Not sure what is going on

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Not sure what is going on

Post by Damon23 on Sun May 08, 2016 7:40 pm

After taking the car out for a run the other day and it running so poorly I got all the parts I needed for a tune up. Cap, rotor, coil, ignition module, plugs and wires. I spent a few hours and replaced it all. The car fired right up with just a hit of the key. I let it warm up to check the timing and the air/fuel. Timing was a little low, set at 5 initial but the emission sticker says 6 at 600 rpm. Another thing that was odd was the plug gap is supposed to be at 60. Anyway, I set the idle bumped up the timing and when I tried to get the engine up to 3k it fell flat on its face. It won't rev. It just bogs down. No matter where I set the timing, no matter what I set the air/fuel mix it just gets to 2-2200 rpm and just bogs down. I'm getting 18 in on the vacuum gauge when setting the air/fuel and the needle is pretty steady. I've dug deeper into the distributor and the vacuum advance is not working but at that point vacuum is irrelevant right? I know that someone has been into the carb, it idles so smooth and all the way up to 2000 rpm but nothing after that. I don't know, fuel pump maybe. It does have the stock exhaust which includes the pellet converter. Maybe that thing is plugged up. Before I did this I was getting a popping sound when I would get on it. Now i'm not. I did find all the ground straps not connected, replaced those and nothing. The battery cable to the starter had welded itself to the tin that surrounds the exhaust manifold which made some nice sparks when the pre-heat metal piece touched (its loose). Oh, and now my gas gauge pegs full, didn't do that before and the clock is working. But still, bogging down. I'm at a loss. It is a 75 Malibu, 350 stock with the 2bbl and a automatic transmission.

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Re: Not sure what is going on

Post by bigredlaguna on Sun May 08, 2016 8:11 pm

Sounds like you aren't getting enough fuel through the venturi nozzles. Since you were getting pops before, I think your fuel pump was slowly degrading in performance and is now incapable of providing enough fuel. You can hook up a fuel gauge temporarily and see if the fuel pressure drops when it bogs down.
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Re: Not sure what is going on

Post by pila on Sun May 08, 2016 8:20 pm

X2...it does sound like fuel starvation alright. Take the line off of the carb & run the starter, after removing to bat lead on the coil. You will see just how much fuel the pump is putting out.
Did you check the fuel filter in the carb inlet fitting ?? Those are notorious for metering fuel even when the pump is working OK...





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Re: Not sure what is going on

Post by jerry46765 on Sun May 08, 2016 8:24 pm

Bad fuel.  If it's fuel from last year, odds are it's crap.  

I struggled with the same problems until we got my kids dirt bike out.  It has a white plastic liner in the tank and I noticed the fuel in it appeared to get darker towards the bottom of the tank.  Drained it into a clear plastic beaker and put a lid on it.  Sure enough, it looks like the fuel separates?  I ditched all the fuel in my storage cans and got new fuel and stuff starts and runs as it should.  

Looks like the shelf life on gasoline is only maybe six months?  I tried the fuel without ethanol in it and got the same results.  Haven't tried fuel stabilizer but I add dry gas in the tank of my cars with carbs.  The dry gas seems improve running marginally until the fuel in the tank can be used.  

Thanks -
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Re: Not sure what is going on

Post by Damon23 on Sun May 08, 2016 8:30 pm

Yes, I even replaced that filter a little while ago. There is another one that is inline before the metal tube that runs up to the carb. I did not change that one. I have a couple of vacuum/fuel pressure gauges. I've never used it to check fuel pressure before. I'm sure I'll have to buy a "T" fitting or something like that. I wonder if that filter is in backwards. I remember pulling it out and popping the new one right in. Of course it could have been backwards from the beginning. I don't know, just throwing things out there.

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Re: Not sure what is going on

Post by Damon23 on Sun May 08, 2016 8:32 pm

jerry46765 wrote:Bad fuel.  If it's fuel from last year, odds are it's crap.  

