i'm stumped.... truck is bogging down like a cheap gas FORD on a tank of DIESEL!!!!!

[Maximum Overdrive]

Could be something in the exhaust. As to the fuel line I would just run some line to a can and run the truck and see if it runs better or not. I had a truck sit for a while like that and it ran pretty bad and had the same symptoms you described. I filled the tank to half and it still ran bad so I drained all the fuel I could out and put all new fuel in it and it ran bad for about 10 mins or so and then cleared right up. I see you said you filled up already so that may not be the problem but I dont know if bad gas floats to the top of a tank or maybe sinks to the bottom or mixes equally well in the rest of the fuel. Good Luck.

[72 CustomCamper]

The reason I thought rubber fuel line was A friend of mine had a firebird that would do the same thing. The car would idle find, but when you give it gas it would fall on it's face. The fuel line had a small pin hole in it so when it needed gas it would spray on the ground, but at idle it would seal up and get enough gas. Hard to say but it is one more thing to check...

Chuck

[mr402]

Jewels,

Centrifigul advance is the same as mechanical advance. Yes, this is the weights on the top of the dist.
You can check this 2 ways.
1st is with the timing light. Disconnect the vacuum advance, make certain to plug it on the carb side. Start the engine and check the timing. As you rev the engine you should see the timing mark advance.
If you don't have a timing light you can check it by removing the dist. cap and trying to gently move the weights on the top. You should be able so swing both weights out pretty easily. Concept is as revs increase the weights try to move outwards thus increasing advance. Once you see how they move you'll see what I mean.

Vacuum advance is usually all in at idle and pulls back as load increases (ie. vacuum is reduced). This helps to keep your engine from pinging under load. These canisters do develop vacuum leaks. Best way to tell is with a vacuum tester. A Kragen might have one you could rent/borrow.

There are lots of other good suggestons on here but from your comments I think you've done a good job of starting to eliminate them as you go along.

Good luck and let us know what you find. Will certainly help to educate us all.

[Huck]

Hate to say this ---ah what the heck----JEWELS, WHAT DID YOU PUMP INTO YOUR FUEL TANK?????
Some folks have been know to pump the wrong stuff into their gas tanks!!!!hehehehehehehehehehehehehehehehehehe

[beenydu]

Just thought I would shoot out an idea. My dad had a 1968 Chevrolet Impala with a 327 and it was acting like it had no power. The sad part about it, we found the problem after it had destroyed the engine. The engine had the original exhaust manifolds with the butterfly valves for warming up. The passenger side stuck closed and finally busted the block. So, that may be an idea.

[weasel29gm]

Dang Huck beat me to it!!!!!!! LOL!!!

[jku72]

A way to check for other fuel line blockages is to disconnect the fuel lines at the carb and feul pump, then blow through that line. Then, do the same with the lines from the gas tank to the fuel pump.
My first reaction to this was that the carb floats were incorrectly set, allowing only a small amount of fuel into the bowls. That allows great idle and low load operation, but the moment you put load on the engine, the fuel consumption of the engine exceeds whats in the bowls and thats it, flat on its face. Inside the carb itself are some check valves, most noteably one the line from the accelerator pump to the port in the throat. If that guy sticks, or gets a itty bitty bit of debris, your done. I know you've said that the carb is new, rebuilt, etc, but it CAN happen. Virtually anything impeding the full flow of fuel will cause this, as has been pointed out. A fuel pressure guage just by the carb will be as invaluable as a vacuum gage if this is not an exhaust problem.
Not to be a boob, but the vacuum lines are to the correct ports?
I feel your pain. Its happened to me. The killer was that somebody had placed an aftermarket inline fuel filter in a hidden location, AND, when I finally found it, it looked clean. Turns out it was in backward, so the dirt wasn't visible. Took me 3 weeks.

[chevymad]

Definatly fuel . When you said it picks up when you quickly pump the throttle is a big clue. When you pump the throttle fast the acclerator pump squirts in extra fuel. The accelerator pump also contains a small amount of fuel when the rest of the carb goes dry. This is what your truck is running on when you pump the heck out of it and it runs better for a second.

I think it can be only a couple of things. Most likely is a clogged sock. You said the tank was almost empty after sitting all winter? Gas goes bad faster when theres less of it. It could have shellac'd the sock up.

It could be a cracked or plugged fuel line on the suction side of the pump. Not as likely on our trucks though because the in cab tank sits so high, you almost dont need a fuel pump when the tanks full.

Or a plugged main jet in the carb. Think this is least likely since you rebuilt the carb and had the same trouble before and after. But still possible.

If you really dont want to pull the sending unit out, you can usually take the gas cap off and blow air back through the line into the tank. This will blow the crap out of the sock...or blow the sock off the sending unit. Watch out though.. with a full tank it may blow gas out the filler neck.

