'37 Pontiac Engine not running right. HELP!

[Guest bofusmosby]

Several weeks ago, I went to take my car for a 20 mile drive, and I noticed a bit of a miss. It had been about a month since it had been started, so I figured it might be a bit of moisture, thinking that a drive might dry it out. Well, before I got home, it really started running bad, and I had to keep giving it some gas as I stopped to keep it from stalling out. Well, I finally got it home, but it wasn't easy. Since the plug wires were in pretty bad shape, I went ahead and replaced the plugs and wires, checked the gap on the points, and cleaned the contacts. Thi is a 6 cyl. engine, and until then, it had run like a top. The previous owner had rebuilt the engine, as well as the carburator (among other things). Before I took my drive, I put more gas in the tank (the gas guage doesn't work), filling it higher that I had ever done before. The reason why I mention this is because the previous owner had also pulled the gas tank, cleaned it out, and applied the "epoxy" sealer/coating to the inside of the tank.

When I start the engine, the engine goes"varoom", then slows, then "varoom", then slow down. If I don't give it any gas, it will stall. All the while it is missing. With the air-breather removed and looking at the fuel "jet", it comes and goes as far as the fuel spray. My step-son-in-law looked at it (a real good auto mechanic) and he tends to believe that its one of several things. First of all he is concerned that maybe some of the coating inside the gas tank may have broken loose (because of me filling it higher with gas), and is clogging something up somewhere. He suspects it might be the fuel pump (its the original one and has never been rebuilt) or maybe the carburator has some trash in it. We removed the large nut covering the needle valve, and there is a fine-mesh screen inside that looks to be real clean. We didn't have enough time to go any further.

One other thing is the distributor. There is of course the large wire that goes from the coil to the center post of the cap. There is also a small wire that runs from the coil to the side of the distributor. This wire inside had come loose from the ground section of the condenser, and the screw was just laying there inside. This loose wire inside looks to be either charred, or from age, all the insulation is gone. I checked with my meter, and there is no short until the points contacts are making contact. I believe hat this is correct.

Sorry to run on with this, but I felt that all the info needed to be said to give you an idea as to maybe where the problem is. I am wondering if I need to remove the top of the carburator and see if there is any trash in the bowl. It was also suggested that I try adjusting the "mixture" screw on the carburator, but I feel that this is something that shouldn't have to be adjusted unless there is a problem caused by something else.

Any opinions or advice on this will be greatly appreciated! Sorry for the long-winded post.

[Guest Jim_Edwards]

There is a whole variety of things that could be wrong, but what you are describing sounds a lot like a vacuum advance problem and/or a vacuum leak problem. Before you go crazy checking all sorts of other things look for a vacuum hose that might be split and/or a leak at the carburetor base. It could also be a problem with a fuel line. To eliminate that potential problem try feeding the fuel pump from a gas can, or just simply dive in and replace all the flexible fuel lines. You might also want to check any metal fuel lines for pin hole leaks which are allowing air to enter the line.

Good luck, ain't anything real major but is one of those things that can be a real pain in the butt to get a handle on quickly.

[Guest De Soto Frank]

Sounds like it might be a clogged idle jet...

Any wires inside the the distributor should be insulated... at least the ones from the coil terminal on the side of the distributor body to the points, and from the points to the condenser should be insulated. If either of those wires is bare / chafed, it might be momentarily shorting, especially when the throttle is opened and the vacuum-advance operates.

Could also be a problem with a flexible fuel line collapsing, or a metal line allowing air to bleed in and compromising the fuel-pump's operation, as Jim noted above.

If the fuel pump has "never" been rebuilt, or was last overhauled a very long time ago, you may want to think about having it overhauled; old fuel-pump diaphragms are frequent victims of modern alcohol-blended fuels.

Antique Auto Parts Cellar in Weymouth, Mass has been doing fuel pumps for decades, using alcohol-resistant nitrile diaphragm material.

As Jim said, it could be any of several things; take your time and check-out & verify one thing at a time, then move on.

[Guest bofusmosby]

OK, here is a small update. I checked for a vacuum leak all over, and could find none. I tried adjusting the fuel mixture screw, and it didn't make any difference from all the way in, to way out (I put it back where it originally was) (is this normal?). I couldn't find any problems with any fuel leaks, or anywhere it could be sucking air with the gas. I even adjusted the timing a bit, then put it back to where it was. It really made no difference as far as any missing goes.

Thats it so far.

