylinder Misfire & Balancing Deviation
Carbon-clogged nozzle spray holes or missing IMA calibration causes uneven cylinder contribution. Recode ECM and verify washer seating.
Fuel Rail / System Pressure Too High
Spill line backpressure or stuck metering valve prevents rail depressurization, creating overpressure risks under load.
Références croisées et compatibilité
Pièces sœurs, variantes de même plateforme et incompatibilités connues.
Protocoles Techniques de Diagnostic & Réparation
Procédures d'atelier vérifiées, seuils de test et guides d'intervention pour cet ensemble.