The Stovebolt Site Forums The Shop Area Engine Shop Troubleshooting cough and stall on acceleration

I rebuilt the Rochester B on my '49 216, and yes, I managed to mess something up. I've rebuilt more carbs than I can count and never had an issue, till now. My truck has been running slightly worse over the past few months(idle a little rough, a little hesitation) so I changed plugs, wires, cap, rotor, points, and condenser, I also rebuilt the carb. Now it runs good but it acts like the accelerator pump isn't working. I took the carb apart and verified to the best of my ability that every thing is where it should be. If I work the accelerator pump with the bowl cover off the fuel in the bowl becomes agitated and jumps about but does not squirt or even splash out of the bowl.
*What should it do when I work the accelerator pump?

*How do I find out what I did wrong and fix it?

Is the pump discharge ball and spring in place?

Don, yes sir. However, I now believe this has nothing to do with the accelerator pump. I just finished rebuilding another carb with the same results. I can drive just fine, but if I tap the gas it stutters, or if I try to accelerate moderatly from a stop or after shifting it stutters. If I really put my foot into it, it backfires through the carb. One more thing is it idles poorly with the idle mixture screw at one and one half turns out. At two and one half turns it idles so SMOOTH!. The same with both carbs. The timeing seems to be right, but I've adjusted it + and - with no improvement.

Look down the throat of the carb with the engine off. Each time you open the throttle you should see a squirt of gas go into the throat. If not something is wrong with the accel pump system. Make sure the float level is correct. You can try raising it a little. Don't care about how many turns the idle jet is out. Set it where it runs the best. Start with it about 3 turns out & slowly turn it in till the engine starts to slow down. Then turn it out till it smooths out, usually about 1/2 turn. Try setting the timing up a few degrees.

I have tried two carbs on this truck in the last two days. Both have just been rebuilt. Both squirt gas when I work the throttle. Both have the float set right. I'm now convinced this is not a carb issue because changing the carb does not change the symptoms. I've adjusted the timing up a little with no luck but will try that again tomorrow. I've rechecked the point gap. I sprayed stsrter fluid around the carb base with no change in idle.

Would a wore out dizzy cause the stumble?

Or vaccume leak?

Bad intake manifold gasket?

Bad cam? (please no, please no, please no)

Sounds like you may have a fuel problem,bad fuel filter or a blocked line.Or a bad fuel pump.Check the fuel flow from the tank to the pump.

Pete

Backfire through the carb?

Try a compression test.

Also, check for a distributor advance not functioning.

Jon.

Checked distributor advance, it works good. I will probably do a compression test but I believe, like Pete suggested, that I've got a fuel supply issue. I checked the fuel flow from the pump to the carb. With the fuel line removed from the carb and cranking the engine, I get an occasional splash of fuel. I put in a new clear filter and with the engine idleing the filter is usually dry with a trickle or small splash of fuel now and then. I've got a pump on order. I did pull this pump and 'hand test' it. If I force the lever in and then cover the inlet with my thumb it holds vacuum. If I cover the outlet and force the lever in, it holds pressure and does not bleed down. I will still replace the pump.

Before replacing the pump, while not try removing the line from the tank at the pump; and running a line to the pump from a different source (like a portable marine gas tank).

You may have a stopage at the supply tube in the tank.

You may have multiple issues. A backfire at the carburetor occurs when there is fire in the cylinder and an intake valve open. Possible causes:

(1) burned or sticky intake valve
(2) incorrect valve timing
(3) incorrect ignition timing

A compression test will confirm/eliminate burned or sticky valve.

Jon.

I almost tested the pump as you've suggested but had to call it quits for the day to go get my paintings framed. So tomorrow morning I test the pump. I will do a compression test regardless of the outcome of the pump test. I do agree it seems I have more than one issue at this point. Thanks for the help on this.

So today I tested the pump as suggested by carbking = made no difference. Ran air through the line = clean. Installed new pump = worked the same. Did a compression test and the numbers surprised the heck out of me,

120
120
119
120
119
120

Checked valve lash = all is good. Timed the engine with the engine not running. EVERYTHING should be adjusted dead on. Yesterday I drove it thirty miles and it ran great as long as I didn't accelerate to fast. But on the drive home it started running rough, stuttering, losing power. What's that leave us?

Carter YF, I'd say.

For some reason it's lean, I had a 250 do the same things, turn out to be the head I ported. Even though it was the head on mine, it was still a lean issue and acted just like yours. Ran great as long as I didn't get into the throttle to quick.

One more time apart and maybe a soaking in cleaner this time and you might get it. Just can't be much else wrong.

Joe

It acts like a carb issue, and I believe it IS somehow a fuel/air/carb issue. If I crack the throttle open and hold it, it will kill the engine if I don't let off. The part that puzzles me is that it acts the same with either of the two carbs that I just tore down, soaked in cleaner, cleaned meticulously, reasembed properly and adjusted perfectly. One is the Rochester B I've run for the past six years. I'd bet money it's air/fuel related, but the fact that it acts THE SAME with BOTH CARBS makes me think it's pre or post carb. At this point I'm lost.

Are you sure it is shooting fuel with the accelerator pump? There should be no question when looking down the throat.

If you choke it, will it accelerate?

Does it have the right gasket at the intake where the carb bolts on?

Joe

I had a 69' Mustang once that did the same thing. To make a long story short, The rod that works the butterfly was worn and after all the "checking" the carb was just worn out. Replaced it and problem solved. Might be worth a check. Good luck. Steven

I would like to thank everyone for helping me with this.

I think that with the help of Steve's (Red 49 Truck) suggestion I've got this wupped.

When the first rebuild didn't work, I pulled the carb off the 216 in the '51 setting in the back yard. This is a Rochester "B" with the "C" cast on the bowl cover and stamped after all the part numbers. The same carb that people refer to as the Rochester "C". It has the wider bolt pattern (for 235?) so I simply used the carb base off the original "B" carb when I rebuilt the "C" carb. It seems that's where the problem was because I pulled the carb base off a third carb (also a Rochester"C") put it on the base of the original rebuilt "B" and she runs fine.

I did notice however that the second carb, the so called Rochester "C" seemed to wake the old 216 up a bit, it ran crisper, accelerated faster, climbed hills faster, and oddly enough, used less gas than I'm used to.

So there you have it. The ONE THING I did NOT change was the cause of all of my trouble. On the bright side she does have new plugs, wires, cap, rotor, points, condenser, fuel pump, fuel filters, rebuilt carb, and timeimg, points, and valve lash all set.

So the throttle shaft was worn out?

Put some new bushing in it and reinstall it, you may find it really does run better.

Glad you figured something out,

jjoe

To be honest, I don't know for sure what the exact problem was. The throttle shaft seems fine, but when I changed out the carb base it fixed it. I hate fixing something but learning nothing.