How to Fix a Complicated Diesel Fuel Injection Pump

Fuel injection pump from a Toyota 1HD-TFuel injection pump from a Toyota 1HD-T

A thesis is a dissertation on original research on a particular subject, as one presented by a diploma or degree candidate.

Thesis Pumps

Every so often, we’re faced with an exceptionally complicated injection pump – one that challenges even the most skilled and highly trained technician. We call these ‘Thesis Pumps’.
Today’s example is from a Toyota 1HD-T, found in a right hand drive Landcruiser imported from Japan (this engine was never sold in Canada originally).
The injection pump incorporates the following, plus all the usual pump and governor features found in an automotive style injection pump:

  • ACAD (auto cold advance device)
  • Boost control
  • Load sensing timing
  • Air conditioning idle-up
  • An adjustable idle buffer

The closest comparison, for those over 40 like me, would be a carburetor from the early 80’s – surrounded by vacuum lines and dash-pots to meet emissions specs, just before the introduction of fuel injection.

Calibrating the pump

With all the add-on devices and advanced features, it takes longer to calibrate this pump than it does to put it together. To make sure every aspect of this pump works properly and interacts with the other components, you could spend 3 or 4 hours in front of a test stand.

If anyone tells you they’re just replacing the gasket and seals, they are doing you a considerable disservice. To properly rebuild and calibrate this kind of injection pump requires time, specialized equipment, and expert knowledge. As always, you get what you pay for.

Fuel Injectors

The injectors from the Toyota 1HD-T are also worth mentioning. Known as 2 spring or 2 stage injectors, they are unusual to North America. Volkswagen TDI engines from 1999 to 2003 used a similar injector. However, while the operating principles are the same, the rebuild philosophy is different. The manufacturer of the TDI injectors, Bosch, sells a pre-calibrated ‘nozzle kit’, which incorporates the internal parts: an intermediate plate, spring, pin, and nozzle straight from the factory. In contrast, the Japanese manufacturers of the 2 spring injectors sell all the parts separately. We invested in the gauge block, dial gauge, and large supply of shims & pins so we can set these up properly.

Just like the pumps, anyone just slapping nozzles into these trucks, without properly setting up both the primary and secondary opening pressures, is doing the vehicle owner a disservice.

There are very few test machines in our industry which can accurately measure both opening pressures, and they cost in excess of $50,000 each. We have two – one in Nanaimo and one in Surrey.

Have you got a thesis pump that requires expert handling? Contact us today.

Source: NW Fuel Injection Service

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