Rusty Bowtie
General Category => General Discussion - Intros => Topic started by: 28chevyguy on March 08, 2019, 10:02:49 AM
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been chasing a gremlin, whenever engine is at full temp starts bogging losing all its power... runs like junk.
runs like a raped ape cold and leading up to operating temp.
carb is brand new , clear fuel filter is always full Im certain its not a fuel issue any more (swapped the Rochester for edelbrock)
Main question: What are the main possible culprits for running bad when warm ?
Spark plug wires would do that, not the plugs them selves i would think?
Engine compresion , maybe worn valve seals not doing their job when engine gets up to temp ?
I want to stray away from replacing things that arent subject to change with temperature.
points wouldnt do that ? conderser wouldnt ?? My spark plug wires are few years old but none of them shock me...
It seems my only options are to change the spark plug wires and do a compression test with engine warm.
can anything think of anything else ?
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I don't want to start asking stupid questions but, how does it idle when it's hot?
Throw a vacuum gauge on there, see if it changes as the engine warms up, maybe you have a crack or intake leak that only shows itself as the engine warms and expands. Also, check fuel pressure when hot. I have seen an old porous pump lose pressure when it got hot.....I'm trying to think outside the box :-\
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Was it running the same before the carb swap? If it was, I would check coil or coil wire. A weak one tends to fail when hot. Like Chopper said, check fuel pressure hot. Sometimes even one year old fuel line hose colapse when under load, or a rust pin hole in steel line near frame.
If new problem since carb swap, I would check for choke not fully open at temp or possible float level too low. That's all I got ;)
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Seems like it may have lost about 3 psi of vaccum when warm .
changes the plugs and wires... same thing.
yes this problem existed before swapping the carb, no change at all.
fuel pressure is good, fuel filter as totally full at all times , I don't think its fuel related.
New Coil , Plugs, Wires, Carb , just swapped the pcv valve . Still same problem , runs like crap under load .
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So.... The longer it runs the worst it gets, now it wont even rev in neutral without coughin spitting, literally no power I might be able to get her up to 30-40 tops....
im leaning toward internal motor problem.... sucks too Ive been driving this 71 olds for 4 years as a back up car with great luck.
all good things come to and end I guess .
I never bring my car to garages but i do know a master tech ... he's rediculous , if he can't fix it or tell me whats up , noone can.
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Check the motor ground.
My dad's camaro ran like that. The only ground it had was a small wire from the electric choke. When revved up it would hardly run. A big black negative cable fixed that.
Maybe look at a vapor lock situation, fuel line getting hot.
My 2 ¢.
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Running out of guess's :( Double check points and gap, usually condenser either work or don't, but not always. Check timing, wonder if chain is lose or jumping? Pull dist cap and turn crank pulley back and forth and see if dist bug is moving tight with it.
Rattiac may be on there with ground situation. My Ramcharger drove me crazy with the vapor lock type thing. No power, bog on hiway after 10mins. Went thru all above, bout went insain! It was a pin hole in fuel line causing it to suck air under load.
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Did you do a compression test on the warm engine?
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Spark plugs can tell a story of being too lean, too rich or water.
I would pull a couple spark plugs and look at them..black and wet could be water in the fuel. Car sits and water settles at base of carb and/or tank (runs good), then is agitated when fuel begins getting pushed around and mixes with the fuel.
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Great suggestions.
I did compression test all warmed up , 120 psi across the board
I ran it down to empty practically twice and filled up half way with 93 octane
All my spark plugs visually seem all even , nothing black or fouled.
SO..... every time I touch the top of the cap ( Points distributor) I get zapped.
This didn't seem to happen the other day but maybe it does this once warmed up.. The wires going to the coil seem soft and broken down. Think I might be on to something. Driving it around cold im still impressed how much power the engine makes... does burnouts through second gear not bad for an old dog . Going to continue from here. good news I don't think my engine is bad.
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new cap and rotor. Waiting to warm it back up now . Still got shocked if I touch the coil wire boot on the center of the cap .
the wires going to the coil are really broken down looking and feel very soft rubbery …. like they're smoked.
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I don't think you should be getting a shock by touching the top of the distributor ::) I might try replacing those wires, if that's not possible check out Rock Auto, you will find new distributors relatively inexpensive, if you decide to give that a try.
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Thanks chopper . yes , going to replace the + and - wirings going to the external coil, try to cut them back as far as i can.
I think im finally onto something here.
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Keep up posted and don't give up!
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replaced the negative wire from the points inside the dist. to the - on the coil . No change .
I still get zapped touching the top of the coil so im stumped at the moment.
also , part of me wants to think its starving for fuel because the plugs look white , not wet . Doesn't look like unburned fuel .
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Check top of coil tower for a hairline crack. Then check coil wire boot for hole, or coil wire for bad insulation. If you can't find any flaws, wait till it gets good and dark outside. Pop hood, start and look to see if any sparks are jumping out and where. You shouldn't get any shock there unless its wet or something is cracked or a bad insuator.
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Make sure the motor has a solid ground to the body and frame. Sounds like you are making contact with the body when messing with the cap and it's looking for a ground (AKA You!)
