383' shuts off' issues, I tried praying, no luck

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crossy

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Did not know definitively where else to post this , so move if needed.

OK so I’m old- I grew up on points & condenser, and one coil for all 8 cylinders. And something called a carburetor. (hey, they still work on lawn mowers!) – Anyway I got this old school mopar Sweptline truck I’m working on with 383, and it’s giving me ulcers. I’ve always been damn good at this sort of resurrection stuff and fairly patient. The truck was sitting for some 30 years. The whole fuel system is cleaned & tank sealed now. The New fuel pump with in-line filter added, NEW points/condenser, cap/rotor, wires coil & plugs. The Carter BBD 2 bbl carb is rebuilt & spotless inside. So the truck keeps just shutting off. It may or may not start right up. It shuts off with a little bit of an accelerated idle then the sucking noise like it’s running out of gas. I actually had the truck running with the whole top of the carb OFF and it’s not starving for fuel when it shuts off (note* Coolest thing I have ever done with a carb}. During the warmer weather it might idle for 15 minutes, but it seems worse since it got colder out or maybe what ever is breaking down is getting worse.? I tried bypassing the resistor, running a hot wire to the positive side of the coil, fiddling with all of Mopars lousy firewall connection and NOTHING seems to make a difference.
 
ADDITIONALLY- The choke does seem to work as needed, I have continually tweaked it, and looking back it does seem to be a bit worse since I rebuilt the carb, but again it got colder out. Although I know what I’m doing rebuilding a carb, it is spotless inside now, there I always worry about cheap generic rebuild kits which this was. (tomco). I really only bought it to get the accelerator pump, which as you can imagine after sitting 30 years was totally dried up on mine. The car bowl was filled to top and float worked and not sunk. I do have some concerns about the ‘different’ design on the carb mounting gasket changing the vacuum draw, but with it sometimes running for 10 minutes or 10 seconds I kinda ruled that out as a problem also. . .
 
Are you sure it's shutting off because of fuel delivery? Or is an electrical component getting hot and killing spark? then not starting right away until the part cools? just asking.....
 
I'm not real intimate with the trucks, but does this one have the heat riser in the passenger exhaust manifold? If so is it working as it should? If it sat is it possible the exhaust is plugged up?
 
Dubob said:
I'm not real intimate with the trucks, but does this one have the heat riser in the passenger exhaust manifold? If so is it working as it should? If it sat is it possible the exhaust is plugged up?
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exhaust is all new from the manifold donuts back. FREE flowing I might add :)
 
no i'm not sure about fuel or ignition , just looking for ideas I may have over looked. Old points ignitions don't havea real hot(blue) cranking spark, and I hope today to get someone to start it and let run while I hold the coil wire off the distributor cap to see if it looses spark, that's the only way I know here by myself how to test that. thanx, Crossy
 
crossy said:
exhaust is all new from the manifold donuts back. FREE flowing I might add :)
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I think he was talking about the "flap" inside the passenger manifold. Anyways, this would cause poor performance, but I have had 2 "flaps" inside the manifolds frozen closed and neither shut the engine off.
 
crossy said:
no i'm not sure about fuel or ignition , just looking for ideas I may have over looked. Old points ignitions don't havea real hot(blue) cranking spark, and I hope today to get someone to start it and let run while I hold the coil wire off the distributor cap to see if it looses spark, that's the only way I know here by myself how to test that. thanx, Crossy
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You can always get another distributor cap and drill a hole in it to check for spark between the rotor and the tower. I'll admit I'm not sure where exactly to drill the hole, but I've read plenty of posts where this is done to check rotor phasing. This would allow you to view the spark as the engine is running without an assistant.
 
A timing light will tell you if the spark quits without taking anything apart or buying extra stuff.
Heck, a tach will tell you the same thing if you know what to watch for, but a timing light is more obvious to tell.

OH!, and check the plug for your distributor and make sure it clean and tight.
I have had intermittent starting and shutting off issues with two different cars because of those damn plugs.
They were getting warm and expanding causing them to loose the connection and shut the engine down.
 
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crossy said:
had the truck running with the whole top of the carb OFF and it’s not starving for fuel when it shuts off (note* Coolest thing I have ever done with a carb}.
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Pretty brave but could have been the hottest thing you've done with one. Good thing it didn't backfire on ya'.

Any cables/wires heating up, battery, alternator, etc?
 
I had two different coils and again absolutely no change- nothing gets hot, wiring is brittle though so I will check that distributor plug. I don't have an extra cap, but I like the drilling a hole idea, but just bought one of those cheap in-line spark view dealys and I saw spark right up til it shut down so aiming towards fuel issue. Don't worry I had my face no where near that open carb till I realized it wasn't going to spew onto the coil. I also check the intake bolts and all were tight. tomorrow is a new day- thanx,
 
Next time it shuts off Don't touch a thing! Measure the voltage at the coil + terminal. You are looking for about 7 volts.
If Zero, move up the line to wherever the voltage reappears and BINGO!
But If the voltage is there, then pop the cap and turn the engine to open the points.Take a small screwdriver and short the points to ground in a stabbing motion so that the short exists for only a split second. You should see a bit of sparking going on, at the tip of the screwdriver. And you may hear the sparking inside the cap as the coil discharges into a wire. You could pull the coil wire out of the cap and near-ground it to see the action.If no action, the ground circuit inside the dizzy, from the point plate to the body may have failed. You can put a jumper wire on your screwdriver and the other end to a good ground and try the sparking thing again. If in now works, go fix that internal jumper. But if still no worky, then you will have to prove the condenser is good, and properly grounded in its holder.Go turn the key off. Disconnect the condenser. Go back and turn the key back on. Try the screwdriver thing again. A spark now means either the condenser is bad, or the circuit came alive at the key-off/key-on cycle. I would replace the condenser, install it properly grounded, secure the ground jumper and put it all back together. Then start the engine, and see if it stays running now.
If it quits again, at least it has nothing to do with the dizzy now.Go back to; Don't touch a thing. Check the coil for voltage at the + terminal, as before, looking for about 7 volts. If it's there, then pull all the wires off the minus terminal, and check the voltage there. Wait! By any chance do you have a tach hooked up there? Well disconnect it! I shoulda thought of that first. Yeah so put it all back together, I bet no more problems.
But if no tach, how much voltage should I be looking for? I got a brainstall. But if zero there, throw the coil away, it's gone open circuit. Ima gonna guess there should be a half a volt or so less on the minus side as on the plus side.
Del? you there? Help me out
You can check the coil out with an ohmmeter. It should have less than 2 ohms, more than 1/2 ohm, through those two terminals and 8000 to 10,000 between the coil minus and the center tower.This is a general number.
 
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I may have found a fuel problem late this evening that I had completely ruled out, I will be away all day tmrw so warmer Thursday may tell me something. thanx, Crossy
 
I was going to add fuel quality,... if it's even fuel. We've had cars on the rollback come in to the dealership dead, tank full of "un-fuel", wasn't water...... but don't burn. One tech
poured some on the floor and tried to light it w/a lighter, NADA,ZIP, not one flicker................
 
all new premium in the tank- I put this truck on the back burner for a while- I ordered a spark checker that I should have had here a long time ago.
 
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