[Guest Jim_Edwards]

OK, here is a small update. I checked for a vacuum leak all over, and could find none. I tried adjusting the fuel mixture screw, and it didn't make any difference from all the way in, to way out (I put it back where it originally was) (is this normal?). I couldn't find any problems with any fuel leaks, or anywhere it could be sucking air with the gas. I even adjusted the timing a bit, then put it back to where it was. It really made no difference as far as any missing goes.

Thats it so far.

Missing? I don't recall you mentioning that missing was an issue. I think I would be checking the position of #1 piston against the appropriate timing mark and the rotor position if there is indeed a random miss. In other words now you are introducing the possibility of the timing chain being stretched to the point it may have jumped a gear or two. Of course the coil could also be a problem as well if it isn't building up a sufficient charge to fire the plugs each and every time.

Jim

[Guest bofusmosby]

Sorry Jim, I mentioned that from the beginning. Maybe I should have emphasized that more. You know, that would be easy to check (a bad coil) now that you mention that. Come to think of it, when I first started looking for the problem (before I replaced the plugs and wires) I tried unplugging each one of the plugs one at a time, and I couldn't find any of them that made much of a difference. I also noticed that the plug wires were leaking, and I was getting "shocked", but it really didn't hurt me with the jolt. I believe that I can use one of the old spark plugs and connect it outside of the engine and see if it is randomly missing a "fire". I can try this on each one, one at a time, and if it is doing that on every one, then that would definately point to the coil. It would also explain the charred wire inside the destributor coming from the coil! So, I could be dealing with this just this one problem instead of a couple different problems. All of this would be a logical explaination as to what happened, and why the problem came to be in the firat place. If that loose wire inside that distributor shorted out (charring the wire), that could have damaged the coil.

Ahhh, finally some logic behind this! Thank you for the idea! I'll check on this sometime tomorrow, and post my findings.

Thank you!

[Guest bofusmosby]

Well, here's an update. The coil is not the problem. I hooked up a spark-plug to each one of the wires one at a time, and there is no miss with the firing. As a matter of fact, going from the spark-plug to the block, there is a real good spark. OK, back to the drawing board. It was definately worth checking though.

[Joseph P. Indusi]

It seems the ignition may be OK. Turning the fuel mixture screw in and out generally only affects the engine speed and smoothness at idle setting of the throttle plate; that is when the car is idling and the accelerator pedal is not touched. Turning the idle mixture screw should produce a definite loss of engine speed at either extreme. I suspect the carburetor.

Joe.

[MCHinson]

I am just a Model A Ford guy, so take my ideas for what little they may be worth.

A few relatively random ideas...

Ethanol fuel gone bad... perhaps water in fuel system

Failing Fuel Pump

Point gap needs to be adjusted (points closing up)

Condensor failing

Coil failing (It takes more voltage to fire the plugs under compression)

Frayed wire shorting out in distributor

[Guest Jim_Edwards]

Well it would seem things are back to square one. It's time for the using of one of the oldest diagnostic tools, the Ear! Time to allow that thing to start missing while sitting in neutral, and then placing the Ear near enough to the exhaust pipe to hear what is going on with the engine. There is no mistaking the difference between a dead miss from electrical issues and a near dead miss or an intermittent miss caused by fuel delivery issues and/or timing issues; as well as an issue with a sticking valve(s). Repeat the test with a helper gradually accelerating the engine to roughly 1,500 rpm. If what you hear with either test is more of a "Sputz" sound than the obvious dead nothing from an electrical failure at least there will be a better definition of what to look for. It wouldn't hurt to repeat this simple test with the vacuum line to the vacuum advance disconnected and plugged and gradually accelerating the engine to roughly 1,500 rpm, or until it begins backfiring. If any rhythmic metallic like ticking/clicking sound is heard at the exhaust with either test method, shut that puppy down.

Next test: With the distributor cap removed, take a hand vacuum pump with a gauge and connect it to the distributor vacuum advance and pump until you note the distributor plate move, making note of the vacuum pressure required to cause the plate to move. If no plate movement is ever achieved or noted, the vacuum advance motor should be replaced.

Jim

[Guest bofusmosby]

Thank you guys for the feed-back and advice. I believe that the biggest problem I am having is accurately describing what is going on. Let me try again.

I mentioned before that the engine when idling would go "varoom" "varoom". When it is doing this, the RPMs of the engine goes up, then the RPMs go way down, to the point of the engine stalling. If I give it a bit of gas with the pedal, or pull out the choke a bit, it continues to do this, but will not stall out because of the higher RPMs. However, when I give it more gas, it stops varing in speed, but the engine is missing, but it doesn't seem to be doing it at regular intervals. Also, when the engine is running at lower RPMs and it is doing the "Varoom", while it is in the varoom stage (where the RPMs increase), it doesn't appear to be missing. Not sure if that gives you any more understanding of what I am hearing or not.

