1996 GMC K2500 Suburban with 350 Vortec V8.
Several times now over the past few months my Suburban refuses to start. It run fine when parked. Let it set overnight and the next day it turns over and, maybe, acts like it might catch but doesn't.
After replacing engine due to other issues, I thought this gremlin was whipped. It hasn't acted up for over a month until a couple of days ago and then the next morning also.
The last time it acted up; I tried pumping the gas to no avail. Then I tried putting the gas pedal on the floor. Not sure which action got results but it started. Run like it was going to die any second but this cleared up it settled down to a normal idle. I never thought to look at what was coming out of the exhaust pipe until it settled down and run right.
The new engine had its own fuel pressure regulator so the original one stayed on the old engine. I thought this cleared up the problem until it started acting up again.
I haven't replaced the fuel pump relay or the fuel pump.
Fuel pump was tested. The mechanic said pressure range was between 60-66 lbs. pressure. Mine showed at 63 lbs. pressure. 47 at idle. I'm not thinking it's the fuel pump as it runs great when it's right. I'm not ruling it out; just looking elsewhere first.
BTW after one of these episodes it'll miss, buck and carry on for a while. Mostly when cold. Feels like a carbed engine when taken off choke too soon.
I sure could use some input here. Any ideas?

 

I've been questioned on here for the "put the gas pedal to the floor" method on here. Glad to here it worked.

So are your fuel injectors leaking?

 

I don't know if they are or not. It does act in a way that reminds me of a diesel engine whose fuel pump has lost its prime. It will eventually start. The longest period was with the old engine. It took it three days to start. When it did it was as if nothing was wrong. It's got me stumped.
How do you go about checking for a leaky spider injector? This is something new for me this spider injector thing.
Thanks.