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49 Packard runs, heats up and starts running rough


Guest Brandonkr

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Guest Brandonkr

Hi everyone, Ive posted on here before on my 49 packard, and have gotton alot of help. But ive still got a problem. My mechanic has replaced every part to the distributor, including rebuilding the carbeurator. It's getting gas just fine too. Everything that is on the outside of the motor has been looked over or replaced. Here's the problem, the starts great and even runs great for the first 3-4 minutes, but as soon as the engine warms up it starts running very rough, like it wants to stall. We think it could be something that's wore out in the valve system, but aren't sure. I'm 17 years old and could use anyone's help at this point. Thanks for your time

- Brandon

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Hi everyone, Ive posted on here before on my 49 packard, and have gotton alot of help. But ive still got a problem. My mechanic has replaced every part to the distributor, including rebuilding the carbeurator. It's getting gas just fine too. Everything that is on the outside of the motor has been looked over or replaced. Here's the problem, the starts great and even runs great for the first 3-4 minutes, but as soon as the engine warms up it starts running very rough, like it wants to stall. We think it could be something that's wore out in the valve system, but aren't sure. I'm 17 years old and could use anyone's help at this point. Thanks for your time

- Brandon

I think your exhaust is stopped up!

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Guest Brandonkr

We took the exhaust off at the manifold and the same thing happens. We're stumped! Thanks for the quick reply though!

-Brandon

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G'day Brandon,

Valve is in the exhaust manifold above where the exhaust pipe bolts on to the manifold flange. It's underneath where the exhaust and intake manifolds are bolted together under the carburettor. Valve should turn freely. It has a spring loaded mechanism, which includes a counterweight, to hold it gently closed when cold. As it warms up it should gradually open until when fully warmed up it's right open to let the exhaust flow freely. If it's stuck use your lubricant/penetrant of choice to free it up by working it gently back and forth. I believe the major Packard parts suppliers should have kits for replacing worn/broken parts. A "quick fix" is wiring the valve so it's always in the open position. Drawback to that is that warming up the engine takes longer.

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Hi Brandon

Have you checked that the (automatic) choke is releasing as it should? There should be a small metal tube from the top of your exhaust manifold, where it slots into a tube passing through the manifold, to a threaded union on the carburettor. This provides heat to move the bi-metallic spring in the choke mechanism. Also, the bi-metallic spring is adjustable to allow you to alter the spring tension acting on the choke flap. To do this you loosen a couple of screws and rotate the spring housing on the carburettor.

Another thought is that the coil and/or condensor could be failing as they warm up (which is typical). Are you confident that both of these parts are good? If not, can you exchange them with known good units? Condensors are cheap, coils less so, but not ruinous and they do not live for ever. (Don`t forget to get the correct voltage coil if changing it).

Hope this helps a little.

Kind regards

Adam..

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Guest Brandonkr

Hi Adam thanks for the response, I just had it running yesterday and noticed something different than what my mechanic had told me, its almost as if the rough running comes in spurts, and as I put the pedal down I can get it to run better for a couple minutes before it starts running rough again a minute or two later. I changed the condensed and coil last year so I think they should be good. The choke I believe my mechanic told me he fixed. One thing I want to say though is that when I cleaned out the gas tank last fall and then put the tank back, as I was screwing the fuel line back on I cracked the nut on the fuel tank, but I thought I got it on tight enough, could the crack be allowing air in the fuel lines and that make it run rough? Thanks for your time.

-Brandon

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Hi Adam thanks for the response, I just had it running yesterday and noticed something different than what my mechanic had told me, its almost as if the rough running comes in spurts, and as I put the pedal down I can get it to run better for a couple minutes before it starts running rough again a minute or two later. I changed the condensed and coil last year so I think they should be good. The choke I believe my mechanic told me he fixed. One thing I want to say though is that when I cleaned out the gas tank last fall and then put the tank back, as I was screwing the fuel line back on I cracked the nut on the fuel tank, but I thought I got it on tight enough, could the crack be allowing air in the fuel lines and that make it run rough? Thanks for your time.

