Trying to decide which Powerstroke/Navistar/CAT HEUI injector is needed for a given application can be very confusing.  In all cases each injector is available under several part numbers.  The best way is to have a look at your old injector(s)!  All of these injectors are have a part number etched on the solenoid.  This solenoid usually has several numbers on it, as well as in some cases a 2 character letter code.  The letter codes for Ford engines are AA, AB and AD, and AE.  Most letter codes on Navistar engines start with a B, with the exception of the T444 which uses  an AC coded injector.  Cat injectors do NOT use a letter code, but normally have a part number on the solenoid.  If you can determine the letter code, then doing a search on the word Powerstroke or Navistar and the letter code will usually give the desired results.  For example:  If you injector is codes AB then doing a search on "Powerstroke AB" (without the quotes) should find the correct injector in our database.  If searching for a BD injector use the search term "Navistar BD" (without the quotes).  For Cat injectors, you will need to search by part number.  Searching by part number will also work for Navistar & Ford injectors.

BY the way ... the other number on the solenoid is the serial number.

Some early Ford Powerstroke injectors did not have a letter code, and had black solenoids.  These are usually always AA injectors.  The same applies to early Navistar injectors, and these are usually AC injectors.

Some Ford Powerstroke engines may also have a different injector (either an AD or in some cases an AE) in #8 cylinder.  Our advice is to put the same part number in as what came out!

Cat 3412/3408 and 3126A injectors have a vertically mounted solenoid.  These also have the p
art number stamped on the solenoid, although it may be difficult to read without removing the injector from the engine.

Cat C7/C9 injectors are also identified by a part number, although not always on the solenoid.  The top of the injector has a small metal plate with 4 screws holding the solenoid onto the injector body.  The part number as well as the 4 digit calibration code is normally located on this plate.  If there is no part number information on this plate, it can then be found on the exposed part of the solenoid, usually near the wire connector.