Varajet carb questions

[DanInMichigan]

Wow.  Searched the web high and low for info on this carb.  1979 varajet on a inline 6 250.

Truck had been sitting for a very long time.  Accelerator pump wasn't working so I pulled carb apart to fix.  The idle mixture screw was already hacked open and the screw was 7.25 turns out.

I put the screw back to 2 turns out.  I wonder if anyone has a ballpark of where this screw should be.  I don't have a tool that will allow me to adjust this screw while the carb is on the engine which is a huge pain. 

Right now the truck revs fine but it won't idle unless it's on the highest fast idle setting.  On fast idle I can see fuel drip out of the main booster.  I don't know if it drips at regular idle because the truck won't idle that low.

My motor has the integrated intake so I can't easily change to a different carb.

Any word of wisdom?

Dan

[Fairlane514]

Quadrajets start at 3-3.5 turns out, so maybe that would help.........

[bd]

Dan,
VaraJet idle mixture can be set anywhere between 1-1/2 to ~5 turns out from the factory.  But, the main nozzle tip-in seems a little early.  The float may be taking on fuel.  Did the float appear blistery when you had it apart, or ooze fuel with a light squeeze?  I also wonder whether there are any vacuum leaks to explain the idle mixture setting.  You may have more than one thing going on. 

This may sound contradictory, but try hovering the carburetor with a shop rag at curb idle to see if you can keep it running.  You may need an assistant.  This will instantly tell you if it is running lean at idle.

IIR, the mixture adjusting tool is not expensive.  I think it's a Thexton P/N 350.  Search the "Fuel System" link.

[DanInMichigan]

Awesome, thanks for the advice.  I did manage to find a "double d" flexible carb adjusting tool at my local NAPA and I hope to try that tomorrow.

I'll post a follow up with my findings.



Dan

[DanInMichigan]

Man this is so frustrating.  I blocked all of the vacuum ports and adjusted the idle mixture screw.  I started at 1 turn out and went all the way to 8 turns, one full turn each test.  None of the settings allowed the truck to idle.  I couldn't really tell a difference between 1 turn or 8. 

The truck will only idle on fast idle with the choke partially closed.  If I force the choke to be open all of the way it will stall.

It will rev up fine and it actually sounds good when revving.  At steady state speed it sounds rough unless the rpms are way up (like fast idle).

I've got the idle speed screw adjusted to the max and that's not enough to keep it running.

So it must be running lean - buy why?  I don't know this carb very well.  Does anyone know much about diagnosing these Varajet 2SE carbs?

Thanks for the help.

Dan

[bd]

Did you try hovering the carburetor with a shop towel to enrich fuel delivery?  Your description sounds like either a major vacuum leak or plugged idle and off-idle circuits.  It may simply be due for an overhaul.

[79gmc15]

Yeah, I would guess that you have a leak. Could be as simple as the gasket or complex as the throttle shaft.

[ralphhemi]

Check to see if the egr. valve is sticking open from carbon  build up 

[DanInMichigan]

I found the problem.  When I rebuilt the carb I used a gasket that allowed a vacuum leak internally in the idle circuit.  I pulled the carb apart and ran a guitar string through the idle passages so that I could visually trace them.  I came to a point where the passage was connected to another passage via a cutout channel on the gasket.  The part that wasn't normal looking here was that the gasket channel actually passed over the inside of the float bowl by maybe 1/8 of an inch or less.  So instead of pulling the correct mixture down to the idle mixture screw it was probably pulling about 100% air.  This was pretty easy to over look...the old gasket came off in pieces and I thought I had chosen the correct one.  I had the remaining gaskets that came in the kit and one of them had no channel.  It was an easy choice at that point because it was the only one that would not allow the vacuum leak.

Once that was fixed and the engine was warmed up I could adjust the idle mixture screw.  It ended up being between 4 and 4.5 turns out, but it smells rich at idle.   I'm going to call it a win though because it's 100% better than before.  I don't yet have the air cleaner on with the little stove pipe and what not.  It can probably run leaner with that all hooked up.

And thanks for the rag trick, it worked good - it did idle better.


Now I have to fix an exhaust leak where the pipe meets the manifold and pull the 3 speed tranny out. 

Thanks for the help everyone!


Dan