32/36 rebuilt, temporarily loss of power

[Marcus33]

I just re-jetted.my 32/36 with the specs found on the forum. I'm getting a wierd power loss after extended idling, for example at a red light.  Car will accelerate normal then sudden power loss. Giving more gas won't allow acceleration, it continues to die off unless I clutch in, lettle idle drop, give a couple taps of accelerator and it's fine. 

After that it will drive normally until another extended idle..

Any ideas?

 

[TobyB]

Fuel supply.

 

Possibly a bit of junk in the float valve...

 

t

 

[Mike Self]

Check the accelerator pump circuit--depressing the accelerator pedal (engine off) should produce a healthy squirt of fuel from the pump nozzle in the primary barrel. 

No squirt =

• trash in the passage that feeds the pump
• a bad diaphragm (did you replace it when you rebuilt the carb?)
• pump linkage not installed correctly
• a clogged pump nozzle

Check it out.

 

mike 

[ISS Werks]

look for a crack in the plastic sleeve on the fuel sender, where the fuel line attaches.  The fuel pump at idle may not be enough to overcome an air leak

[popovm]

21 hours ago, TobyB said:

Fuel supply.

 

Possibly a bit of junk in the float valve...

 

t

 

Could it be a float level issue too? Junk in the valve is more likely given that the carb was opened up recently….

[Marcus33]

Thx guys, I did have the floats off and on, I'll double check they are set to 41mm. 

I had replaced the accelerator pump diagram, but it was a cheap one, I have a new oem, I'll throw that in.

I'll also check fuel line. I know I do have a back flow issue. If the car sits too long, I notice it takes some time for fuel to get pumping into the fuel filter. I was planning to put a check valve at the truck junction 

[Marcus33]

Bit of an Update,

I ripped apart the carb again and double checked the float height, also I changed my float valve back to the one I had before this problem.

I replaced the gas pedal diagram. I notice when a pump the accelerator, fuel only pumped into the bowl from one of the two holes that look to feed the bowl from that diaphragm- is that normal?

I ran the car, same issue.

 

I then added a fuel check valve in the tank before the  plastic line. I thought this solved the problem, I drove it a couple days with no issues. But then I went out of town for 3 days, and drove it yesterday for first time and  the problem returned.

Variable here is temperature, it was probably 10*c warmer yesterday than the other two days after I installed the check valve. Besides that the car sat for 3 days. 

Could it be air pocket in line or something?? 

I'm going to throw a fuel pressure gauge on and see if I see a pressure drop, I also have an old mechanical fuel pump I may swap in to see if that does anything

Lastly, I started running premium fuel when this started, but I'm sure that's a coincidence...

 

 

[John76]

12 hours ago, Marcus33 said:

fuel only pumped into the bowl from one of the two holes that look to feed the bowl from that diaphragm- is that normal?

Yes, the 32/36 only squirts gas into the primary. 

The 38/38 squirts into both primary and secondary throats.

 

RE the hard start after sitting.  The float is vented to atmosphere and the gas we get these days evaporates very rapidly... more so in warmer weather.  Modern fuel injected cars are totally sealed, so don't have this "evaporation" issue.

If the phenolic spacer is missing between the intake manifold and the carb, the heat from the engine can quickly evaporate the fuel from the float bowl. Also, using a non-stock air filter can heat the carb.

Putting the fuel filter between the mechanical pump and the carb helps keep the fuel cooler since it is in the air stream from the cooling fan. Also using the fuel return valve allows fuel to circulate back to the tank instead of sitting stationary in a hot environment. These things plus the check valve near the tank will certainly help but not fully cure the problem. As mentioned in this forum, a better solution is an electric fuel pump.  

 

John