I struggled with the same problems until we got my kids dirt bike out.  It has a white plastic liner in the tank and I noticed the fuel in it appeared to get darker towards the bottom of the tank.  Drained it into a clear plastic beaker and put a lid on it.  Sure enough, it looks like the fuel separates?  I ditched all the fuel in my storage cans and got new fuel and stuff starts and runs as it should.  

Looks like the shelf life on gasoline is only maybe six months?  I tried the fuel without ethanol in it and got the same results.  Haven't tried fuel stabilizer but I add dry gas in the tank of my cars with carbs.  The dry gas seems improve running marginally until the fuel in the tank can be used.  

Thanks -

I just put in 12 gallons of new fuel. Now, that does not mean it had some old gas in it but it was pretty much empty when the transport dropped it off. I guess it could have got some gunk in it from running low. But if it had bad gas wouldn't it run like crap all the time? It runs so smooth up to that 2k rpm mark.

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Re: Not sure what is going on

Post by jerry46765 on Sun May 08, 2016 8:39 pm

Do you drive year round or seasonally?

I have a few cars that are summer driven only. No matter what I've done, they always run great when I put them away and run like crap when I get them out. After seeing the kid's dirt bike fuel, I realized what was going on. Fuel is garbage.

Not sure I would make a big science project out of it until you can run the tank empty and try again.

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Re: Not sure what is going on

Post by ant7377 on Sun May 08, 2016 8:44 pm

I would get that extra fuel filter out of there too,even just for now and also try running it without the gas cap on. see if maybe it has the wrong cap and is making a vacuum in there. That will cause fuel starvation too.
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Re: Not sure what is going on

Post by Damon23 on Sun May 08, 2016 8:49 pm

I just bought a few months ago. But in about 4 gallons and it sat for about 3 weeks. I fired it up and ran it and was never happy with the way it ran. Now, since I've done the tune up the shudder is now a bog. It's got fresh gas in it now but I really need to replace that other filter and see about putting in a "T" to check the fuel pressure. Got to pick up a new vacuum advance though. It is not holding pressure and does not move when I test it. Check out all these goodies from my day of working on it.
Plugs and rotor

Burned up wires on the passenger side


Cable from battery to starter. It had welded itself to the tin that covers the exhaust manifold. No wonder it shot out sparks randomly.


Pulled this out of the distributor but don't know how to test it.

Springs and all move freely

This plug looks like a few others i've pulled out and they only have a hour or so of run time on them. Not sure if the gap at 60 is too much. They look carbon covered. Too rich?

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Re: Not sure what is going on

Post by ant7377 on Sun May 08, 2016 8:54 pm

60 is too much. 35-40 is good. No offense but from the looks of things there you got some fixing to do. Clean up the weights on the distributor and smear a little oil on them so they move good. The burned up plug wires could be why its bogging and not revving too.
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Re: Not sure what is going on

Post by Damon23 on Sun May 08, 2016 9:09 pm

All that stuff has been replaced and it is still not revving. The weights do move good but I did clean them up a bit and oil them. I'll pick up some new plugs when I get the vacuum advance and reinstall after change out the lower fuel filter.

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Re: Not sure what is going on

Post by dynchel on Sun May 08, 2016 9:16 pm

Make sure the rubber line over the rearend isn't dryrotted & sucking air or collapsing. I ran into problems from this twice in my life. Plus it's a cheap easy fix.
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Re: Not sure what is going on

Post by ant7377 on Sun May 08, 2016 10:07 pm

dynchel wrote:Make sure the rubber line over the rearend isn't dryrotted & sucking air or collapsing.  I ran into problems from this twice in my life.  Plus it's a cheap easy fix.

