Powertrain, generic (extended)

P2A8E Alternative Fuel Pump A Performance

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modePossible

P2A8E reports that alternative fuel pump A no longer delivers what it should, a mechanical or hydraulic fault rather than an electrical one. Such pumps move liquid fuel, typically LNG out of a cryogenic tank. A patent application now held by Cespira, US20080302111A1, shows how a controller can judge them from the delivery line pressure alone: each time the pump is commanded on, pressure has to climb from a lower to an upper set point within a known range of slopes. A clearly flatter rise means lost volumetric efficiency, and a falling pressure means the pump cannot even keep up with the engine. The document names worn piston seals, leaking static seals or check valves, dirt in the fuel and a weak hydraulic drive as causes. No manufacturer publishes P2A8E or its limits.

Likely causes

Worn dynamic piston seals in pump A
Leaking inlet or outlet check valve of pump A
Hydraulic drive of pump A delivering too little force or speed
Impurities in the fuel passing the filter and damaging the pump

Symptoms

  • Malfunction lamp on
  • Power loss at high load, gas pressure sagging
  • Pump runs noticeably longer to refill the accumulator
  • Engine switched to reduced output or diesel-only operation

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€800–6,000
Time3–10 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

alt fuel pump aalt fuel filter

Related codes

P2A8FP2A90P2A7FP2A80

References: law.cornell.edu, patents.google.com, patents.google.com.