Erratic problem

[Reds]

I apologize for dropping this thread and not reporting back as to whether or not I have fixed it. Just after my last post (7/14/10) I started a long hard battle with cancer. After chemo, cranial base surgery, and brain surgery I am pretty much recovered. No sign of live tumor at this point. I was able to start working again and playing with my '41 this July. I still have the same problem with it. It has run fine for the last couple weeks. But today it was bucking and snorting before I got out my driveway. Stopped and pulled the top off the carb - plenty of clean gas. Pulled the line off the carb and the fuel pump is pumping nicely when I turn it over. Started it and watched inside the carb and no fuel dripping in there. Pulled the plugs and they are all dark but not to the point where they are fouled. I am going to pull the ignition switch this weekend and check the connections. Also going to put a dial indicator in #1 cylinder, find TDC, and get a timing mark and pointer on the front pulley. Then I can check the timing with a light. Thanks for the previous answers and help with my problem. I will post more as I get to work on it.

[flatjack9]

Sorry, but you can't see the piston through the plug hole. Need to use something flexible, like a tywrap maybe to fish in the chamber to get over the piston.

[Don]

set a volt meter in seat beside you and hook to hot wir from ign sw,to resister ,see if you lose voltage when it misses or bucks, use a analog meter so you can see it move.

[dono50]

I would check the gas cap to make sure it is vented correctly. You mentioned it seemed like it was running out of gas.

[40cpe]

I'm glad you are doing well after all those treatments and surgery. These old cars loose their importance when health or family are at risk.

[G.M.]

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Red it sounds like sticky valves. There is a white residue that forms on the valve stems. Drop down to 10 or 12 MPH in high gear and step on the gas, as it picks up in speed you get the slight bucking. With the engine running drizzle MMO down both sides of the carb for a few minutes keeping it running then put the rest of the quart in the gas tank. Don't be skimpy on the MMO. I have seen this at least a 100 times and it works every time. When it pulls out smoothly in high gear the problem is gone. G.M.

[rotorwrench]

Intermittent problems are usually related to intermittent discrepancies. Crap rolling around in the fuel tank or water for that matter will either occasionally block the fuel pick up tube in the tank or it will suck up a slug of dirty water. The sticky valve discrepancy is real. They will work fine for a while then start sticking just enough to slow the valve opening & closing which plays hell with the valve timing and can give you intermittent missing or after fire in the exhaust. Ignition intermittent problems can be due to leaky condensers or worn out spark plugs. An old worn distributor shaft can give intermittent problems with the rotor contact and breaker dwell. Carburetors and fuel pumps rarely have intermittent problems. Internal blockage, leakage, or bad accelerator pumps generally give trouble all the time.

[Tinker]

Red glad you are doing well with your health!

Originally Posted by 36 flathead

did you try swapping out your condenser. I had the same problem on my 36 and that fixed it.

I had the same problem with my 38pu. Hesitated/bucked under load only. Idled great. But once you take it for a run it would run poorly.

Switch out the condenser ($10), cleaned the points, and rotor contacts. Now it runs like it should.

Good luck!

[Mart]

Jeez, sorry to hear you've had such a rough time. Glad you have made a good recovery though.
Mart.

[OldDad]

Anybody up there near Scranton that could help Reds drop his tank and flush it out so that that problem could be taken out of the loop? That's easy for me to suggest, since I'm 3000 miles away, but if there's something in the tank intermittently blocking the outlet, it won't go away by itself. Otherwise, I'd vote for a bad (new) condenser, or bad ignition switch, or bad wiring from the ignition switch to the coil. Might try bypassing the ignition switch by running a wire directly from the battery to the coil. Nothing worse than an intermittent problem to diagnose! And I don't discount GM's valve theory -- just have never experienced it myself.

Good luck to you Reds, and I admire your perseverance in the face of adversity. Been dealing with your health challenges in my family over the last few years, and it takes a lot of personal fortitude to pick yourself up and get on with your life in spite of it all.

[OldDad]

Just dawned on me that you folks over there on the other side probably have a few other things to think about right now than Reds pickup. Hope you can all push Irene off into the deep end!

[kiwi88]

Hi Red. Just came across your thread while trying to sort a fuel problem I have. Thought I'd check in and see how you and car are doing. Sincerely hope your both sorted now.

[Reds]

KIWI, I just saw your post. My problem has still been coming and going. But I have narrowed down the cause, but not the fix. I was thinking that I had a fuel or electrical problem. But earlier this month it started running rough when idling too. The original problem was only when it was not idling. I hooked up a vacuum guage to the windshield wiper port on the carb base. The vacuum was at 12 and when I revved it up the vacuum dived down to about 2 and then started bouncing all over. I thought I would try my other vacuum guage for the hell of it. The truck was running and when I pulled the first vac guage off of the hose the engine started idling nice. So I have a vacuum problem but a strange one. When I create a huge vacuum leak by opening up the vacuum line to the outside air it ran nice, idle or revved up. Hook the vac line back up and it started running fine again. I have not had time to play with it this week, but will try to fiddle with it some more this weekend. I am going to try running a hose from vac. port at base of carb into the cab. I will start the truck and drive it with my finger over the hose. If it starts missing I will pull my finger off and see what happens. Maybe I will have my son work the finger in the hose thing while I drive. This is driving me nuts. But at least I know that I have a vacuum problem not a fuel problem or electrical problem. Thanks for asking about it. I just bought some MMO and Risoline - I'm going to drizzle the MMO down the carb while it's running.

[Mart]

It must be running too rich if creating an air leak makes it run better.

Maybe?????

Mart.

[41ford1]

I had a problem that it similar to what you describe. The truck is is also a 41 and converted to 12V. It would start and run fine for a while. Then run like crap and quit. What I found was a bad wire and loose connection at the input side of the ballast resistor. This is with a Mallory breakerless ignition and a can type coil that needs the resistor. There were actually two problems going on at the same time. The bad connection and a dirty tank. It kept me hunting for a while.

[sonny]

I agree with gearhead. I had the same problem and found the wire inside the distributor was grounding out.

[flatjack9]

I don't believe there are any wires inside of the 1941 distributor. OOPs, just reread your original post and see you have a Mallory distributor.

[36Bill]

My 36 does about the same things and I have tried most of the fixes listed here. I hope there is an answer.

Bill

[flatjack9]

I agree with Mart. If it runs better with an air leak, you are obviously too rich. Possibly a bad power valve? Float set too high? At idle can you look down the throttle barrels and see fuel dribbling from the boosters?

[gearhead1952]

Flatjack beat me to it. Maybe a leaking power valve.