HEUI Injector Parts, Operation, and Modifications
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HEUI Injector Parts, Operation, and Modifications Original posts from DieselStop.com Archives >> Power Strokes 1994-1997 (11/01-7/03) by Swamp Donkey (edited for clarity by SaintITC, PDF by F250_ ) --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- In Edit: The Application Guide link is corrected; I'm having modem problems, so if I'm slow to answer posts or disappear from the Forum for a while, you know why; Carpentractor has a nice injector diagram on his web site, but I can't post the link. Look in his Northeast Rally download postings for *.jpg2. (As of October 2017, since Carpentractor’s site has either changed to a new web address or is just no longer available, so alternative diagrams have been included below.) Let me preface this post by saying that I know perfectly well that I'm not supposed to disassemble or modify an injector, and that doing so will void the warranty, affect the calibration, yadda, yadda, yadda. Those who feel this way can click the "Back" button on their browser right now! Those who want more power, for less money, keep reading. This is the first of 2 or 3 posts dealing with the injector. Part 1 is Injector Parts, Part 2 is Injector Operation, and Part 3 is Injector Modification. Please confine any replies to this post to the injector parts, and how they are assembled, not to how they work. Forum member rwoody loaned me an injector (and a cam!) when I was by his place in OK last week, and I've spent five days taking it apart and figuring out how it works, with an eye towards understanding how to modify them for more power. In short, I believe that for those willing to do some of the work themselves, some tremendous power gains are available for a lot less money than most companies are charging. At this point, I'm NOT advocating people start pulling their injectors to tweak them--I'm saying let's put our heads together and study how they work until we thoroughly understand their operation, and the ramifications of any modifications. Then we decide if we want to tweak them. To follow these posts, you will need to go to www.dipaco.com , download several files, and then print them out so you can see everything at once. If you have an injector to take apart and follow along, that will be even better. The files linked below are attached at the end of this document for convenience. PowerStroke Injector Parts http://www.dipacodtech.com/core/media/media.nl?id=608&c=744110&h=b733b2a81f1fe8f23956&whence = http://www.dipacodtech.com/core/media/media.nl?id=598&c=744110&h=6797cd4dc59c0d385e38&whence = Injector Plunger and Barrel http://www.dipacodtech.com/core/media/media.nl?id=600&c=744110&h=5956a18b50ad1296ab84&whence = http://www.dipacodtech.com/core/media/media.nl?id=650&c=744110&h=93ad0f4294602a4ab75e&whence = Injector Nozzle http://www.dipacodtech.com/core/media/media.nl?id=599&c=744110&h=a45538a78c9433c8fdeb&whence = Injector Application Guide http://www.dipacodtech.com/core/media/media.nl?id=667&c=744110&h=2ae307382f7897a77654&whence = All parts are machined to metric dimensions, and the poppet, piston, plunger and barrel are held to tolerances that far exceed my .0001" (.0025mm) micrometers. HEUI Injector Parts, Operation, and Modifications Original posts from DieselStop.com Archives >> Power Strokes 1994-1997 (11/01-7/03) by Swamp Donkey (edited for clarity by SaintITC, PDF by F250_ ) --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- Part 1. HEUI Injector Parts Start with #FI-77. There are 46 parts in the injector, grouping into several sub-assemblies. The 4 solenoid screws go through the solenoid, through the spacer, and into the adapter. The 4 assembly screws go through the adapter into the piston and valve body. The piston and valve body screws into the body. The 6 dowels just keep things aligned during assembly, but do nothing else. The first O-ring goes inside the adapter, and the sleeve fits inside the poppet shim and into the adapter. The O-ring seals the sleeve into the adapter. The adjusting screw goes through the armature and into the poppet valve. The poppet spring is sandwiched between the poppet valve and the sleeve. When assembled, the armature is on top of the adapter, about half of the poppet is inside the adapter, and half of poppet and spring are below it. The lower part of the poppet fits inside the piston and valve body. There are 2 O-rings after the piston and valve body; one fits on the outside of the valve body to seal it to the body, the other fits inside to seal the piston. The piston fits into the bottom of the piston and valve body. The retaining ring is a snap ring that goes on the upper end of the plunger; the retaining washer seats on the ring, acting as