Dart doesn't like nice weather: Dieseling/Hot start problem

[Dodge72]

Of course, when the weather is as sunny as can be and 65 degrees, The Dart gets cranky. Started yesterday when it began to diesel real bad. Worse bout lasted about 5 seconds and actually sounded like a whole diesel engine under the hood! Got under the hood and saw my fuel boiling. Moved the fuel line off the valve cover. I turned down the idle too, as low as it can go. Seemed to help, but it's still giving me a stumble when shut off and sometimes diesel for a second. After diving it all day, I parked it for a. hour before work. Came back, and it cranked forever! Sounded like it was starting, but failed to idle. Finally got it running, but now idle is SUPER rough ( probably turned the idle down too far). Took another car to work.

So here's the thing...

Timing at 5 BTDC.
Only diesels when it's fully warmed up, not when sitting for an hour or more.
Never dieseled in winter.
Only this week switched to 87 octane. Before I was using 89 and no problems.
Going to check my spark plugs.
Have a 180 thermostat.

Heard carbon deposits could affect this. Any way to test for that?
Maybe it's overheating? I don't have a working gauge.
Again, ONLY began yesterday when the weather got warm and my octane level switched. Anything helps, will have more info tomorrow!

 

[Slantsix64]

try putting a thick carb base gasket check ballast resistor do you have points? that happened to me when i had a bad condensor

 

[Dodge72]

My carb gasket is 3/8ths, so it's pretty thick (unless there's a thicker one?). I have Mopar EI, and the ECU has a grounding strap. I thought the ballast just failed on you, no warning. Besides, the hard to start condition really only happened once after an all-day driving in both traffic and cruising. Hopefully it doesn't happen again after I turn the idle back up and it's all cooled down.

EDIT: Oh, I feel like I ought to mention another odd problem I had twice. I have had twice whenever I have the brake pedal fully depressed (I have power brakes), and then shift into reverse, it would stall immediately, like shutting the key off. Restarts immediately, and if I just ease into the brake by not depressing it fully, it backs up without a hitch. Does not do this in any other gear, and doesn't do it all the time. Dunno if this is related (in terms of fuel or spark).

 

[Dodge72]

May have found the problem on the spark plugs. They have some deposits both soot and ash colored on the tip and electrode...not good, but then again it might be the center of my dieseling problem? The two pictures show both sides of the same plug.

 

[mguner]

Carb and cam? Vacuum at idle? Possibly transfer slots exposed causing a rich idle condition. Secondary metering system may be open if vacuum is low again causing too rich idle. PCV valve may need cleaning as well. How many turns out from bottom on idle mixture screws?

 

[Dodge72]

I've got a Carter BBD and a stock cam. My carb mixture screws are 2 3/4 turns out from bottom. When I removed the PCV valve to move my fuel line, there was a drip of oil that came out and some on the bottom. This is a stock valve cover and had the baffle on the bottom to prevent oil from splashing. Vacuum, I'm not sure, I don't have a gauge.

Checked the rest of the spark plugs (Except #5, it's being a bear to come out). Turns out the one pictured (which is #3) is the worse one by far. #1 does have some deposits but they are minimal and black, not ashy. The others do not have any deposits on them, they are just blackened slightly and and wet.

 

[mguner]

May have an intake valve stem seal gone on #3 probably weak on some others. You should be ok on the carb stuff I was wondering about. Never hurts to check float level and make sure the floats aren't taking on fuel. You should be able to run a lot more base timing and then be able to back off idle screw. Just make sure you don't over advance. Lots of info here about adjusting advance curve.

 

[Dodge72]

I was thinking that too, I've been suspecting something with the valve seals because of my oil loss, didn't think about it affecting my spark plugs so quickly. Going to be replacing #3 spark plug, maybe #1 too just to be safe, and to see if there is any improvement.

 

[mguner]

That slant should gain more pep with around 10-12 degrees timing.

 

[Dodge72]

So I replaced #1 and #3 with new NGK plugs (same as my others). Went driving around town, did an errand, came back and shut the car off. Did not diesel....as bad. No actual cylinders firing off like before, it's more of just a very quick, half-second shudder of the engine when it's winding down. I wonder if since I am having some oil leaking into the combustion chamber, would there be carbon deposits that would have to be removed?

 

[RedFish]

Factory timing spec of like 5 btdc was for real Gasoline. You'll need more timing to run todays moonshine/fuel.

 

[mguner]

Factory timing spec of like 5 btdc was for real Gasoline. You'll need more timing to run todays moonshine/fuel.

Plus the timing advance increases RPM so you can close the throttle plate more which is often the main cure for run on.

 

[BlueDream]

I wonder if since I am having some oil leaking into the combustion chamber, would there be carbon deposits that would have to be removed?

Your carb is flooding the motor when it dumps all the fuel out, so you gotta crank and crank and crank before it'll light off again. I also think running stock timing and a lower octane fuel is a bad idea. Bump up the timing to 10-12* advanced as mentioned, and go back to 89 octane as well and see what happens. Octane helps delay the burn and higher octane fuels are less prone to engine run-on. Since it wasn't dieseling on 89 octane, and it is dieseling on 87, this should be a red flag for you.

If you don't have a working gauge, that's an issue. Your engine could be running hot and igniting the fuel that's getting into the cylinders after you shut the car off. This would be less apparent with higher octane fuel, like you were running before. Get a temp gauge, see if it's running too hot.

Carbon buildup shouldn't be a huge concern, IMO. All engines ingest oil to some degree. Some worse than others. Oil ingestion is a much bigger problem on direct injection engines since they don't have gas flowing over the intake valves. They get coked up with carbon pretty quickly and it can wear the valve guides out, which just makes things a lot worse. Your valves are self-cleaning, and as long as there's not a lot of oil getting in your engine, I wouldn't worry about it. Not right now at least.

So... Get a temp gauge, bump up the timing, switch back to higher octane, and stop the fuel from boiling out of the carb. If none of that helps... well... we'll cross that bridge when we get to it.

 

[Inertia]

plus the timing advance increases rpm so you can close the throttle plate more which is often the main cure for run on.

^^^^ bingo ! !

Increase timing, reduce idle speed, adjust idle mixture, check for vacuum leaks or a (air cleaner?) hose off.

 

[Dartswinger70]

My Moper used to act up in summer weather, 90's. It was a vapor lock issue. Funny, the car would shut down, Id get it off the road, the OL would start complaining, I would say,"we have to sit here 10 minutes or so, then it will start up' it would act up once in an hour or so of cruising, I moved the fuel line 3/16 of an inch away from the headers, never happened again.