accelerator pump question (3 Viewers)

[alf]

Facts: 79 2F with stock Jim C rebuilt carb. The carb was rebuilt but not installed for almost 2 years and just sat on my work bench.

Issue: Accelerator Pump is very slow to react and is very stiff. If actuated by hand by pulling up on its lever assembly the pump squirts nicely. When actuated off the skinny pedal it moves slower than a snail. The linkage looks good but it just takes it damn time moving up which gives me a very lean condition off idle. No power, hesitation and an occasional pop thru the carb.

Side note: the truck has historically been hard to start when warm as I assume a lot of heat coming of the headers plus some exhaust leaks boils any remaining fuel in the carb. If you pump the gas pedal just right (couple of strokes to the floor and hold) stick your tongue out and touch your nose you can usually get her to start. However, if you pop the hood and crank up on the accel pump lever instead of using the skinny pedal to primne the carb she fires up no problem without any tongue wagging or nose touching.

I have replaced the accel pump but did not mess with the clip or ball bearing.

Should the accel pump be this hard to move or so tardy in its action of the pedal.


ALF

 

[Pin_Head]

You can adjust the stroke of the pump by bending the verticle actuator rod to make it pump earlier.

Hot restarts are usually under rich or flooded conditions in carbed engines. The starting routine is to hold the skinny pedal to the floor but don't pump it. Then start the engine and let up on the foot feed when it catches.

 

[alf]

Pin,

Specifically should the accel pump react so slow and take so much leverage to actuate?

So if the hard start is flooding why does the manual accel pump action cause it to fire right up. I would think this would flood the engine worse.

If it is flooding what is the culprit?

A hard start after a stall on an obstacle is no fun.

I am thinking about pulling the carb, intake and header. Then pulling the top of the carb and inspect and clean out all the passages. Then reinstall and see if it helps.

Alf

 

[Pin_Head]

It shouldn't take much effort to run the pump. Take the pump rod out and check if it is installed correctly. Maybe the return spring is wrong too.

Pumping the gas before a hot restart is usually counter productive because it makes the mixture even more rich. Just the fact that the air is hot and less dense makes it more rich. Have you tried the hot restart drill that I mentioned?

 

[rusty_tlc]

Is the piston seal still made out of leather?

The pump on my '70 use act the same way. A little petroleum jelly would usually soften it up and correct the condition.

If the carb sat unused for a while the seal part could be stiff and this may be the problem.

 

[alf]

Adjusted the pump, set the timing back to factory (it was at 15 advanced), dribbled seafaom down the carb. I went for a test drive a and blew out all the seafoam and she ran pretty darn good. Power was back and not hardly a hesitation. Still need to pull the carb a take a look. I am pulling 17.5 hg steady on the vac gauge so vac leak not an issue. I still thing it is running lean.

What is interesting is that if i mash the pedal while in neutral she still coughes and sputters but under normal dirving conditions it doesn't.

I have a sneaky feeling that I am not done with these issues but at least I am able pull the soft doors, drop the top and enjoy the most excellent Atlanta day. Blue skies and 72* with a nice breeze and no humidity.

kls

 

[acy76]

Bumping this up as search turned up very little on this problem. Hoping this may help someone in a future search.

I was having the same issue and the cause turned out to be a blocked accelerator pump discharge jet. It was slow to move, stiff and sprayed very little. Finally it stopped spraying any fuel at all.

What threw me off initially was that if I removed the plunger arm, the pump moved easily. Reconnecting everything and it was back to a "stuck" state once again.

To fix, I unglogged the jet with a tiny wire and some brake cleaner (I removed the top of the carb and the pump plunger; more importantly, I also removed the stopper (the part that covers the smaller bore that the fuel comes out of into the carb throat) to perform this. This was on a 5/70 F155 carb but as I recall others are similar in design.

After unblocking the jet, the pump actuates normally with little effort.

 

[Duckless]

Facts: 79 2F with stock Jim C rebuilt carb. The carb was rebuilt but not installed for almost 2 years and just sat on my work bench.

Issue: Accelerator Pump is very slow to react and is very stiff. If actuated by hand by pulling up on its lever assembly the pump squirts nicely. When actuated off the skinny pedal it moves slower than a snail. The linkage looks good but it just takes it damn time moving up which gives me a very lean condition off idle. No power, hesitation and an occasional pop thru the carb.

Side note: the truck has historically been hard to start when warm as I assume a lot of heat coming of the headers plus some exhaust leaks boils any remaining fuel in the carb. If you pump the gas pedal just right (couple of strokes to the floor and hold) stick your tongue out and touch your nose you can usually get her to start. However, if you pop the hood and crank up on the accel pump lever instead of using the skinny pedal to primne the carb she fires up no problem without any tongue wagging or nose touching.

I have replaced the accel pump but did not mess with the clip or ball bearing.

Should the accel pump be this hard to move or so tardy in its action of the pedal.


ALF

This is a super old post but this saved me hours of time and multiple head injuries. Had the same symptoms of stiffness with the accelerator pump. Plugged nozzle turned out to be it. When forcing the pump by hand it was working due to by passing the nozzle and pushing past the gasket into the carb body. When I cleaned the nozzle, it worked as it should and stiffness and short throw of the pump were gone! Thank you for posting that