Injectors and Glow Plugs
When you order an Elsbett kit to install on your own, you have to send your fuel injectors to Germany to get them modified. This process takes a bit of specialized skill and was easily completed by Alexander at the workshop, but it wouldn't be easy for a do-it-yourselfer. Alexander uses a "Pop Tester" to determine the threshold pressure at which each injector releases fuel into the cylinder. Then he changes shims to adjust this threshold to the proper parameter for SVO fuel. He also changes a shim or washer which determines the depth that the injector protrudes into the cylinder.
Alexander sets up the pop tester for Mercedes injectors while Mimi and Luke prepare relay wiring.
Mercedes injectors screw into the engine, but TDI injectors clamp in and require a special tool for removal. This is kind of a reverse pile driver - After removing the injector clamp, Alexander screws this tool onto the top of the injector and "hammers" upwards to remove the injector from the engine...
Here's an injector unclamped and ready to come out. Note the glow plug below and to the right of the injector.
Here's Alexander using the tool to remove a TDI injector.
A view of Kent's injectors removed and disassembled
A closer view.
November 7, 2005 update: Todd asked for a more detailed description of the injector modifications. Here's what I recall:
1. Pop-test unmodified injector (Alexander noted that Kent's unmodified injectors registered a lower threshold than "normal" - if I recall correctly, they "popped" at about 200 bar, and he expected to see about 220 unmodified. After modification, I think they popped at about 250 bar. I heard someone say that Todd's injectors also popped at a lower than "normal" threshold before modification.
2. Replace a small component that Rachel called a "hat" (Unfortunately, I didn't get a photo, but see the above illustration showing where it is and roughly how it's shaped)
3. Replace a shim to change the pop threshold (Sometimes Alexander had to change the shim thickness - I think it was one of Todd's injectors for which I sanded a couple of shims down until the threshold tested about 250 bar. Going from rough memory, seems like Alexander estimated 192 thickness and I sanded the first shim to that but it was too thin to achieve the proper pop threshold. On the second try, he estimated 198, and when I finished that one, it worked fine.
4. Replace another shim (washer)) that fits around the base of the injector body and determines how far into the head the injector goes.
It was cool to watch the pop tests. Alexander presses down on the pump handle until the pressure reaches the injector's threshold, then it "pops" and a cloud of fuel mist instantly fills the coke bottle. In this photo, he had just tightened an injector onto the pop tester, and was about to put the coke bottle under it and do the pop test.
Here's Kent's TDI with RED fuel supply line and high-pressure injector lines, GREEN return lines, and BLUE glow plug wires. Hope you don't mind the paint job, Kent!
Glow plugs were replaced on all cars - I don't know the characteristics of the new ones except that the hot part inside the engine is a bit longer, and presumably they are hotter or at least rated for longer duty cycles. On the older Mercedes, the new glow plugs are wired differently as well. The stock Mercedes had series-wired glow plugs - if one burned out, they all stopped working. The new plugs are wired in parallel, so they must be rated for 12 volt operation instead of 12/5 for the originals.