I need some help/advice about the extremely low/non-existent fuel pressure I’m experiencing. Here’s a little background on what I’m working with. I have a 78 F150 Super Cab with a 460. I just completed an electric fuel pump conversion for a carb setup. The electric fuel pump is a Carter (p/n P4595). I have a 100 micron fuel filter before the pump and a 40 micron filter after the pump. The fuel line goes into an Edelbrock bypass style 160 gph fuel pressure regulator (p/n 174133). I have the return hose (going back to the fuel tank) connected to the port coming out of the bottom of the regulator, the fuel line coming from the gas tank is going into the left side and the fuel line going to the carb is exiting the right side of the regulator (this is how the instructions say to connect the lines). I have a 0-15lb Marshall fuel pressure gauge (p/n LS00015) mounted on the front of the fuel pressure regulator. All of these parts are brand new and I just got this setup installed this weekend.

Ok so here’s the problem. When I start the engine, there’s only a slight trickle of fuel going into a clear/see through Fram fuel filter I have inline right before the carb (between the fuel pressure regulator and the carb). The fuel pressure gauge started out reading 2 psi, but dropped to zero. I have no idea how the engine is running because it doesn’t look like it’s getting any fuel at all. So I tried adjusting the fuel pressure regulator and no matter if I have the adjustment screw all the way in or all the way out (or anywhere in between), the fuel pressure doesn’t change. I should be running around 5.5 to 6 psi to my Edelbrock carb, but it’s not anywhere close to that. And the fuel filter should be full and there’s barely any fuel in it at all. I don’t understand why I have no fuel pressure. I have the exact same setup on my 79 Bronco and I don’t have this issue. The only difference is I’m using a cheap Holley fuel pressure regulator on the Bronco (p/n 12-803). Can you guys advise?

 

One fuel filter is as good as ... if not better than a dozen ... as the first one to stop up will stop all flow. A single fuel filter after the pump & before the FPR is enough. If a filter is angled so that there is a air pocket trapped above the exit side, it may well just stay an air pocket forever, as air will stay above while fuel goes past it below through the exit. Any air trapped will be under the same pressure as the fuel. Should be on the outlet side ... should it not? I put a Holley 12-803 on 10 or so years ago, my gauge is on a tee that uses a short hose, I just insert it between the FPR and carb for testing / setting only, then remove it. I recently looked at the diaphragm in the cheap Holley FPR, it looks new so I just carry my new one as spare. It can be changed in minutes with just a Philips screw driver, no readjusting even. It stays set at 5.5 psi.

 

True on the filters.

Are there in & out marking on that regulator?
Thought in was on the bottom?

Also what dose the pump put out maybe it dose not need the regulator?
Dave ----

 

Try removing the filter before the pump. I am pretty certain that most of the electric pumps are ‘pushers’ and not ‘pullers’. They like to be mounted close to the tank and without any restrictions before them. I’m guessing that the pre-filter is causing too much restriction for the pump to work effectively.

 

TBear853--The reason I have a pre and post filter is because I read some instructions that advised to set it up that way. But you make a good point about the filters. Regarding the air pocket.....I didn't even think about that and it makes perfect sense. I'm praying that's all it is. I will work on seeing if I can remove the air from the system and see what happens. As far as the ports on the fuel pressure regulator....the diagram in the instructions shows the two ports on the side are inlet/outlet ports, the port on the bottom goes back to the fuel tank, and the port on the front is for the fuel pressure gauge. That's how I have it set up. I have a Holley 12-803 on my Bronco and it works fine. This Edelbrock FPR was a lot more expensive and I'm having issues, but the more I think about it, I think you're right about the air pocket.

FuzzFace2--Cartercarburetor.net claims it puts out 6-9 psi and 72 gph. Summit Racing claims it puts out 5-9 psi and 50 gph. Someone on the Amazon comments section stated it puts out 8-12 psi. So who knows, but it sounds like I need a regulator because from what I understand the Edelbrock carbs only want 5.5 to 6 psi.

Mwoj--That's a good idea. If I can't get the air out of the system (if there is air in it), I will remove the pre-filter and see what happens. I have the pump mounted in front and at the bottom of the tank (lowest point I could get it and as close to the tank as possible).

Here's the FPR instructions....

