back fire 31 model a

[lenmissy]

what causes back fire when trying to start 31 model a len

[pat in Santa Cruz]

depends on if you just did something to it or not and if you're talking about through the carb or muffler.

[James Rogers]

Manifold leak.

[Mike V. Florida]

What is your procedure when you start your A? Where are the levers, do you use the choke, where is the GAV set?

Let us know what procedure you use.

[TinCup]

When I first bought my coupe it was because of the valve clearances.

[rotorwrench]

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Any un-burned fuel escaping through an exhaust valve during compression can cause an after fire (explosion in the exhaust system). Causes could be a sticky or burned valve, valve not seating well, cam timing could be off, or intermittent ignition troubles.

A back fire through the carburetor is usually caused by a lean condition with the carburetor. This can also be caused by a leaky or sticky intake valve. May also be an intake valve adjustment or cam timing problem.

[lenmissy]

ajusted timeing spark is up choke is out i will have to check timeing when it was running no power under load len

[pat in Santa Cruz]

if it did not backfire prior to adjusting the timing, there's the problem. follow this procedure:
http://www.abarnyard.com/workshop/timing.htm

do you use the Ford dist body, or a cap with wires to the spark plugs? With a cap, the wires can get crossed and it will backfire when trying to start, but will not start. To get the timing that far off using the original dist body, you have to position the rotor incorrectly.

[Purdy Swoft]

Originally Posted by lenmissy

what causes back fire when trying to start 31 model a len

From yesterdays thread Backlash 31, It seems that you have got the timing way off. after reading Pat in Santa Cruz post it occured to me that you may be tring to set the rotor tip with the wrong contact in the distributor cap body. I will try again to walk you through the timing process that I use. If you are standing on the passenger side of the engine snap the clamps and remove the top distributor cap that the coil wire connects to. Leave the distributor cap body that the plug wire straps connect to in place. You can look in to the distributor and observe the rotor and the contacts in the distributor cap body that run through the cap body to where the spark plug wires connect. The front contact on the passenger side in the distributor cap body is the number one contact. When the timing pin drops into the indentation on the timing gear, lift off the rotor and loosen the slot head screw that holds the distributor cam. place the rotor back in place and rotate the cam untill the trailing or rear edge of the rotor tip is pointing at the number one contact in the distributor cap body with no clockwise backlash. Go back and read my posts yesterday on backlash and maybe it will be easier to understand. If you try my method and try to add in part of someone elses method you will end up with an engine that probably won't run at all .

I know it can be challenging for a person to set the timing for the first time, But you gotta get tough, its not that hard and setting points and timing is something that you really need to be able to do as a model A owner.

If you have an old rotor cap that is no good you can break off the little thin steel contact strip on top, then turn the rotor cap over and drill a hole about 7/16 through the rotor. you can install it on the distributor cam and you cou tighten the screw that holds the cam while holding the rotor in place with the pointer correctly pointed. After tightening the screw check that you don't have any clockwise backlash. You may need to repeat the loosen, adjust, tighten process a few times before you get the back lash out. This makes a good cheap timing tool that you can take with you in your tool bag. Good Luck.

[lenmissy]

When i tighten the screw the rotor can still move rotor back and forth one half in will try again today len

[pat in Santa Cruz]

Originally Posted by lenmissy

When i tighten the screw the rotor can still move rotor back and forth one half in will try again today len

you have a worn drive gear and/or shaft, and there is a lot of backlash. It is important to remove all backlash in order to get accurate timing. The cam moves counterclockwise when the engine is running. When timing it, rotate the rotor clockwise to remove the backlash until the points just close as the point rubbing block is moving down the lead edge of the cam. Then tighten the screw. If it moves further clockwise when tightening it, not all the backlash was removed. You want it so the points are just at the point of opening when all backlash is removed. It will still have the movement when rotated counterclockwise, but when the engine is running that will not be much of an issue. Using a tool like the one Purdy describes, or one of the metal rotor wrenches common from suppliers will help hold it in place as you tighten it.

[Purdy Swoft]

Originally Posted by lenmissy

When i tighten the screw the rotor can still move rotor back and forth one half in will try again today len

Yes it will. If you re read my previous posts on backlash , the object is to move ALL of the backlash to the counter clockwise side where it does not effect the timing. You need to keep trying untill when you tighten the cam screw the trailing or back edge of the rotor tip is pointing at the number one contact and won't move back or in the clockwise direction. You will still have the 1/2 inch backlash but it will all be in the counter clockwise or foward direction, where it WILL NOT effect timing. It is also VERY important to check the points. I always set mine at .022 for optimum results. If the points gap is very much less than .018 it will cause you to loose power.

