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Username Post: qudrajet fuel filter ?        (Topic#360035)
Mad Professor 
Contributor
Posts: 115

Reg: 12-30-08
03-03-20 08:38 AM - Post#2787862    

Hi folks.

1985 C10 305 H motor. Still has all the emmisions crap on it

Started to have problems starting. Put in new set of plugs. Would fire if a shot of gas or starting fluid but no run.

Disconnected fuel line and gas pumped when engine turned over. So I'm thinking filter or stuck float.

The inline filter in carb was in good shape, but it has a built in check valve (plunger/spring) that seemed hard to depress. I took it out and inside of filter looked new. I put it back together without the check valve and truck started right up.

I'm headed to parts store to get a new filter but am wondering does the fuel system really need that check valve.

No signs of fuel starvation when driving, I was worried the mech fuel pump might have been on way out.

Anyway, thoughts on the inline filter/check valve?

Also still wondering if playing with carb might have released a stuck float.

62 Willys wagon
67 CJ5 Buick V6 w/OD
68 Camaro RS/SS , 69 LT1 350, M22
73 C10 292 6, M21 muncie/hurst, 3:73 posi
85 C10 305, SM465
89 S10 baja package







Edited by Mad Professor on 03-03-20 08:39 AM. Reason for edit: No reason given.

 
junky 
Valued Contributor
Posts: 3438

Loc: Northeast CT
Reg: 06-27-10
03-03-20 08:50 AM - Post#2787864    
    In response to Mad Professor

The spring holds the filter against the nut, and if the filter gets clogged, it will push against the spring, and allow gas to flow into the carburetor. Be extremely careful putting the nut back on, since if you strip the threads, the carburetor is junk. The nut that used to be sold to repair the stripped threads didn't work all that well, and many times it would leak. I always turn the nut backwards to find the spot where the thread starts, and then draw a line across the nut and the carburetor with a marker, so I knew exactly where to start the nut going back on. Even an experienced mechanic can make a mistake when it comes to these fine threads in a die cast housing.

Never argue with an idiot. He'll drag you down to his level, then beat you with experience.


 
Mad Professor 
Contributor
Posts: 115

Reg: 12-30-08
03-03-20 01:16 PM - Post#2787878    
    In response to junky

No, this is a spring and check valve inside the filter itself. It's part of the rubber seal that butts up to the large housing nut on the inlet side.

You can remove the seal and the plunger/spring is inside the filter, held in place with a rubber appendageinside the filter. You can remove both the plunger and spring. It is a built in check valve inside the filter itself. The new replacement has the same setup, but the check valve/plunger is free to move.

It seems that the rubber must have swelled and prevented the plunger from being able to move.

It cut off the fuel just like a clogged filter. The other spring that butts up to the carb side of the filter did not compress, as you suggested above if the filter gets clogged.

Anyway I'm happy it's not the fuel pump or that I'd need to take carb apart

I suspect cause may have been some crap gasahol corn/gas that had more than 10% corn juice. Even 1985 trucks were rated to run 10% ethanol.

62 Willys wagon
67 CJ5 Buick V6 w/OD
68 Camaro RS/SS , 69 LT1 350, M22
73 C10 292 6, M21 muncie/hurst, 3:73 posi
85 C10 305, SM465
89 S10 baja package







 
beagrizzly 
"11th Year" Gold Supporting Member
Posts: 2123
beagrizzly
Age: 70
Loc: south texas
Reg: 08-04-12
03-03-20 01:26 PM - Post#2787879    
    In response to Mad Professor

Mad,
You asked a question that no one has answered yet.
If I may offer some hard won advice?

Put a new filter in, but do not get the one without the valve. You are correct in assuming that it is a check valve. What it does is hold the gas in the carburetor, so after it sits the fuel will not drain out.

When your car sits for some period of time, the fuel drains back down past the fuel pump into the tank. When you try to start it, no fuel in the carb, so you have to crank it long enough for the fuel pump to get gas all the way back from the tank to the carburetor.

With gas held in the carburetor by the check valve, you have enough for the accelerator pump to give you a shot or two. That is usually enough to start the engine.

So, pull it out if you want, but down the line with a little age you are going to be back on here asking why you have to crank the engine for a long time after it sits, or maybe why you have to get a coke bottle of gas to pour down the carb to get it to fire up.

My two pennies. Spend them wisely,

Griff

if you're gonna be a bear..................

