Car Stalls When Putting in Gear

I was recently asked about a Thunderbird that dies when putting the transmission in drive.

This could be caused by a vacuum leak, or possibly it is starving for fuel. Knowing that this particular vehicle has a multitude of vacuum hoses going to the carburetor, I would go with a vacuum leak 1st.

Disconnect all of the vacuum lines from the carburetor and plug off the vacuum ports on the carburetor. If the problem goes away you know it’s a vacuum leak causing the problem. Connect the hoses, one at a time until the problem returns. Obviously if the problem returns when connecting one of the lines, you have found your problem. The hose may have a hole, or something it connects to is leaking.

The carburetor itself could be leaking vacuum. You can spray carburetor cleaner around the mounting plate and the throttle body. If the idle changes, or smooths out, then you found the problem.

If you rebuilt the carburetor check to make sure you installed all of the gaskets correctly. The wrong gasket could leave a passage open to air causing a vacuum leak.

If it is starving for fuel, then you have all sorts of things to look for. 1st, if the carburetor hasn’t been rebuilt, then it may just be dirty, clogging up a passage. The float valve could be sticking, not allowing enough fuel to flow in.

The fuel pump pressure could be too low. Test the fuel pump pressure with a fuel pump pressure tester. On a Thunderbird it is probably around 5-7 lbs, but always check your motors manual for the correct specification.

The float valve could be sticking closed not allowing enough fuel to enter.

The float could be adjusted incorrectly. Check the float level.

I’m sure there are several things I haven’t even thought about. Let me know if you have any suggestions. I would appreciate it.

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