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signorc

Engine stalls and won't restart till it cools down

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Hello everyone,

I can drive the 302 for hours on highways with no issue at all....but as soon as I get off the highway she'll stall.

She'll also stall  if I take her for a ride up a few hills and engine temp goes up quick.

Once it stalls she won't start back up till engine cools off (about 30 min).

I tried swapping the coil to a new one as soon as it happens but no luck. Timing was also checked and is ok.

Here are the results of each cylinder done wet & dry.   Also, 1 & 8 have a little oil on the spark plugs.

Cydr  dry     wet
1       125     140
2       117     135
3       117     135
4       105     117
5       120     140
6       125     148
7       120     133
8       122     140

302 engine not rebuilt. Still original intake manifold with original Autolite 2100 carb which I rebuilt.

Any ideas are very much appreciated.

 

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That's a tough one to diagnose on the internet. No starts are usually fuel or spark problems (the holy trinity is fuel, spark and compression, and since the car runs, compression is probably ok). My first thought would be fuel. Are the floats and choke working properly? Carburetor bowl boiling dry when hot? Good spark plugs and wires?

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Are the stock points ignition still being used?  Have you checked for spark at a spark plug during the time it will not start?  That's the very first thing to do to narrow the problem down to spark or fuel.  If there is spark at the spark plugs and the motor will not start I guess it could be vapor lock like unilec is thinking and a phenolic spacer might help.  That is not common for Autolite carbs.  How hot is the motor running?  Fuel line between the pump and carb getting too hot can also cause vapor lock.  Are the carb idle air-fuel mixture screws adjusted correctly?  

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I have an MSD ignition installed.

The fuel line from pump to carb is covered and sealed with a rubber hose so it can't be that.

Once, when it stalled, I opened the carb to see if the fuel bowl was dry or boiling and it wasn't.....so it's not vapor lock.

the choke works properly.

the engine isn't getting ridiculously hot when it stalls....as a matter of fact the antifreeze doenst even boil into the overflow bowl.

before installing a phenolic spacer (which will give me clearance issues with the hood) I'd like to understand if the stalling is due to a carb or spark issue.

I guess I'll have to try with new spark plugs and adjusting the idle air-fuel screws.

it's been doing this since I bought the car in 2001. 

yes, I live in Italy :)

 

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What type of MSD ignition do you have?  First thing to determine is if there is spark when it will not start.  If you find no spark at the plugs then also check for spark coming out of the coil.  A spark tester makes it a little easier.  I use one like this for high output electronic ignitions.  But there are many others. https://www.tooltopia.com/otc-tools-6589.aspx?utm_source=bing&utm_medium=cpc&utm_campaign=PLA&scid=scbplpOTC6589&sc_intid=OTC6589 

If there is no spark anywhere and you have one of MSD's CD type ignition systems (not the ready to run distributor)  here is a simple test to determine if it's the magnetic pickup in the distributor or the ignition box. https://www.holley.com/support/troubleshooting_techniques/

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7 hours ago, signorc said:

I have an MSD ignition installed.

The fuel line from pump to carb is covered and sealed with a rubber hose so it can't be that.

Once, when it stalled, I opened the carb to see if the fuel bowl was dry or boiling and it wasn't.....so it's not vapor lock.

the choke works properly.

the engine isn't getting ridiculously hot when it stalls....as a matter of fact the antifreeze doenst even boil into the overflow bowl.

before installing a phenolic spacer (which will give me clearance issues with the hood) I'd like to understand if the stalling is due to a carb or spark issue.

I guess I'll have to try with new spark plugs and adjusting the idle air-fuel screws.

it's been doing this since I bought the car in 2001. 

yes, I live in Italy :)

 

you didn't answer my first 2 questions so i can't help you.

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Sorry Barnett468,

I answered so many questions that I forgot to answer your first 2 :(

The carb is a rebuilt original Autolite 2100 2bbl.

It stalls in 3 scenarios:

1.  idling for about 45 min

2. After having pushed the engine up hills (for about 10 min) and temp increases

3.  As soon as I get off the highway after having driven it at high speeds for many hours

I rarely drive it in cold weather, so all the above scenarios hold true for spring, summer & fall temps

Thanks for any input :)

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So here's the update :)

Adjusted the 2 idle screws to 3 turns out....and  now idles beautifully.

Checked that the MSD 6AL works properly and it does.

Got the engine to stall by itself after 45 min of idling.  Checked for a spark.  None to be found till I changed the coil to a new one and it starts right up.

So I'm assuming the issue is the coil.  Why would it stop functioning properly?

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Also, I looked at all 8 spark plugs and they were all white..... so she's running a bit lean.  I turned the idle screws out 3 full turns.

Would having the engine running lean have an issue with the coil?

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