Blowback our of the TBI

[Buffalo90]

Got a 91 K2500 5.7/350 TBI. Just put new edelbrock cylinder heads and intake in. New distributor and ignition coil, as well as starter and battery. All new parts on accessory drive. TBI is the original one. Went to start it up and it’s cranking but it’s blowing back fumes out of the TBI every second or two while cranking. I checked timing on the distributor and it’s pointing at the number 1 cylinder’s wire while at TDC, so I know I’m not 180 out. I know I got fuel pressure because the intake of full of fumes after cranking. Compression’s good because of the blowback. Pulled one of the plugs out to see if I had spark while cranking. I didn’t. Not sure why. Any suggestions?

 

[evilunclegrimace]

Your timing is off, recheck it

 

[skylark]

I'd bet that your valves are adjusted too tight.

 

[Redneckgeriatric]

Got a 91 K2500 5.7/350 TBI. Just put new edelbrock cylinder heads and intake in. New distributor and ignition coil, as well as starter and battery. All new parts on accessory drive. TBI is the original one. Went to start it up and it’s cranking but it’s blowing back fumes out of the TBI every second or two while cranking. I checked timing on the distributor and it’s pointing at the number 1 cylinder’s wire while at TDC, so I know I’m not 180 out. I know I got fuel pressure because the intake of full of fumes after cranking. Compression’s good because of the blowback. Pulled one of the plugs out to see if I had spark while cranking. I didn’t. Not sure why. Any suggestions?

Compression’s good because of the blowback.? ?????????? i am totally stumped on this one! but it is either what mr. grimace said, or what mr. skylark said, or its catastrophic damage like bent pushrod, came lobe, cam timing, etc!

 

[PlayingWithTBI]

I checked timing on the distributor and it’s pointing at the number 1 cylinder’s wire while at TDC, so I know I’m not 180 out

Is it pointing at #1 at TDC of the compression stroke?

I agree with what all the others suggest.

 

[Erik the Awful]

To the OP: Having it pointing to #1 while at TDC is not an indication of having it timed right. Having it 180* out means it's pointing at #1 while at TDC, but on the wrong stroke.

To other commenters: While there could be tight valves, bent parts, etc., that doesn't explain the no spark.

Buffalo90, stupid question here, but you do have the spark plug grounded while you're checking for spark? Do you have power to the coil?

 

[Buffalo90]

Distributor rotor is point at #1 cylinder wire at TDC. If I’m understanding what you said correctly Erik, then I’m 180 out. That correct?

Ignition coil is a brand new MSD meant to replace original so I should be good there.

Definitely could’ve tightened the rockers too much as this is my first rebuild. No matter how many YouTube videos you watch there’s always room for error.

I think I’m going to reset the valves to start. Then see if going 180 around will work. If that doesn’t work then it’s time to go buy an actual spark tester.

Any other suggestions are appreciated.

 

[SAATR]

To verify that you're on cylinder #1 TDC compression stroke, pull the driver side valve cover and watch the valves open and close as you turn the engine. When you see the intake valve starting to close as you are rotating, put long piece of coat hanger or copper wire down the spark plug hole. Slowly rotate the engine and when the intake valve closes, begin watching the piece of wire. When it stops moving upward, you are at #1 TDC compression. Install the distributor at #1 with the engine in that position.

 

[mariodave]

How did you adjust the rocker arms?

 

[Supercharged111]

To verify that you're on cylinder #1 TDC compression stroke, pull the driver side valve cover and watch the valves open and close as you turn the engine. When you see the intake valve starting to close as you are rotating, put long piece of coat hanger or copper wire down the spark plug hole. Slowly rotate the engine and when the intake valve closes, begin watching the piece of wire. When it stops moving upward, you are at #1 TDC compression. Install the distributor at #1 with the engine in that position.

You can also just shove your finger in the spark plug hole and bump the starter until you feel compression, then do the coat hanger thing.