Jim, unfortunately, I do not have any kind of hand pump to use, or for that matter, nothing but basic tools. In the future, I will be getting some, but thats in the future.

I am leaning more and more towards the fuel pump, or the carburator.

PLEASE, keep the ideas coming. I REALLY do appreciate it!

[wmsue]

Hi

When you checked for vacuum leaks did you check the carb base and intake manifold? I would try and spray water (some people use a light oil) on the gasket areas and listen for changes to the RPM and see if it runs better for a second or two.

Keep us posted

[Guest bofusmosby]

Thank you Bill for the suggestion. No, I can't say that I went that far. If the weather is good enough this weekend, I'll give it a try.

[rick60]

You can use a manual choke to check for a vacuum leak. Pull the choke out and observe engine performance. If the car has an automatic choke partially cover the carb with a rag. If the engine performance improves you have most likely have a vacuum leak.

[Guest bofusmosby]

When I give the car some gas with the pedal (or the manual choke) the engine runs better (doesn't vary in RPMs) but the miss(s) is still there. Just in case there was trash in the line, while the car was running, I covered the air intake to try to free anything that might be blocking the lines. No difference with that. I had opened the vacuum line before (while the engine was running) when I was working on the wipers, and even though I could tell a difference with the way the engine was running, the engine right now is not running like that. I really don't think that I am dealing with a vacuum leak, but then again, I am no mechanic, thats for sure.

Please, keep the suggestions coming, and thank you!

[sambarn]

This screams crud in the fuel line or cracks in the rubber section on the fuel line to me. Ive had very similar problems in both the 34 chevy and 27 marmon. Pull the lines at the tank and carb and blow air through the line. If you tie a pantyhose catcher on the end of the line, you see anything that blows out. you could also run the carb off of a remote tank ( I use a lawn mower tank suspended from an old IV stand) to see if there's a difference. This worked very well for me to determine fuel delivery issues versus all the other issues I have had.

[Guest southwell]

50 years ago i had the same trouble with a 1937 pontiac, i tryed every thing even ground the valves. no change then my dad told my about a steel sleve that goes in the manifold under the carburetor. this was burned out so i made one out of a piece of exaust pipe and the problem was solved. jim lose

[rick60]

Larry is talking about the portion of the intake manifold that heats the base of the carb. It is possible for this area to corrode and cause an internal vacuum leak. It would be similar to a modern engine that has an EGR valve stuck in the open position. You must remove the carb and inspect the intake manifold passages. Look for any holes that allow exhaust gasses to enter the intake. Look at the area directly below the carb. If you have a service manual there may be a picture to give you an idea where to look. Look for the diagram for the heat riser.

[Guest bofusmosby]

One thing I forgot to mention. On the passenger side of the engine, there is an "engine breather tube" that mounts to the side of the engine. The opening is below the engine. This car (the engine had been rebuilt about 2-3,000 miles ago) Does not blow any smoke from the exhaust, however, I noticed the last time I ran the engine, that there was some sort of white smoke exiting the engine breather tube. Maybe this is normal because of the engine missing, but just in case, I figured I'd mention this in case it meant something.

[rick60]

Those are fumes from piston ring blow by. That is a normal condition. I was going to suggest a timing chain that may have jumped time. The chain and gears should have been replaced during the engine rebuild. It sounds like a vacuum leak to me. If you can't locate an external vacuum leak, Larry's suggestion may be the cause of your problem. i previously owned a '50 Pontiac with an eight cylinder. This problem was the cause of a misfire on #3 cylinder. My intake had a hole the diameter of a pencil eraser. Good luck.

[Larry Schramm]

That tube that goes down the side of the engine is/was called a "road draft tube" and was the crankcase ventilation system before the PVC valve and plumbing.

[wmsue]

Hi

Do you have a vacuum gauge to connect to the engine? It can tell you a world of info. Most Chilton and Motor's book have charts with illustrations to determine vacuum leaks, timing, etc. If you have trouble finding a chart, I can copy one and email it to you.

Good Luck

[Guest Jim_Edwards]

One thing I forgot to mention. On the passenger side of the engine, there is an "engine breather tube" that mounts to the side of the engine. The opening is below the engine. This car (the engine had been rebuilt about 2-3,000 miles ago) Does not blow any smoke from the exhaust, however, I noticed the last time I ran the engine, that there was some sort of white smoke exiting the engine breather tube. Maybe this is normal because of the engine missing, but just in case, I figured I'd mention this in case it meant something.

