[70FuselagePilot]

Greetings fellow mopar lovers!

I own a Chrysler Newport with a big block motor (1970). The motor has a 650 Edelbrock AVS carb (w/electric choke), sitting on a spacer and then Edelbrock performer aluminum intake. The spacer is to prevent vapor lock (used to be a huge problem).

The car runs great, however it won't start after cooling for several hours and/or sitting overnight. It has no problems starting when its really, really hot outside or if it has been previously running, but let it sit for several hours overnight and it is not very hot outside in the morning, it is a BEAR to start. I usually have to keep cranking and cranking and cranking it while pumping the accelerator pedal (I know it is flooding the carb). but this is the only way to get it to start. It will finally barely catch after what seems like hours of cranking it. I've also noticed what appears to be small drops of gas on the driveway underneath the car while doing this....strange I cannot find any fuel line leaks.

After all that, when running - its fine. Anyone had this problem before?

 

[Bob Lincoln]

Is the choke closing enough? It should fall 'shut', basically open about 1/8" while the fast idle screw sits on its cam to hold the throttle open a tiny bit.

 

[1968NewportCustom]

When mine did that it was actually spark issue and timing. =?) Yay for pertronix!

 

[70FuselagePilot]

Is the choke closing enough? It should fall 'shut', basically open about 1/8" while the fast idle screw sits on its cam to hold the throttle open a tiny bit.

While I was cranking her yesterday I could see that the choke plate was closed (or to approx 1/8"), which I guess means the choke is working properly, but it was still hard to get started.

When mine did that it was actually spark issue and timing. =?) Yay for pertronix!

That could be an issue, but I don't think so in this case. I converted the motor over to mp electronic ignition from original "points" setup about 6 mons ago. Just recently went on a 4hr trip one way to car show and ignition timing/spark seemed to be dead on.

 

[Bob Lincoln]

With the (engine off) air cleaner lid off and holding the choke open, pull the throttle from closed to wide open, and observe whether a steady jet of fuel is shot out by the accelerator pump.

 

[70FuselagePilot]

With the (engine off) air cleaner lid off and holding the choke open, pull the throttle from closed to wide open, and observe whether a steady jet of fuel is shot out by the accelerator pump.

Yes, I've observed that as well, each time It is full and steady stream of gas.

 

[Bob Lincoln]

OK, so it doesn't appear to be a mixture problem per se. However, if there is a vacuum leak, such as the carb or space having a faulty gasket, or not being torqued enough, you could get an air leak when cold that seals up on expansion when hot. Another possibility is a split vacuum hose, such as PCV or brake booster.

 

[70FuselagePilot]

OK, so it doesn't appear to be a mixture problem per se. However, if there is a vacuum leak, such as the carb or space having a faulty gasket, or not being torqued enough, you could get an air leak when cold that seals up on expansion when hot. Another possibility is a split vacuum hose, such as PCV or brake booster.

Yeah, I read you....and its frustration as all Heck. I tried spraying "gumout" all up under the carb where it bolts to the spacer/intake manifold, and then where the intake bolts to the heads.. while the car was running... and I could not notice any bubbles, nor was there any change in the idle speed.
Would ambient temp make any difference to a vacuum leak?? When she's hot she turns over easy.......

 

[68RT]

When cold and not cranking, the choke should be FULLY closed. if you have 1/8" open before cranking, you will not be actually choking very much. I am actually a bit puzzled though by the statement that you get a full stream when you pump the throttle. That should give you enough fuel to start the engine when cold. Procedure for cold should be 1) Step on the throttle about 1/2 way to allow the choke to close and give you a partial stroke of the accellerator pump. Also, that should set the high speed when cold cam to the correct postition. 2) turn the key and it should fire up. I would be checking each item stated to make sure that they are working in sequence.

 

[70FuselagePilot]

When cold and not cranking, the choke should be FULLY closed. if you have 1/8" open before cranking, you will not be actually choking very much. I am actually a bit puzzled though by the statement that you get a full stream when you pump the throttle. That should give you enough fuel to start the engine when cold. Procedure for cold should be 1) Step on the throttle about 1/2 way to allow the choke to close and give you a partial stroke of the accellerator pump. Also, that should set the high speed when cold cam to the correct postition. 2) turn the key and it should fire up. I would be checking each item stated to make sure that they are working in sequence.

Ok, I'll check again, but pretty sure there was a very slight opening. If so then maybe the problem is a vacuum leak then?. If it is closing completely then have to rule that out.
Yes, for sure I get a full stream of fuel when I pump the throttle. I've seen it, plus after a few times of doing this the distinct smell of fuel can be smelled, so I know that part is operating.

 

[70FuselagePilot]

well, got under her hood the other day to try and find out what is going on. It looks as though the choke plate is not closing shut upon start up. I confirmed with a test light that it is getting 12v pwr (its an electric choke). So it should close completely shut when the ignition key is turned (rather than stepping on the throttle half way)?

 

[Bob Lincoln]

No, the electric choke is simply a heater coil mounted inside the bimetallic spring that causes the choke to open faster, for lower emissions. The choke should snap shut when you step on the throttle, the bimetallic spring in the choke causes it to snap shut. Then the vacuum choke diaphragm (vacuum 'pulloff') opens the choke to the proper distance as soon as the engine starts (usually about 1/8"), and holds it open until the choke spring warms enough to pull it wide open as the engine warms up.

