Replaced intake gasket, now won't start - backfires...
 

I have a 1990 S-10 Blazer, 4.3L TBI, 2WD. It wouldn't idle and was running lean (code 44) - I found an intake leak on rear passenger side. Yesterday I replaced the intake gaskets. I forgot to mark the distributor before pulling it, so I attempted to reset base timing. Got #1 cylinder to TDC and re-seated the distributor aiming it at #1 point. When I tried to start it, it would backfire through TBI and never start. I'm guessing I didn't get the timing right - either didn't have set to proper TDC or distributor should be positioned differently. Any thoughts - timing or something different? What position should distributor be in when seated at TDC? Thanks in advance.

sounds like your 180* off are you sure you were at TDC on the compression stroke. both valves should be closed

That was it...tried it again making sure piston was pushing out air when setting TDC. Cranked right up. Now I'm back to my original problem (I was hoping it would be fixed after changing intake gasket)...I'll start a new thread for that issue. Thanks again.

Check the gasket between the intake and throttle body for leaks. Also could be the large hose going to the brake booster or bad brake booster if your brakes seem hard to push. Could even be a cracked throttle body too.