[Blue_71]

we figured it out

this morning we decided after i rewired Shorty's (the 69) starter, that we would play with it some... we couldnt figure out anything but that it was for sure a gas problem...

we called my grandpa and drug him out here to look at it..we retested the fuel pump, checked the filter, checked the float level, couldnt find anything wrong.... everything looks perfect.... my grandpa who has been working on cars 60+ years was even stumped... (we had 4 people walking around the truck scratching heads)..

finally, we said what the heck it cant be any worse, lets use Bloo's old carb (my 71 C10-- the factory 2 barrel).. i come home, got it off the shelf where it has been for over 3 years, bolted it on, and WALA!! no more problem.. well, after gas going everywhere from a loose top plate and then shooting out the top from a stuck float

the general consensus is that there is a plugged hole somewhere in the carb, as everything appears PERFECT in the carb

[krue]

Not to be a smartie, and I am no mechanic, but when something starts going wrong on my vehicles I always go back to the last thing I did to it and see how I screwed it up.

[Touch_Of_Madness]

Like I said: Its not easy to diagnos anything on line. Because the only information those of us have out here is whats stated.

When ya rebuild a carb take the dissassembeled sections to a parts cleaner (commonly called a hot tank). There is normally shops around (parts stores even) that have tanks to dip carbs in to clean them out. They do a lot better job than a can of carb cleaner ever will and they get into the ports that you may not see when you rebuild it. When you had mentioned you had rebuilt the carb I had presumed that you had the sections cleaned. Pardon my error.

When I was a mechanic the information from the customer was normally all we had to go on unless the vehicle did it in person. Most of the time it didnt. But other things that the vehicle did added to the correct diagnostic venue. That however is rather hard on line. And a wrong diagnostic will cost the person money in the long run.

Thus this will be the last time I attempt a diagnostic on line. A friend of mine (another mechanic) said it was a mistake to do that on line. I can now agree with him.

I am glad for you blue71 that you discovered the problem.

[Blue_71]

i cant really take credit-- it was my grandpa who figured it out, it was just my carb that fixed it...
i do want to say, and im know jewels does to, eeryone of you were a great help and everyone had great ideas, we were totally stumped on the problem... we tested most of what everyone said, and it still wasnt showing up anything so we had my grandpa come out to see what was going on..

with what you said about the trying to diagnose online Touch Of Madness, i can totally understand what you are saying... it is extremely hard, but you and everyone involved helped tremendously

[Canadian72GMC]

Just a hunch, something I have seen a few times while I was wrenching......take out the in-carb paper filter, there is a little black roll over valve in the paper filter. Remove the little white valve and the spring and reinstall the filter in the right direction. Heavy spring goes in first, the hole in the fuel filter should face the fuel line. From what you have described(pumping the gas pedal it takes off) you definitely have a fuel supply problem. Did you test the "new" fuel pump?

[jewels.]

Originally Posted by krue

Not to be a smartie, and I am no mechanic, but when something starts going wrong on my vehicles I always go back to the last thing I did to it and see how I screwed it up.

oh no no no no no no no no you dont!


the last thing i did to the truck was NOT the carb rebuild.... you have NO right to be a smartie here, krue.... when i did the carb rebuild, the problem did NOT change.... the problem started long before the carb rebuild, and continued to exist as the exact same problem directly after the carb rebuild..... it looks like a stinkin spec of dirt in stuck in the carb somewhere causing this hellatious problem.... here is what we did (in 30 degree raining, snowing weather, mind you...:

ok - bottomline... we tested almost everything....
vacuum advance - just fine
timing - just fine
fuel filter (checked again) - just fine
fuel lines - just fine
fuel pump (into a metal bowl) - just fine
exhaust - just fine - but giving little power....
centrifugal - just fine...
carb --- well --- that is the problem... and it isnt the carb rebuild.... when josh's grandpa (60+ years of mechanic experience - yeah he's old) looked at it - he said "it isnt the rebuild... its something else..." he start blowing thru ports on the carb (yuck - i bet gas in your mouth tastes awful!) and turning the carb upside down.... he told me to tear it apart and find where the spec of dirt was because he was baffled.... he said the vac accel pump works fine... the float is set right... all the parts of the rebuild are there.... he isnt quite sure what the heck is wrong with the carb... but he said there must be a spec of dirt somewhere causing the issue....
so... i'm gonna tear it back apart today, and i'm also gonna tear apart josh's 3 yr old carb too and rebuild his... cause let me tell ya, his carb looks like it died 30 years ago! but it still runs... i'm still not convinced that we found the problem... but i have to prove it all wrong today.... i'll keep ya updated....

jewels.

p.s. --- josh (Blue_71) --- YOU ARE ON MY LIST!!! you are taking over my post when it was time for the punchline by giving the farm away! i'm gonna kick your ass if you dont give me a monstrous apology --- cause that reaction is what some kid would do! you owe me bigtime!!! you punchline stealer whore!!!!

[jewels.]

Originally Posted by Touch_Of_Madness

Like I said: Its not easy to diagnos anything on line. Because the only information those of us have out here is whats stated.

