For some reason I can't get my truck (3200, 235) to idle below 1100 rpm without immediately stalling. It starts right up with the choke pulled out. Once it is pushed in at around 1100 rpm it dies. I've done the following:
1. Checked for intake manifold leaks with a propane torch. Did not notice a change. But can't idle below 1100 rpm so it's hard to tell if anything changed.
2. Borrowed a friend's homemade smoke machine and shot some smoke into the intake. No visible leaks.
3. Tried 3 different carburetors. - all stalled out at around 1100 to 1000 rpm.
4. Checked ignition coil with gauge. It's normal.
5. Replaced spark plugs.
6. Points and condenser look good. Tuned truck a few weeks back and dwell was normal.
7. Replaced fuel filter from tank to pump.
8. Replaced fuel filter from pump to carburetor.
9. Checked vacuum advance line for leak. Nothing found.
10. Tee'd in fuel gauge between mechanical fuel pump and carburetor. Got around 3.5 PSI at 1100 rpm. It held at 3.5 for a few minutes after the engine was off.
11. Vacuum gauge shows 19" of mercury at 1100 rpm.
The manual says that the fuel pump should operate at around 3.5 to 4.5 PSI. Is that at a normal idle of say 600 rpm? Isn't the PSI reading of fuel delivery inverse to vacuum? High fuel PSI to low intake vacuum and vice versa? Does that PSI reading sound normal or below normal for that rpm? I'm getting discouraged at this point. Not sure how to proceed.
Thanks.
Mark
