I need vacuum diagrams for the fuel system

PKING

MEMBER
1986 FORD F-250
45,000 MILES

Replaced original CA emissions 4 barrel carburetor with standard 4 barrel and need help/photos showing hoses connected to proper places please. The original carb was California emissions and the replacement is a standard 4 barrel. Since I replaced the carb, the truck won't run on the front fuel tank. I have been able to get it to run on the front tank by swapping a few vacuum hoses but then the brakes seem to go out. I plugged the vacuum hoses from the old carb that didn't fit on the new carb and I have intermittent missing now and then. Even with the original carb it was a hard start in cold temps and still is. I think it's a vacuum problem with this new one but I can't find any photos or manuals to show me the proper places to connect the hoses. Anything relating to replacing a CA emissions carb with a standard would be great! I still have the old carb and can take photos if necessary. Thank you in advance.

3 Replies

RIVERMIKERAT

MECHANIC
6,110 POSTS

You lost brakes most likely because you removed the vacuum line to the brake booster. Trace the fuel lines from the tanks to the tank selection valve and then to the carburetor. The tank selection valve sounds vacuum operated. Trace the vacuum line to the engine compartment and hook it up to a vacuum source. Here is the vacuum diagram for the 6 cylinder engine. If you need a different one, let me know what size engine you have.

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Wednesday, October 5th, 2011 AT 4:09 AM

PKING

MEMBER
2 POSTS

Thank you so much for your response. The engine is a Ford 460 A/T V8 with 4bbl standard Holly p/n:0-80457S carb. I would greatly appreciate a diagram for this engine. Do you think the EGR valve could be causing the miss at idle? I'm going to check for leaks from the engine all the way to the tanks.

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Wednesday, October 5th, 2011 AT 6:03 AM

RIVERMIKERAT

MECHANIC
6,110 POSTS

There are 3 possible configurations. I have attached images for all 3.

A faulty or clogged EGR valve can can cause a miss, but it isn't likely. It's most likely either a vacuum leak, low compression, a bad stator in the distributor, or maybe carbon traces inside the distributor cap causing arcing between terminals.

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