Acceleration problem

[greg g]

Are you getting proper fuel flow in terms of quantity. I had a similar symptoms and found a piece of debris in he fuel pump that allowed idle and moderate cruise 25-30, but would surge and stall with hill climbing or brisk acceleration. Also is your rubber fuel inlet hose new and in good condition?

[Lloyd]

I also thought it would be interesting to follow some advice that was given earlier and rig up a gravity fed fuel supply just to take the fuel pump out of the equation and see what happens. I'll also check for vacuum leaks.

I think what Don said about using a pressure gauge is the best way to determine if it is a fuel pump. It does not use much pressure, I think I read somewhere it only uses about 3 psi but maybe someone else could verify or correct that. If you do use another source for fuel be aware that you are cutting out the fuel line all the way back to the tank. That does not eliminate the possibility that it could be drawing air or partial blockage somewhere along there. What stands out to me is that you said it held a steady rhythm. Seems that would certainly be fuel or air flow. Gets to a certain point, rpm or vacuum then the mixture is compromised which is causing it to drop back down. Thats what Im hearing anyway. Try testing with a vacuum gauge, watch it at an idle then bring it up slowly till it starts surging. Not sure what to look for but it may be an indicator.

[JerseyHarold]

Have you checked the automatic choke return spring?  Disconnect it while the engine is warm and tie the  butterfly open and see if that helps.

[Joe Flanagan]

I'm trying to rig up a gravity-fed fuel supply straight to the carburetor, cutting out the fuel pump. I have a fitting with a hose barb threaded into the carb but coming up with a leak-proof container with a fitting for the hose has me stumped at the moment. Has anyone done this before? 

[Don Coatney]

Sit a lawn mower can on the fender and fill the fuel line so it will siphon.

[Joe Flanagan]

The carb itself (or siphon action) will pull the fuel in? 

[Don Coatney]

siphon action

[Joe Flanagan]

OK let me try that. I eliminated the vacuum advance as a suspect by the way.

[Joe Flanagan]

I managed to run the engine with fuel straight from a container to the carb, cutting out the fuel pump and everything upstream of it. The problem is still there, so either there is something in the carb that I have not discovered yet or this is one of those fuel problems that turns out to be electrical. Next step is to remove the distributor and have a look at it. I did spray carb cleaner around the base of the carburetor while the engine was running and it didn't change anything. I haven't checked the intake manifold or any other possible sources of a vacuum leak but I will be doing that soon as well. Also, I wanted to mention that I have not yet tried Jersey Harold's suggestion but will do that too.

Edited April 6, 2015 by Joe Flanagan

[Joe Flanagan]

I pulled off the distributor and found that the small wire inside was broken. Looks like that was my problem. Also, when I move the breaker plates by hand, there is some resistance and a weird clicking noise, as if there is some obstruction there. I will disassemble tomorrow and investigate further. Anyone know of a source for that tiny wire inside the distributor? I used the smallest gauge insulated wire I could find and crimped and soldered ring terminals at either end. I had no trouble with it until now. I think the constant flexing caused the wire to break at the soldered connection.

Edited April 7, 2015 by Joe Flanagan

[JerseyHarold]

I guess it proves the old saying that 95% of carburetor issues are electrical.

[Young Ed]

http://www.napaonline.com/Catalog/CatalogItemDetail.aspx/Distributor-Lead-Wire-Primary/_/R-ECHLW76_0194175601

Edited April 7, 2015 by Young Ed

[Mark Haymond]

Young Ed's link to the Napa distributor wire should get you exactly what you need. Such a wire that has to work during years of flexing is usually made up of multiple strands of really tiny, flexible, copper wires.

[Joe Flanagan]

Thank you, Ed, for that link. I expect to be back on the road soon. 

[Jeff Balazs]

I am a bit baffled. I just don't see how a broken wire could produce a rhythmic running cycle? I am sure it was a contributing factor......but I would have to think there is more to this.

 

Jeff

[Lloyd]

I am a bit baffled. I just don't see how a broken wire could produce a rhythmic running cycle? I am sure it was a contributing factor......but I would have to think there is more to this.

 

Jeff

 

I was thinking the same thing.

Not sure which wire it was, although I know on mine the ground to the base plate is the one that gets the most abrasion.

But perhaps when the breaker plate moved at a certain rpm or vacuum then the problem presented itself? If it was the ground wire then perhaps the points were grounded till the plate moved..

Either way it certainly is a problem. Also the clicking in the distributor, maybe somethings hanging the breaker plate as well.

Be interesting to see if after going thru the distributor it takes care of the problem.

Keep us posted Joe, I'd like to hear the outcome!

Edited April 7, 2015 by Lloyd

[Don Coatney]

I am a bit baffled. I just don't see how a broken wire could produce a rhythmic running cycle? I am sure it was a contributing factor......but I would have to think there is more to this.

 

Jeff

RPM change may have been moving the advance plate just enough to make and break the connection???

[Jeff Balazs]

RPM change may have been moving the advance plate just enough to make and break the connection???

Well I suppose? Hopefully you are right. The skeptic in me is still wondering though. I guess time will tell.

 

Jeff

[Joe Flanagan]

I'll have the new wire in a couple of days and I'll let you know what happens. 

[Joe Flanagan]

There was more going on inside my distributor than I thought. It has two small lead wires and both were broken. Also, the c-clip that keeps the vacuum advance arm on its pivot post was missing and every time it moved, the arm rode up the post and made a clicking noise when it hit the recessed area where the c-clip is supposed to go. That was the sound I was hearing. The vacuum advance mechanism was still attached to the post but only by luck. 

 

Here's one of the two broken wires:

 

 

Here's the vacuum advance arm and the post that was missing its c-clip:

 

Edited April 8, 2015 by Joe Flanagan

[Lloyd]

Thats the ground wire to the breaker plate. When I first took mine apart I thought there should have been enough contact elsewhere that you really did not need that. Just a for sure thing.

Maybe when the vacuum advance pulled the breaker plate it broke contact, dropped rpms then regained contact? Fix the wire and see what happens...

 

Your distributor is set up a little different from mine:

 

[Don Coatney]

It appears the wire from the coil to the distributor needs some attention too.

[deathbound]

Heat shrink will help lessen the strain at the connector.

[greg g]

That wire looks pretty stiff for the application. Needs to be flexible enough to allow the breaker plate to move in either direction with as little impairment from the wire as possible. Hope your replacement has more flex.

[Joe Flanagan]

I agree. It wasn't the best replacement for the original wire. It looks like the NAPA replacement is identical to the original. I'm picking it up today.