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jdemaris
04-07-2005 05:51:42
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Re: jdemaris Injectors in reply to Windancer, 04-07-2005 02:39:46
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Our Jettas are the older ones - both 1991s - no turbos, no electronic controls, etc. My wife drives back dirt roads up and over a mountain. In the winter she drives a Subaru Impreza and averages around 22 MPG. In the summer, with the Jetta deisel, she averages 39 MPG. I think that's amazing. We checked it once on a highway trip and got 49 MPG. As far as mechanical injectors and wear - basically, all an injector is, is a spring loaded valve and seat, with a tip beyond it with small holes in it for fuel to spray out of. Every time an injector fires, the valve opens and closes. You adjust the pressure at which it opens by the tension put on the spring with an adjustment nut. After a while, the valve and seat gets worn/hammered and it's shot - just like valves and seats do in the cylinder head of an engine. With many big injectors, you can buy a brand new valve and seat and install it into the old injector body. So, this way, the moving parts are all new - i.e. a rebuilt injector - more-or-less, as good as new. But, with a pencil injector, those parts are NOT replaceable. For that reason, they used to be called "throw-away" injectors. Didn't matter much when they cost $36 new. But now, over $100?? The so-called "rebuilt" pencil injectors are usually just taken apart, cleaned, maybe the valve and seat lapped a bit, the orifices cleaned out with wire, and that's it. When the valve and seat gets hammered, it gets wider. When it gets lapped, it gets even more wider. The wider they get, the worse they work. Typical pencil injector for a Case 188D (Roosamaster/Stanadyne) has orifice holes sized at .010", and the opening pressure set around 3000 PSI.
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