I've got fuel and spark... why won't she start?

[Phillip]

Hi All!
I'm afraid I'm one of many to make my first post a cry for help. I'm at the end of my rope with our 84' Caprice Estate 305. The short story is, I rebuilt the Rochester Quadrajet meticulously, assuring everything was done right, and now she won't run. The car ran before the rebuild, but there was a lot of gas smell in the cabin (hence the rebuild). At this point it'll crank, start to fire and quickly die. It doesn't seem to matter how much or little gas I give it, I'll sometimes get a couple seconds firing and sometimes nothing. When I first spark tested, the spark seemed inconsistent. I bench tested the ignition coil, found it was out of range and replaced it. Now it seems to fire a little stronger, but still won't run for more than 2-3 seconds. Spark test looks great though. I was pretty confident it was getting fuel, because the jets are spraying fine, and at one point I took the carb off after an attempted start, and could see fuel had entered the manifold.

In this whole process I've discovered the source of the fuel smell is from leak back at the filter nut. Worn out threads on the nut (and probably the carb inlet) mean it doesn't seal well. I've tried stacking washers, and using thread tape rated for fuel contact, but nothing stops the leak. Nowhere seems to sell a replacement nut, and I really don't want to get into replacing the carb at this point. Only concern is if it's leaking so much that the engine is starved, but I highly doubt it. Out of desperation, thinking maybe it is short on fuel, I tried a little starter fluid and got no firing at all.

I'm out of ideas, so all suggestions are most welcome!
Thank you

 

[oldsofb]

Have you tried a spark tester on a plug wire to see the strength of the spark? Are the plugs maybe fuel fouled?

The obvious seems to be the carb since it ran before, but you also threw in the coil change, so who knows now.

Were the plugs wet after a couple of sort of runs or no fires?

 

[Phillip]

Thanks for the reply. I did check for wet plugs, and no they aren't, so I don't think it's flooded. I don't have a park tester, but perhaps should invest in one. Thinking about just changing rotor, cap and plugs. They're all in okay shape, but maybe at this age she needs a good strong spark to fire.

Would you agree that it can't be a fuel problem though, since starting fluid didn't work?

 

[TURNA]

https://quadrajetparts.com/self-tapping-inlet-fitting-p-131.html



Or it the threads are no good use this one

https://quadrajetparts.com/self-tapping-inlet-fitting-long-p-132.html

 

[DRIVEN]

Massive vacuum leak?

 

[Phillip]

Thanks Turna! That'll save me replacing the carb.

DRIVEN I did consider that and replaced a couple cracked lines. I'll do some more digging around the bay to see if I can find something that got knocked off in the process maybe.

 

[DRIVEN]

I wouldn't expect a little vacuum hose crack for what you're describing. I'd look at possibly the wrong base gasket or something like that.

 

[Phillip]

I'd look at possibly the wrong base gasket or something like that.

Wrong base gasket for the carb? I compared it to the original and it was the same. Trouble is how to test for a vac leak without the engine running...

 

[DRIVEN]

Then I dunno.

 

[pontiac guy]

choke the carb off entirely. hold the butterfly closed or put your hand over the airhorn. If its a big vacuum leak it will start. you may have to adjust how much you choke it off.