I think we may be getting very close to defining the real problem with the revealing of "white smoke" from the vent/draft tube. Once a rebuilt engine reaches operating temperature there should be little or no color to the vapors being emitted from the vent/draft tube unless water/coolant is somehow getting into or collecting in the crankcase. A definite miss and those vapors is suggesting there may be either a head gasket issue or a casting crack between a water jacket and an oil gallery. So now the big question; "Is or has there been any noticeable change in coolant level?"

[Guest bofusmosby]

As far as the "smoke" from the engine breather tube, I have not let the engine run very long since it has developed this problem, so I do not know if this smoke will go away when the engine warms up. I would assume that the timing gear and chain were replaced when the engine was rebuilt, but since the engine wasn't even cleaned or painted when it was rebuilt, I really don't know what was done by the previous owner.

I do not have a vacuum guage, but my son-in-law will be coming back down here in several weeks, and he has all the equipment that may be needed. I have not noticed any coolant level change, but I guess I need to give it a closer look. If there were a cracked block, or a bad head gasket, wouldn't some of the coolant show on the oil dip-stick? Also, when I was driving the car for about 10 mikes when the problem got bad, there was no overheating going on, staying at about 180 on the temp. guage.

More food for thought. Geezzz, now I have to wonder if I am dealing with a cracked block. I hope this is not the case.

[Guest Jim_Edwards]

As far as the "smoke" from the engine breather tube, I have not let the engine run very long since it has developed this problem, so I do not know if this smoke will go away when the engine warms up. I would assume that the timing gear and chain were replaced when the engine was rebuilt, but since the engine wasn't even cleaned or painted when it was rebuilt, I really don't know what was done by the previous owner.

I do not have a vacuum guage, but my son-in-law will be coming back down here in several weeks, and he has all the equipment that may be needed. I have not noticed any coolant level change, but I guess I need to give it a closer look. If there were a cracked block, or a bad head gasket, wouldn't some of the coolant show on the oil dip-stick? Also, when I was driving the car for about 10 mikes when the problem got bad, there was no overheating going on, staying at about 180 on the temp. guage.

More food for thought. Geezzz, now I have to wonder if I am dealing with a cracked block. I hope this is not the case.

The area I changed the type size on above is greatly telling in many ways. Any reputable engine builder or even a half ass engine rebuilder would have made some effort to clean the block. I would candidly question the previous owners concept of what constituted a rebuild. I will also say that before a rebuild the engine should have been at the very least magnafluxed to reveal any head or block cracks before proceeding with the rebuild.

It is possible that if coolant is getting into the crankcase you might find a droplet or two on the dipstick but a better indication would be rust building up under the tube cap portion of the dipstick. It may be sucking enough to cause a miss but not sufficient to be obvious on the dip stick.

Coolant getting into a cylinder will typically be evidenced by a discoloration of the spark plug porcelain given sufficient exposure time. If you haven't yet, I'd pull all the plugs and examine them as they are removed. If you find discoloration you'll at least know the cylinder having the issue. Another way to tell is to let that sucker warm up, missing or not, and check for any wetness or unusual vapors at the exhaust pipe. Of course a very small amount may be insufficient to produce results at the exhaust.

Jim

[Guest bofusmosby]

Jim

I replace all the plugs and wires a few weeks ago, and there was no discoloration seen. The plugs were replaced anyway, but the ones that were removed were still good.

I'll run the engine for a while today, and check what you suggest, and thank you!

[Guest bofusmosby]

OK, I got under the hood of the car and made some checks. First, there is no sign of water on the oil dip-stick, or any sign of any rust. I checked the coolant again, and the level is holding constant. I started the engine, and used the manual choke to get the egine RPMs up, and for the engine to wrm up. When I give it some RPMs, the speed doesn't vary, it just misses. OK, when the temp.guage got up to 180, I checked the exhaust, and noted no strange smell, also there was no water or moisture inside, it was clean. I checked the engine breather tube, and there was no sign of any "smoke". However, when I let the idle run slow to the point of it almost stalling, THAT is when I see the smoke, but it isn't much. I really don't think I am dealing with a cracked block/head, or blown head gasket. I have had cars of mine develop these problems years ago, and this car is exhibiting none of those symptoms, except for the missing. Lets just say that I am "praying" this is not the case. If it is, then this car will be parked for a long time.

