Carburetor Troubleshooting 1985 Ford F150

1985 Ford F150

Truck loses power intermittently

My truck, a 1985 Ford F150 5.8 liter V8 4-barrel Carb,  has dual fuel tanks not sure that is necessary for this problem. I have changed the fuel pump fuel filters, had the fuel pickups rebuilt in the tanks and had the carburetor rebuilt. The problem is that when driving in high temps (above 90 degrees) the truck loses power intermittently, similar to running out of gas, typically starts on an incline and problem does not always appear. Any advise on what is going on would be helpful.

Sounds like the float level needs to be adjusted in the carburetor. The fact that it doesn’t seem to happen until you start on an incline is what leads me to this thought. The other thought would be vapor lock when the temp is over 90. Leave you fuel cap off once and test.

Carburetor Troubleshooting

The best way to diagnose a bad carburetor is to eliminate all other possible sources of the problem. If the carburetor is suspected to be the problem, first perform all of the adjustments.. If this doesn’t correct the difficulty, then check the following. Check the ignition system to make sure that the spark plugs, breaker points, and condenser are in good condition and adjusted to the proper specifications. Examine the emission control equipment to make sure that all the vacuum lines are connected and none are blocked or clogged. Check the ignition timing adjusting. Check all the vacuum lines on the engine for loose connections, splits or breaks. Torque the carburetor and intake manifold attaching bolts to the proper specifications. If, after performing all of these checks and adjustments, the problem is still not solved, then you can safely assume that the carburetor is the source of the problem.

Holley Model 4180-C 4-V (Dry Adjustment)

The float adjustment is a preliminary fuel level adjustment only. The final adjustment (Wet) must be performed after the carburetor has been installed on the engine.

With the fuel bowls and the float assemblies removed, hold the fuel bowls upside down and turn the adjusting nuts until the floats are parallel with the top of the fuel bowls.

Holley Model 4180-C 4-V (Wet Adjustment)

Fig. 4: Holley 4180 float level adjustment
carburetor float adjustment

NOTE: The fuel pump pressure and volume must be to specifications prior to performing the following adjustments.

  1. Operate the engine to normalize engine temperatures and place the vehicle on a flat surface.
  2. Remove the air cleaner, and run the engine at 1,000 rpm for about 30 seconds to stabilize the fuel level.
  3. Stop the engine and remove the sight plug on the side of the primary carburetor bowl.
  4. Check the fuel level. It should be at the bottom of the sight plug hole. If fuel spills out when the sight plug is removed, lower the fuel level. If the fuel level is below the sight glass hole, raise the fuel level.
    Do not loosen the lock screw or nut, or attempt to adjust the fuel level with the sight glass plug removed or the engine running as fuel may spray out creating a fire hazard.
  5. Adjust the front level as necessary by loosening the lock screw, and turning the adjusting nut clockwise to lower fuel level, or counterclockwise to raise fuel level. A 1 ⁄ 16 turn of the adjusting nut will change fuel level approximately 1 ⁄ 32 &inch; (0.8mm). Tighten the locking screw and install the sight plug, using the old gasket. Start the engine and run for about 30 seconds at 1,000 rpm to stabilize the fuel level.
  6. Stop the engine, remove the sight plug and check the fuel level. Repeat step 5 until the fuel level is at the bottom of the sight plug hole, install the sight plug using a new adjusting plug gasket.
  7. Repeat steps 3 through 6 for the secondary fuel bowl.
    NOTE: The secondary throttle must be used to stabilize the fuel level in the secondary fuel bowl.
  8. Install the air cleaner.