missing or stumbling on acceleration
 

Hi Folks,

This one has me baffled-not that that is hard to do sometimes. Here are the symptoms. Upon acceleration in 1stgear she is fine, move to second she is fine 90% of the time, third gear and she stumbles, misses and stumbles an coughs but she still accelerates. Then when she hits about 40-45 all is well and she cruise just fine.

What I have done: I opened up the GAV-no change, Altered the spark-no change, cleaned the plugs, changed the carb-all no change. No I am running the 3X plugs and #1 just started leaking oil out of the gasket area between the base and small part of the plug-not sure what to call it. Some sooting of the base but the ceramic was clean albeit dark grey/black. The dist. body had all of the electrical arcing evidence on the bottom half of the steel studs. Here temp is around 180 at the top and 170 at the bottom of the radiator.

Theories: coil going bad when under a load? maybe the condenser-I did change that awhile back and no real difference. I am going to change plugs this week to see what happens.

Thanks,

Mike

Re: missing or stumbling on acceleration
 

Remove the gas cap give it a try, change any fuel filters, the paper ones that clog from the inside, clean fuel screens. Your GAV should make a change leaner or richer, and the carburetor needs adjusting. That oily looking stuff leaking out of #1 plug is probly gas soaked carbon. I'am thinking your running way to rich and have a low fuel flow problem

Re: missing or stumbling on acceleration
 

I am thinking it is a carburetor problen rather than something in the electrical system.

Re: missing or stumbling on acceleration
 

I would tend to agree. The carburetor has three stages, idle, intermediate and high speed. It sounds like it may be something with the cap jet and through the intermediate stages. I would clean the carburetor out good, take the jets out, clean passages, blow it out with air and see if that helps.

You didn't mention checking the point gap? My experience with a coil going bad, is that it usually starts off fine, then down the road when it gets hot, the problems begin.

Re: missing or stumbling on acceleration
 

Classic symptoms of running too lean.

Re: missing or stumbling on acceleration
 

This site is for the Zenith carburetor but if you have another brand the principles are the same. This site has a lot of valuable information.

http://model-a.org/default.html

Re: missing or stumbling on acceleration
 

The point gap is .023- a bit large but doable. I will check fuel flow and see what I have as there are no filters in the system, I do have a magnet that collects the rust particles in the bowl.


Mike

Re: missing or stumbling on acceleration
 

The larger point gap shouldn't cause missing, a bad spring on the points would do that but it would happen all the time. I would take the carb apart and find some dirt to clean out.

Re: missing or stumbling on acceleration
 

[QUOTE=Big hammer; I'am thinking your running way to rich and have a low fuel flow problem[/QUOTE]

Bit confused here about a low fuel flow problem causing it to run rich. Would not low fuel flow cause it to run lean? I had similar symptoms with my car and it was an ignition problem. All the timing procedures were correct. Turns out that with a combination of some of the specs. being on the high side and some on the low side it all added up to cause a problem. Start by finding TDC and go up from there and get every thing "spot on" in the center of the specs. and see what happens. I chased my problem for a couple weeks before finding out this. Model A's seem to have a remarkable way of having a fuel problem when it is an ignition problem and the other way around.

John

Re: missing or stumbling on acceleration
 

Sir you turned my words around, the carburetor is running rich ( period) it's running so rich that it maybe using up the available fuel
When drinking a strawberry shake you get a brain freeze ( to much shake) and then you suck up a piece of strawberry and the flow stops lol
His problem is the carb is way to rich ( sooty plugs #1 plug has liquid leaking around the outside of it) and maybe running the carb dry.
Adjusting the carb idle mixture and idle speed may take care of the rich mixture, and I hope he has a carb inlet filter that could be dirty/ clogged. The only electrical issue could/would be with dirty/fouled spark plugs ...hopefully
His words first gear is alright , second gear is 90%, third gear stumbling or missing until 40-45 mph and then all is ok!

Re: missing or stumbling on acceleration
 

I didn't mean to turn your words around but I now understand what you are saying. The electrical or fuel question has been discussed many times and I stand by electrical being the problem. No offense taken or given, time will tell - hopefully. After opening the carb on my car 2 times cleaning and replacing some jets, GAV seat, checking the float level and replacing the needle valve - NADA. Barn member nkaminar graciously drove 7 hrs. round trip on a holiday week end and sorted it out in about 45 minutes and he would only accept a bar-b-que lunch. My quote in your post is what happened to me.

John

Re: missing or stumbling on acceleration
 

We are good! The most important thing is getting them back on the road and enjoy a drive!

Re: missing or stumbling on acceleration
 

Yep and no na,na's when we find out the solution.

John

Re: missing or stumbling on acceleration
 

Just a thought - when considering a rich mixture by spark plug soot. Consider a 24 Hp engine of 200.5 cubic inches and max. of 18 gph and approx. average of 15 gph. fuel consumption with a compression ratio of 4 1/4 to 1 it is amazing to me that the spark plug soot is not closer to coal.

John

Re: missing or stumbling on acceleration
 

Remove and clean the carburetor jets, especially cap and main jet.

Re: missing or stumbling on acceleration
 

Well took apart my Marvell and Zenith carbs today and both had clean bowls. I left my air nozel at my In Laws place so could not blow out any passages. I have tomorrow off so will clean everything then and let you all know what I find.

Mike

Re: missing or stumbling on acceleration
 

Get a can of Deep Creep spray and use it in the all the passages before blowing them out.

Re: missing or stumbling on acceleration
 

A spray can of carb cleaner with the straw works very well, use eye and hand protection! Put the straw on the opening and watch it come out or where will it blast out, that's why use eye protection.

Re: missing or stumbling on acceleration
 

Old farm remedy that was taught to me many years ago:
1. park auto and turn gas off and let gas in carb flow out
2. unhook gas line and spray automatic transmission fluid into the carb
3. rehook gas lines and crank vehicle and let the automatic transmission fluid clean the carb
4. this should super clean the carb if the problem is within the carb
5. if this does not help you can cross carb problems off your list

Re: missing or stumbling on acceleration
 

I have been soaking them in Seafoam overnight. When I get home I will empty them out and then blow out each jet. I have great flow when I turned on the gas, so I re-installed the fuel filter and magnet.
Mike