[Guest B1rdman]

i think you may have answered your own question.

the screw should not have came loose and any wires going

in to condenser should be on and tight.

i think you have a problem right in the distributor

and got so deep in other areas you forgot that.

it will not run right if condensor is loose or bad.

gene

This wire inside had come loose from the ground section of the condenser, and the screw was just laying there inside. This loose wire inside looks to be either charred, or from age, all the insulation is gone. I checked with my meter, and there is no short until the points contacts are making contact. I believe hat this is correct.

[Guest bofusmosby]

Will any condenser work for this, as long as it is the same physical size? I don't believe the 12 volt would be any different than the 6 volt, would it?

[nearchoclatetown]

Right Bo. Don't even need a condenser, but the points will burn faster. A good way to check one is to disconnect it, if engine starts and didn't before it is shorted internally.

[Guest papaw]

Ok Jim let me tell you what happen on my 36 and took forever to find. The hot lead to the coil runs through a metal tube from the ignition to the coil. The old insulation had worn in a few places and would short out to the metal casing. (from Ignition to coil) The car would run great sitting still, but any movement it would short just enough to cause it to miss. Finally one day it quit for good (a year later) and finally found the problem. The cable housing goes into the cap on the coil. Twist off and see what your wiring looks like. Mine was in the middle of the casing so had to pull the ignition and cable out and rewire. This could be what caused your condensor to short also.

[Guest bofusmosby]

Sorry, there must be a misunderstanding. The Condenser is not shorted. Also, the contacts on the points are not pitted. Just in case it was having a contact issue, I used 600 grit wet/dry sandpaper to clean them up a bit. That made no difference. I also thought that the plug-wires could be a problem, so I had replaced them a few weeks ago. Again, that made no difference. I also replaced the distrib cap, and again, no difference.

[Guest papaw]

Weather your condensor shorted or not if the wire has any fraying it can short out in the tube. You said the wire was fried to the condensor. It really don't matter as mine was fine also but it doesn't mean this can't be your problem. Not hard to check as the ignition and coil type casing and coil cap are one piece. Just a thought as I know mine drove me crazy for a year. Neil

[Guest bofusmosby]

I understand what you are saying, but I don't think that is the problem. That being said, I'll be sure and check that out the next time I look under the hood. I disconnected each spark-plug one at a time, and connected that loose wire to an extra spark-plug, and layed it on the engine block. I did this on every one of the plug wires, again, one at a time. I saw no sign of any miss-fires on that plug. I really don't believe that to be the problem. Now, if there isn't enough fuel getting inside each cylinder, or for some reason, there is not compression on all the cylinders (a stuck valve) that could cause this. I try to NEVER be arogant, and I openly admit that I am new to all of this. I appreciate each and everyones advice and suggestions, and take them all seriously.

Keep them coming, I could really use the help!

[Guest papaw]

Next time you have the car running reach under the dash, and wiggle the cable going from the ignition switch, to the coil cap. It will tell you real quick. You can't get to it under the hood.

[Guest bofusmosby]

Thats easy enough to check. I was thinking of removing the threaded cap on the coil, but since it has probably never been removed before, that was going to be a real pain. Thank you!

[Mark Simmons]

You might also want to check out the distributor shaft for to much movement side to side. I had a couple of old Plymouths with flathead sixes that were having the problems that you are talking about. Both had loose shafts in them and allowed the points to to misfire while the engine was running. Also take a good look at the distributor cam for excess lobe wear. Just my 2cents worth and these are easy to check on. Mark

[Guest Fitz]

Like said before me, the steel tube under the carb, inside the intake manifold must be without any hole.

This tube is heated by the exhaust gas when the heat riser valve is in close position and corrode the tube over the year by the outside. I saw some like this, you can remove it and press a new one in, it's quite easy.

The inside surface must be smooth. It's happen on one barrel intake most of the time like yours.

Take time to look at it.

Fitz.

[Guest bofusmosby]

Thank you. Does the minifold have to be removed to make this repair?

I checked my "motors" manual, as well as the 37 Pontiac service manual, and there is nothing there showing what you are talking about. I did do a google search, and saw some examples of doing this repair on much newer cars. I am assuming that they would be basically the same.

[Guest Fitz]

No, you can do it while in place, but it's easier on the bench, and cleanier too.

When the carb removed, you can see the sleeve longer than the intake surface (I know the 49-54 are this way) for about 1/8". This sleeve run into the intake, mostly 3" long.

Take you finger and look for small hole, if you feel some, the exhaust is suck by those or this hole and go inside the engine, the idle is very difficult to maintain with this kind of problem.

Fitz.