 

Ok on the in's & out's but brings up a question.
How is the return restricted?
If it is not then what keeps the fuel from going in the regulator and right out the return?
If you dont have it restricted is there a way to pinch it off for testing?
Dave ----

 

FuzzFace2--I'm a little confused with your question of "how is the return restricted". I didn't know a return line was supposed to be restricted. Is it supposed to be? I've never heard that before. So to answer your question, it's not restricted at all. I have a 3/8" fuel line connected to the port that goes back to the tank at the FPR and at the other end it's connected to a port that dumps into the fuel tank filler neck. No restriction at all, just free flowing. But that's how my Bronco is set up also and I have no issue with it.

And I understand your question regarding "what keeps the fuel from going in the regulator and right out the return?" That makes sense. But to answer that question, I'm assuming the solution to that problem would be designed into the FBR somehow. Maybe with the adjustable screw on top? I have no idea, I'm just assuming. You would assume that if the return to tank line was supposed to be restricted somehow, they would mention that in the instructions. But there's no mention of it that I can find.

And yes, I can pinch off the return line and see if that makes a difference. I will try that.

Yesterday I tried to address the air pocket issue by turning the FPR upside down so the air would exit out the return port going back to the fuel tank. I even turned the key on to activate the pump and flow fuel through it hoping it would force the air out. That didn't work. So plan B is to remove the pre-filter and see if it's causing a flow restriction. But I'm currently waiting on a couple fuel line fittings to arrive on Friday before I can do that. So Sunday I will remove the filter and see what happens. If that doesn't produce positive results, then I'm going to remove the post-filter and see what happens (process of elimination). Part of me wonders if the FPR instructions are wrong because on my the Holley FPR on my Bronco, the fuel line coming from the gas tank that provides fuel is connected to the port on the bottom of the regulator. But on this Edelbrock FPR, that port is the return to tank port. I'm wondering if the return to tank port on the Edelbrock should be the fuel supply port and one of the ports on the side should be the return to tank port. Who knows; {'m just brainstorming at this point.

Your thoughts?

 

Is that the Bronco with the Holley 12-803 FPR? It doesn't use a return line as far as I know, just has two outlets on opposite sides, inlet is in the bottom. I do see where Holley recommended a course filter before the FPR, and a finer filter after it ... but I have just one after my pump in the line to the FPR. It's enough.

The only way you'll get all the air out is point the filter outlet straight up, and even then next week will maybe be air in there again unless you keep it pointed straight up. That air is trapped, but fuel flows out under it.

 

Tbear853--The Holley FPR I'm using is the 12-803BP. I misspoke earlier when I said I have the 12-803. I forgot the BP on the end of it. This is the return style Holley FBP. The instructions with the Holley recommend a pre and post filter, like you stated. This is why I set mine up this way. But I'm going to remove the pre-filter for testing purposes. I hope this is just an air pocket issue. I'll keep working on this and see if I can figure it out. I'm waiting for some fuel fittings to arrive and then I can work on this some more.

 

I have the trapped air pocket deal going on with my Wheel Horse and my two Gold Wings always had it. Only the clear cased filters do it you know. (Well, except those glass bowl filters like on some old farm tractors ... but they did have the exit at the top.)
My '77 does not have it, 'cause I use a metal cased 3/8" inline filter on it .... or maybe it does and I just can't see it. All my Fords have metal cased filters.

Back in the '70s a friend and I were in a local speed shop, he bought one of those glass with replaceable element filters and even some spare filters for it. It was a glass tube between two chrome ends with O-rings to seal. I was there when he put it on, one of us tightened it to stop it leaking ... it suddenly leaked big time. He ripped the remains off, chucked it all in the trash & went back to a plain all metal filter ... problem solved was my thinking. He was sure the air bubble was because of the leak ... and I have no idea why I told that story. Perhaps just to brighten your day?

 

a courser pre filter for the pump is to protect the pump from particulate that might (read that as likely) be in your gas tank. the finer post filter is to protect the rest of your fueling system from the possibility of something going wrong with the pump and the pump itself sending bits of itself through the rest of the fuel system.

in this case, 2 filters are absolutely better than one because neither by itself is able to offer the same protection to the at risk components. the 3rd one you have does seem pointless to me, but these filters would decrease volume and not pressure. it would only impact pressure when the volume can't keep up with the demand. if the line only has 2 psi when not running and drops to zero when running, you might have a volume issue, but you for sure have a pressure issue. if you want to run without a prefilter like others do here, it's your fuel pump you are putting at potential risk and you can just carry a spare, but a filter will more than likely slowly clog and give you some running issues before it leaves you on the side of the road where i don't think you'll get the same warning with a pump going out... i'd prefer to get gas on me in my driveway when i planned a time to change the filter rather than on the side of the road.

