1973 cs 3.0 breaking down

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inmantua1

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At starts fine then after I drive for a while it car turns off and wont start again.
We have changed all gas lines filter and pump. Points condenser spark plugs, wires rotor cap,
The. Switched to electronic ignition. Replaced resistor. Still runs great then suddenly stops running. Any ideas? What's left?
 
A short in the wire to the tach will do that, especially if a wire is weak or frayed. I had this same problem in my 2002, I had the wrong ballast resistor and I think that fixed it. At least my fingers are crossed.
 
Maybe you should replace your engine........

Why would you start replacing parts when you have no idea what is wrong?


Answer this- when your car doesn't run- is there no spark or is there no fuel??
 
Fuel and spark

Fuel pumps through to the carbs and we get spark to the tips of the plugs.
 
If you really have fuel and spark and the car won't run- check your rotor.
 
Sounds like a loose connection or bad wire (if it happens randomly or suddenly). Does the engine need to cool down before it will work again?

Have you checked the wires that run to the idle fuel shut off on the driver's side of the zenith carbs? IIRC, if those are disconnected then the car will not run (or start). With the ignition switch on there should be 12v at these wires. These wires come to a connector behind the brake booster.
 
If the car runs fine but suddenly dies and won't start it has to be that spark or fuel is going south.

Fuel- pumps sometimes die slowly. A car can run at idle but once on the road there's not enough volume to keep up. Once that happens floats can stick closed. A small guage in the outlet of the pump should indicate 2.5 lbs. Not 2. Trash, rust, etc. that add to restrictions won't help.

Spark- the battery , switch ( likes to come apart), all the way to the coil should be checked for voltage. Since you changed the condensor, go back and check the ceramic resistor on the fender well and double check the coil connections since switching them can have bad consequences.

Ceramic resistors can go bad, crack underneath, and generally get extremly hot when going bad. So heat is not good.
 
I have a suggestion a little out in left field, but it happened to my 2002 and it's a known issue in some circles.

You have to vent your fuel tank so that when fuel is drawn out, air can replace it. Normally this is done through the gas cap (some caps do not allow it, by design) or through the charcoal canister and back through the evaporative control system. If the charcoal can was removed (as by now most are) and the line plugged, the tank may not be vented. Use some gas = increasing vacuum in the tank, and after a bit the pump can no longer draw fuel from the tank.

Long shot, but if you've been there, done that, it all makes sense. The engine will stall quickest when the tank is most nearly full.
 
Honolulu said:
You have to vent your fuel tank so that when fuel is drawn out, air can replace it. Normally this is done through the gas cap (some caps do not allow it, by design) or through the charcoal canister and back through the evaporative control system. If the charcoal can was removed (as by now most are) and the line plugged, the tank may not be vented. Use some gas = increasing vacuum in the tank, and after a bit the pump can no longer draw fuel from the tank.
Click to expand...

I like Honolulu's theory. There's an easy way to test it: just drive without the gas cap (don't do a lot of hard cornering, especially if the tank is full!). If the car doesn't die, then vacuum build-up in the tank seems probable.

Another question: Does the engine always run for the same duration before quitting? Or is the pattern more random? The former would point toward something like a clogged tank vent. The latter to something like a broken wire that occasionally shorts out.

When you write: "car turns off and wont start again", how long do you have to wait before it will start again?
 
responses starting with the first

HB Chris - How do you check for short in wire?
61 porsche - I am currently having trouble with starter. I have a new one ready to install what would ignition switch have to do with it stopping running? ONce it stops it sounds like it wants to start but has no gas.
sfdon- will try the rotor. the mechanic says doesnt think it is the problem but will try anyways.
61 Porsche - Fuel pump is new and so is ceramic resistor.
Honolulu - I will try driving without gas cap and see if that works
Jmackro - It will not start again till next morning
 
Switch serves several functions, ACC, start, and run. Pull the metal cover off the bottom of the steering column / wheel, find the switch, while turning the key see if the part with all the wires is loose and moves. if so, push it with one hand back while trying the key.

You haven't said what happens when it dies. For instance, do the idiot/ warning lights on the dash stay on, glow red, etc? If the lights stay on then at least there's power to the switch and past it. Will it crank?

To check spark, first check for power at the ceramic resistor with the key on for a moment. Then the coil + side.

Carbs actually have wiring to fuel shutoff solenoids and chokes. Start at the front and check for loose, etc. They're easy to knock off.
 
Strange....In case you haven't thought of these guesses- I assume you have gas and spark in restart attempt. Perhaps spark is not hot enough? You say you have starter problems. Are you sure your battery is in good shape? If OK, then, I would remove ignition switch supplied voltage connection and jumper coil to battery (with fuse in line if you are so inclined). If it starts, you at least know the problem's in the ignition switched circuit.

Other thoughts- Something funky happening with high voltage ignition wires when hot? Check out restarting attempt in the dark. Perhaps you can notice stray arcing somewhere.
 
troubleshooting engine

I always use a pretty simple methodology to figure out where to focus for an engine that won't start/run:

FAST:

Fuel- got gas to cylinders? y/n
Air- no blockages, properly metered flow? y/n
Spark- start at plug and work back if needed
Turning- is starter turning (in this case obviously yes)

Rarely do multiple things fail simultaneously; one failure may cause other symptoms or damage, but look for the root cause and then make sure it explains the overall symptoms.

Figure that out, then replace broken/damaged stuff.

My two cents.

Best-
Matt
 
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