You can rebuild them but the problem is you have no way to calibrate them. If you can't calibrate them your flow rates are going to be all messed. Be like setting all your plugs all at a different gap. And in this case you stand a good chance of burning a piston. You might call KDavid. Think at one time he was going to try rebuilding some on that truck he bought. If it's missing you could also have a wiring harness problem on that engine. The harness that is in the valve cover that goes to the injector is soaked in hot oil and susceptible to breaking.
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Charlie Weaver USN/ENC 1965-1979