Ok..

Replaced the fuel pump... Just in case..

Found: Cap on carb vac outlet was orange hard plastic, fit very loosely, and had a hole.. Replaced

Found: Vac tube from booster to auto trans (I think) had a hole in it.. Replaced..


SO FAR.. (drove a bit today) NO issues any more.. Fingers crossed

 

Also check the vacuum line connection down at the auto tranny's modulator to make sure it has a good connection there too. Sometimes the diaphragm in the modulator fails and causes a vacuum leak.

Think you may be onto something here... kinda sounded to me like it could have been a vacuum issue. Let us know your results.

Normally I wouldn't tee off of the brake booster line to the tranny but rather use a fitting with 2 or more nipples (one large for the booster, 1 or more small ones for accessories/tranny). Just ensures a good solid vacuum signal to the tranny's modulator. Have seen known cases that the booster draw can sometimes interrupt the vacuum signal to the tranny when the brakes are depressed. Not in all cases, but in some.

 

So..... It really was a lot better...

And then....

Started doing it again, but to a lessor degree??

IDeas?

 

I think you should keep looking for vacuum leaks, check the gaskets at the base of the carb and make sure they aren't leaking. I had that happen and it drive me nuts for weeks. Just grab a can of carb cleaner and start spraying the gaskets and anyhting else that's sealing or powered by vacuum.

Keep looking, you'll find it!

Sam

 

I've also used Acetylene (from a Oxy/Acetylene torch set) too. It's a little more flammable than carb cleaner and the engine picks up on it more noticeably then carb spray. That and the Acetylene won't damage any paint or finish of the areas you're spraying.

I do agree, keep checking for vacuum leaks. Vacuum advance unit, power brake booster, transmission Vacuum modulator, anything run by vacuum including the intake manifold where it connects to the heads, carb and carb base, ect, etc...

 

Ok.... Been driving her for a few days..

Starts right up..

Choke works correctly...

runs ok..

Shuts off...

Sometimes DIESELS when you shut it off..

Every few times I start up AFTER its warm, it wont idle, dies, will keep running IF I rev up and keep the revs up..

After a few mins it starts running ok..


Changed the fuel pump, changed the fuel line, replaced a bad vac cap, and a bad line.

Did the spray test anywhere I could...

Advance in the dist springs back fine..

Pinched off all the vac lines looking for issues, but not while its messing up.....

Whats next? Float? Carb Gunk? Eddelbrock 4bbl easy to pull apart?

ANY suggestions appreciated! HATE intermittant!!!!

 

Sounds like you've go a big vacuum leak somewhere. It's an FE, so it could be the intake manifold... Mine leaked and depending on hot warm/cold it was, or the weather and humidity it would leak differently. Drove me nuts.

Try one of those big 3/8 thick isolating gasket under the carb to keep away the heat, maybe that'll do it? Wouldn't hurt to pull the carb apart and check it.

I hate to say it, but an intake sounds likely. And on the FE's there a PAIN to check/diagnose.

Sam

 

Hmmmm... well the problemcouldbe in the carb itself. Whenit's idling, turn in the fuel idle mixture screw (one at a time) all the way till it stops. Does the engine really fall off or die when you do this? if it doesn't really change much, you definitely have a internal carb issue.

Now... i'm gonna get alot of moans and groans for this one... Do you have a good Holley or older Carter AFB laying around that you can use? It's my personal opinion that Edelbrock has done something to this AFB design. I've had nothing but trouble with these carbs ever since Edelbrock bought them out. I can't put my finger on it, but damn near every car that I've had to work on with carb troubles like you describe have had Edelbrocks on them. A buddy's '74 Duster is having similar issues too, and he's running an Edelbrock now. When i built the engine for him i had a Holley on it and he didn't have any troubles with it (idiot changed them cause the Edelbrock was shinier and more blingy... whatever... To buck the theory I'm still running a 750 Edelbrock on one of my 460 trucks. I just can't seem to get it ironed out, no matter what I try. It diesels much like yours does. Call my crazy, but that's all I can figure with those... I've got an older Carter AFB on my '69 F100 and it runs superb.

 

Pack rat,

Could you report your idle vacuum? I am asking this because if your step up spring in your carb are too stiff, your carb will not be operating off the idle circuit causing your truck to diesel at shut down.

 

Ok...


Suspecting the vacuum advance unit..


When I apply vacuum to the unit manually, it hardly moves at all.. Just a degree +/-


How much should it move when I apply vacuum?

How hard should it be to move?

 

What are you manually applying vacuum to? Confused.

 

The vac advance unit on the distributor

 

Yes, the advance plate in the distributor should move quite a bit. it may be a little stiff as it has an internal spring to fight against the vacuum. When you have this manual vacuum source on the advance, does it hold it with out leaking down?

Lance Hogan has a good question. What is your engine's intake manifold vacuum, at idle, in park as well as in drive?

 

where do I measure from, base plate of the carb?

 

IDLE: 17,5

DRIVE: 15