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Q-Jet Check Valve Fuel Filter Application?

BigBen

BigBen

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Hey all,

Want to try a fuel filter with a Check Valve on my Q-Jet.

Local parts guy doesn't want to help unless I have an application he can look up.

Does anyone know what application used the check valve 'standard' in the fuel filter? (Small one "in" the front of the Q-jet on my '74 K5).

I thought I'd find it with 'search', but I couldn't find it again.

Thanks!

-Ben
 
maybe...

I think they started using them around 1975??...I'd guess its between 1976 and 1980 they were used..

I seem to recall the AC part # being GF 471 ??..(the "long" style paper cartridge filter with a check valve)..I could be wrong,I'd have to go dig them out, and see for sure!..

I have a few dozen of them stashed away in a box of parts a freind gave me when he cleaned out his shop--I never use them,I feel the "in carb" filters are a joke!...(when they clog up,the spring behind them lets it move back,and gas by-passes it!)..plus you strip the threads in the carb if you remove it more than a few times..:crazy:
 
Check out the Olds 350's from the late 70's, and say, an Olds 307 from the 80's. Just spread the years out, GM varied how cheap they were over the years.

IIRC, the check valve filters have a white "button" on one end of the filter that is normally open on the "lesser" filters.
 
OK, Just got back from AutoZ*n*.....
(Can't get away from the idea of a $20 gift card for every $100 you spend).... if you know what you need.

The filter I was looking for was listed for a '78 Blazer with a 305. All the 350s wanted the longer filter. (probably for a reason?)

The auto-zone cheapie part numbers on it were:
FF1103
G470

Which appears to stand for:
AC Delco: GF 470

I think another one would be:
WIX: 33051



This may restrict flow, but the first thing I want to learn is if it helps on the long crank times when the truck sits for a while.

I'm in the process of ordering a new Carb and I'll redo all the filter components with better stuff then.
 
How long are you talking about sitting?

Gas will evaporate if it sits a long time, but of course the well plugs are a known issue as well. You shouldn't have long cranking times probably in excess of a week if it's solely from evaporation, I NEVER had that problem with my Q-jet.
 
If it's within a day or so, it starts right up.
If you start talking 2,3,4 days... it can take up to 20 seconds of intermittent cranking to get it fired up.

I've got a boat-load of issues with this carb which I won't bore you with here... (P.O. was a 'hack' mechanic and it was missing choke parts as well as other parts when I got the truck, not to mention the change from stock engine to a 383 that I did).

I'm going to place an order soon with SMI carburetors out in California and try to fix this once and for all.

http://www.smicarburetor.com/

I'm looking at the check valve filter as more of a 'test' than a fix. If the problem goes away, I'll learn something. If it doesn't, I'll learn something!

My whole fuel system behind the pump is 33 years old and undisturbed. It will probably be time for me to re-work the plumbing (lines and filters) when I get the new carb.

-Ben
 
dyeager535 said:
but of course the well plugs are a known issue as well.
Click to expand...

I have seen this problem to be more common than any other. Quads are really bad about leaking here till the float bowls are emty and then you have refill them before the engine will fire.
 
yup..long crank times..

My plow trucks sit for weeks or months without being fired up sometimes..I tired of having to crank them over for 20 seconds too,only to have the battery croak just as the motor was about to fire up!--and have to jump start it..:mad:

I tried using the OEM gas filter in the carbs,didn't make any difference that I could see..also replaced the fuel pump,and ran new fuel hard lines in case rust had pinholed them..no change!..what cured it for me,was adding a "helper" electric fuel pump ,close to the gas tank--then all I had to do was hit the switch,and let the pump run a few seconds--then it would fire right up on the first turn!..:D ..

The only trouble with that is NO oil pressure had a chance to build up before it fired up,after all the oil had drained off everything in the motor,from sitting so long!--and I could hear every lifter and bearing in the motor clacking for several seconds until pressure built up!..I learned to crank it over for about 5 seconds,THEN turn the electric pump on!..then it would fire up and run quietly!...

