I have a 1995 GMC Sonoma with a rebuilt 4.3 liter vortec v6 and cmfi injection the engine turns over but won't start before it would start sometimes and iff it started the first try you were good if not it wouldn't till hours later or the next day. I replaced the fuel pump and ignition module they both work. The engine will start on ether (starting fluid) so I know its a fuel problem its not the crankshaft position sensor and I dont think I have enough fuel pressure but I think the only thing before the test port and past the pump is a filter and it sounds like a mechanical failure can anyone help me figure out the problem
I had the same problem with my 1094 vortic engine,
It would start when starting fluid was sprayed into the air intake.
I was convinced that the fuel pump was good because
when I would disconnect fuel line from output side of filter it would pump a stream of gas for about a foot.
Based on this I thoght the fuel pump had to be good.
But not so, I found out that it was working But
it did not have enough pressure.
I replaced the fuel pump and filter and solved the problem.