 

[70FuselagePilot]

Gotcha. This morning I went out before starting the car and pumped the accelerator pedal just a small bit. This in turn caused the choke "butterfly" to close completely shut. I then adjusted it a bit by rotating the choke spring housing so that there was about 1/8th of an inch cracked open. I got back in...I barely turned the key in the ignition and the car fired right up instantly....after sitting all night!! Now it IS rather warm outside today, so I don't know for absolutely sure if this solved the problem, but she did turn over much faster...with just flick of the key. Tomorrow morning I'll get out there real early before the heat and humidity comes up and try to start her absolutely COLD. If she performs like she did this morning (hoping!) than I guess the issue is solved. Trying to trouble shoot this and get it squared away because when the fall season comes and it gets chilly out again I do not want to be in the driveway cranking and cranking and cranking trying to get started up.

 

[70FuselagePilot]

Update.
Unfortunately my nagging problem still not solved. Just went out to try and start the car. Pumped the accelerator pedal a just a wee bit to reset the choke to close the choke.....and then turned the key. No dice, just kept cranking and cranking and cranking. I tried pumping the pedal a bit thinking perhaps a few quick spurts of fuel into the carb would do the trick....no go, still cranking but no catch. End results: the scent of fresh gasoline wafting about in the air. I can almost guarantee later today when its warmer outside she start right up with just a flick of a turn with the key.

This has got to be the most frustrating but simple problem ever, probably a simple cure to this I'm just overlooking.
1. Get in car:
2. slightly depress pedal-resets choke plate to closed position (I was driving around yesterday, choke is in open position)
3. turn ign key-starter spins motor:
4. rotation begins vacuum thru carb
5. fuel mixes with air
6. getting a nice spark
7. ignition SHOULD occur.

I've confirmed all this is happening, am I missing something?

 

[Bob Lincoln]

So, none of us has asked, when was the last tuneup done (mileage and date)? What was replaced in the tuneup? 1970 originally had breaker point ignition. Has this been converted?

Marginal parts become evident on cold starts.

 

[70FuselagePilot]

I don't believe this stems from bad/old parts or tuning....but I'll pull her skirt up for all to see: 383 4bbl stock manifolds, dumps into flowmaster cans.

The top end has been refreshed, heads came off got 3 angle valve job, threw in a bunch of new MP parts (valves, springs, push rods, retainers, lifters..etc), along with MP 383/440 magnum spec cam, Cloyes double roller timing chain, Bosche water pump, new MP electronic ignition w/ distributor (orange box). Edelbrock 600cfm AVS carb on Edelbrock aluminum intake, new AC/Delco alternator, Hayes fan clutch. Most of this was done about 6-7 months ago at a speedshop in Delaware. She runs like a top going down the road, good idle, oil pressure and plenty of torque/pwr.

What really perplexes me is again, this symptom ONLY occurs when it is cooler outside....as soon as its hotter outside she flips right over.

 

[Bob Lincoln]

So...again...how old/how many miles on the distributor cap, plug wires, ignition rotor and plugs?

If they're recent, then it's likely a mixture problem. As 68RT said, the choke should be FULLY closed when you step on the gas, and will pull open very slightly AFTER it starts. If it's not fully closed, it probably won't start when closed. You said you adjusted it to open it 1/8" after it had snapped shut. That may be causing the no-start now.

There is a fast idle screw that sits on one of several steps on the 'cam plate' on the side of the carb. The hot idle screw is adjacent to it. To adjust these properly, you step on the gas about 1/3 of the way down, and the choke should snap shut, and when you release the gas pedal, the fast idle screw will sit on one of the steps. It should be adjusted in or out to sit on the specified step (as called out in carburetor instructions or shop manual). When you start it, you then do a fine adjustment to the specified fast idle speed, which may be on the order of 1200-1500 RPM or so. When the choke opens as it warms, the cam plate drops out of the way and the hot idle screw sitting against its stop is what controls the hot idle, and it has its own spec.

Also, the vacuum choke pulloff, or vacuum diaphragm, has linkage to the choke plate, and there is a specification for how far it pulls the choke open immediately after cold start. Too little, or diaphragm failed and won't actuate, and it will run very rich, stall, puff black smoke out the tailpipe. Too much, it will stall immediately. It's adjusted by holding vacuum on it with engine off and cold, and pinching or spreading the linkage to get the right measurement of the choke opening.

 

[70FuselagePilot]

Dizzy cap, ignition rotor and plugs all within 6-7 months old, fairly new....all of that came with the new MP electronic ignition upgrade. To date I guess there is under 35K miles on those parts. The carb is a fresh rebuild, less than 500mi on that. The sprk plug wires are a few days old as I noticed after a recent trip a couple got burned on the exhaust manifold so I installed new accel 8mm core wires.

I went outside and she just kicked right over with barely turning the key. A few hours ago all I could do was get her to crank. I haven't noticed any puffs of black smoke at all nor does it stall out. I had the carb recently rebuilt by Edelbrock and I've put about or less than 500 miles on it since than. I'm no carb expert, but I have noticed the choke plate slowly open after starting the car to a total of about 90 degrees perpendicular to horizontal.

 

[70FuselagePilot]

just a little more background info: I'm getting around 16hg of engine vacuum at about 850-900rpms. I know this is probably extraneous info but just trying to diagnose what's going on here. The carb seems to be operating properly (readjusted choke to close completely when starting cold). I'll go out later when she's stone cold and check the settings you mentioned, see what happens then. Thanks!

 

[68RT]

What is the carb number so we can get the choke settings for it so you can verify that they are all correct. For the choke only, you have the choke closing sping setting, choke Unloader adjustment, Fast idle linkage (includes fast idle cam), and choke vacuum break. They must all work together or you do have trouble. Everyone tries the closing spring, but all settings must be correct for good cold starting.