705503AT Unit Pump for GE GEVO 12 Locomotive

A module of this kind is a different purchase from an injector. The high-pressure pumping element, the roller plunger and the solenoid valve arrive built into one body that drops into the engine block and is held by its flange, so the job is a straight exchange rather than a pump overhaul. Because the GEVO-12 fires twelve cylinders from twelve separate modules, a fleet workshop rebuilding a set orders twelve, while a single module is the normal order when a fault is confined to one cylinder. The engine keeps running on the remaining modules either way, which is why a failing module is often only noticed when the balance figures are read rather than when the locomotive is taken out of service. Depots that hold the reference number against the unit itself, instead of against a catalogue line, avoid the wrong-build trap altogether.

Parameters marked Not published are not asserted anywhere on this page and no figure is substituted for them further down. Where a depot needs a specific reading, the bench sheet for the module you receive can be requested with the order.

The working parts inside the body

Summaries of stored codes are grouped on our fault code pages, and the list above should be read alongside live cylinder data rather than instead of it.

A module closing its valve late or leaking past the seat does not fail suddenly. The first sign is usually an exhaust plume that changes colour before the balance figures move: black smoke diesel under load points to a cylinder receiving more fuel than it can burn, while white smoke diesel at start-up and at light load more often follows a cylinder that is not firing cleanly at all. Neither colour identifies the module on its own, because an injector side fault produces the same plume, which is why the balance reading is taken next.

Where delivery falls far enough, the control unit protects the engine and limits output. By that stage the fault is usually visible in more than one place at once: a cylinder well outside the fleet norm, a rising return flow, and a fuel figure that no longer tracks the locomotive’s own history. A module that has begun to leak internally can also produce fuel starvation symptoms on the cylinder it serves — the pumping element still strokes, but the trapped volume escapes past the seat, so the event is short and late. Because the engine keeps running on the remaining modules, that pattern is easy to mistake for a control fault, which is why the mechanical reading should come before the electronic side is suspected.

A cross reference diesel list is only useful when it names the engine as well as the number, and on this article the engine is the whole point: the module is built for the GEVO-12 cam and would not serve another cylinder count without a change of build. Treat a result that returns a Bosch family reference on its own as half an answer, and check it against the maker field as well. Read as a diesel part number check, the grid above runs from the reference number through the two maker numbers to the short forms, and every one of those routes should land on the same module.

The maker side of the numbering is where most confusion starts, because two maker numbers describe one article and a supersession number list will often show only one of them. The label on units of this build prints the two maker fields together, GE PT number 84E901259G5 and GE CAT number 332X1021, and the label is the field that settles which build the module is. Where a buyer’s paperwork carries only one of them, the Bosch reference on the plate is the second check that closes the gap. In practice the fuller route is a part number lookup diesel against the number on the body rather than against the locomotive model, because the model covers too many production years to identify one body.

The body also carries an engraved field and a square code, reproduced here only so a buyer can recognise what they are reading. The photograph on this page shows the engraved string 720GG030045 on the flat face and the stamping 00317 in the roller window; both are build markings of this article and neither is a part number to order against. If your old module carries a number that does not appear in the grid, send us a photograph of the body before ordering and we will check it against the reference group.

One question that comes up at the bench rather than at the desk is how to tell a weak module from a tired engine, and the honest answer is that a compression test diesel reading on its own cannot do it. Compression tells you about the cylinder and the valves; it says nothing about how much fuel the module delivered or when. The two readings have to be taken together, and the cylinder that shows both low compression and a delivery figure outside the fleet norm is the one where the module and the bore need separate attention. Where the number on the old module is unreadable, a part number lookup diesel run against the body marking rather than against the locomotive model is what narrows it down, and our diagnosis pages set out the order to take the readings in.

Beyond the module itself, the two things that go wrong most often on a service programme for this engine are filter discipline and record keeping. Holding the filter interval is a maintenance habit rather than a parts decision, and it is the one that decides how long the pumping element in this module lasts. Keeping the balance readings on file after each exchange is the second: the next weak cylinder is found by comparing against the previous set of figures, not by waiting for a fault code. The third is simpler still and is often skipped on a rush job — note the engine timing marks and the cam position at the exchange, so the relationship between cam and module can be re-checked later without stripping the covers again. Operators running this engine alongside other commercial diesel parts in a mixed fleet use our parts glossary to keep the terminology straight between the pump side and the nozzle side, and the fleet programme page for standing-order terms across a workshop’s whole range.