Since sorting out my charging issue ive been using my car everyday, and enjoying every minute, even took her to work a couple of days, but while out in her today she started running real bad, I had to keep her in N at stop lights and keep the revs up in case it died, felt and sounded like it wasn't firing on all 8, so nursed it home and took a video as soon as I got her on the drive.
I pulled the plugs...they were all clean and dry, I thought it might be fuel so I removed the glass bowl on the pump and there was sediment in the bottom, so I pulled the carb and took it apart...and nothing.

Any ideas guys?

 

Nigel:

At first I though a vacuum hose had come off until you sped the engine up and it sounds like a constant miss. I would be looking maybe for a bad or loose plug wire first. It sounds like an ignition miss to me.

 

I agree. Sounds more electrical than anything else.

Pull and replace plug wires one at a time (Carefully! OUCH!!), and see if removing one of them does NOT affect the idle (the others may make it stall).
The one that you can pull of and nothing seems to happen is the bad one.

Once you find it, inspect that wire, and the distributor cap for defects, cracks, and carbon trails.

- Eric

 

X2 with Eric.

 

I thought it was electrical too but the leads and the cap are brand new, but I'll give that a go tomorrow
And post a video of me getting electrocuted

 

Now that's an old, sad tale...

- Eric

 

It could be a bad spark plug, it may have had a crack in it. The points could have come loose and moved. The cap may not be seated all the way. Did you make sure your valve train was oiling right?

 

Might also check the points. As mentioned, check the distributor cap and rotor. Slight possibility it could be the condenser. I'm betting though it's one of the new components.


Did it backfire when this happened? If you can't find anything else, try a compression check. Could be a stuck valve. Find the dead cylinder or cylinders first. Then you can go further down the troubleshooting tree.

 

I do check the valve train regularly especially as i've been driving it, and whilst i'm in there I drench everything in oil just in case it isn't getting enough.

No back fire, just driving along and it started happening, I could feel it and hear it, so pulled over and looked under the hood and I could see the engine really jumping around as you see in the vid.

 

I had brand new components in my rebuilt 455 including AC Delco sparkplugs, new wires, and GM HEI. Developed some issues like running super rich. I thought I'd squared them away and the car went off to paint shop for six months. When it returned it was hard to start and when it did there was clearly a miss like yours. I thought about shorting out the wires one by one but in a drawer of my tool box was a seldom used infrared heat 'gun.' Why not? I thought and got it out and pointed the red laser at the header tubes close to the engine. All were reading about 400 f. except one that was reading about 185 f. Ah ha! New components can and do fail.

A quick trip to the local NAPA store for a new sparkplug and replaced the one in the misfiring cylinder. Started right up and is running fine. That infrared reader has a new-to-me use in diagnosing.

These devices have gotten very reasonable in the USA and maybe in England? About $30 here. I originally bought it to read engine coolant temps in a 1994 Chevy LT1 I had in another project car and was having some intermittent cooling issues. Since I sorted that out about four years ago the infrared reader has just sat in the drawer until the other day.
Jerry

 

Two sets of wires ago I had a new set with one wire that had no carbon inside the wire, drove me nuts till I finally found it by elimination. I too thought that new wires couldn't be defective. Check everything you touched or replaced lately ,the problem probably lies there.... Tedd

 

With so much stuff made in China, quality is a thing of the past. You cannot always assume that new is always good. I bought a set of reproduction spark plug wires from a company that most of us buy lots of stuff from and the car would not even start with them.

 

Well it's 11.17 am and i've been out there since 9.30am, and I can't even get the SOB to start, I can smell fuel but I haven't the energy or the heart to pull the carb yet again to see what I might have done wrong yesterday.
I need to save my pennies so I can send this thing to a qualified mechanic.

Cheers guys.

 

Does it have a spark?

- Eric

 

While looking down into the carb with the engine off and operating the throttle, do you see fuel spraying from the nozzles? With engine running and idling while looking in there do you see fuel dribbling?

 

"I need to save my pennies so I can send this thing to a qualified mechanic"

Nigel:

At the point you are, this may be a good idea. I am guessing you are at the point where this is not fun anymore. You don't want it to quit being fun and none of us want that for you. I think finding a good mechanic would be worthwhile. Have them tune the car and test it and then you can take it from there. These old cars are supposed to be fun and enjoyable. Besides, we enjoy having you here. I will PM you later today on the fan shroud.

 

I agree with Red. But....I'd only go to a shop and mechanic if you know they know how to work on carburetors. I've given up here in the states getting anyone who can work on these things. You are probably at least as good an expert at the Olds now as most mechanics.


Ask a few questions. The last time I took one of my cars in to get a smog check I had to show him how to check the timing. Had no clue. Vacuum advance, what's that? Then he complained at how unreliable "Those old cars are."


Air, fuel, spark....

 

Aw, c'mon.

If there is one place where the Brits have historically excelled, it is in blundering ahead when it makes absolutely no sense to do so, and so saving the day.

Nigel has come so far with this machine, and overcome so many obstacles, that I think he is just on the verge of total victory, which will taste the sweeter if he's not had to surrender in order to obtain it.

This guy keeps banging his head against the wall until the wall falls down, which is a very different thing from banging your head against the wall and getting nowhere.

I suspect that this problem is one of those things that a fresh set of eyeballs would spot right away, and it is a darned shame that Nigel does not appear to have any mechanically-inclined neighbors who can stop by and make a suggestion or two, as it was in the old days.

Nigel, just take this one step at a time, as you've done before:
Check for spark.
Check for fuel, or for improvement with added fuel.
Confirm valve and spark timing, if there is any chance that they've changed (even if there is no chance, in the case of the ignition).

Just step back, re-visualize the whole thing, and go at it from the beginning.