I had the same problem. Id stiil get that other filter out of there though,just to see.
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Re: Not sure what is going on

Post by pila on Mon May 09, 2016 1:22 am

The hoses on the fuel tank pick-up can get rotten anytime, on an old vehicle.  Mine ('74) started dribbling on the floor when I was installing headers, ( "what's noise back there ? )
Glad I wasn't using the torch back there then !

And as for that grungy distributor harness and condenser, toss it. I just bought a new one from Jegs, for around 12 bucks, but Summit has them also. The harness includes the condenser. I keep a spare when using an MSD module...

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Re: Not sure what is going on

Post by bigredlaguna on Mon May 09, 2016 9:34 am

Did you change the module in the distributor? Make sure you use the grease underneath it so it won't cook itself. If it is really ignition related, the module is a common failure point. Most of the time the engine just dies but I have seen some that limp an engine along. Their would be extreme popping and backfiring and then it would die in short order.

I would still check over the fuel system first, then get the ignition in good shape. Carburetor problems are not always carburetor problems.
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Re: Not sure what is going on

Post by jerry46765 on Mon May 09, 2016 12:29 pm

Yes, it appears there are more issues than fuel.

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Re: Not sure what is going on

Post by 73ss on Mon May 09, 2016 1:35 pm

"It does have the stock exhaust which includes the pellet converter. Maybe that thing is plugged up."

I would take a close look at that converter. If it is in fact original to the car that would be amazing it is still on there after all these years. Looking at your burnt plug wires you were getting mis-fires. Mis-fires kill CATs. Not being able to rev past 2500 is a tell-tail sign of a plugged cat. When you rev does the exhaust have a hissing sound? You probably will not be able to dis-connect the cat without cutting pipes unless you get lucky. I don't want to tell you to start cutting up your exhaust but???? Does anyone remember the "Test pipes" from back in the day?
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Re: Not sure what is going on

Post by testpilot61 on Mon May 09, 2016 1:44 pm

OK!  Just my 2cents worth.  In line filters can be put in backwards. There is usually an arrow pointing you in the right direction on the side of the filter.

If all the fuel system is working and you have all the electrical stuff repaired/replaced and you still have the same problem then take a hard look at the "Original Catalytic converter" to determine if its plugged.  They can give you fits as they will pass just enough exhaust for the car to run up to an RPM and fall on there face.  I removed mine from my 76 installed a section of exhaust pipe (downpipe)and Shazam it ran like a top.  

Your on the right track so keep digging.  You will get your ride running in good form.

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Re: Not sure what is going on

Post by Damon23 on Mon May 09, 2016 6:45 pm

I think the problem is licked. Put everything back together with the new vacuum advance. Fired it up and let the choke open up. I hit it once and it sort of stumbled and bogged. Hit it again and smooth as silk. The old vacuum advance had a leak and would not move. I was told that if it does not move so I get no advance so the timing would be off and make if fall off. Gotta go out but will get back with it tomorrow and take it out for a spin and see. It sounded good for a 2bbl wide open.

Thank you for all the things to check. I will for sure get rid of that converter and replace that rear line in the back. Along with the extra filter and I'm going to replace those TX plugs for the RTS45's and gap them to 45. I was told that the TX plugs are a 60 gap plug for the early HEI's but the new module I have is probably pretty standard for all HEI's which take the 45.

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Re: Not sure what is going on

Post by Hs1973 on Tue May 10, 2016 8:57 am

Now when we are on the subject of fuel Lines. All of you do your self a favor and tjek all your fuel Line hoses. Fuel know a days attack rubber and can eat a fuelline from the inside, this could end bad. We just had a corvette burn up from a leaking fuelline catching fire. I always tjek mine from front to back everytime i open the hood.
I know its kind of off topic but its none the less a thing that needs attention. Espesially cars that are not driven all winter can catch fire when fuel Lines burst.

Also i would not mess alot with an old hei, a fresh new one can be had for a small amount, mine was a totally different car to drive after i Got a new hei in it.
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Re: Not sure what is going on

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