assuming your new parts work correctly (not necessarily something we can rely on just because they are new) i would guess that either you're pre-filter has clogged up (or the sending unit/sock, or there isn't enough fuel in the tank) or it's the way you have the pressure regulator installed. if you install it incorrectly. my gut is that it's the pressure regulator... i'd swap the inlet and outlets around even through they appear like you can use them either way and then play with the adjustment screw. I've installed a pressure regulator backwards and it sort of sounds like what you are experiencing. if that didn't work, i'd rig up the fuel pressure gauge to be inline before the regulator for testing purposes. you'll have ruled out the regulator completely doing this.

 

You can see why I asked if your FPR was hooked up right after seeing how the Holley FPR is hooked up.
Both look and adjust the same so why not plumb the same?

As for the resistance on the return line.
What keeps the fuel from going into the FPR and right back out the return to the tank?
Liquid will always find the easy path and then might be back to the tank and not the carb.
That is why I said to pinch off the return line and see if the carb gets fuel.

I ran a Holley blue pump and FPR, no return on my drag car and never had any issues and would run them again if I had to.
It was a simple system Fuel cell in trunk> short brade to a Fram canister fuel filter> hard Alum line to engine bay into the FPR> braided line to carb.
I did run a FP gauge think was in the other port on the FPR.

As for the filters you can see into they will all show "air trapped" but never give any issues when running.
NEVER EVER RUN THEM GLASS FILTERS!
The glass can crack / break and spray gas all over and catch fire.
Dave ----

 

Tbear853--You did brighten my day with your comment. I actually chuckled out loud...LOL. Once upon a time many years ago I used one of those glass filters you were talking about and had the same leaking issue. I removed it, threw it in the garbage and never used one of them again. They are garbage!!

Uzikaduzi--I totally agree with you about the pre and post filter setup and that's why I followed the instructions and installed a pre and post filter. It makes total sense on why they suggest to set it up this way. And they are not the cheap fram filters either. The pre-filter is a 100 micron filter and the post-filter is a 40 micron filter. I do have a cheap clear fram plastic filter between the FPR and the carb and the only reason I have this filter is so I can see if there's fuel flowing or not. Had I not had this filter, I would have never known I'm having the issue I'm having. I've heard they're not very good filters, but who knows if that's true. But that's why I have the other 2 filters. The only reason I'm going to remove the pre-filter is to see if it makes any difference. The air pocket might be in that filter. Who knows. Once I get this resolved, I plan on running pre and post filter, just like I have on my Bronco. I have the hoses to the FPR set up exactly how the instructions say to connect them (instructions posted above). But where the return to the tank port is on this Edelbrock FPR is where the fuel supply line is on the Holley. I don't understand why they're different, but I just might swap the lines and see what happens if removing the pre-filter doesn't reveal the problem. Question.....threading the adjustment screw on the FPR in farther (turning it clockwise), that increases the fuel pressure....correct? And loosening it (counter clockwise) reduces the pressure???? Do I have that right?

FuzzFace2--Yeah, plumbing it the same makes sense. But I just followed the instructions because I assume the manufacturer knows more than I do. But since it's not working, I'll swap the lines and see what happens. I will also pinch off the return line and see if that makes a difference.

 

idk if different regulators are different and I don't have tons of experience, but tightening should increase pressure i think (clockwise) like you said, but once you figure out what i think is a volume rather than a pressure issue, you'll be able to see right away which direction does which... i don't think it's that you are adjusting it incorrectly because i'm guessing the first thing you tried was turning it all the way in and then all the way out without change right?

 

uzikduzi--Yes the very first thing I did was adjust the screw and no matter how much I tightened or loosened it, it didn't change the psi or the flow. You mentioned you think it's a "volume" problem. I'm trying to wrap my head around that. I'm using 3/8" fuel line from the tank, back to the tank and to the carb. Where do you think the issue is in relation to volume? Do you think the fuel pump can't keep up with the volume (maybe the flow back to the tank)? Someone mentioned needing a restriction. Should the fuel line going back to the tank be smaller that the others; say maybe 5/16"? Would that create enough restriction? The volume issue doesn't make sense to me since I have the exact same setup in my Bronco and I don't have this problem. The first thing I'm going to do when I get a chance is pinch off the return line and see what happens. That may answer some questions. Then I'll address the air pocket issue and go from there. Hoping to work on this Sunday.