engine won't start (used to...)

[hplacecf]

hi.

need help with 'engine not starting' issue.

1979 Chevrolet pickup. project truck (not driven on the road yet).
8 cyl engine 350.
4 barrel carb (I think quad-jet).
all looks original.

it started and ran fine last autumn, and the year prior to that - it never had any starting issues of any kind.
I started it a couple of times over the winter - no issues.
this spring I started it up and it ran fine - but after running about 10 minutes it stalled.
I have not been able to start the engine since.

I tried 'starting fluid'.
when I use starting fluid the engine DOES start and runs for a couple of seconds until it uses up the starter fluid. it does this every time, so the engine 'can' start and run.

made we wonder if it was getting fuel.

a couple of days later (after letting it sit without trying to start it) I disconnected the fuel line from the carb, replaced the fuel filter (since I was in there anyway, and as a test - new fuel filter would be 'dry').

I cranked the engine - without starting fluid - and it still would not start.
I then disconnected the fuel line again and found that there was now fuel in there, and the new fuel filter (that I had just put in there 'dry') was saturated and 'wet' with fuel. so, it appears that fuel is getting to the carb.

any ideas on what I might check next?

thanks

[MountainGoat1966]

Sounds to me like gas is getting to the carburetor, but not in it.
The float/needle valve may be stuck shut.
Try tapping on the carb body with a screwdriver's plastic handle (so you don't damage anything) a bunch of times, crank it and see if it gets gas in the float bowl and starts.
Other than a stuck needle, it could be clogged jets if some crud found its way in.
I assume the choke is working properly and closes for a cold start .....

[bilfman]

If it had a filter I would suspect fuel pump. It is working enough to wet the new filter but my guess is it is not pumping enough fuel. Take off the line again and have a buddy turn the truck over and see if fuel is pumping out should be about and ounce and a half per pump. Also since it has not been run much it could be a rusty gas tank instantly plugging the filter. And lastly , it has been known for a person to install another filter in the fuel line somewhere , under truck by tank, along a frame rail etc. Check that too, may be an old inline filter in there somewhere . Are you changing the in carb filter or an inline?

[hplacecf]

Originally Posted by MountainGoat1966

Sounds to me like gas is getting to the carburetor, but not in it.
The float/needle valve may be stuck shut.
Try tapping on the carb body with a screwdriver's plastic handle (so you don't damage anything) a bunch of times, crank it and see if it gets gas in the float bowl and starts.
Other than a stuck needle, it could be clogged jets if some crud found its way in.
I assume the choke is working properly and closes for a cold start .....

I will try the tapping as suggested and report back. If it IS a stuck needle, and tapping does not free it up, where exactly is that on a gm 4 barrel so I can inspect it?

If it IS clogged jets, how does one clean them?

forgive my ignorance about quads. I am familiar with old gm singles, so I am aware of the key parts and functions of a carb, but not a quad.

thanks

[hplacecf]

Originally Posted by bilfman

If it had a filter I would suspect fuel pump. It is working enough to wet the new filter but my guess is it is not pumping enough fuel. Take off the line again and have a buddy turn the truck over and see if fuel is pumping out should be about and ounce and a half per pump. Also since it has not been run much it could be a rusty gas tank instantly plugging the filter. And lastly , it has been known for a person to install another filter in the fuel line somewhere , under truck by tank, along a frame rail etc. Check that too, may be an old inline filter in there somewhere . Are you changing the in carb filter or an inline?

all good ideas, thanks

as suggested, I took off the fuel line, cranked the engine, and gas does pump out 'at what appears to be' the rate you mentioned. so, not that.

I inspected the filter. it is the one in the carb I replaced (and the only one I can find in the fuel line) and it is clean. so, not that.

[MountainGoat1966]

If the problem lies inside the carburetor and tapping on it doesn't un-stuck it, you will need to disassemble the carb.
One thing you need to be aware of when working on Q-jets, when reassembling, extreme care must be taken when reinstalling the top portion as the metering rods hang down and are very easily bent or damaged trying to line them up with the main jets..
In order to line everything up exactly where it needs to be and get a perfect alignment to make for a smooth assembly, you almost need five hands with tiny fingers, all working independently to hold each part in place while setting the top on the main body.
Q-jets are tricky, but when done right, they work quite well and dependably.
If you decide to rebuild it, you may as well JB weld the well plugs where they are prone to leak in later life.
Do a search for the topic, there should be several threads about it here explaining the subject in detail.
Keep us posted how you make out with it.

[hplacecf]

still no good...gas not getting 'into' carb

• tried tapping on the carb as suggested (many, many times).
• cranked it several times while pumping the gas and it did not start.
• stuck my finger into one of the back 2 large bls until I hit bottom, and it was dry.
• stuck my finger into one of the front 2 small bls as far as I could get my finger in there, and it was dry.
• so, just as we guessed, gas not getting into the carb.

from what I can see, fuel gets right up to the point where it enters the carb, but no further.

• if I spray in a lot of starting fluid the engine runs for several seconds.
• if I spray in a little starting fluid the engine runs for a couple of seconds.
• so, the engine can start and run if it gets something to burn.
  
  before all of this happened it ran extremely well for an old carb, so I hate to take it somewhere and get it rebuilt (as that will cost $) just to fix a simple blockage somewhere.so, as a start, i will take a chance myself at taking off the top of the carb and seeing if I can locate the issue.
  Once it get the top off, what and where should I be looking?
  
  any ideas or references to other threads, pics, etc. is welcome.
  
  thanks

[MountainGoat1966]

Manually operate the float by hand with the float hanging down, watch the needle assembly to see if it travels up and down in the seat. Remove the pin from the float and see if any crud is in the seat.
That is the point where gas enters the carb.

[hplacecf]

Originally Posted by MountainGoat1966

Manually operate the float by hand with the float hanging down, watch the needle assembly to see if it travels up and down in the seat. Remove the pin from the float and see if any crud is in the seat.
That is the point where gas enters the carb.

thanks!

I will give it a try and report back