My '39 Dodge engine needs some diagnosis...

[DodgeDan]

Hey folks,

The flathead six in my '39 Dodge is running terrible after sitting for the past winter. I usually do not have any issues bringing it out of hibernation, but this time something is definitely not right. She'll start and run, but it's not running right. I'll try to explain, it'll be smooth, then all of a sudden run rough, and knock and shake, then it'll go back to running smooth for a few minutes, then back to knocking and shaking for a few minutes... back and forth at random. You can actually hear an audible clacking. I installed new plugs and new wires, it made no difference. When I changed the plugs I did a compression check and I'm getting 60psi on all six. Any ideas on what else to look at? I know she's older than what you guys are about on this forum, but it's pretty much the same engine, and I thought maybe you'd help out your car's older sibling. Thanks much.

Dan

Edited May 3, 2012 by DodgeDan

[TodFitch]

Dirt in the gas? How does the sediment bowl on the fuel pump look?

[greg g]

sounds like a sticking float or needle and seat. Have you checked fuel flow?

[Don Coatney]

Dirt in the gas? How does the sediment bowl on the fuel pump look?

I agree, it is a fuel problem.

Not sure what smiley face to use so I maxed out to the legal limit

I will now sit in the corner for a bit.

[DodgeDan]

Much appreciated guys, thanks for chiming in. I'll clean the needle and seat, and I'll clean out the sediment bowl and give her a try. Thanks again folks.

Dan

[DodgeDan]

Pulled the needle and seat, cleaned and blew out. Dropped the sediment bowl, cleaned out. Still running bad, hard to describe. It's a violent knocking, will smooth out then start banging again.

[Suess]

Have you tried pulling the spark flug wires one at a time to see if you can recreate the knock?

[greg g]

Hows yer oil pressure?

[DodgeDan]

I'll need to start her up tomorrow and see what the oil pressure gauge reads, I'll check and post tomorrow. Greg, I just noticed you're from Syracuse, small world, I'm originally from East Syracuse. I'm not living there now, but I was born and raised there. I still go to most of the local Syracuse area car shows though, (not with my Dodge though, too far of a drive).

Thanks again for all the help, I need to get this figured out...

[cole18cars]

Maybe some rodents chewed some electrical wires. Shorting out, or grounding out. I put one of those leather boots on the rear drive shaft, and something ate the better part of it over the winter.

[meadowbrook]

Have you looked for a vaccum leak?

[DodgeDan]

Haven't had time to do anything else, been working. I'll be able to spend a little time on it tomorrow hopefully and see what I figure out.

[hudson1948]

Haven't had time to do anything else, been working. I'll be able to spend a little time on it tomorrow hopefully and see what I figure out.

It sounds to me like one of your valves might be sticking causing the lifter to bang around because the valve is stuck in the up position. Then when it smooths out the valve temporarily un stuck itself. Try pouring marvel mystery oil down the throught of the carburetor while reving it up.

[John Reddie]

Hudson, good advice. This makes sense. Try the Marvel Oil treatment. Good luck to you.

John R

[DodgeDan]

That makes sense, I was kinda thinking in that direction too, because it was fine when I put it away last fall, maybe something is sticking from sitting all winter in the garage. I will try that and let you know how it goes. I appreciate all the help folks, big time!

Dan

[DodgeDan]

I tried the Marvel Mystery Oil today, no luck... The engine will run smooth a few seconds, then it's pop, pop, pop, pop, pop, pop......................................pop,pop,..................................................pop, pop, pop, pop......................pop, ...................................................pop,pop.................................................pop, pop, pop, pop, pop, pop, pop,....................pop, ..........................................pop, pop, pop,..............................etc.... it does it under at idle as well as under acceleration at higher rpm. It does not smooth out under load.

[desoto1939]

Check the breaker plate inthe dizzy. I could be worn out and the unit is not rotating correctly or it might need to tightend down there are two mounting screws that hold the unit in the body of the dizzy.

I had a friedn with a 39 Desoto that was having a similar problem and an old time mechanic told us to replace the breaker plate and this solved the problem.

Hoppe this helps. The breaker plate is an Autolite IGS3004. I might have a few nOS at home if this is the problem.

Rich HArtung

Desoto1939@aol.com

[John Reddie]

Dan,

Is it possible to remove the side valve covers and run the engine at idle? This way here you can see if one of the valves is hanging up when the problem occurrs. It does soung like something is sticking. Keep trying the Marvel Oil treatment. It's good stuff.

John R

[hudson1948]

Hey folks,

The flathead six in my '39 Dodge is running terrible after sitting for the past winter. I usually do not have any issues bringing it out of hibernation, but this time something is definitely not right. She'll start and run, but it's not running right. I'll try to explain, it'll be smooth, then all of a sudden run rough, and knock and shake, then it'll go back to running smooth for a few minutes, then back to knocking and shaking for a few minutes... back and forth at random. You can actually hear an audible clacking. I installed new plugs and new wires, it made no difference. When I changed the plugs I did a compression check and I'm getting 60psi on all six. Any ideas on what else to look at? I know she's older than what you guys are about on this forum, but it's pretty much the same engine, and I thought maybe you'd help out your car's older sibling. Thanks much.

Dan

Another possibility , might be a bad condensor, or if you still have the original armored cable to the coil, maybe its shorting under the coil cover. I've seen a lot of those frayed. Also I've seen loose wires at the coil or distributor. Check the distributor cap for carbon tracks. All possibilitys.

[DodgeDan]

Okay, I replaced the breaker plate today, no change, still running with an erratic idle, smooth then rough, and the whole shakes when it hits a rough spot.

The coil and shielded cable were changed the year before last.

So far in trying to resolve this issue I've changed the cap and rotor, plugs, wires, points, condenser, and breaker plate, so I don't think it's electrical.

Dan

[Dodgeb4ya]

You should do a compression test and see if a valve is sticking. I have had the same issue before. The engine starts making a clacking/ knocking noise and runs very rough. I learned to let it idle smooth if it would for 1/2 hour then oil; slash would lube the valve stems and the engine ran fine from then on.

Is your gas old-some of it over 2 years/ stale? That will cause sticking valves as will cold/damp storage. Not running them often eough too will cause this issue.

The clacking/knocking noise can sound kinda scary.

I think you have a valve issue. The popping is another clue. Is it popping out the carb or exhaust?

Bob

[DodgeDan]

Well, I did a compression test a few weeks ago when I started trying to diagnose the problem, showed 60psi across all six. The gas tank was topped off last fall before storage, and it would have been topped off on top of older gas already in the tank, the garage is not heated, so it is indeed cold and damp in the colder months. It really does not get run that much either, only a few times a year over the summer for a few shows. I'll try letting it run for quite a while out in the driveway. It's popping out the exhaust, not the carb.

Dan

[Robert Horne]

This new type gasoline does not have much shelf life..

At winter I drained all my gas out of my 38 Coupe and used the gas in

my truck. Now I just put in a couple of gallons at a time until I get back

on the road. I do similar with the mower, cycle, etc.

[greg g]

60 psi is about 40 low for an engine in decent condition. was your test done with dry cylinders on a cold engine, or did you put a bit of oil in each cylinder before takig the reading?

Simple question with all the changes you made are your plug wire correct as per firing order?

[DodgeDan]

Cold, dry engine. Wires are definitely on correct. I let it run for a half hour, got somewhat better, but was still very evident. I'm thinking I'll try some Seafoam in the crankcase, think that'll free up any sticky valves?