Quadrajet "No Fuel" Quandry.... Help?

[BigBen]

Ok all,

I've done some searching and cannot figure out what is wrong with my Q-jet. I'm not very experienced with carbs at all, so I may be missing something obvious here.....

'74 K5 Blazer with a 383 and a Q-Jet.

Been running pretty well for about 1000 miles (& 2 years) since I got the new engine in and running.

Dove home the other day with no problems. I let it sit a few days before I drove it again as I have done many times before.

The other morning I went to start it and it didn't fire after cranking for quite a while. (Usually takes about 12 seconds when it's been sitting) This time I tried it for about a minute (on and off) and nothing happened.

I pulled the air cleaner and didn't notice any gas smell. In fact, I looked under the choke plate and didn't see any gas when I pushed the throttle to run the accelerator pump.

She'll start to sputter to life with some starting fluid or gas in the carb, but can't keep it going. I figure this means I have spark, but no fuel.

I pulled the fuel line off tonight and found that the pump is indeed pushing fuel through when I'm cranking. I pulled the filter (Small one on the front of the carb) and it is wet with gas. I even tried to start it without the filter with no success.

So, my fuel is being stopped somewhere after the fuel filter and before the primaries. Also this went bad all of a sudden. It wasn't gradual.

This has pushed me WAY past most of my carb knowledge.... any ideas to help me figure this out CK5 Gurus????

Any and all help is appreciated!

-Ben

 

[readymix]

1. clean the jet
2. replace the float(if it has a hole in it)
3. replace the fuel finter anyway
I bet #1 or #2

The reason that you have to crank the engine for 12 sec or so after it has sat is due to a casting defect in the Q-Jets. The fuel in hte float bowl leaks through the defect and down into the intake. Then when you turn the engine over the bowl has to fill again before any fuel can get through the jet

 

[pauly383]

Bingo !

I had the pleasure to rebuild my original one ( still have it in box ) in the parking lot at the lake while I was fishing . Piece of crap from vacuum line on vapor can sucked in and blocked it .

 

[dyeager535]

Sounds like a stuck float to me, either that or the clip that pulls the needle out of the jet (inlet) broke and the needle is sitting in the jet.

You can try tapping the carb with a rubber mallet or the like (be gentle, that pot metal is pretty weak) and see if you can get fuel to move. If the float is stuck up, which it would have to be to shut off fuel flow, that should knock it free, and you should see fuel while hitting the accelerator after cranking a bit, since you know fuel is ATTEMPTING to flow through.

Even with a clogged fuel inlet filter, you will get fuel flow as long as it's installed correctly. Thats what the spring is for. When the filter is flowing as it should, the spring keeps the filter seated, which keeps the fuel going through the filter. When/if the filter plugs, the force of the fuel pushes the filter against the spring, which allows the unfiltered fuel from the pump to bypass the clogged filter. Pretty ingenious/simple way of getting around possible poor owner maintenance.

Also, if you replace the filter, an Oldsmobile fuel filter from approx. 1970-90 will net you a fuel filter that is identical in size I believe, except that it incorporates a simple check valve, which prohibits fuel from draining back to the tank.

 

[BigBen]

Hey all,

Thanks for the quick replies.

Sounds like I need to be looking at the jets/float.

As I've stated before, I'm somewhat new to the insides of a carb. I'm familiar with the theory of a float, but I've never torn into one.

I'll start with a little tapping and see if that helps things out.

Either way, it sounds like I'll have to dive inside to keep this from happening more.

How much of the carb needs to come apart to get to the float? Should I leave the carb on the truck or pull it out?

Is this deep enough that I should just do a rebuild while I am in there?

Also, if I pull it out, is there a way to repair the defect ReadyMix referred to? I hate cranking for so long everytime it sits for a while.

Thanks again for the help.

-Ben

I'm hoping to get the rig running for the weekend here along Lake Michigan. It's amazing the looks you get because so many people have never seen a topless '74 around here.

 

[dyeager535]

To fix the leaking well plugs, you need to pull the whole carb.

To mess with the float, it can be left on the vehicle. But you might as well pull it and rebuild, at it's age it's probably dirty inside, can't hurt.

Rebuild kit is about $20 at most parts places.

 

[BigBen]

Much tapping and banging last night.

No fuel flow.

Looks like fixing instead of driving this weekend.

Thanks for the help so far,

-Ben

 

[R72K5]

i always remove the fuel filter from the inlet and the spring too and run an external fuel filter on these carbs

on my 81 i dont have a fuel filter at all, anywhere

no problems

at all


if your accelerator pump is not pumping the two jets of fuel in the top of the carb(look down in there and see when you turn the throttle by hand) then you have float stuck down or fuel filter problem, and maybe even also a bad accel pump

if fuel filter removal doesnt do it then sounds liek youll be having to remove the airhorn assembly off the carb and checking adjusting the float level



good luck

 

[BigBen]

Hey Guys,

I got the rebuild kit and we dove into the carb this weekend.

The clip was missing between the float and the needle.... and the needle was stuck.

Got the top half rebuilt and back on the truck and got it started.

Thanks a TON for your help.

-Ben

 

[pauly383]

Cool , glad its fixed . Was definitely blocked then ( albeit with itself )