When ya rebuild a carb take the dissassembeled sections to a parts cleaner (commonly called a hot tank). There is normally shops around (parts stores even) that have tanks to dip carbs in to clean them out. They do a lot better job than a can of carb cleaner ever will and they get into the ports that you may not see when you rebuild it. When you had mentioned you had rebuilt the carb I had presumed that you had the sections cleaned. Pardon my error.

When I was a mechanic the information from the customer was normally all we had to go on unless the vehicle did it in person. Most of the time it didnt. But other things that the vehicle did added to the correct diagnostic venue. That however is rather hard on line. And a wrong diagnostic will cost the person money in the long run.

Thus this will be the last time I attempt a diagnostic on line. A friend of mine (another mechanic) said it was a mistake to do that on line. I can now agree with him.

I am glad for you blue71 that you discovered the problem.

hey now --- dont go runnin from helpin ppl the board because of that.... i wasnt expecting a miracle by posting on here... and i wasnt expecting a mechanic to fix my problem online - and for free! --- i am a mechanic on the side, and i was looking for ideas... nothing more... i think anyone who expects to diagnose things online correctly is crazy... i was just looking for suggestions and help.... if you walk away and promise to never try to diagnose problems online again, what good will this board be? cmon - we are all intelligent - no one would hold you to your diagnosis anyways....

hey - and all of you are taking josh's word that i made a crappy carb rebuild --- let me say --- THE CARB REBUILD IS NOT THE PROBLEM!!!!! there is nothing wrong with the rebuild.... i DID soak the carb.... the carb is clean.... the carb itself has a defect, and we dont know yet what it is.... so dont go off of this thread thinkin that the problem with the carb is the rebuild, because as i said before, the problem existed BEFORE THE REBUILD.... wait - let me say it again -
THE PROBLEM EXISTED BEFORE THE CARB REBUILD. THE CARB HAS A DEFECT SOMEWHERE - NOT SURE WHERE YET....

josh - if you post again incorrectly, i'm gonna beat the livin **** outa ya!

jewels.

[jewels.]

Originally Posted by Canadian72GMC

Just a hunch, something I have seen a few times while I was wrenching......take out the in-carb paper filter, there is a little black roll over valve in the paper filter. Remove the little white valve and the spring and reinstall the filter in the right direction. Heavy spring goes in first, the hole in the fuel filter should face the fuel line. From what you have described(pumping the gas pedal it takes off) you definitely have a fuel supply problem. Did you test the "new" fuel pump?

the carb has a ceramic fuel filter that works fine....
the new fuel pump works just fine --- pumps gas just fine...

the problem is almost 99% in the carb.... but not with the rebuild kit parts.... its got to be a plugged port or jet or something that didnt come clean after the rebuild.... the carb was soaked in cleaner, and it still didnt fix the problem....

my brain is beginnin to think that the metal casting of the carb has a shaving sticking somewhere or something... because carb cleaner didnt take care of it.....

who knows... i'll find out, i'm sure...
jewels.

[Blue_71]

i'd like to issue an apology-- i stepped out of my place in posting what was wrong with the truck... it wasnt my post, my truck, or my problem... i apologize especially to jewels and to anyone i may have misled

i would like to say, if it came across that way, i apologize, but i never said (or meant to say) the carb rebuild was the problem... the rebuild was PERFECT, there was nothing wrong, out of place, or not clean... it is just a defect somewhere in the carb, such as a plugged hole or??? its not something that jewels did wrong anywhere.

again, my sincerest apologies to Jewels for my stepping out of place

[jewels.]

apology accepted....

but dont think for a minute thats why i'm mad.... that was only the start of it...
but this is OT....

sorry to all for the OT....

jewels.

[68w/sbc406]

glad you got the problem diagonsed, now on to fixing it for good. and congradulations on a perfect carb rebuild

[Touch_Of_Madness]

**Tips his hat to jewels**

Then I guess one more addition to help would be ok.

A carb has what are called circuits (though not electric they are what is referanced when diagnosing problems) its easier to track a problem when you know what circuit is giving fits. All mechanics know this but even mechanics forget the basics sometimes. Off the top of my head the following are the circuits for a two bbl carb.

1. Choke Circuit. Either manual or electric.
2. Idle Circuit.
3. Intermediate, Off idle, or also called Part Throttle Circuit.
4. Throttle Pump Circuit or Wide Open Throttle Circuit.
5. Float Circuit.

Aside from the mention of your float sticking. Part throttle is where it sounds like your problem lies. Aside from the metering jets most of that circuit is passages. That means taking her apart and cleaning everything from the float bowl out to the horns. And before anyone tries to be a SA. Horns are one of many common names for what the passages are called that the air flows down to the throttle plates. And yes that would mean the name would imply 'Air Horns' which means everyone has air horns on their pickups. . .

To track a passage? Take a twist tie and rip the paper off it so you just have the fine little piece of metal and use that to feel through the passages to find out which one is plugged. Dont force it if you find an obstruction carefully see if you can work it out by moving from one end of the passage to the other. Logically it was pushed down from the fuel and would come back that way easiest.

Also make sure that the jets are free of crud or debris.