This was Interesting

[scorpion1110]

So I am working on the 55 handyman.

I have been putting in a new wire harness but also cleaning stuff up that bugged me and was related to initial start and break in.

Today I wanted to clean up the fuel lines. Previously the 5/16th hard line ended and ran into a clear fuel filter, which ran into the mechanical pump. The pump fed into another filter which in turn ran the dual feed lines to the carbs.

I posted a while back about the car being hard to start and possibly running an auxilary fuel pump. Rather than that I decided to add a check valve at the carbs right before the pressure gauge with a 40 micron fuel filter just before the pump. The clear filter was just for a visual when we set up the motor; I wanted to insure against any crud that came out of the tank, even though I flushed it, and I wanted to see when I had fuel to the pump.

So I open the lines at the carbs and they are dry. I install a Russell check valve with AN6 fittings at the carbs feed line.

Then to the main line. I decided to just cut the rubber line at the filter, and then was going to dump the fuel filter into a jar- the filter was full.

So I opened the line and...

The fuel disappeared. It was sucked out of the filter as soon as I opened the lines before the pump. Ok, so there was a vacuum pull towards the tank? It wasnt gravity because it was gone in a sec. Not sure what was going on, but I suspect this was impacting my fuel delivery issue.

I shortened the hard line and inserted an Earls filter and then to the pump. I thought of a second check valve before the pump but decided against it.

The motor isnt ready to start up yet, as I am not done with the motor wiring.

It just seems odd that the filter was pulled dry immediately, and by the way when I opened the rubber line, it was empty as well.

Thoughts?

Scorp

[Rick_L]

I can't speculate about your "vacuum" situation. However, I would not put a check valve in the line from the tank to the pump, and I wouldn't put anything finer than a 100 micron filter which is pretty coarse. Both the check valve and the filter are too much restriction for a suction line.

[WagonCrazy]

2 filters + a check vave in the line + another filter just before the carb

You have a restriction in the line somewhere. My bet is it's filter related. Pull them all out and plumb it without any filter (temporarily) to see if the problem goes away.
Then put 1 NEW filter in before your fuel pump somewhere and you're good to go.
Put a "serviceable" filter in...one that you can quickly pull out, open up, flush clean, reassemble, re=install....

[scorpion1110]

Thanks Rick-

So there was likely suction still holding from the pump, which broke when I cut the line and the fuel pulled back. It was quicker than I expected.

So do you really think the 35-40 Micron before the pump is a problem for general street use? What you are saying is the current thought pattern, 100 microns before pump, minimum 35 after and 10 if you have FI. My friend who is an old racer said that the 40 micron before the pump wont impact it for street use. If its a real issue, I want to pull it apart before I button up the passenger side because I can get to everything.

The check valve is right before the pressure gauge and at the end of the feed from the pump.

Ideally I would like to leave it alone, and save some $$$ and time, but will pull it back apart if its going to cause me headaches.

Scorp

[chevynut]

Do you have a vented cap on your fuel tank? These tanks aren't vented and they need to have a vented cap or you can create a vacuum in the tank from pump suction or temperature changes.

[Rick_L]

55 and 56 do not use a vented cap. Instead, there are 2 notches in the cap seat that allow ventilation.

[BamaNomad]

55 and 56 do not use a vented cap. Instead, there are 2 notches in the cap seat that allow ventilation.

Hmmm... Now THAT is great information... Thanks Rick..

note. And if the tank has been replaced, especially with a custom one, the two notches *may* not be there, which would require a vented cap!

[Rick_L]

The filler pipe is the one with the cap seat and notches in it, it is a separate piece and usually would be re-used when replacing the tank. They are available repro though, and I think those have the notches just like the originals.

[chevynut]

The point is......check and make sure the tank is getting vented. My filler neck has this notch in it. It's not hard to imagine that it could get plugged with a soft cap gasket, dirt buildup, or whatever.

10102

[chevynut]

I don't understand why you would need a check valve after the mechanical pump. Isn't the outlet valve of the pump essentially a check valve? If fuel is draining back, it seems to me that the pump outlet check valve must be leaking.

[scorpion1110]

So CN, this is the ongoing hard start issue. I thought, and perhaps wrongly that fuel was washing back from the carbs. I could see it held before the pump, but the lines after were dry. Fuel is going somewhere.

Nothing is leaking but perhaps the fuel pump is faulty- its new, but that doesnt mean anything.

So my plan is to take Rick's advice, plumb in a 100 micron filter before the pump, and then run to a Fuel Lab 10 micron with a built in check valve after the pump but before the carbs. Regardless of the pump situation thats the right filter set-up to the carbs.

I was hoping to get the wiring sorted, and then run the 55 for a while. However, I have a 12 bolt posi from a 70 chevelle, which I am having cut down to fit the Wagon. He's going to take it apart, powdercoat the housing, shorten it to 60", reinstall the 3:91 gears with new Moser axles. Once the stock rear is out, I am pulling the tank, replacing it and running a 3/8 line with an electric pump.

Its done then and its only money right? :)

And not a word about an FI conversion, otherwise I am going to install my SY1 intake with an 830 cfm carb, and send you a pic everyday.

Scorp

[markm]

Sounds like a cool project with an excellent choice of parts.

[scorpion1110]

So I ended up walking things back a little as I laid out the fuel system. I am running an old school hotrod, street driven with the vintage vibe and the right mix of old and new. When I looked at the filters I didnt like the sizing. They were simply too big for the look I want.

So I need some more opinions from the Group.

My plan was to run this 100 micron before the electric pump:

10165

Its rather gigantic.

So I went looking for a 100micron that would support the Airtex marine pump I am using to prime my system. It will be as noted above a 100 micron fuel filter to electric pump (to prime) to mechanical pump to 35 micron to check valve to carbs. Had to switch out the $175 Fuellab 10 micron filter as well because its also huge (Its for sale :)

So I went searching for a 100micron that would be smaller and work with the Airtex pump and found a perfect fit Edelbrock shown here:

10166

Only I realized upon receipt it specified diesel:

10167

I bought it off Ebay and the ad didnt mention diesel. Of course I saw when I received and then went looking to see if Edelbrock made one for gas. They do but its 40 micron.

It seems the Diesel filter is only made at 100 microns and the gas at 40. I want to use the 100. I did some web reading and I cant see that there is a difference between the filters.

Can anyone think of a reason that the 100 micron diesel filter would be a problem? its perfect size.

Thanks, Scorp

[Rick_L]

The problem I'd suspect, if it was a factor, would be that the glue they use to glue the pleated element to the end caps dissolves or is otherwise affected by gasoline or especially ethanol.

[scorpion1110]

Rick would you give it a try?

[Rick_L]

My thought is there is a reason they labeled it the way they did.

A filter is too cheap to try to use a questionable one.

[scorpion1110]

My thought is there is a reason they labeled it the way they did.

A filter is too cheap to try to use a questionable one.

And the answer from Edelbrock tech was......

No issue using the 100 micron with regular pump gas.

So if you are looking for a smaller 100 micron for pre-pump filter, and you dont want one the size of a beer can, here you go.

Scorp