You are right on the part #'s...

AC GF470 or WIX 33051 = short paper in carb filter with check valve..
AC GF471 or WIX 33052 = long paper in carb filter with check valve..


I read in a GM book,that the real reason for the "check valve" is to "prevent fuel loss out of the carb in a rollover accident"!!...how THAT is supposed to help is beyond me!..:what: :screwy:
 
I also have this problem. My q-jet has less than 5000 miles on it and it isn't a daily driver. I HATE that it takes so long to start if it sits for a week+. It's embarassing. You have your pride and joy with over a million dollars invested, you are ready to rock and then your truck won't start. I have a Holley electric fuel pump and a one way check valve (anodized aluminum from earls) and it STILL has this problem. Would this filter with a built in check valve help? (sorry for the hijack)
 
How is your pump wired? If it's wired on when the key is in run, it's as simple as turning the key, waiting a few seconds, and having it start. :)

Even EFI vehicles are REALLY this way, that's why the pump runs when you turn the key to run for a few seconds, while it builds pressure. It's a quick process, but I still don't just roll the key over from "off" to "start" when I hop in the rig.
 
Turn the key, let the pump run. Crank the motor. You can even hear the change in the sound of the pump when it internally allows the fuel to bypass when the bowl fills up. How many times do you pump the gas? Do you hold the pedal to the floor until it starts?
 
It seems like yours should start when you do it like that... not sure what to say. I'm pretty new to trying to figure out the intricacies of the fuel system.

I'll put the new filter in and let you all know if it seems to make a difference after the weekend.

-Ben
 
Two pumps max, but typically that was just to set the choke on a "cold" engine.

I got rid of the carb, but it ran fine for me. :)
 
check valves..

A mechanical fuel pump has "check valves" built into it--has too,in order for it to pump!..so I kind of doubt adding the check valve style filter will change anything..

I'd guess the fuel is either evaporating out of the carb's bowl,or leaking into the intake by the "well plugs" after sitting,rather than the fuel line becoming airbound from fuel retreating back towards the tank(pinholes in the steel fuel lines can cause long crank times,but no leaks too!)..

...todays "gasohol" fuel evaporates very quickly,I spilled about a pint while filling my mower the other day,and it was GONE by the time I got the speedi-dry to mop it up!..:eek1:

I think adding a universal electric pump is the quickest and cheapest solution..I wired mine up to a pushbutton,so I could use it only when I first started the truck after a long "nap"..once I got it running,it would start on the first turn every time,until I'd park it for a week or so,then it'd do it again...:crazy:
 
I think whoever wrote the GM book you mention was smoking crack. No offense of course, that just sounds like the stupidest reason I've ever heard.

I can't see it being for any reason other than to prevent (or attempt to) siphoning from the carb back to the tank. Since the carb is invariably higher than the tank, the pump is certainly going to "bleed off" fuel over time. That doesn't mean the pump is bad, but it's just not going to be a 100% seal over days or weeks. I'd assume the simple check valve would just add another boundary to the fuel flow back to the tank.

GM bounced back and forth on using those check valve filters, so there had to be something different about them. It certainly couldn't have been safety, because after a certain date, that's all you would have seen.
 
OK, I never do a very good job with following up on what I learn, so here we go:

I put the check valve fuel filter in almost 2 weeks ago. Driving the truck around last week I seemed to notice the truck catching faster when it sat for a day or two.

Then I went to California for the weekend last week and the weather hasn't been perfect here this week. I got in this morning after letting the Blazer sit for a week. The start routine took as long as it did before. Several 4-second craking sessions and then it caught.

So.... my personal finding is that it MAY have helped on 1 or 2 day starts, but there was no appreciable difference when the truck sat for a week.

I orderd my Carb from Sean Murphy a week or two ago, so it should show up soon. Then I'll hopefully see all sorts of improvements in running and starting. :)

-Ben
 
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