-Brandon

Hi Brandon

Air drawn in through the pipe would not be an issue here (unlike on a diesel), in fact external leakage would be the worry at the tank end. More likely is the float level being incorrect at the carb, or the fuel pump being unable to maintain the float level. Has the carb been rebuilt? Do you know whether the float level is set correctly?

Could it be, from your testing of it, that the engine runs ok when it receives a squirt of fuel from the accelerator pump and then runs weak otherwise? This might also be a sign of blocked jets, or indeed, a manifold air leak.

If you are confident about the ignition system, i would be sceptical of the carburation as I have outlined here. Can you expand upon what has been done so far, and what you can confirm? Then we can go from there.

We need to get the car out on the road soon, so let`s see what can be done.....!!!!!

Adam..

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If you had a dirty tank did you check and clean the screen in the bottom of fuel pump. That could have filled with junk if there is no aftermarket inline filter before it. There were two types of screens used inside the bottom metal bowl -- one is an actual fine mesh screen and the other type is a bunch of thin plates stacked together with tiny slots on the edges. If you did not check, that might be a worthwhile project. Be advised, you will most likely need to buy or make new gaskets f you take the bowl off.

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Actually a cracked nut on the fuel line could be your problem. A suction leak between the tank and the carb could limit the pumps ability to supply enough fuel. On start up the car runs off the fuel in the bowl then begins hesitating from fuel starvation and shuts off. Cranking the engine to restart again fills the bowl and the cycle is repeated. Fix that cracked nut.

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Guest Brandonkr

Hi restorer 32, I ran the car yesterday and I think I've made a diagnosis. It runs good until I give it gas and I assume use up all of the fuel in the bowl, then It starts running rough until the bowl fills up again at idle. I'm pretty sure I have a bad fuel pump(considering the original one is still in it). I think I'm going to put a 6v fuel pump on and see what happens. What do you think? Thanks

-Brandon

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Actually a cracked nut on the fuel line could be your problem. A suction leak between the tank and the carb could limit the pumps ability to supply enough fuel. On start up the car runs off the fuel in the bowl then begins hesitating from fuel starvation and shuts off. Cranking the engine to restart again fills the bowl and the cycle is repeated. Fix that cracked nut.

Remove fuel line and submerge in a can of fuel, manually fill fuel bowl of carburetor, crank up engine and check volume of flow and see if it pumps air bubbles. It should have a strong flow free of bubbles in about 5 seconds.

You could also remove spark plugs to remove strain on starter and battery, submerge fuel line and crank the engine for 10 seconds or so.

SUCKING AIR CAUSES LESS OR INCONSISTENT FUEL DELIVERY.

Most folks just add a fuel pressure guage at the carb and position so you can watch it while driving, that will tell the story about fuel delivery.

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Guest Brandonkr

Ok, I think I know what I'm going to do, I have a 6v fuel pump that will work but I don't know anything about installing it, is it an easy job? Would it be ok to put the electric pump in and leave the manual one on too? Where would I put the pump at? I've heard to put it under the drivers side door on the frame? One more question, where would I connect the wire to in the ignition system to let the pump work properly? Thanks for everyone's previous advice, I think im on track to get this thing out of the barn!

-brandon

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Brandon, You are not listening or you are ignoring good advice given. Put a fuel pressure guage on it at the carb. Adding an electric pump won't fix anything if your pump is good or if you are sucking air at the tank connection. TROUBLESHOOT IT, DON'T JUST THROW PARTS AT IT.

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Guest Brandonkr

Texasjohn, your advice is good but I don't own a fuel pressure guage, how much are they? I don't want to put much more into the car, I have the fuel pump but no guage.

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Harbor Freight carries a couple different kits, the least expensive is appx $30, get a coupon for discount. You can rig it up a couple different ways. Tee in guage directly at carb or install a permanent schraeder valve on the tee so you can just screw on the guage line when you want to check it. The kits come with some fittings and short pieces of hose. It may not come with a schraeder fitting, that would have to be sourced if you want one.

You also need to go ahead and plumb your fuel line temporarily with a piece of hose and submerge in a bucket with some fuel already in it to check for air and whether or not you are getting good fuel delivery from the pump.

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