My car died!

[Young Ed]

Been chasing a stumble at freeway speed in the 48. Swapped on a rebuilt carb that I got. It was rebuilt who knows how long ago and I dont know how well. Now here is the issue. Car was running ok with just that stumble. Put new carb on dumped a little gas down it to give it a head start on getting filled. Car started right up. I let it run for maybe a minute. Then I put the aircleaner back on and worked on getting the horn wire ran back down the steering column. After that maybe 45min later I decided to go for a test drive. Car started right up. I pulled into the alley and got to the far end. Slowed to look for traffic and it died. No restart. After a few minutes I called a neighbor and we towed it back to my driveway. Now it was pretty late so I haven't really checked much. I did check to make sure I didnt knock the coil wire off or something when I was working on the horn wire. Could this "rebuilt" carb possibly be so bad it wouldn't run at all? I've personally never seen a carb so bad a car wouldn't run but that doesn't mean it couldn't happen. The carb is a little bit later style that has auto choke linkage on it but I didnt think that would really matter just for the purpose of testing the carb. The whole idea was to determine if hte carb was the cause of the stumble or not and go from there.

I will be checking this thing out more tomorrow after work-any ideas what to check appreciated.

[Norm's Coupe]

Ed, it's strange it ran with the old carb and not the rebuilt one. I would eliminate that first. Put the old carb back on and see if it makes any difference.

[Normspeed]

Maybe the choke flipped shut?

I'm with Norm, stick the old carb back on and see what happens.

[james curl]

Maybe you ran out of gas, stranger things have happened. Make sure the fuel pump is putting out the correct amont of fuel to run the car.

[Young Ed]

I'll be trying these things after work. I may pull the top off this carb and have a look before removing it completely. So strange that I couldn't even get a sputter out of it.

[1just4don]

One of those stone filters in the carb inlet?? Maybe knocked some rust loose changing it?? grit from somewhere got where it shouldnt have?? Float stuck??

[Young Ed]

No fuel line goes right into the carb. There is an inline filter in that line which I changed about a week ago. I also changed the rubber fuel line from the original to a modern piece of hose. So far no change in the freeway driving until last night when I didn't even make it to the freeway!

[Guest Jon Dalrymple]

Ed,

Give me a call, I have your heaters. I have misplaced your number but I think you have mine.

Later dud,

Jon D.

[Young Ed]

Jon glad to see you remembered how to post I do have your number still. Might be next week before I have time to come over there. We'll see how the after work repairs go.

[david lazarus]

Check and replace your inline fuel filter, also drain your fuel tank (if you are not 100% confident that it is Ok). I had a very similar problem and crud in the tank had clogged the filter.

Dave

[greg g]

Take a bit of low pressure compressed air 10 to 20 lbs, and blow back through the line into the tank. the tank has a porous bras sfilter at the pickup, is it is blocked the air will blow the crud out of the holes. Also check the fuel pump for proper flow. Disconnect the line at the carb and direct into a suitable container, a 20 oz beverage bottle works well. then pull the coil wire and have an assistant crank the engine while you count pump strokes. You can see the pump strokes clearly with the gush of gas. Count 12 strokes and stop you should have 6 to 8 ounces of gas in your container. Any less indicated a blockage. Also make sure your conections are tight on the suction side of the pump. If you changed the hose and have an air leak on the tank side of the pump, it will compromise the pumps pulling ability.

finally most pumps have a fine brass partical screen in them. These can also get blocked and cause problems.

[Normspeed]

Since the no-run situation came up right after a carb swap, I'd have to swap the old carb back in there first. Odds are against some other problem popping up at the same time the carb was changed.

[Jerry Roberts]

Before you do any of the things mentioned above , pull the air cleaner and look down the carb and see if you get a good stream of gas when moving the accelerator . If no gas then you should do some of the other things mentioned . If you do have a stream of gas look for an electrical problem . But you know that allready Ed .

[Young Ed]

Ok the car runs again here's what I did. Looks like a few of you had it nailed while I was out working on it. I pulled the air cleaner and looked for gas spray. nada. Pulled the top off the carb and nothing looked out of the ordinary so I swapped back to my old one. Something bad wrong with that supposedly rebuilt carb. Before I put my old carb back on I did take all the guts out and sprayed it down with carb spray. There was some fine sediment in the bottom but nothing too horrible.

