i have a 1968 dodge camper special with a 383. this is my first vehicle i have ever worked on it was a gift. it sat for 6+ years, I got it running and driving about 8 months ago with a carb rebuild ,new fuel pump, new plugs, tranny rebuild, whole new brake system excluding the line for now. my problem is that it was running fine for the 8 months until the other day as i am driving home from work i notice a little sputter then hesitation when i accelerate and backfire out of the carb and exhaust at seperate times. then i parked it and could not start easily and when it would start it would sputter and bog when i press the accelerator and sometimes die. so today i replaced plugs, plug wires, points and condenser. and got it started again. ran it around the block noticed a little hesitation then when i accelerated more hesitation went away and seemed fine, like normal, and stayed that way until i turned it off and back on later i had the same problem drove it around the block again and same issues as before, now it will no longer start again. I am not a mechanic i am just trying to do the best i can but i am at a loss. please some advice is greatly needed.

 

I would start by changing the fuel filter and any rubber lines in the fuel system,
especially the ones at the tank sending unit.
is it a 383 or 318

 

Could be a lot of things.

Could be electrical drop in th harness to the ignition system

Find the ballast resistor, and with key in "run" but engine off, check the voltage on the resistor. You want the highest reading, one will be near battery and one will be low, ONLY if the points are closed. If both are high, put your meter on the coil NEG terminal (distributor connection) and bump the engine until the reading goes low. Then check the highest side of the ballast and compare that reading to the battery. It should be within a few tenths of a volt.

Coil going bad. Only way to find out is to replace

Bad coil wire. Measure continuity with an ohmeter. Shake it as you do so. Then check the spark by rigging a gap or buying a spark tester. You MUST use the key to crank the engine and NOT by jumpering across the starter relay, so that the resistor bypass circuit will be operative.

(Sounds like the plug wires are pretty new?)

Fuel delivery issues. I'd go over the thing carefully from tank to carb. Replace any rubber connector lines, look for added filters inline. Dual tanks? Suspect the valve. Buy a parts store vacuum gauge, which you can also use to check fuel pressure. Also check the pumping volume into a can. If you download one of the service manuals here on this site, there's a section on checking the pump.

A camshaft going flat can cause this kind of problem, but usually a rythmic backfire from one cylinder.

 

Thank you guys for your responses. I have also noticed that there is no difference in sound or timing mark when i unplug the vacuum advance.

 

It may noy as it is likely ported vacum and the tube will only see vacum with slight throttle opening.

I'm leaning toward restricted fuel delivery from your description of symptoms. With old fuel systems that sit for awhile, debris begins to break loose and plug it up. A quick fix could be compressed air blowing back to the tank (not through the fuel pump) clean line upto carb with new filter. You'll probably still need to open up the carb to check and clean any debris from it.

Sounds like you have gas to start and get going but it drinks it up faster than it gets pumped back into carb when you drive for awhile.

 

Thank you again. its getting better. another thing that i can't wrap my head around is that there is a massive noticeable difference when it is warm. it runs ok while cold and i can put it in gear and drive fine with little hesitation, but when it is warm and i try and drive i get alot of hesitation and it dies when i put it in gear or sit to long in gear without pushing the accelerator. any ideas?

 

I would check points, and compression first. But if it runs worse as it warms up, this indicates a too rich fuel mixture. A cold engine needs a richer mixture than a warm one. Check your choke operation and float levels in carb.

 

I have no idea of your technical abilities, so don't mean this as a "slam."

Do you for certain know how to set breaker points?

1---Mopar single point distributors are some of the worst on the planet ('cept maybe for British MGs) for distributor wear. When they get sloppy both points dwell and timing are affected

2--You must set points before you set the timing. Check the points dwell while running, both slowly acellerating the engine with vacuum on/ off to see if there is a radical change in dwell. Severely worn distributors, and / or improperly set points can "go" completely open or completely closed and cause a miss

3--If in doubt on timing, "go advanced." If "the book" calls for 5, try 10* initial. Always good to check both mechanical and vacuum advance. I ALWAYS use a piston stop first, to confirm or "fix" timing mark accuracy, then measure around the balancer and "degree" the balancer out to at least 55* in order to check timing. If you have a "delay" or "dial up" timing light, use that but with a grain of salt. Some of 'em are not accurate.

4--RESOLVE TIMING and ignition issues before you fuss with the carb.

5--Check ignition supply voltage. To do that, turn the key to run, engine OFF. Make sure the points are CLOSED. To do that, measure from the NEG coil terminal to ground, and if you show battery voltage, the points are open. Bump the engine until that voltage goes LOW

Now switch your meter leads to: One lead on the battery POS post, the other lead on the regulator IGN terminal (The push on terminal). You are measuring harness voltage drop between the battery, l through the harness and switch, and back out to the ignition and regulator. You are hoping here, for a VERY low reading, the lower the better. You want NO MORE than .3V. (Three TENTHS of ONE volt.) If you read more, you have a problem. s

6---Condenser. A "new" condenser does not mean "functionally good." This in fact is true of ALL parts, even moreso today with import parts

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CARB

1---Have you checked the acellerator pump shot? Look down the throats, use a light if necessary, and block the choke open so you can see. Move the throttle, and an INSTANT and STRONG shot of fuel should shoot from the pump nozzles

2--Did you set the idle mixture warm? You want to "peak" the idle mixture for RPM or vacuum reading, then just "touch" them to the lean side.

3--What does the engine do "goosing" it at rest? Is it responsive? Doesn't sound choked?

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Other random thoughts:

Stuck heat riser butterfly. This is the thermostatic valve in one exhaust manifold (usually passenger) which closes when closed to aid it warming the carb. It should move freely, and have a "spring" to it's movement

Collapsed/ other restriction in the exhaust system

Plugged/ dirty air filter. Make a short trial run with it removed

Timing chain / sprockets badly worn and "skipped" a tooth.

Generally poor engine condition. Run a compression and or leakdown test. Valves, rings, etc, or even a leaking head gasket.

Worn or so called "flat" camshaft.