97 GMC Yukon Won't Start 5.7L V8

[nate70500]

I recently got a 1997 GMC Yukon SLT 5.7L Vortec V8. It turns over but wont start. A small bit of white smoke comes out of the exhaust when I try starting it. If I unplug the boot from spark plug #3, the truck starts immediately. But if i reconnect the boot when the truck is running it shuts off instantly. Heres what I've checked so far:
Usual no start things (battery, alternator, starter)
New ignition coil and ignition control module
new spark plugs
tested spark plugs and got a spark on all
4 months ago (or less) all of the following was replaced:
distributor/cap/rotor
spark plug wires
fuel pump
fuel filter
fuel lines
fuel pump relay
I've tested the fuel pressure and get 63 psi so its definitely getting fuel. The truck is not throwing any codes either.
When I removed the distributor cap, there was a lot of corrosion on the contacts. It is the United Motor Products distributor cap vented with all brass contacts. I cleaned the contacts but it didn't make a difference.
I'm not sure where to go from here, I contacted united motor to get the distributor cap and rotor replaced under warranty but they don't seem to think that the distributor cap is the issue. Any ideas?

 

[PG01]

What about disconn any other plug wire or just #3 kills it

 

[nate70500]

What about disconn any other plug wire or just #3 kills it

Just #3 kills it. If I do it with any other plug theres no difference

 

[PG01]

Just #3 kills it. If I do it with any other plug theres no difference

Swap that #3 wire to another cylinder and see if it follows.... the wire might be shorting out.....obviously 1 that reaches ....

 

[nate70500]

Swap that #3 wire to another cylinder and see if it follows.... the wire might be shorting out.....obviously 1 that reaches ....

I'll give it a try tomorrow. Thanks

 

[exp500]

My. guess is look closely at cap, especially center term- by #3 probably a hole burned thru. Spark going everywhere but where you want it. United DCR820X usually a good choice. Rockauto also has Packard Wires cheap. NGK or Delco plugs . Also check your Cam retard offset should be 0 +/_ 1 degree at 1000-1500 rpm cheap android scanner will do it. If you burned cap there is a reason. Hope you used a factory coil, not a high output. Was that the cap that came with new United distributor? that looks like a DCR820X but isn't, Ask me how I know.

 

[nate70500]

My. guess is look closely at cap, especially center term- by #3 probably a hole burned thru. Spark going everywhere but where you want it. United DCR820X usually a good choice. Rockauto also has Packard Wires cheap. NGK or Delco plugs . Also check your Cam retard offset should be 0 +/_ 1 degree at 1000-1500 rpm cheap android scanner will do it. If you burned cap there is a reason. Hope you used a factory coil, not a high output. Was that the cap that came with new United distributor? that looks like a DCR820X but isn't, Ask me how I know.

I put new delco plugs in a couple weeks ago when it first stopped running. The coil is a factory coil, not high output. It was the cap that came with the distributor. Ill take a closer look at the distributor cap tomorrow when I check the wire

 

[nate70500]

My. guess is look closely at cap, especially center term- by #3 probably a hole burned thru. Spark going everywhere but where you want it. United DCR820X usually a good choice. Rockauto also has Packard Wires cheap. NGK or Delco plugs . Also check your Cam retard offset should be 0 +/_ 1 degree at 1000-1500 rpm cheap android scanner will do it. If you burned cap there is a reason. Hope you used a factory coil, not a high output. Was that the cap that came with new United distributor? that looks like a DCR820X but isn't, Ask me how I know.

and now I have to ask how you know its not the DCR820X? lol. I assumed mine was a DCR820X because thats the only one that I found that looked like it

 

[liquify33]

#3 has a long travel to it in the cap.
If your cap is funky $15 and 15 minutes will fix that. I replaced the cap and rotor that came with my aftermarket distributor and it has helped sort some issues.

 

[east302]

#3 has a long travel to it in the cap.
If your cap is funky $15 and 15 minutes will fix that. I replaced the cap and rotor that came with my aftermarket distributor and it has helped sort some issues.

Same thing here. Delco caps seem to be the most reliable.