Now my car runs but it still has a little surging at 55-60ish. So I have cleaned out the carb, swapped that flex line for the fuel pump, changed fuel filter, pulled the bottom off the fuel pump and checked for gunk. I did find 2 little round bb's of rubber in the bottom of the fuel pump but I still have the issue after removing those. Oh checked dwell and timing and they were ok too. Starting to run out of things to check. Gas tank was professionally cleaned and sealed. It does have a homemade ferrul in the line and old steel line between the tank and the pump rubber hose. After the trip this weekend I may replace the ferrul with my real one and redo that steel line.

[Normspeed]

Ed, the original stumble could still be the carb. That little spring loaded brass needle assembly inside the carb can get pretty badly worn at the tip. There's also a tiny gasket down in that piston bore, that can go bad. That's where a parts carb and a good kit can come in handy. I had to go through both of mine twice and cannibalize a third carb to get them really right.

Also, good time to check the vacuum advance for leaky diaphragm.

Oh, and not likely but bad plug wires, dirty or worn cap/rotor can give similar misses. Just tossing stuff out here...

[Young Ed]

Vacuum advance was bad and already switched to a checked out ok used one. I know it could still be the carb. I was trying to eliminate or determine if thats what it was by switching. You can see how well that worked out! I did have some trouble with that brass needle piece you are talking about sticking. I sanded it and got it to move pretty freely but its not 100%.

[Normspeed]

That piece tends to stick at the very top of the stroke but when the carb is together it's slightly depressed by the top plate of the carb so it never reaches that point.

For such a simple little carb, it does have its little intricacies. And quirks!

[Norm's Coupe]

Ed, if you know for sure the carb is at fault and you've already rebuilt it once, I'd just pony up for a new carb. At least that way, you know it's good to start out with.

Another question first though. Does it stumble only when it's cold or does it do it all the time? If it does it only when cold it could be your heat riser sticking and causing the problem.

[Young Ed]

It does it at freeway speed. Sometimes even as low as 45. I don't know for sure its the carb. I tried that other one to see if I could determine that one way or the other and that carb was so bad the car wouldn't even run. We've got lots of these things around so I may raid one from a car that I already know runs well. Thats a PITA but it should tell me lots.

Oh Also my heat riser doesn't have the weight or spring but it does move freely.

[bob westphal]

Are we talking about a stumble or a surge? Explain what you call a stumble, what happens and how and when. A surge is when the engine actually decreases and increases in rpm at a steady throttle and always is caused by a vacuum leak or a too lean condition. A stumble is when you press on the throttle the engine hesitates for moment. This condition is usually caused by a lack of fuel going into the engine, ie: accelerator pump, or ignition problems, ie: weak spark, timing advance, etc.

[Young Ed]

I think a surge is a better description of the issue. At steady high speeds the engine doesn't run smoothly. It makes it feel almost like the is lurching ahead but its a little more subtle then that. If I had a vacuum leak wouldn't I have issues at low speeds too?

[Norm's Coupe]

Ed, the heat riser will normally only cause poor running conditions when cold if it's not operating as it should. That can normally be overcome by use of the choke longer when the heat riser isn't working right. If your having problems all the time, it has to be something else like Bob mentioned. Just going to be a process of elimination until you hit on the right one.

[Young Ed]

Certainly am having problems all the time. It gets really annoying when you are traveling long distances. Which I will be tomorrow!

[Young Ed]

Ok a little follow-up. Bought a parts car and rebuilt the carb off it. High speed surging seems to be solved now(only did a mile or so length on the freeway) but now I've got a low speed issue. Car wants to stall when pulling away from a stop. Jeez I can't win. Ideas?

[greg g]

Stumble from stop to go is likely related to tha accelerator pump. Are you getting a god squirt of gas when the throttle is openend. You should see a good squirt witht he choke open just under the choke plate. Also you should check the step up circuit inside the carb. when looking at the carb from the front the step up is on the left and consists of a small plunger needle and spring affair. thei should move up and sown freely against its spring with light pressure. Normally manifold vacuum holds the plunger down against the spring, and holds the needle down in the jet. As you step on the gas and manifold vacuum decreases, the spring can push the needle up and out of the jet providing more gas into the air flow. As vacuum increases, it pulls the plunger back down and shuts off the extra flow. There is a slot cut into the carb to gasket to provide vacuum to a port in the bottom of the carb. Make sure this slot is alligned with the port and the port is clear. If both these circuits are operating as designed and you timing is correct, you chould not have any off idle stumble or miss through acceleration. At least non that is fule related. The next issue would be to assure your vacuum advance and mechanical advance are working properly.