Inline Fuel Filters VS Factory Quadrajet Filter

[jtfred]

I've been thinking through the issues I had with a clogged filter on my most recent trip. 150 miles nursing the coach up the hills of the North Shore
of Lake Superior gave me some time to think.

The PO of my coach did quite a few modifications when he had it. I am lucky that his workmanship was very good. One of the changes he made was to
switch to electric fuel pumps. Each tank is rigged with its own fuel pump and an inline filter. The pumps are connected to run of the dash tank
switch. When I was having my fuel supply issues last Thursday I reasoned that I could switch from the main tank to the auxiliary tank, thereby
avoiding the inline filter on the main tank and continue on. That did not work. My problem wasn't resolved until I replaced the filter on the carb.
Once that was replaced I was restored to full power. Over the weekend I also replaced the inline filters to be on the safe side and have a full set if
filters in the spares kit in the coach.

So are my inline filters just acting as pre-filters? Should I run with just the inline filters and pull the carb filter? I'm okay with a "belt and
suspenders" approach but am just wondering what others have done.

Thanks again!

John
1978 Eleganza
Grand Marais, MN
--
John Fredrikson
Fayetteville, GA
1978 Eleganza

 

[LQQKatJon]

I know many take out the carb filter. But you just proved it is a good thing to have. I would not want that junk clogging up the carb itself.

it is important to know where your filters are, just in case. Some get a fuel supply issue and change the carb filter, and have no idea there is a
filter somewhere under the frame of the coach.

--
Jon Roche
75 palm beach
St. Cloud, MN
http://lqqkatjon.blogspot.com/

 

[Carl Stouffer]

The carb filter really IS your "last line of defense". If a little flake of rubber or some kind of sediment comes loose between your last in line
filter and your carburetor, it will be caught by that filter. It is my understanding that the filter in the carb inlet is a finer filter than the
available in line filters as well.

That said, if you have clean fuel tanks (you might) and can count on always getting clean fuel (you can't) it would be almost as good to just put an
additional filter in the rubber line right before the fuel pump. It is also somewhat risky to change the carb filter too often because, if you're not
really careful, you can strip the threads that the filter housing screws in to. Mine is still in there.
--
Carl Stouffer
'75 ex Palm Beach
Tucson, AZ.
Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive, Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American Eagles,
Solar battery charging. GMCSJ and GMCMI member

 

[johnny]

If you loosen the carb mounting bolts, you can start the line into the filter space by hand to insure it isn't cross threaded. Run it all the way in
by hand, snug it with two wrenches, then retighten the carb mount bolts.

--johnny
--
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell

 

[jtfred]

> If you loosen the carb mounting bolts, you can start the line into the filter space by hand to insure it isn't cross threaded. Run it all the way
> in by hand, snug it with two wrenches, then retighten the carb mount bolts.
>
> --johnny

That is what I did when I replaced the filter on Thursday it just seems that every time I do anything with the lines up there I end up chasing a leak.

Clearly the carb filter was catching more than the metal inline filters so they might not be the best. I am thinking about possibly swapping out the
inline filters with something like this:

https://www.amazon.com/Moeller-033320-10-Micron-Separating-Filter/dp/B07V3NPMBC/ref=pd_cp_263_1?pd_rd_w=y4i3r&pf_rd_p=ef4dc990-a9ca-4945-ae0b-f8d549198ed6&pf_rd_r=DVV2B4BEFX00HE0YMD95&pd_rd_r=f1449e80-a8af-11e9-b120-f170bfc69993&pd_rd_wg=GRc9O&pd_rd_i=B07V3NPMBC&psc=1&refRID=DVV2B4BEFX00HE0YMD95

And then pull the carb filter so I don't have to risk cross threading or leaking on top of the engine.

John
--
John Fredrikson
Fayetteville, GA
1978 Eleganza

 

[jim kanomata1]

Never run with out the carb filter as that is the safty filter in case ant
particulets are generated after the pre filters.
What is plugging up your filters is not particulets, but gum. It will pass
through the filter.
We have few GM delivery trucks here and have removed the final filters at
times and regretted doing that.
People clean the bottom of the tanks, but not the top where the gum is
collected and the NEW Ethanal is washing them down.

On Wed, Jul 17, 2019 at 1:38 PM John Fredrikson via Gmclist <

> > If you loosen the carb mounting bolts, you can start the line into the
> filter space by hand to insure it isn't cross threaded. Run it all the way
> > in by hand, snug it with two wrenches, then retighten the carb mount
> bolts.
> >
> > --johnny
>
> That is what I did when I replaced the filter on Thursday it just seems
> that every time I do anything with the lines up there I end up chasing a
> leak.
>
>
> Clearly the carb filter was catching more than the metal inline filters so
> they might not be the best. I am thinking about possibly swapping out the
> inline filters with something like this:
>
>
> https://www.amazon.com/Moeller-033320-10-Micron-Separating-Filter/dp/B07V3NPMBC/ref=pd_cp_263_1?pd_rd_w=y4i3r&pf_rd_p=ef4dc990-a9ca-4945-ae0b-f8d549198ed6&pf_rd_r=DVV2B4BEFX00HE0YMD95&pd_rd_r=f1449e80-a8af-11e9-b120-f170bfc69993&pd_rd_wg=GRc9O&pd_rd_i=B07V3NPMBC&psc=1&refRID=DVV2B4BEFX00HE0YMD95
>
> And then pull the carb filter so I don't have to risk cross threading or
> leaking on top of the engine.
>
> John
> --
> John Fredrikson
> Fayetteville, GA
> 1978 Eleganza
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

