1997 4 door 262,000. Replaced FP 6 months ago w ac/delco, new filter. When key on no fuel pump prime. When turn key off 2 sec prime. Relaced relay no change. Prime it it runs fine with 58-64 lbs. when cranking 0psi but when primed 58-64psi. leakdown drops to 56 when shut off. holds at 56 for 15 minutes. Also going at speed it quit then started back on its own. did this once. this is when start issues began. maybe ignition switch?

 

update. when it cut out on me I replaced relay. this is when priming issue started. if off more than 20 minutes must prime to start with new relay in. Switched back to old relay and it starts fine but wants to stall. new relay,prime, no stall. perplexing.

 

When the ignition is in the RUN position, (engine off) the pump should run for ~2 seconds and shut off. When the ignition is in the CRANK position the pump should run continuously. Those are two separate circuits from the ignition switch. The ignition switch on 1997 is unique to that year and it's very common to have problems like you're describing. In the underhood fuse panel, locate the CRANK fuse. Both terminals on the top of the fuse should show battery voltage when the starter is engaged. If not, the ignition switch is the most likely cause. https://blazerforum.com/forum/articl...-switch-33465/

 

I am having the same trouble, thanks for the post. Got lots more reading todo

 

Thanks Hook. I have been reading up in this forum and it sounds like the switch is one of those things that make you "huh"

 

heres the rundown, new ignition switch, fuel pump, filter, plug, map sensor, icm, coil, plugs, wires, dist. cap, crank sensor, relay, all from the dealership. fuel pressure at 58psi at idle goes to 62 psi when shut off for 25 minutes. Must prime to start. once started runs great. One thing that is different is that new fuel pump does not shut off after 2 seconds when key is on but does shut off after 2 seconds when key is turned off. Pump also runs on accy. driving me crazy. any ideas