Fuel Filter Before Electric Pump?

PurpleBeeper · Mar 13, 2017

I have a relatively new Holley Blue electric fuel pump mounted on rear cross member right above the stock fuel tank sending unit. The stock tank has a dual outlet mini-sump on it with 5 hole-saw-cut holes in the bottom of the tank under the sump.

My fuel pressure (regulated) is set at 6psi, but I've noticed that every once in a while the fuel pressure (mechanical gage on hood) is dropping to about 1-1/2psi. I have 2 fuel filters. One is mounted BEFORE the fuel pump & the other is mounted before the carburetors.

I read on another post where a guy also had two fuel filters mounted like me, but he was running a mechanical pump (I'm electric only) and also having an intermittent low fuel pressure problem. One member said that he shouldn't be using a fuel filter before the pump.
Is this also true when running electric only? I DEFIINTELY can't go lean running nitrous.

On a related note..... whenever my car goes onto a flatbed tow truck (forwards or backwards) the angle of the car going onto the truck scrapes the fuel line/nipple & causes a massive fuel leak. Anyone know of an angled 3/8" nipple or a hard metal option? I "think" the sump outlet is 1/2" pipe thread, but it might be 3/8"....not sure. THANKS!

lewtot184 · Mar 13, 2017

never run a cellulose type fuel filter on the suction side of a fuel pump; mech or electrical. you can use a screen type (something easy for fuel to flow thru) on the suction side but i wouldn't use anything less than 100 microns. basically, if in doubt don't use a filter on the suction side.

747mopar · Mar 13, 2017

I don't think I'd run without a filter, I'd research the options and just find a better filter rated for above your needs. Is there a pattern to when it drops? Mine only did it under hard acceleration and it was the pump.

Mike67 · Mar 13, 2017

There is a reason electric pumps have to be mounted as close to the tank as possible...they are designed to push volume not pull it.
The addition of a low micron type filter like Lewot stated adds resistance to the low side and decreases thier efficiency .
I wouldnt have much more than a screen on the low side...

Mike67 · Mar 13, 2017

https://m.summitracing.com/parts/ea...-performance&gclid=CML5tb3109ICFQEvaQodG5EAZg

PurpleBeeper · Mar 13, 2017

747mopar said:
I don't think I'd run without a filter, I'd research the options and just find a better filter rated for above your needs. Is there a pattern to when it drops? Mine only did it under hard acceleration and it was the pump.

I've got TWO in-line filters. I've never run a second filter before the electric pump until I added the "sump". I think I'm going to take Lewtot & Mike67's advice and just take that filter out. There really wasn't any "rhyme or reason" to when the fuel pressure would drop & I noticed it when at idle at a stoplight both times. It would just drop really low for about 60 seconds and then jump back up to 6psi.

The first time was in cold weather and the carbs didn't feel hot + I've got somewhat insulating nitrous plates under the carbs (probably not vapor lock). The second time it happened, I pulled over right away and removed the gas cap while the pressure was still reading 1-1/2psi and the pressure stayed low (not a tank vent problem).

lewtot184 · Mar 13, 2017

i'll bet the pumps cavitating when the pressure drops. i've seen guys at the track put filters on the suction side of an electric pump and the pump pull the the cellulose apart and create a mess. the funny part is watching the guys run up and down the pits asking people why their car is a second slower,...lol. keeping a constant fuel flow will actually help the pump run cooler extending it's life. a return back to the tank will prevent the pump from constantly dead heading which will help longevity.

747mopar · Mar 13, 2017

I'd think about lowering your mount, I've been looking into switching mine to an electric pump and talking to Aeromotive and others and they all say the number #1 thing that kills them is having to pull fuel.

As far as filters go, I've got a Summit screen style filter on mine that I can't see how it would restrict anything (3/8" line with about an inch round screen). Just insurance.

Sounds to me like these other cases of filters causing problems are a matter of not using the right type or size to me?

Shorthorse · Mar 14, 2017

747mopar said:
I'd think about lowering your mount, I've been looking into switching mine to an electric pump and talking to Aeromotive and others and they all say the number #1 thing that kills them is having to pull fuel.

2X If the pump is mounted too high the input side will drain back into the tank so every time you start the pump it will run dry until it sucks the fuel up into the pump. It might only be for a very short period of time but after prolonged use it will take a toll on the pump.
Holley installation instructions -
"The pump MUST be located below and as close to the tank as possible. This is necessary to allow for an adequate fuel supply. The pump is designed to push fuel and not designed to
pull."

65hemi · Mar 14, 2017

As recommended by Aeromotive, I have a 100m filter before the electric pump and a 10m after the pump.

