So what micron in line fuel filter would be needed for EFI. Since my carb filter got pluged after an in line filter?

[Bob Dunahugh]

Since my carb filter got plugged with an in line filter before it. And now I'm going to EFI. So I will have in line filters to protect the vane fuel pumps again. As I'm not the brightest bulb on the tree over Throttle body EFI.  Shouldn't I protect my TB like the carb filter protects the carb with a lower micron filter? So bottom line. Does a TB need  more, or less  filtration then a carb?  Bob Dunahugh  78 Royale

[James Hupy]

Well, tbi only has a pressure regulator and a couple of injectors that come into direct contact with fuel. I don't know the size of the holes in the tip of the injectors, but, I bet they are larger than 5 microns. Anyone know for sure? They seem to be rated in pounds of fuel per hour. But, a plugged up filter will foul up their performance, I am sure. I would think that a longer, larger diameter filter would provide a longer service life, even at the smaller filter rating. 

Jim Hupy

On Aug 24, 2017 6:59 AM, "Bob Dunahugh" <yenk...@hotmail.com> wrote:

Since my carb filter got plugged with an in line filter before it. And now I'm going to EFI. So I will have in line filters to protect the vane fuel pumps again. As I'm not the brightest bulb on the tree over Throttle body EFI.  Shouldn't I protect my TB like the carb filter protects the carb with a lower micron filter? So bottom line. Does a TB need  more, or less  filtration then a carb?  Bob Dunahugh  78 Royale

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[wizwing]

10 micron is good.  GM TBI injectors have a filtering sleeve around them.  

Sent from my Verizon Wireless 4G LTE smartphone

[wizwing]

I was just looking at the ratings of the Racor filters I normally use. One has to pay attention to the words nominal and absolute when you're looking at the Micron ratings. The rule of thumb I've always followed is the absolute rating of 100 microns in front of the pump and 10 microns absolute after the pump in front of the carburetor or injection system. I see the 10 Micron absolute matches GM's recommendation for EFI. The percentage number which follows the word absolute is often different from manufacturer to manufacture but usually above 90%. To put things in perspective the human hair is 2 microns so 10 microns is going to stop anything that might harm a fuel system. In old dirty industrial and Marine systems we often caused ourselves more grief than necessary by installing a 10 micron filter when a 20 would have given us no problem at all.

[James Hupy]

Mercury Marine used to have a line of fuel filters that would separate fuel from sediments and also WATER. They would plug up at the drop of a hat. But, no water got through them into your diesel engine. You only have a little problem with water in a gasoline engine. But, a diesel is a really different animal. Water in one of those babies gets really, really expensive, particularly direct injection engines. Gordon is fairly much right on the money with particle size requirements for gas engines. If the filters are doing their jobs, develop a change interval that doesn't leave you stranded, and go on with life. Maintain your coach. You will enjoy it a whole lot more.

Jim Hupy

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