a seat for the spring. When assembled, the spring and 2/3 of the plunger are inside the piston, the rest of the plunger fits inside the barrel. The upper side of the barrel mates to the piston and valve body. The retaining spring girdles the barrel, and holds the check ball in position on a vent hole in the side of the barrel. This valve allows oil or fuel that leaks past the piston or plunger to be vented into the fuel supply, preventing "hydrolock" of the injector. See FI-69 for a close up. The check ball and check plate are sandwiched in pockets between the stop plate and the stop. The ball lets fuel into the barrel, but closes off during injection. Then the plate lets fuel into the spacer sleeve, and from there into the nozzle, but closes off to prevent fuel from flowing back into the barrel from the nozzle when the nozzle needle closes. The nozzle needle fits inside the nozzle tip; the spacer sleeve fits against the nozzle tip, and the lift spacer sits on top of the needle, with the stop pin on it, going inside the spring. See FI-68 for a detail view. The spacer sleeve is not shown in FI-68. The spacer sleeve mates with the stop on the top end. The stop pin limits the travel of the needle to about .38mm, and getting slammed against the stop 2-3,000 times a minute by up to 18,000 psi takes its toll. When assembled, everything from the barrel to the nozzle tip is inside the body, and the only parts which are really visible are the adapter, piston and valve body, barrel, stop plate, spacer sleeve, and nozzle tip. More to come, stay tuned. Conversion Factors: 1" = 25.40mm -- 1mm = .039" (39/1000) .10mm = .0039" (39/10,000) .01mm = .00039" (39/100,000). For comparison, a sheet of paper is about .10mm, a hair is .04mm. If a number is preceded by ± that means I had difficulty getting a consistent measurement, with the uncertainty generally being less than .10mm. Measurements were taken with a digital caliper reading to .0015"/.01mm, and double-checks done with a .0001" micrometer. Both were calibrated with the same 1" standard. Spring rates were calculated using the wire diameter, coil diameter and number of coils, but could have ±10%-15% error, or possibly more. Part 2 HEUI Injector Operation It is assumed that you have thoroughly read and understood the previous post before reading this one! The solenoid and poppet control the flow of high pressure oil into and out of the injector; the piston, plunger and barrel pressurize the fuel for injection; the check balls/stop plate control fuel flow direction and the nozzle assembly controls when and how fast the fuel sprays through the tip orifices. HEUI Injector Parts, Operation, and Modifications Original posts from DieselStop.com Archives >> Power Strokes 1994-1997 (11/01-7/03) by Swamp Donkey (edited for clarity by SaintITC, PDF by F250_ ) --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- Solenoid and Armature: When the solenoid is energized by the PCM/IDM it creates an electro-magnetic field which pulls the armature upwards. The armature's maximum travel is limited to .50mm, the difference in thickness between the armature (4.97mm) and the solenoid spacer (5.47mm). This .50mm can be slightly less during injector operation due to the oil film present, and can be reduced if the adjusting screw is loosened. When the adjusting screw is fully tightened, the top of the poppet is flush against the bottom of the armature. When the screw is loosened, the armature is able to move freely up and down between the screw head and the adapter. If the screw is too loose, the armature will contact the solenoid before it contacts the screw head, and the poppet will not open. The screw has a thread pitch of .5mm, so if it is loosened by 1 turn or more, the poppet will not move. On this injector, the top of the poppet is flush with the top of the adapter, meaning that if there is any wear on the lower (oil inlet) seat, and the adjusting screw is fully tightened, when the solenoid is de-energized the armature will bottom out on the adapter before the poppet is fully on the lower seat, and it will no longer seal. Thus, high pressure oil will flow in the lower seat and out the upper seat. The screw can be loosened 1/4 to 1/3 turn to allow the poppet more down-travel to seat more fully without limiting the up-travel. (I am beginning to wonder if this screw really adjusts anything, or if Dipaco misnamed it.) HEUI Injector Parts, Operation, and Modifications Original posts from DieselStop.com Archives >> Power Strokes 1994-1997 (11/01-7/03) by Swamp Donkey (edited for clarity by SaintITC, PDF by F250_ ) --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- The Poppet Valve: The poppet is a 2-way or shuttle valve, controlling both the high pressure oil's entry into the injector and its exit.