--
Jim Kanomata
Applied/GMC, Newark,CA
jimk
http://www.appliedgmc.com
1-800-752-7502

 

[Ken B]

My daughter and I once moved a coach from California to Indiana. It had one of those big Wix filters in line and also one filter in the carb. The
tanks had rust in them and everyday we had to change a filter when the engine quit. The filter we changed alternated daily between the big Wix one
and the carb one. So the in carb one was catching stuff that the big Wix one missed. We carried two spare of each filter during the trip and bought
a few more along the way. After doing it once, my daughter could change either filter in 5 minutes or so.

Keep the carb filter in place. If it is not catching stuff then you will never need to change it. If it is catching stuff then it is definitely
needed.
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana

 

[Tom Lins]

> My daughter and I once moved a coach from California to Indiana. It had one of those big Wix filters in line and also one filter in the carb.
> The tanks had rust in them and everyday we had to change a filter when the engine quit. The filter we changed alternated daily between the big Wix
> one and the carb one. So the in carb one was catching stuff that the big Wix one missed. We carried two spare of each filter during the trip and
> bought a few more along the way. After doing it once, my daughter could change either filter in 5 minutes or so.
>
> Keep the carb filter in place. If it is not catching stuff then you will never need to change it. If it is catching stuff then it is definitely
> needed.

I have to agree with Ken. When we bought our current GMC we picked it up in Missouri we ended up doing the same thing for the 1300 miles home to
Florida. We would drive for several hours and when we had trouble getting up the hills we stopped and changed both the inline filter and the carb
filter. We had a few other issues like the battery isolater and alternator but with some help from the GMC community it was just an adventure not a
disaster.

--
Tom Lins
St Augustine, FL
77 GM Rear Twin, Dry Bath, 455, FI-Tech EFI
Manuals on DVD
http://www.bdub.net/tomlins/

 

[chris tyler]

Racing or doing HP work with Q jets it is common pracice to remove the filters for better fuel flow. QJs are my favorite stret carb but one of their
limitations is the single fuel inlet and needle/seat.

That said, I dont think the flow is going to be an issue in our application. An a 450-500 hp application, it might.

I do recomend a pre filter that will capure most of the contaminents and increase the life of the QJ filter- which can be tricky to replace. I
boogered a couple when I was learning as a kid.

Personally, I run a glass "view all" filter at a low point down by the fuel pump. Double clamped with FI rated hose. Never had a leak, but if it does
it goes to ground. I can tel at a glance if there is water in the fuel or a lot of particles, its reusable, and privides an easy way to drain the
tanks via the carter electric pump.
--
76 Glenbrook

 

[michael1]

I have been doing a lot of research into fuel filters and electric fuel pumps over the past couple weeks.

One thing I have learned, is you do not want to put a 10 micron filter between the pump and the tank.
The pumps are designed to "pump" and not "suck" and a 10 micron filter is very restrictive.
Most fuel pump manufacturers recommend 80-100 micron filters between the tank and the pump.

Then all manufacturers recommend a 10 micron filter after the pump.

I am going with 85 micron filters between the tanks and the pumps.
I have a 10 micron fuel water separator that will be placed right after the two pumps are tee-d together.
I just put the fuel filter back into the carb after learning about all the particles that can come from the hoses and lines.

Hopefully I can get this all installed this weekend.
--
1973 GMC 26' Glacier - Unknown Mileage - Has a new switch pitch transmission with Powerdrive

 

[Jim Hupy]

Those 10 micron filters can be plugged by water droplets. Ask me how I know.
Jim Hupy

On Thu, Jul 18, 2019 at 8:12 AM Michael via Gmclist
wrote:

> I have been doing a lot of research into fuel filters and electric fuel
> pumps over the past couple weeks.
>
> One thing I have learned, is you do not want to put a 10 micron filter
> between the pump and the tank.
> The pumps are designed to "pump" and not "suck" and a 10 micron filter is
> very restrictive.
> Most fuel pump manufacturers recommend 80-100 micron filters between the
> tank and the pump.
>
> Then all manufacturers recommend a 10 micron filter after the pump.
>
> I am going with 85 micron filters between the tanks and the pumps.
> I have a 10 micron fuel water separator that will be placed right after
> the two pumps are tee-d together.
> I just put the fuel filter back into the carb after learning about all the
> particles that can come from the hoses and lines.
>
> Hopefully I can get this all installed this weekend.
> --
> 1973 GMC 26' Glacier - Unknown Mileage - Has a new switch pitch
> transmission with Powerdrive
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>