The Stovebolt Site Forums The Shop Area Engine Shop Idles all day but dies when stopping

1963-64 C-10 3sp column shift 230 I-6 Rochester BV. Truck will idle all day at 600rpm. Go for a drive and when you come to a stop it will stumble and die. Sometimes but not always you can push in on the clutch and let it slow and gently apply the brakes and it will stay running but if you hit the brakes harder it will die. Fresh tune up and carburetor has been rebuilt within the last 6 months. My buddy is at his wits end and I have been no help. What is he dealing with?

Added info; The Truck accelerates really well and pulls strong under load.

I'm not an expert but I'd readjust the float level while waiting for the experts.

I'd have to agree with Wally.

I had the same issue. It would idle just fine in the driveway and nearly die while waiting at a light. I also noticed after a run and leaving it idling while I went to open the garage door, it would idle slower and slower until it died. The fix for me was to open up the idle screw a turn. I'm guessing that the under hood air temp was hotter while waiting at a light and after a run so the mixture needed to be richer.

Often, this is a symptom of the idle mixture set to rich. Would suggest readjusting the idle mixture screw AND throttle positioner screw to a leaner mixture with a greater opening of the throttle positioner screw.

Jon.

Jerry, go back to the post of June 26 thru July 2 of 2013. I don't believe I would pull off air horn to check floats yet. These old buggers can be touchy. I always start by gently turning the air mix screw all the way in and count the number of turns. It is fine to do this several times because a small amount of dirt or thread chard can get between the needle and seat. I always time my Stovebolts with a static light when possible especially when my customers have your problem. If that doesn't work after you adjust idle let me know. I can go out to the barn and maybe we can communicate over the computer. Jon has good advice and try and try again usually works. Ed

Since the float level puts the gas in the bowl within a fraction of an inch below the venturi, any stop other than a very gentle one can cause gas to slop over into the airstream and create an over-rich idle mixture. Try dropping the float level just a little to allow for some level change during a normal speed stop and see if the situation improves. A leaky float with a bit of gas inside it can also cause problems at idle by letting the float level creep up, but that should also be a problem when standing still, not just when stopping.
Jerry

Tried the mixture adjustment since it was the easiest to get to. No difference. It still dies when stopping normally. If he pushes in the clutch a 1/2 block from the stop and slows down gently the engine keeps running. I guess next is pulling the carburetor and adjusting the float level.🛠

Look at air horn to float bowl gasket. Hopefully somebody didn't use 2 gaskets here. The BV will warp just like the B and BC. If some not-so-clever person put 2 gaskets in there at some point in time (hoping to stop the continuous dribbling), you can see below what might happen. One gasket shrinks or moves out of the way and you have a brand new and unique fuel-slosher. (image of a model B used in the study I did 2 years ago) Good luck.

Jon G is correct, Here is a lengthy explanation but, this will cure the malady that makes so many hate the Rochester model "B". Yup, your going to have to take the carb. completely off. Take the air horn off (4 thick headed screws), put a flat steel measure on both the bottom side and the bowl if either one shows warping salvage screws and remove all parts and toss the two pieces in a bucket. Buy a good rebuilt carburetor from a real carb. re-builder, check with carbking above. If the horn and bowl are good proceed as follows; pull up the accelerator pump, if it has a blue cup and a flat bar with a slot you have a BV, however and this is where it gets weird it can have a round shaft and blue plastic OR leather cup. I personally prefer leather but, it's not about me, long story for later. This is extremely important and the main reason so very many dislike the Rochester model "B". Once you remove the accelerator spring (a very light about 1.6 inch long spring), inspect the bottom to see if there is abnormal wear like a high spot wear, lightly sand and set aside. NOW & THIS IS CRITICAL look in the accelerator well, and at about 10:00 (carb front pointing to the left), at about 10:00 will be a hole at the bottom of the well. This is where the problem with model "B's is, at about 4:00 will be what many think is a second hole but it's only a dimple or it may be a hole, the dimple is a undrilled cast. You will have to have a very bright light and a long needle bent at a 90 degree angle or a dental pick. If there is no hole but the well has two balls (smaller than a BB), if there is one hole and two balls that causes idle problems the proper ball is aluminum. The rebuild kit has three balls two steel and one aluminum, one steel ball is for the metering jet and the other (same size) is for the accelerator pump well that has two holes. justhorsenround put the un-needed steel ball into your storage drawer in a bit of grease. Depending on altitude a #58 metering jet should work just fine for a BV. No instructions with any rebuild kit will explain this and some just instruct to put both balls in well??????????? Precisely set the float and check to make sure the brass bladder does not touch the bowl walls or have a major dent or crack,hole in float. Touching the wall will also cause the problem your friend is having. Simple carburetor that can cause major problems. DO NOT overtighten four screws on air horn, will cause warping. Check all the small holes on bowl bottom and throttle body, sometimes may have to drill extra hole in gasket. Doc

Jon, Doc, Jerry, thanks for the suggestions and photos. I think his plan is for us to remove the carburetor this weekend and try to sort it out. I know the carburetor was rebuilt 3-4 years ago and at the time nothing was warped. The kit used was not Ethanol friendly but the owner swears the truck has never had Ethanol in it. Guess we’ll see. Know some things to look for and tests to perform now. Will report the results.🛠

Let us know please. Thanks. Doc

Well, my buddy shows up at 7am this morning. I haven’t had my coffee yet. He said it died at every intersection the 35 mile trip unless he pushed in the clutch and mostly let it coast to a stop. Told him I’m not working on a hot engine so coffee it is. Went out about 30 minutes later and took the carburetor off. On the bench the tear down went as planned. Using a machinists metal ruler and feeler gauges I checked the surfaces for warping. Straight as they could possibly be. Checked the float setting and found the float drop to be 1/2 inch off. Completed the tear down finding no obvious problems. Carburetor cleaner and compressed air showed all passages were clear. Polished the power valve with 1500 grit wet sand paper and cleaned it. The accelerator pump was leather and I replaced it with the leather one from the kit he brought with him. Reassembled paying close attention to float settings and which metal balls went where. Flipped it upside down several times to make sure the float wasn’t sticking or hanging up. All good. Set the air mixture screw at 2 turns out from gentle seat. Reinstalled the carburetor checking the gasket to make sure the vacuum passage was unobstructed. Hooked up all the linkage and spring. Ten seconds of cranking and it fired right up. Idle settled down after the choke opened. Fine tuned the adjustments and off we went for a test drive. First stop I saw a smile come to his face as it came to a normal stop without dying. Thirty minutes and 12-15 stops and it appears the problem is solved. I’m calling it good.🛠