Stock carb I guess? Reads like it needs a cleaning and refreshing. I've used Holley power valves and accelerator pump diaphragms in them. If the accelerator pump diaphragm leaks, fuel will be pulled through the shooters as the engine sucks air down the carb throats.

 

Thanks for the reply. I didn't give the entire repair history of this engine, but the carb is a Ford 2150 and it has had a new kit installed in it twice. Accelerator pump diaphragm is new as are just about all the moving and non mving parts in the carb. Other than a tiny bit of throttle shaft play, the carb was and still is a good rebuild candidate. Frankly, I'd even throw a new rebuilt carb at it and hope for the best.

If I didn't mention it, the carb stumbles just off idle and then recovers nicely so that the run circuit and mid range power are restored. WOT is no issue.

As I tried to convey in past posts, I have systematically covered every fuel / vacuum / ignition possibility trying to narrow down the potential root cause.

It might just need a 65 year old retired mechanic who has worked on one of these to figure it out. My Dad and younger brother are both gone now.

Life is what happens while we are all busy making other plans!

 

I feel your pain. The 2150 is a great little carb. Too many running issues get blamed on the carburetor. One axiom I'll never forget - the problem likely isn't where you think it is.

I can't be of much help without my hands on the vehicle and LOTS of time, there are too many variables. I'll tell you this - I removed ALL emissions from my 2150 except the PCV, completely re-tuned it, and it runs like a sewing machine. I'm a firm believer in simpler is better. I too had an off-idle issue, just a slight stumble, for awhile. This was way back in the beginning, and I hadn't gotten around to all the wiring yet. Turned out there was no engine to frame ground! I built one, problem instantly gone. Runs like EFI. Don't let anyone tell you the 2150 is junk, it'll run with the best of 'em when everything else is in order.

Good Luck with it and enjoy the ride!

 

Been procrastinating on this follow-up for some time, but can open the garage door and run the vehicle without running it outside. Just recently saw a few videos on YouTube for tuning tips for the Chineseium 2150 brand new knock off carburetor in the $100 range on Amazon. Hmmm

Considering ordering one of these to hopefully eliminate the loose throttle shaft issue if nothing else. I am going to re-torque the intake manifold bolts, re-check the timing and disconnect all the vacuum lines except the PCV. Then we'll see if it can start and run cleanly. I may even disconnect the air pump.

 

There were a couple different check valves used by Holley for the accelerator pumps. One is a small ball captured in a loose recess by a staked in place metal strip. Another type involves a rubber cupped disc with a center stem that is secured in place. These check valves allow the accelerator pump to fill as it relaxes, but they close when the accelerator pump is used, so fuel can then only be pushed out to shooters. If either type doesn't seal instantly when the accelerator pump is tickled coming off idle, fuel just goes back into the float bowl, not out through shooters in the throttle bores ... and hesitation occurs. I'm not recalling what the Ford carburetor uses, I do recall the pump is placed differently on the carb body..

Another thing, Holleys have an adjustment where one sets a sprung plunger screw to move instantly above idle on the plastic accelerator pump cam. I am not sure how the Ford carb is so adjusted, but there should be a means.

 

Saw a video on YouTube regarding a 2150 rebuild. Good ol' boy from the Carolinas I think. Gonna pull the carb and chase all those small passages with a strand of wire from an old cable. I think there may be some gunk from ethanol in it. We used brake cleaner on most of the passages and thought that was sufficient. Don't know if the check ball in the accelerator circuit was re-seated when we did the rebuild, but I have plenty of check ***** to replace it with. I know the throttle shaft has a small amount of play in it, but just about every carb I've ever fiddled with does / or did.

I keep thinking about those Chineseium 2150 knock offs and wondering if that might solve the problem (or introduce a new one!) Something I noticed on the 'stock' carb: - It has / had an external vapour solenoid from the cannister to the bowl vent. I removed the solenoid when the power lead broke off and the part became unobtainium. The Chinese 2150's have a bowl mounted vent actuator that opens and closes with throttle position. Has nothing to do with off idle performance, but does change the way the carb operates I think.