Mike67 · Mar 14, 2017

Just to add, theres a big difference in a Holley Blue and an Aeromotive , Magna type pump...

furyus · Mar 14, 2017

Im using a Carter electric fuel pump. The high output one. I'm running a spin on marine style filter. Looks like an oil filter. Anyway, when setting it up, I had it as close as possible to the tank. I had the filter before the pump. Wouldn't pull fuel. I changed it to the filter after the pump, and no problems. I would take out, or move that filter from before the pump as others have said.

not so famous bob · Mar 14, 2017

furyus said:
Im using a Carter electric fuel pump. The high output one. I'm running a spin on marine style filter. Looks like an oil filter. Anyway, when setting it up, I had it as close as possible to the tank. I had the filter before the pump. Wouldn't pull fuel. I changed it to the filter after the pump, and no problems. I would take out, or move that filter from before the pump as others have said.

well I got to be diff. I have always ran a two filters before the pump, but I run the pump from behind the tank, w/ two (2) 1/2" metal inline filters coming out of the tank, then into a y and in to the pump. all 3/8" pipe till it hits the pump. the pump is a fast 2.0 inline w/ a return on this current car. ( 505",68 barracuda.) I ran a superstock hemi the same way w/ holley type pumps, a 406sbc vega, a 406 sbc gmc p/u, never had any problems what so ever !

747mopar · Mar 14, 2017

Mike67 said:
Just to add, theres a big difference in a Holley Blue and an Aeromotive , Magna type pump...

Yeah, my last pump from Holley was made overseas and is my last one lol.

I'm paying close attention to all the electric fuel pump related post just to get an idea of what everyone is doing so nevermind me hehe.

PurpleBeeper · Mar 14, 2017

You guys have been very helpful. My pump definitely "runs dry" when I turn it on for about 3-5 seconds. Years ago I tried to mount it lower down, but couldn't find a spot (protected by frame) where it would fit since I've got exhaust all the way out the back. I ended up putting it on the rear cross-member which IS higher than the tank. When I used the stock fuel nipple (on the sender) the hose was only about 6" long, but it's much longer now that I'm taking fuel out of the "sump".

Hmm.... anyone have a good idea of where to put the electric pump on a '70 that's not hanging down below the back bumper? Also, any ideas about how to buy/install a fuel pump cut-off switch? God forbid I get rear-ended & the fuel pump stays on. My Mustang has some type of "inertial switch" in the trunk to cut off fuel in case of a wreck. I'm still running the less-than-safe under-dash switch for my fuel pump (soon to be pumps).

At least for now I'm going to just remove that pre-pump filter.

747mopar · Mar 14, 2017

not so famous bob said:
well I got to be diff. I have always ran a two filters before the pump, but I run the pump from behind the tank, w/ two (2) 1/2" metal inline filters coming out of the tank, then into a y and in to the pump. all 3/8" pipe till it hits the pump. the pump is a fast 2.0 inline w/ a return on this current car. ( 505",68 barracuda.) I ran a superstock hemi the same way w/ holley type pumps, a 406sbc vega, a 406 sbc gmc p/u, never had any problems what so ever !

Talking to guys like Don at FBO it's seams they like to see a #10 supplying the pump then a #8 going to the regulator and then #6 to the carb? Makes perfectly good sense to me, 10 because it's not being forced and has to supply the pump without any push, #8 so it can deliver plenty of volume before being regulated and returned and then #6 because at that point it's there and under pressure so nothing is restricted? This is how I'll likely set mine up using a sump like purplebeeper did.

747mopar · Mar 14, 2017

PurpleBeeper said:
You guys have been very helpful. My pump definitely "runs dry" when I turn it on for about 3-5 seconds. Years ago I tried to mount it lower down, but couldn't find a spot (protected by frame) where it would fit since I've got exhaust all the way out the back. I ended up putting it on the rear cross-member which IS higher than the tank. When I used the stock fuel nipple (on the sender) the hose was only about 6" long, but it's much longer now that I'm taking fuel out of the "sump".

Hmm.... anyone have a good idea of where to put the electric pump on a '70 that's not hanging down below the back bumper? Also, any ideas about how to buy/install a fuel pump cut-off switch? God forbid I get rear-ended & the fuel pump stays on. My Mustang has some type of "inertial switch" in the trunk to cut off fuel in case of a wreck. I'm still running the less-than-safe under-dash switch for my fuel pump (soon to be pumps).

At least for now I'm going to just remove that pre-pump filter.

I've been contemplating using this setup. Initially fairly expensive but the replacement pumps are very reasonably priced. I have side exit exhaust so I'm good although you could fab a bracket coming off of your floor or elsewhere that would lower it.

Mike67 · Mar 14, 2017

On my wifes mustang I just bought a used inertia switch on ebay and mounted in the trunk. Has a reset button and also doubles as a theft deterent.
If we go anywhere or even when its in the garage I can thump the switch and it opens the circuit...
A lot of people use oil pressure switches, but I prefer the inertia type...

furyus · Mar 15, 2017

Mike67 said:
On my wifes mustang I just bought a used inertia switch on ebay and mounted in the trunk. Has a reset button and also doubles as a theft deterent.
If we go anywhere or even when its in the garage I can thump the switch and it opens the circuit...
A lot of people use oil pressure switches, but I prefer the inertia type...

View attachment 404361

I use both inertia switch from a Mustang, and an oil pressure switch with the pump run with a relay.

68 HEMI GTS · Mar 15, 2017

I run filters before and after on both my cars with electric pumps. I don't run real fine ones though In front of the pumps, just something to catch larger debris and protect the pump. I also have that same sump on my dart, I'll post a picture later.

Fuel Filter Before Electric Pump?

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