If you wanted to remove all of the backlash you may have to replace the distributor shafts, oil pump and distributor drive gear and maybe even the camshaft. If you are having trouble setting the timing, you can only imagine the problems and EXPENSE you would have with a procedure like that. If you adjust the distributor cam so that ALL of the backlash is in the foward or counter clockwise direction, the backlash will have NO effect. Keep trying, if it gets TOO stressfull stop and meditate. It is not that hard, My wife can do it and so can you.

[lenmissy]

thanks day 3 coming up i an getting close len

[Purdy Swoft]

Originally Posted by lenmissy

thanks day 3 coming up i an getting close len

I hear you!!! Probably one of the problems can be that when you tighten the cam screw the distributor shaft is turning a little bit and putting clockwise backlash at the cam and rotor tip. It may help if you hold the cam a little past the point that you want it to arrive, after tightening. This method will give the shaft a little room to turn as you tighten the cam screw without adding clockwise backlash. It will be trial and error for a couple of tries until you find the correct amount to lead the cam so that after tightening you won't have clockwise backlash. Any clockwise backlash at all will contribute to retarded timing and loss of power. Good luck.

[1931 flamingo]

Most vendors now sell a dist cam wrench (w/inst) that is simple to use and I think fool proof. After finding TDC on #1 And setting point gap, w dist cap on the dist but top off, install the tool over the cam, loosen screw, turn tool 2 turns CLOCKWISE until edge of tool touches #4 pin on the cap, tighten cam screw, Job done. Approx $10. Works for me
Paul in CT

[lenmissy]

update still have not got the tin can running a friend is coming out on thurs hope he can len

[rollingsculpture]

OK so i have a question if the point gap spread is from .018 - .022 what is the difference in spark at the plug for each gap .018-. 019. 020. 021. 022 im trying to understand if the gap is wider at .022 than at .018 than the spark lasts a micro second longer? how does that help or hinder the performance ? also if the spark is jumping a wider gap doesnt that diminish the strength of the spark at the plug wouldnt some of the energy dissipate in the transfere through the points ?curious minds want to know and i too am trying to get my engine set just perfect enough that i can hand crank it with minimum number of trys, so far my engine starts anywhere between the 4th to 7th crank up from 9oclock to 12 position .

[rotorwrench]

Points gap is all about dwell time or how long the points are closed and/or open. The condenser has to charge to specs during that period when the points are closed. If the point gap is wider, the dwell time is shorter. If points dwell time is erratic then the high tension spark will also be erratic. The condenser resists current flow if working properly so it keeps the primary side of the ignition from trying to jump the point gap as the points open. This keeps arcing of the points to a minimum and the points last much longer

Kerby

[Purdy Swoft]

Originally Posted by rollingsculpture

OK so i have a question if the point gap spread is from .018 - .022 what is the difference in spark at the plug for each gap .018-. 019. 020. 021. 022 im trying to understand if the gap is wider at .022 than at .018 than the spark lasts a micro second longer? how does that help or hinder the performance ? also if the spark is jumping a wider gap doesnt that diminish the strength of the spark at the plug wouldnt some of the energy dissipate in the transfere through the points ?curious minds want to know and i too am trying to get my engine set just perfect enough that i can hand crank it with minimum number of trys, so far my engine starts anywhere between the 4th to 7th crank up from 9oclock to 12 position .

The wider gap of .022 gives the coil more time to build up before the next firing, it is only miliseconds but everything counts and it gives a stronger spark at the spark plugs. In other words more dwell and it has a similar effect of adding a model B distributor cam. The other advantage is with the wider gap, it gives more time before having to re set the points. as the fiber block wears down on the points the gap begins to close and you slowly lose power untill it gets to the point that it gets harder and harder to crank and sombody will have to re set the points. It is said that the points wears the most in the first 1000 miles

[Purdy Swoft]

Originally Posted by lenmissy

update still have not got the tin can running a friend is coming out on thurs hope he can len

Sorry that my advise hasn't helped more. I don't know what else that I can say about backlash and the trailing edge of the rotor tip. I am already sounding like a broken record. Maybe by now, you have the timing correct and other problems are keeping it from running. Maybe the spark plugs are wet and the battery is getting low. If the battery is low, in many cases it won't have enough power to turn the starter and fire the distributor. You need a strong blue spark. Maybe you have the dreaded so called modern points, they are hell to adjust and famous for shorting out with no visable reason.The list could go on an on. All I can say is good luck and keep us posted.

