Holley Accelerator pump probem

[nwjones18]

I've got an old Holley 4 barrel that I'm having problems with. I've rebuilt it and on the bench the accelerator pump seems to function fine can hear air being moved by it. After I put it on the truck and put gas in it refuses to pump it is like its frozen. You can't move the plunger no matter how hard you push it. It will remain frozen until I loosen the seal and it loses pressure then it will work freely again. This carb has the metal ball style 'check valve' and its gaped at .013 which is within spec. Any ideas?

 

[Merkava_4]

You didn't forget the accelerator pump cam did you ?

 

[Chris142]

Sounds like the accelerator pump squirters are plugged up. Remove them and see if it will push gas with the squirters out

 

[The_Eric]

Barring any mechanical assembly problems, did you get the correct metering block gasket installed? Maybe got a rear gasket for vacuum secondary in there?

Maybe some pictures to help visualize?

 

[punisher]

Good advice all. Verify no mechanical problems, reach under carb and manually press lever over diaphragm to see if it is actually locked up. In order, pull off squirter, verify ports open on it and hollow bolt, partially cover squirter opening in carb body to keep check ball and weight (if installed) from shooting out, and try pressing on diaphragm again. Still locked, pull bowl, inspect bowl gasket for correct install, ditto on metering block gaskets. Most problems like this are just a simple linkage screw up. Never have run across a bad/incorrect gasket yet, but most of my Holley work was on 4150 double pumpers and primary and secondary setups are the same. Possible I guess some gasket sets might not have a hole punched for accel pump circuit--just haven't run across it yet.

 

[nwjones18]

Thanks All! I pulled off the squirter and it wasn't clogged up, but when I poked around under it with a scribe it started working! Must have been a piece of trash in there. Working well now.

 

[Merkava_4]

Those pump cams usually have two holes in them for two different settings. One hole will give you a low volume squirt over a longer time. The other hole will give you a high volume squirt over a shorter time.

 

[The_Eric]

Originally Posted By: nwjones18
Thanks All! I pulled off the squirter and it wasn't clogged up, but when I poked around under it with a scribe it started working! Must have been a piece of trash in there. Working well now.


Good to hear. Sounds like the weighted check valve was stuck. Have seen it happen before... Should have thought of that.


Originally Posted By: Merkava_4
Those pump cams usually have two holes in them for two different settings. One hole will give you a low volume squirt over a longer time. The other hole will give you a high volume squirt over a shorter time.



Not quite. The two and sometimes 3 holes are for proper actuation at higher throttle openings. Think staging at the drag strip. If the throttle is already open several degrees while you're up against the brakes or Trans brake, you're going to lose a fair bit of pump output. Rotating it to the second or third position can restore that output.