Hello all. I'm new to the forum and also to mopar car products. I have a 71 plymouth fury III with the 360 in it.

I'm having issues with the car running.

Ok, the car runs like a champ when cold. As soon as the engine temp gets up to normal operating temps, it starts to act like it's flooding out. Bogs downs, hard time idling at times, skipping, raw gas smell coming out the exhaust.

Things I've done to try and correct the problem.
1. Cleaned the carb. Edelbrock 1405.
2. Changed the carb to a holley 650 vac secondaries. Same problem!
3. Replaced the alternator and voltage regulator. Both were bad.
4. Checked and regapped the plugs.
5. Plug wires are new. Cap looks good an clean inside. No scoring on the contacts.

The car does have a aftermarket electronic ignition. And I'm stumped on what else to try.
Any help, ideas would be greatly appreciated!!

Thanks, Robert

 

Sounds like vapor lock. Or over heating the fuel in the fuel lines prior to the carburetor.

Start with running a plastic spacer between carb and intake and then rerouting the fuel line AWAY from all source of engine heat.

Search Vapor Lock on here. Many posts about it.

 

Thanks PK1. I've done all that too. The motor is stock except a mild cam. One friend of mine told me to try changing the coil? Could of lost it's oil for cooling. If that doesn't work, I'm stumped again.

 

coil is sealed and unless cracked should be ok if primary and secondary voltage are in spec. You can test those with ohm meter. Directions are on here. Search for it.

If its good move it away from heat.

I would re tune carb when the motor is good and hot.

When you say: runs good when cold... Do you means, runs good when choked? Or just good with low outside temps and engine not fully warmed?

What is vacuum cold start? And what is vacuum hot?

 

Ok. I'll look on how to check the coil.

Runs good when the engine is cold. When it gets to operating temps is when my symptoms occur. I've tried tuning it hot. No difference.

Not sure on the vacuum. Don't have a gauge.

 

Crazie -

Always a good idea to check the vac, but just for giggles, check the output pressure on your fuel pump. (Vac/pressure gauges are cheap.)

Assume when you pulled the plugs, they all had the correct color and were dry?

Couple of things.

Not vapor lock. That "usually" happens on a hot engine when the the engine has been shut down, not while running. The fuel pump should supply enough pressure to keep the fuel liquid. Assuming your temp gauge isn't showing hot, right?

Doubt it's the carb, since you said you tried two different models and got the same results.

If there were an ignition problem, the spark plug burn color should reflex that. Next time it's running poorly, stop the car (let it cool) and start pulling the plugs. See if any/all are wet and note color.

Archer

 

Archie, I would NOT rule out vapor lock, although it might not be the "root cause."

Fuel pump might be weak, the fuel system might have gum or dirt, or one of the suction connector hoses might be collapsing -- and they certainly would tend to collapse more readily when hot.

The cause of this problem is probably relatively simple, finding it might not be

I agree that a coil going bad can certainly act this way

I'd be tempted to rig --even temporarily-- a fuel pressure gauge. You need to take steps to do this safely so far as preventing fire, etc. You can use a "store bought" vacuum/ pressure gauge.

To check the ignition, warm up the engine "nice and hot" until the problem definitely appears. Then check the spark, by cranking the engine USING THE KEY and not by jumping the start relay

Use a grounded probe, like a screwdriver and clip lead, hold this near the top of the coil tower with the coil wire removed. Have a partner crank the engine and look for a nice hot blue spark.

Alternatively you can buy "test" spark gaps, or make one from a plug. Open the gap up to 1/4", rig a clamp so you can see it through the hood gap, and use a SOLID core wire. If the wire is "in the air" --not close to metal, you can even use low voltage wire for this

Bear in mind that the Mopar ECU has a capacitor (condenser) built in JUST LIKE the old points distributors used, and these can go bad with heat as well.

 

440 -

Here's my way of looking at it. Generally vapor lock happens between the pump and the carb, that's where the highest fuel pressure should be, hard to get a collapsed hose under those conditions. It's also should be the highest temperature, so there might be a trade off.

Vapor lock between the tank and the pump, while possible, I'd guess is more rare. Add to this the fact that he's claiming a fuel smell out the exhaust also argues against VL or a low/no fuel condition . Certainly not impossible, but a little lower on the list.

Agree that a fuel pressure /vac gauge is a good idea.

Regarding the ecu, it's been my experience that a bod one (and I've had that) typically shows it's face on start up or high rpm. Certainly possible, but just doesn't fit.

Still curious about what the plugs look like.

Either way, it's always going to be in the last place he looks.

Archer