Motorcraft 2150 Acceleration Problem

You press on the gas pedal and the engine seems to bog down. What to do?

1st let me say that there are issues besides the carburetor that can make this happen, but since I'm in the carburetor business, I will assume everything else has been taken care of and concentrate on the carburetor. Also I will assume the carburetor has been rebuilt. If not, then that is where I would start.

Most likely this problem lies in the accelerator circuit. Here are some things to look for.
  • Make sure the return spring is between the accelerator pump diaphragm and the carburetor body.
  • Is the red umbrella check valve installed and the big end is on the pump diaphragm side?
  • Check the check weight in the main discharge. This is the middle hole under the venturi cluster. The check ball goes 1st, then the check weight. You can check the check ball to see if is is sealing by holding the check ball down (use a brass drift punch), and operating the throttle. You should feel some pressure because holding down the check ball is sealing the main discharge. If you suspect the ball isn't sealing, then use a brass drift punch to tap on the ball a few times, which will help form the hole around the check ball.
  • Using thin wire, run through all of the small holes and passage ways. Ethanol will leave deposits behind that normal cleaning will not get out. Pay special attention to the venturi cluster. There are some very small passageways in this assembly and it is very common for them to get plugged up.

After all of this is done add some mineral spirits to the float bowl and operate the accelerator pump. You should see fluid come up through the main discharge (where the check ball and weight is). Replace the venturi cluster and operate the pump again. You should get a fairly strong stream of fluid out of both sides of the venturi.

Do all as mentioned here and you should be able to eliminate your hesitation problem, or at least eliminate the accelerator pump circuit as the cause.




I have a tech question, if you can help. I have a Motorcraft 2150 carb and noticed that one of the idle mixture screws is longer than the other. Is this correct or should they both be the same? In fact, I order two from you and one seems to go in further than the other. Is this correct? Thanks for your help.

Both screws should be the same length. Motorcraft didn't use 2 different sized screws in any carburetor. If the screws go in at different depths in order to get the idle to smooth out and there is more than 1/2 turn difference, then there is something wrong on one side of the carburetor.

Update - Solution to this problem was a dirt. Cleaned out and all was well.


2100, 2150 Differences

Watch a video about the differences:



Cleanout Plugs
Part 85-50

2150 Carburetor

Check Weight
Update: We now have the check weights available, click here to purchase. Please note this does not work on every 2150. Some use a spring.

Accelerator Pump Diaphragm Relief Hole
2150 Accelerator Pump

The hole at the bottom of the pump diaphragm cover is a relief hole. Any fuel coming out of this hole indicates the diaphragm is bad and should be replaced.

The other hole just below the pump diaphragm is a relief hole for the power valve. Any fuel coming out of this hole indicates the power valve is leaking. Not all 2150 carburetors have this hole.

Notice the deep cover over the power valve. This indicates this carburetor has a 2 stage power valve.















Q: I rebuilt my 2150 with your recommended kit. Now the vehicle run on a second or two after turning off the key. Any suggestions as to what could be causing that? I’ve changed nothing else, just the carb rebuild.

A:I think it's running too rich.
Check the needle for any damage to the viton tip. Any pressure put on the tip when installing will damage the needle.
Check the bottom of the float bowl for any dirt. Dirty gas tanks, lines, or fuel filter can re introduce dirt into the carburetor causing the needle to not seal.
Gently hold the float up to close the needle and suck on the fuel inlet hole. It should not allow air to pass through.
Last but not least check the float level.
Also does the carburetor have an idle solenoid. It may need to be not closing the throttle fast enough.

Motorcraft 2150 Acceleration Problem

You press on the gas pedal and the engine seems to bog down. What to do?

1st let me say that there are issues besides the carburetor that can make this happen, but since I'm in the carburetor business, I will assume everything else has been taken care of and concentrate on the carburetor. Also I will assume the carburetor has been rebuilt. If not, then that is where I would start.

Most likely this problem lies in the accelerator circuit. Here are some things to look for.
  • Make sure the return spring is between the accelerator pump diaphragm and the carburetor body.
  • Is the red umbrella check valve installed and the big end is on the pump diaphragm side?
  • Check the check weight in the main discharge. This is the middle hole under the venturi cluster. The check ball goes 1st, then the check weight. You can check the check ball to see if is is sealing by holding the check ball down (use a brass drift punch), and operating the throttle. You should feel some pressure because holding down the check ball is sealing the main discharge. If you suspect the ball isn't sealing, then use a brass drift punch to tap on the ball a few times, which will help form the hole around the check ball.
  • Using thin wire, run through all of the small holes and passage ways. Ethanol will leave deposits behind that normal cleaning will not get out. Pay special attention to the venturi cluster. There are some very small passageways in this assembly and it is very common for them to get plugged up.

After all of this is done add some mineral spirits to the float bowl and operate the accelerator pump. You should see fluid come up through the main discharge (where the check ball and weight is). Replace the venturi cluster and operate the pump again. You should get a fairly strong stream of fluid out of both sides of the venturi.

Do all as mentioned here and you should be able to eliminate your hesitation problem, or at least eliminate the accelerator pump circuit as the cause.


Gas is Accumulating in the Intake Manifold

One possible cause for this is the main discharge might be leaking. The main discharge has a check ball that seals the discharge hole until accelerating.

To test:

Run the engine.
Turn the engine off.
Look down the carburetor throat to see if gas is trickling down the bore. It should not be.

If you see gas then the check is probably leaking. Tap the check ball gently so that it forms a bed for the check ball.

The accelerator pump circuit can be tested by filling the float bowl with mineral spirits, then pump the gas while holding down the check ball inside the main discharge. Gas should not be coming out of the discharge.

Another possibility is gas might be siphoning from the float bowl due to a bowl vent not open, or a gas cap that is not vented. 




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