You have learned an incredible amount over the past few months, though I'm not sure that you realize how much, and it will all come together soon.

- Eric

 

There is no question Nigel has done an outstanding job with this car. I just don't want him to get discouraged and toss in the towel. He does have the benefit of some very good advisors on this forum and I know he is capable of getting it finished. I also suspect it might be somewhat of a problem finding somebody in the UK that is familiar with a 53 Oldsmobile. It has to be his decision. I would rather see him finish it himself.

 

The day is almost over Eric, another week at work looming, I may have another go next weekend.

You hit the nail on the head my friend.

This is upsetting for me to hear DFitz, this is the kinda crap I expect over here, not in the land that made these beautiful cars in the first place...the times they are a changing.


Enjoy the rest of the weekend guys.

 

Nigel,


I didn't want to discourage you. As the guys have said, don't sell yourself short. I think you've learned a lot more than your average mechanic will know about your car. Give yourself some credit.


As Eric said, fresh set of eyes can't hurt either. Good luck next weekend.


Dave

 

You need not get electrocuted. Just pull the plug boots back and ground each one with an insulated screwdriver one at a time. As the guys said when you get one that makes no difference, that's the problem cylinder. If they all make a difference then go to the carburetor.

 

Got home early today and wanted to fit my new Pertronix Ignitor and flamethrower coil hoping that would solve my misfiring problem, but it didn't, even though the leads plugs and distributor cap are brand new, I decided to swap them too...still no difference.
It would seem that cylinder 5 on the left bank is the culprit, and everything I have replaced has not cured the problem....

 

Have you tried swapping the #5 wire with another wire to see whether the problem moves to the other cylinder?

- Eric

 

We need to see if you actually have spark on that cylinder.

 

That wont affect anything will it, being in the wrong firing order?

Just pull that plug, leave it in the lead and start the car to see if it sparks?

 

No -- Switch the ENTIRE wire, both ends.



Set the end of the wire so that it is about 3/4" from grounded metal and crank the engine while watching it - should get a decent spark.

Then insert the spark plug and brace it against grounded metal and do it again - the spark should be bright blue-white and "fat," not orange and skinny.

- Eric

 

The leads are a brand new set on today Eric, so it certainly isn't them thats the problem, I'll do the spark test thing a little later as I have an Airport run to do now.

 

Sadly, with everything new coming from China, Mexico or the Third World, there is indeed the possibility that the "new" is in fact defective.

 

Definitely a spark there....



So all I can think is that there is no petrol getting to that cylinder.

 

I never tried to diagnose a spark via YouTube, but that spark (in the second video) looks too orange to me.

How do the other cylinders look?

And how far will the spark jump between the wire and ground, without the spark plug?

- Eric

 

I see Eric is faster at the draw than me regarding the puny looking orange shock but I will leave this post up.

Ha ha, I've been there and gotten that shock. You were a good sport to post that kind of embarrassing video.

With regard to the second video, that spark does exist but it looks weak to me. Its yellow instead of blue and doesn't look strong. You might pull one of the other plugs and do the same test to compare. All sparks are not created equal. MDchanic mentioned that in post 27 above.

I had this same issue with a miss in my 455 and when I checked the bad plug it had a puny yellow spark even though it was a brand new AC Delco. A new plug was the right fix. It only costs about US $2 for a spark plug.

If that doesn't do it and your suggestion that cylinder might not be getting fuel is correct, it would almost have to be because the intake valve is not lifting to admit fuel mix. That would be rare but not unknown.

You can pull the valve cover on the side with the misfire and visually check to see if all intake push rods are lifting an equal amount. If one is suspect then checking the lift with some kind of measure is in order. A collapsed lifter is possible. Also it seems to me I read a long time back some of the early Olds 303 V8s were known to have a soft cam problem where the lobes wore off prematurely. Either could cause the intake valve to not lift. Someone more familiar with the 49-53 engines could refute or verify my supposition about the possible soft camshaft issue.
Jerry

 

I would x2 on comparing spark on an adjacent cylinder or one on the other side. If they look similar, its time to pop off the valve cover and check the valve operation.

 

Thanks very much guys.

I cant understand why after putting electronic ignition with new high quality leads and plugs that i'd have a weak spark....but I'll check those things tomorrow.

 

... Aahhh... The divine mysteries of life...

- Eric

 

_____________________________________________

Does your new ignition call for a full 12 volts? Did you maybe use the original ignition lead that is supressed to 8 volts or so for the original factory coil? If you check other plugs and they are weak spark that might be the reason. The failing cylinder may just have had lower compression than the others and so could not fire correctly. I know it sounds sort of far fetched but you wouldn't be the first one to use that 8V supressed lead where 12 V. is generally needed on electronic type ignitions.
Jerry

 

Indeed...lol

 

Jerry, you make an excellent point.

- Eric

 

after 100k miles on my old 6 cyl truck i started getting an intermittent misfire at WOT and if starting from a stop on an incline....eventually i found the plug wire carbon core was not under the metal end of the plug wire so the carbon core was sparking everytime and after 8 years or so the core had receded in the wire enough that it would intermittently misfire (no code thrown) the clue was a burnt spot where the wire fit into the coil pack...point is part worked for 100k w a manufacturing defect....new parts have defects too.

heres a pic i used to have an x-ray image showing the core had receded into the wire but i cant locate it ...the wire was cut and you can see where the core is burnt inside and where its still good on the other side.

 

Well that's something else I didn't know about Jerry, I used all the old wiring, accept for the supplied red and black attached to the ignition module which you connect to the new coil...these are all good and valid suggestions, but the problem is that this cylinder dropped out on the old points system with the previous leads and plugs, all this new stuff has been added to try and cure this dead cylinder.