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Used the old windex with ammonia trick on the cap and wires last night, the new coil wire from napa was made incorrectly , the electrode wire was folded back and sticking out of the boot !! Swapped wire and no more sparks .
the window and ammonia trick is super useful... I imagine repair shops can't use that trick during the day !!!
Car still does the same thing after warmed up. Im going to add another ground from engine to car just for good luck .
I'm going to unhook the main + wires going to the coil and measure the voltage , should be around 9 volts. Going to look into replacing this wire as well being that it is original and soft , the copper is brown and probably not the greatest conductivity. Also should re-check and compare the voltage when the car starts acting up .
I believe there is a built in balast resister somewhere leading from the + coil wire that i was told runs into the bulk head. Also a "R" wire coming from the starter to the coil to give full power while starting, the car starts right up so i doubt that is a the culprit.
Being a points setup there should be a ballast resister somewhere... maybe it is breaking down.
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think I might have found it. The coil reads 4.9 - 5 volts in the run position and running goes down to 4 volt. when being revved it seems to drop to around 3.5 volts . im starting to think someone long ago did some funny stuff with the coil wires , Im reading one goes to the start "R" terminal for 12 volts at the coil cranking only. The other wire should come from bulkhead with a resistor somewhere in line . It seems both crappy wires go down towards the starter and one is taped up, some big cobb job lookin thing.
gotta jack the car up and get down under there or im thinking just run a 12v switched wire to a ballast and to the coil and be done with it. I was under the impression the coil should have around 9 volts . Pretty amazed the car even runs at all like this .
**EDIT, Unhooked , i do have 11.9 volts at the coil wire .
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I guess it was the condenser , buddy hooked up a cap at the coil and it seems to be fine now.... I just cant believe it …. not going to argue with the Oldsmobile she rarely asks for much . had it running for over an hour and all seemed well . thanks for all the help and suggestions .
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Good for you!!! I know how frustrating this stuff can be! glad your Olds is up and running 100% That's pretty amazing to me. I don't think I can ever remember one going bad.
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I had a condenser go bad in a 66 Chevy II I used to have. This one just quit while getting off the hi-way on an off ramp. Went to the auto parts store and got a new one and drove it home. Glad you found it!
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If I remember correctly with a bad condenser the car barely runs at all, just spits and sputters warm or cold.
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I remember grabbing one after my brother charged it up. He thought he was so funny.
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28 Chevy, glad you got her up and going. I've never had one go bad as you described, but have heard of such. Most of mine either worked or didn't. The '58 Vette had one go bad when warm, but it would just die.
Ghost, lol, high school days. I was never around capasitors(condensers) other than cars. They had them in dist, along coil, radio and generators. Freshman year electronics class was a shock fest by a couple teachers assistants. You learned real quick not to catch anything they thru at you ;D
We reclaimed a lot of parts from old electronics, and I did help the smarter assistant build a "safe" capasitor discharge set up (instead of the screwdriver short out) Box with on/off, volt meter, a couple inline resistors, two insulated aligator leads. When I became teacher assistant (jr/sr years), I only did it once..... to my assistant trainee ;)
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I dropped it off at my buddys shop. he says he started it up , let it run a little and apparently it just died and wouldn't start back up , they pushed it in , let it cool down a little got it started , then hooked up the (what I thought was the RF cap ) to the NEGATIVE at the coil and apparently that was the magic touch, said it instantly started running better. He didn't actually pull the cap and swap the condenser. I originally unhooked this supposed RF cap on the coil thinking it could be causing the issue , im 99% sure it used to be on the POSITIVE side of the coil . I dont understand . all he did was hook that up to the neg / coil and apparently its all good??? I had it running for an hour and 10 minutes afterwards, kept driving around , parking , driving ... the dang thing wouldnt act up . When i got the call that car was all fixed I would have bet you every dime in my pocket that it didnt fix the problem and he probably didnt let it warm up long enough... you know ... thinking the worst. I am still reluctant to drive it too far as of right now , time will tell....
probably one of the strangest things I have seen so far . makes ya feel like a noob .
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Well, it's all good news in the end. I know it had to be weighing on you.
....I learned about magnetos the hard way......... :o
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Just thinking if it was a SBC I would just drop in a "one wire" HEI distributor ... I suspect there is one to fit your Olds?
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Yup, that is the back up plan … they make HEI for anything... I even got one for a ford 302 a few years back.
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Yup, that is the back up plan … they make HEI for anything... I even got one for a ford 302 a few years back.
There must be one in your local salvage yard.
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28chevyguy, you inspired me!! After reading this thread and your predicament, it sounded very similar to the problem I have with my son's Camaro. One day it was running ok, then it just started running like crap. Backfiring through the carb, 0 vacuum, Wouldn't stay running. After a lot of work, trial and error and asking for advice, I narrowed it down to the coil or the distributor.
I have had a new coil for the car sitting on my workbench for over a month, I put off installing it because, in my mind, I knew it wouldn't make a difference. Anyway, today I went out and put the new coil in the car........It started right up!!! I took it for a spin, it ran great for a 6 cyl.
Thanks 28chevyguy for giving me the push I needed, that you didn't know you gave ??? ;D
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That's great Chopper , ya cant beat that... you know they say 90% of carb problems turn out to be ignition related.
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Haha, I'm not sure I ever heard that, but I believe it now!