1960 Biscayne (the 6T)
2005 Yukon XL
2007 GMC Sierra Classic 8.1
2009 Silverado
2011 Escalade ESV


 
Mad Professor 
Contributor
Posts: 115

Reg: 12-30-08
03-03-20 05:50 PM - Post#2787896    
    In response to beagrizzly

Bear,

I agree with your explanation of the purpose of the check valve.

The truck was dead to starting up, so I traced the problem to the check valve, removed it, then went to the parts and $1.50 got me a new filter. It's in the glove compartment for now, as no garage and rainstorms this afternoon.

I'm not sure if others here have ran into this problem? The filter itself was in excellent condition with no crud at all inside. I'm just glad it wasn't a fuel pump.

I suspect what swelled the rubber inside the filter was too much ethanol in the fuel we have. I can get non-ethanol 93 premium but it's about $0.80 a gallon more than 87.

I won't run the corn gas in ANY of my small engines, 2-strokes, tractors.

The 9N ford will drink it, but I always run it though and not let it sit. No rubber in the fuel system, but that stuff corn gas makes "snot" if if it is left to sit.

thanks for reply,

MP

62 Willys wagon
67 CJ5 Buick V6 w/OD
68 Camaro RS/SS , 69 LT1 350, M22
73 C10 292 6, M21 muncie/hurst, 3:73 posi
85 C10 305, SM465
89 S10 baja package







 
someotherguy 
Senior Moderator
Posts: 29177
someotherguy
Age: 50
Loc: Texas
Reg: 08-01-03
03-04-20 09:05 AM - Post#2787929    
    In response to Mad Professor

What Junky said should not be overlooked, though. I'd take it a step farther and say I would not replace that filter in the housing; I would omit it and pray the fitting went back on without damaging the housing - and find an alternate solution for outside the housing. At this age it's difficult to find a Quadrajet that isn't ready to disintegrate into dust when you pull the fuel filter, at least in my experience. And yes, the repair fitting often leaks. I've seen more than a few engine fires from repair efforts in that area.

Richard

06 Silverado ISS / 06 Silverado SS / 06 300C SRT8


 
junky 
Valued Contributor
Posts: 3438

Loc: Northeast CT
Reg: 06-27-10
03-05-20 02:48 PM - Post#2788001    
    In response to Mad Professor

I am always wanting to learn, so I stopped at the local auto parts store, and had them look up the filter part number for a 1985 Chevrolet Quadrajet, and it was the filter that I was already familiar with and described above. Could you please give me the brand and part number of the filter that you were able to purchase that has the check valve in it? I could surely use a check valve on my 1969 Cadillac Quadrajet, because it will siphon back to the tank when it sits for a while. thanks Junky

Never argue with an idiot. He'll drag you down to his level, then beat you with experience.


 
someotherguy 
Senior Moderator
Posts: 29177
someotherguy
Age: 50
Loc: Texas
Reg: 08-01-03
03-05-20 10:40 PM - Post#2788023    
    In response to junky

Not sure what applications they came on but I've seen them; they're the ones with the rubbery looking cap at one end. Here's a page with some clear pics -

https://quadrajetparts.com/long-paper-carburetor -f...

That particular page is the long filter but short ones are available with the valve, too. Not recommended for high performance apps that need more fuel flow.

Richard

06 Silverado ISS / 06 Silverado SS / 06 300C SRT8


 
Mad Professor 
Contributor
Posts: 115

Reg: 12-30-08
06-20-20 01:03 AM - Post#2796748    
    In response to junky

Hi been off site for a while. Will be posting another thread as some idiot broadsided my truck and will be seeking advice on sources of body parts.

The fuel filter I purchased was from Carquest/Advance Auto.

I was very careful in removing the housing and it was in good shape. I gave it a dab of anti-seize when I reinstalled the filter. It is tricky to start the threads but all went together O.K.

As far as carb parts sources, these guys have a stock of NOS/OEM parts. The real deal made in USA NOT Chi-Com

quadrajetparts

junky, I'll look at the box the filter came in for part # from carquest. I saved the old filter and put it a parts box as it still filterted O.K. with the check valve removed

62 Willys wagon
67 CJ5 Buick V6 w/OD
68 Camaro RS/SS , 69 LT1 350, M22
73 C10 292 6, M21 muncie/hurst, 3:73 posi
85 C10 305, SM465
89 S10 baja package







Edited by Mad Professor on 06-20-20 02:17 AM. Reason for edit: No reason given.

 
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