62 Hawk - Idles fine but misfiring when accelerated

[Pas62GTHawk]

UPDATE: 6/22/2010

Wolfie/Steve called it right! Bad diaphram. I pulled the hose off carb and sucked on the hose and found NO resistance. I cut the hose 1", plugged it and pushed it on the carb tube to block air leak off the carb..

A new Echlin vacuum advance part #VC680 (Google) for my Delco distributor costs $18 at PepBoys (5 day special order) and $5 at Allied Parts (in stock)

I was told car will run but with decrease in gas mileage until I can install new part.


Thanks everyone who posted!
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62 GT Hawk, 289 ran fine but now idles ok but engine doesn't rev properly. Lightly misfires and stutters, power loss.

I'm experiencing misfiring... but without the one backfire I had that may have been the reason for the blown the wire out of the condenser a few months ago.

What do you supposed caused that!? Related to my problem now?

The car fuel pump was removed and blocked. It now has Heavy duty aftermarket Carter inline fuel pump and new filters. Fuel is visible in clear filter 3 ft from carb.

The distributor was changed out 5 years ago by trusted Studebaker mechanic. Vacuum seems strong but not sure if the advance mechanism is responding, don't know how to check.

Discovered the condenser was the problem a couple months ago. The wire was blown out of the condenser. What do you supposed caused that!? Related to my problem now?

There is an electrical draw somewhere. Battery drains and is low or near dead after 5 days of sitting. Installed a green shut off on negative post.

I read somewhere to look into rewiring or doing something to the pink and green leads to coil.

I replaced the condenser and new points (gap is match cover or .17 is my guess) and things seemed to work. Rebuilt the carb due to a worn excelerator pump. I see gas is barely seeping out of the front. Can only tighten screws so much! One screw on side is not able to tighten well.

Removed Autolight plugs (less than 5000 miles on them but 5 years old) they and the .35 gaps look good. Lightly sanded and cleaned them up. One plug on passenger side #3?? or #5?? had a light tan color on the electrode ceramic.

Replaced the coil using my Avanti coil. No difference in problem.

Should I replace the 5 year old distributor rotor next? The brass has a slight play in it, a wiggle.

The 5 year old distributor cap may need to be replaced too?

Any suggestions out there?

[wolfie]

Pull the hose from the carb end and try to draw air through it. It should raise the idle slightly. If you can draw air through it the diaphram is bad, No change in idle means something is stuck. Steve

[11SecAvanti]

The black wire from the condensor. They will fall out when the condensor is very old and deterioration has set in. Nothing blew it out, it just deterioirated up inside from the material plating and fell apart. But you replaced it anyway.

Nearly impossible to trouble shoot something over the internet. Best to set your points with a feeler gauge or better a dwell meter. You need to find out where the timing is at. And you need to confirm that engine is wired correctly. Check and recheck the firing order from the distributor to each plug. Should be 1/8/5/4/3/6/7/2 I believe. It is marked on the intake manifold runner in the front. I forget myself sometimes.

Those glass filters that are clear are rather small and IMO limit fuel flow. And may be related if the power is down. Most likely though something is wrong in either the fuel carb delivery of the fuel to the engine or an electrical issue with either the points, timing, plugs, plug wires, distriubtor cap, rotor, or coil. You will have to divide and conqueor. A good running stude motor requires at a minimum good compression, qualilty electrical system, and quality fuel delivery from a carb. And watch out for a vacumn leak somewhere also. Hope this helps you out. Good luck.

[maxpower1954]

From what you described, it sounds like a typical Prestolite distributor worn-out advance weights problem...if it still has a Presto (OEM equipment). Common problem at around the 60,000 mile mark or so. Pull the cap and check the advance weights pivot points for wear/play. Russ Farris

[Stu Duglee]

Instead of messing around with the old Auto-lite in my 63 GT, I installed a Mallory/Uni-lite from Mr. T-bolt.I also installed a in-line ballast resistor , new coil & new spark plug wires.I'm using NGK V- Force plugs gapped at .045,yeah that's right.I do a lot of Hwy. driving & I'm getting 20+ mpg at high speed.The thing is get out & drive it,if mine sits a couple days I gotta give it a rip other wise it ain't happy. Drive it like you stole it at least once a month.

[Bud]

Several things can cause misfiring under load, such as worn or fouled spark plugs, defective plug wires, weak coil or low primary voltage to the coil, defective or out of adjustment points, bad condenser, a carbon track in the cap causing crossfiring, lean fuel mixture or tired Prestolite distributor. My 62 Hawk developed a misfire last year and I found that the carbon rod in the cap had broken and fell out. If there is someone in the area that has an engine analyzer, I would recommend having a diagnosis done as it will probably be cheaper than using the shotgun method of parts replacement. The firing order is 1-8-4-3-6-5-7-2 with #1 on the left front of the engine. Bud

[StudeRich]

We just had a 63 Lark doing the same thing. Close examination revealed the accelerator pump was fine with the engine shut off. When it is running, the stream was weak. (internal problem) Everything checked out, so a good used carb is what fixed the problem.

MIKE

[Pas62GTHawk]

Steve, You called it correctly: Bad diaphram causing big air leak of the carb. Plugged the hose on tube. Will buy a new diaphram an install it.

Thanks,

Curt