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[GMCnet] Fwd: What micron filter works best for US both. EFI/Carb [message #347865] Sun, 15 September 2019 14:49 Go to next message
Mike Kelley is currently offline  Mike Kelley   United States
Messages: 467
Registered: February 2017
Karma: -2
Senior Member
To All:
A very interesting question (see attached) - could this be why we as GMCers are seeing so many fuel delivery problems?
Not being a mechanic - I don’t know - but pose it for the rest of you to ponder! Seems to me to be a big difference tween 2 microns and 20 microns!
Mike/The Corvair a holic

Sent from my iPhone

Begin forwarded message:

> From: Bob Dunahugh
> Date: September 15, 2019 at 2:36:13 PM CDT
> To: "mpk10102@gmail.com"
> Subject: What micron filter works best for US both. EFI/Carb
>
> The Qjet carb is a 2 micron carb filter from what I understand . I have a filter that was installed 5 weeks ago in a Qjet. The adhesive that held the steel ends on. Came loss. That contaminated the carb. Next had to clean the carb. Then test it on a flow bench. So why did that filter come apart? Could this same thing happen to an EFI filter?
> Next. If a Qjet required a 2 micron filter according to GM. What does my GM, 454 TB require that I have. I have in line filters just before my two 13 LBS. EFI pumps at the rear now. Most small in line filters seem to be 20 micro. As I see it. Isn't my in line filters just sorting out the big rocks? Shouldn't I have a smaller micron filters to protect my EFI pumps, and TB? Are some of the EFI/carb pump issues. Because our pumps aren't properly protected? Does that GM TB have a filter/screen? I think of our 78 Royale. Like Apollo 13. Failure IS NOT an option. Been that way for 16 years. Never been towed. YET.
>
> This might be of interest to those on the GMC net. Maybe someone could post this there. I've been monitored on the GMC net by Billie Massy since back in June. I lost interest in posting. And quit posting on the net back then. Bob Dunahugh 78 Royale since 2003.
>
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Re: [GMCnet] Fwd: What micron filter works best for US both. EFI/Carb [message #347913 is a reply to message #347865] Mon, 16 September 2019 07:32 Go to previous message
Michael Leipold is currently offline  Michael Leipold   United States
Messages: 318
Registered: April 2011
Location: Greensboro NC
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Senior Member
I did a lot of research on pumps and filters before setting up my system.

Most fuel pump companies recommend a 100 micron filter before the fuel pump.
Most pumps are designed to push fuel and having a more restrictive filter before the pump may cause problems.
Most fuel companies recommend a 10 micron filter after the pump.
It is easier for the pump to push through 10 microns than pull through.
The stock fuel filter should be retained in the carburetor to prevent any contaminants from entering the carb as a final check point.

Addressing Bob's concern below, unless the pump manufacturer recommends a smaller micron value than 100, you are only adding extra work on the pump.
<100 microns passing through the pump should not damage it, trying to suck fuel through a 10 micron filter will wear it out quicker.

That is what I found out, of course, it all could be wrong


1973 GMC 26' Glacier - Unknown Mileage - Has a new switch pitch transmission with Powerdrive Smile
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