Here's the deal; put fuel pressure gauge to test; 1) when cut on (not start) pressure jumps to around 40 the once fuel pump cuts off pressure drops rapidly.
2) Checked fuel pressure regulator no gas coming out so assume fpr is good. Checked vacuum on hose running to fpr. With engine turning over pulls about 5 psi.
3) Pinched return line turned key on (not start) pressure shot up around 60 and slowly dropped down.
4) With engine turning over fuel pressure gauge shows pressure dropping.
NOTE: hi/low/accumulator setup, kolibar harness, new injectors, every sensor new. Was running but really rough. Was trying to check plugs pulled one when truck was running and it died. Since then can't get to crank.
1) 40PSI for a priming pressure sounds right. rapidly dropping off after the prime isn't right. Eventual drop off will happen but it should hold 30+ PSI for several minutes after it is primed.
2) Unless the pump is running, no gas should come out of the regulator, from later comments I think it is working correctly. But I am confused by "With engine turning over pulls about 5 psi". By "turning over" do you mean running or spinning the engine with the starter? with the "5" number I am guessing you really mean 5 inches of (mercury) vacuum and not 5 PSI. 5 inches of vacuum while cranking I can believe. Anything else just sounds wrong. Just very confused by this comment.
3) this shows the pump is capable of making the correct pressure. By capping the return line you effectively took the regulator out of the picture. You are looking at deadhead pressure of the pump. Also pinching the return line will stop any flow through the regulator including leakage (except through the diaphram but you would see that when you pulled the vacuum line off and there would be gas inside of it). So with the line pinched off and pressure still dropping after a prime, it is either dribbling out the injector(s) or more likely leaking back past the internal check valve in the high pressure pump. An injector leaking that much would have severly flooded that cylinder with as much as you have been playing with this.
4) This sounds correct. 40 PSI prime. cranking the engine (I presume on the starter and not actually running the engine, part of the confusion about your termonology from #2 ) pulling vacuum on the regulator (again from the confusing termonology in #2) would reduce the pressure in the fuel rail to 30 something. The whole idea about the regulator is to keep a constant fuel presure IN REFERENCE TO MANIFOLD PRESSURE. What that means is manifold vacuum is trying to pull fuel into the engine at idle through the injectors. Under load there is little or no vacuum pulling on the fuel. By changing the pressure as you see it on a gauage with manifold vacuum the pressure of the fuel in reference to the vacuum in the engine is always the same. Much easier for the primitive computers to figure how much fuel is going into the engine.
So with all that deciphering, I think the check valve in the fuel pump is bad as well. Want to confirm? cycle the pump to get 40 PSI and while at 40 PSI clamp off the line from the pump to the fuel rail/gauge. If you are blocking the return through the leaky pump check valve the fuel pressure should drop much slower if at all.
No to try and read even more between the lines, are you trying to fire up a freshly installed EFI engine?
