Model A looses power

P

pcpat

Junior Member
I recently put my Model A on the road after several years of restoration. It seems to have been running fine for a while but I now have a stange issue that I'm trying to figure out and I'm looking for ideas... All seemed to be running great, I pulled into a gas station, filled up the truck. (First full tank after sealing the tank - prior to this I've only been using 1/2 tanks making sure nothing was leaking).
I pulled away from the pumps and the engine started backfiring, no power - then it weant to surging (power then no power) still backfiring, I couldn't even make it out of the parking lot.
I checked the timing, and verified it was spot on.
I pulled the fuel line off and checked the gas flow, it was flowing at a good rate, no blockage was noted I did notice gas leaking out the carburator mouth.
I drained the gas out of the carburator, opened it up and noticed a little loose rust in the bottom carburator, cleaned it out, cleaned the carb filter and sprayed out all the jets.
Put the carb back on my Model A and it ran fine for about 10 minutes, then it all started over again, backfire power surging, etc and still dripping gas out the mouth of the carburator.

Looking for ideas on where to go next - Thoughts? Let me know what other details anyone may want?

Thanks you,

Pat
 
Hello, Maybe filling up tank caused rust to be dislodged in tank , you may also run a small wire through the carburetor drilled passages, I had some problems like what you described took carburetor apart a couple of times not until I wired out it did that get rid of problem this was a cast iron Zenith pushed out a lot of rust buildup.Good luck.
 
Always start simple, ..... remove the gas cap & try again.

You didn't confuse the radiator cap (no vent) with the gas cap ??
 
after reading your statement, seems like once it warms up is when this occurs,after you worked on it said it ran for a bit,warmed up? then quit power, is your coil decent or new? Or low compression,timing retarded, Carb float needs adjusting maybe hanging up, that would cause loss of power,backfire would be a faulty condenser or defective coil.
 
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We recently sealed a 28 tank and left the tank empty for 3 or 4 days to allow the sealant to thoroughly cure. The fuel line tubing and fittings were all cleaned and reconnected to the tank and the carburetor. The tank was filled with 5 gal of fuel followed by starting the engine. We took the car for a ride and noticed the it would not accelerate. Running at slow speeds was fine but when accelerating the carburetor was definitely not getting the correct amount of fuel. The tank was emptied along with observing the fuel flow as it was emptied which seemed to be adequate. After careful inspection of the exit hole in the tank as viewed through the fill collar we noticed small pieces of sealant attached to the exit. Using a long thin probe the pieces were able to be removed. The car was refilled and a test drive immediately indicated the engine accelerated normally. Even though the fuel flow initially appeared to be correct it apparently wasn't enough for accelerating.
 
Thank you for the replies, I will re-clean the carb with the wire as suggested tomorrow night.
As for the Gas Cap, that was one of my thoughts as well, but running with the gas cap removed gave the same issue (I verified it was a vented cap).
As for the stuck valve thought, would this cause the issue?

Pat
 
Pat, I'm going to suggest the opposite here. Half tanks worked fine but a full tank caused trouble...one symptom was fuel dripping from the carb. Sounds to me like the extra head pressure from the full tank is making fuel leak past the needle/seat in the carb and flooding it. Try a partial tank of fuel again, and if that cures it swap the needle/seat for a new one.



Terry
 
FLoat valve is open....possibly float is not set at the right height or bad float valve. Also sheck the condenser.
 
x2 all above, easy basics first.

I use a borescope camera on my phone to examine the fuel tank. I didn't see anyone mention a pencil filter for the top of the fuel valve at the tank.

If you had your spark plugs out, make sure you torqued them to 25 foot pounds. Our club had a car that one plug was leaking, and the car would not run over 30mph. Torqued the plug and symptom gone. It didn't backfire though.

The main and cap jets in the throat may be leaking at their bases. My middle finger is long enough to verify that one; yours may not be. Drop the bottom of the carb and check that on the bench.

Test your switch by jiggling the key in, out, left right, up down with engine at warm fast idle. Check all connections from the starter switch to the points for loose ring terminals, fraying or corrosion. Clean your grounds at the frame and the distributor. Clean bright metal.
 
- I just ordered a new float valve to see if that helps with the fuel dripping, thanks for that suggestion.
- As for the pencil filter, I was kicking myself, when I put it back together and made the first fill up I realized forgot to put in the filter - but I said I just sealed the tank - what could go wrong...
- I checked the spark plugs and all 4 are all nice and tight
- Good thinking on the switch, I just replaced the ignition cable and points recently, but didn't replace the switch. I'll try that this weekend along with replacing the condenser

I'll let you know what I come up with - gonna be a rainy weekend so I wont have much of a chance to road test it
 
Old mechanic rule.. “if you think it’s fuel the problem is ignition, if you think it’s ignition the problem is fuel”

Sounds like she cools down, runs fine then breaks up.. coil/ condenser/ wire between the distributor plates..
 
Here is what I have done so far:
- I drained the gas and installed a pencil filter in the tank
- Replaced the Condenser
- Removed and cleaned the carb and in doing so replaced the float valve and took a thin wire to all the passageways and jets to ensure nothing was blocking
- I looked at the exhaust manifold and noticed the number 1 exhaust port was showing black carbon from where it looks to have been leaking, I was able to put a small wire between the exhaust and the block which is possibly what may be causing the backfire. I had another manifold that has a heater built on it, looks to be in good condition when I put a straight-edge on it so used that to swap it out
- In swapping out the exhaust manifold I noticed my manifold gasket had a budge around the rear intake port, possibly from me not torquing it properly a few years ago, I'm waiting on a new manifold gasket which is on order
I also noticed my gas filter was full of rust partials from when I didn't replace it after sealing the tank, so a new gas filter is on order
- As for the coil, the one I'm using is relatively new, changed out a few months ago, so
I'm hoping that's not the issue
- As for the gas cap, I ran it with the gas cap off when first started having the issue but it did the same thing so I ruled that out
Thanks again for all the help, once I get the gas filter and manifold gaskets installed I give an update
 
With the history of a rusty tank, and a rust contaminated fuel filter, I would inspect the sediment bowl screen, either glass bowl type, or cast iron type for residual rust particles.
 
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A model T’er had an issue that it would only on 3 cylinders, any 3 with one spark plug removed. Turned out the muffler was plugged by a mouse house!!! Something to check waiting for parts.
 
The Exhaust Manifold Gasket has been replaced, I installed a different (not warped) exhaust manifold replaced the float valve and cleaned carb. The engine is now Idling faster so I had to turn it down some. I took Rob Doe's suggestion and replaced the ignition switch. I have already replaced the Gas filter, installed a new condenser, I checked the sparkplugs (all tight), made certain there was nothing blocking the exhaust.

A little dark outside right now but now I'm ready for a test drive - hopefully tomorrow
 
I wanted to thank everyone for their inputs. Its running better than ever - more power and a lot smoother.
 
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