[lenmissy]

I have the car for ten years the car is flooding cranking to long battery charger is on points at 20 have little play in top of dist going to change it set timing at least 25 times it fires and wants to go to much gas cleaned plugs to many times have a new carb going to change it I am wandering if tow it would be help full had it for day going to have happy hr now len

[MCHinson]

lenmissy,

Have you checked the carburetor float to make sure it is not leaking and causing a too rich fuel condition?

[lenmissy]

have a rebuilt carb going to change it len

[rollingsculpture]

Len Did you try swapping in a new/different coil ?

[Purdy Swoft]

Originally Posted by lenmissy

I have the car for ten years the car is flooding cranking to long battery charger is on points at 20 have little play in top of dist going to change it set timing at least 25 times it fires and wants to go to much gas cleaned plugs to many times have a new carb going to change it I am wandering if tow it would be help full had it for day going to have happy hr now len

I've had problems with spark plugs that acted like you describe. I was using the low cost motorcraft plugs. The car was slow to crank and would flood and the sparkplugs would get wet with gas very quickly. After flooding and drying out the plugs a few times it didn't help any more. If it did crank it would back fire and run terrible. This is the way they can act even if the plugs are not very old, after flooding. If you've got any spare plugs it may be worth the trouble to try them. good luck.

[lenmissy]

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have a rebuilt coil going to put it in len

[marc hildebrant]

"I have the car for ten years the car is flooding cranking to long battery charger is on points at 20 have little play in top of dist going to change it set timing at least 25 times it fires and wants to go to much gas cleaned plugs to many times have a new carb going to change it I am wandering if tow it would be help full had it for day going to have happy hr now len "

Len,

I'm interested in following this tread, but I can't understand what you are saying. Could you please add periods/Capitals/etc. ?

Marc

[Purdy Swoft]

Originally Posted by lenmissy

have a rebuilt coil going to put it in len

Make sure that the coil polarity is correct. I have a coil polarity tester that really comes in handy. if the coil is reversed it can still run but the spark will be weaker and can cause difficult cranking. Sometimes a jump start with 12 volts will give it the boost that it needs. I am sort of leaning in the direction that bad spark plugs could be the problem. It could still be timing issues. I remember that you said you are cranking with the spark up and that is correct but if the timing is a little retarded you could try advancing the spark a few notches and see if that will help. If the starter kicks, you will know that is not the problem. It could be a valve or valves stuck in the open position and you would lose compression. A good way to check is to place your thumb tightly over the spark plug hole and turn the engine with the starter. When it comes up on compression stroke it will pop your thumb off the hole. Any cylinder that this test fails will likely have a stuck open valve. I can only guess, If you lived nearby, I would help. Good luck.

[lenmissy]

when to the old school never had never had high teck stuff type with on finger but you get the picture len

[lenmissy]

If stuck valve is ther something to free them len

[Purdy Swoft]

Originally Posted by lenmissy

If stuck valve is ther something to free them len

Yes, stuck valves can be un stuck. Have you performed the thumb compression check? If so and some of the cylinders failed the test let us know. I will try to give info.

[Freddie (Memphis)]

dear len you can type with one finger and still insert punctuation so we can all read your notes a little better if nothing else put a couple of spaces after a sentence so we will know where one sentence stops and another begins thank you very much someone on here can probably help you but it sure is hard to read your postings when you dont use any punctuation your friend freddie

[lenmissy]

had it running for 5 min. ran rough muffler smokes to much gas from cranking will check thumb compresson

[rollingsculpture]

Originally Posted by lenmissy

I have the car for ten years the car is flooding cranking to long battery charger is on points at 20 have little play in top of dist going to change it set timing at least 25 times it fires and wants to go to much gas cleaned plugs to many times have a new carb going to change it I am wandering if tow it would be help full had it for day going to have happy hr now len

i just experienced a similar thing last night and after checking the timing, swapping out the coil and eventually running the battery down i finally discovered that the throttle screw setting was too low and i needed to pull down on the throttle lever to allow the carbuerator to open up and get some air and fuel through it , usually i did not need to pull the lever down to start it up but i had changed the idle speed recently (and apparently too low)and that was my undoing . basically it only wanted to turn over , chug once than quit , finally after checking everything else i pulled the lever down and hit the starter sure enough it fired right up . hope this helps someone else who may come accross this problem as one more thing to check

[lenmissy]

Are you guys ready rollings sculpt idea was right.Changes coil fires up like a trooper what a hassel now i can play with with my 40 ford thanks guys len