Question about possible vapor lock 95 4.3
 

I recently purchased a 1995 Blazer with the fuel injected 4.3. My wife was having issues with it starting this morning, and after she brought it home, we could not get it to fire. When we first tried to start it, the engine attempted to start, but would not catch. Subsequent tries met with less success, which led me to believe the fuel filter was clogged and needed replaced. It had been sitting for some time before we bought it.

We left it sit for about 90 minutes and went about our business, then just for laughs I tried to restart it and it fired off almost immediately, and ran normally. Is it possible for vapor lock to be the culprit, or should I still plan on getting the fuel filter changed?

No, yes.

But how does a clogged fuel filter allow the engine to run normally until you shut it off and then re-start after you leave it sit?

i would change the filter anyway. if it was sitting for awhile the gas could have had some sediment in it and now its in the filter. simple job done with 2 wrenches and a little bit of time. the filter is less than 10 dollars. plus with a new filter, the fuel pump doesn't have to work as hard to maintain the proper pressure which will make it live a little longer.

sorry, but sounds like the fuel pump is taking a few last gasps before dying. after a short hot soak the brushes and windings may not turn, once the pump cools down completely it will run agin for a while.

Agree with the fuel pump is on its way out. Grab a fuel pressure gauge and find-out for sure before going to the trouble of dropping the tank...as it could be the relay, but not likely.

I don't know that I can afford to replace the fuel pump right away. Will keeping the fuel tank as full as possible help keep the pump cool? And would a partially clogged fuel filter make it heat up faster?

Doesn't matter how much fuel is in the tank. The fuel return line is directed into the "well" that the fuel pump is mounted in. Whenever the fuel pump is running, the "well" is filled with fuel and the pump is completely submerged, (that's what keeps it cool). Check fuel pressure and leakdown like LannyL81 suggested, and post the results.