Fuel Pressure Regulator Question...

[Wild Mango]

Stick with it. The terminal voltage with the pump running should be within 5% of the battery terminal voltage with the pump running. However, if the connections to the pump are dodgy the pump won't be getting the juice, those Carter connections with the knurled studs are not the greatest for on and offing.
Restrictive line fittings will impede flow but they will not impede static pressure (pump pushing against a block). Are your initial pressure readings static? They must be to give you a base line. If the pump will not reach rated pressure against a static block, then;
1/ Input to the pump is severely restricted.
2/ Pump is not getting full electrical power.
3/ Pump is faulty.
4/ Pressure measurement is inaccurate.
Since you keep getting 4.5psi as a reading my nasty suspicious mind thinks 4/. This is the commonest one I see from customers.

As Claude Cessna said, extracating himself from another wreck, "I don't like these things right now but they will never beat me".

 

[Screaming Metal]

Stick with it. The terminal voltage with the pump running should be within 5% of the battery terminal voltage with the pump running. However, if the connections to the pump are dodgy the pump won't be getting the juice, those Carter connections with the knurled studs are not the greatest for on and offing.
Restrictive line fittings will impede flow but they will not impede static pressure (pump pushing against a block). Are your initial pressure readings static? They must be to give you a base line. If the pump will not reach rated pressure against a static block, then;
1/ Input to the pump is severely restricted.
2/ Pump is not getting full electrical power.
3/ Pump is faulty.
4/ Pressure measurement is inaccurate.
Since you keep getting 4.5psi as a reading my nasty suspicious mind thinks 4/. This is the commonest one I see from customers.

As Claude Cessna said, extracating himself from another wreck, "I don't like these things right now but they will never beat me".

Yea Mango.....I think he ought to dummy everything up on the work bench as much trouble as he's having with this thing....:rofl:.....he ought to read 12.5 or at least 12.0 volts at the pump...........if his battery was way low.....it'd still build pressure.........probably within 5-10% of full....which.......with a 12 or 14 psi pump....be well over his 4.0-4.5.............I think he might need to try another pump to check things out..........certainly that holley blue pump won't never be taxed but darn.............

 

[Hotrod46]

I checked the voltage to the pump and it shows to be almost 12 volts.

Engine

Sorry to see that you're still having trouble. The wire feeding your pump should be big enough to supply full battery voltage (at the pump) with almost no voltage drop (with the pump running). With the engine running, your system voltage should be around 14 volts. You should be seeing that or VERY close to it at the pump.

If the wire is under sized or not supplying full voltage for some reason, you may need to install a dedicated relay circuit to supply the pump.

Try running a heavy gauge wire (10-12 gauge) temporarily directly from the pump to the battery. Also, make sure you have a GOOD ground, even if that means running a ground wire directly to the battery.

Everything Metal and Mango have said is good advice.

Good luck.

Mike

 

[Screaming Metal]

Engine

Sorry to see that you're still having trouble. The wire feeding your pump should be big enough to supply full battery voltage (at the pump) with almost no voltage drop (with the pump running). With the engine running, your system voltage should be around 14 volts. You should be seeing that or VERY close to it at the pump.

If the wire is under sized or not supplying full voltage for some reason, you may need to install a dedicated relay circuit to supply the pump.

Try running a heavy gauge wire (10-12 gauge) temporarily directly from the pump to the battery. Also, make sure you have a GOOD ground, even if that means running a ground wire directly to the battery.

Everything Metal and Mango have said is good advice.

Good luck.

Mike

Yea HotRod......I think its possible a combination of things in his case, voltage drop.......if he's got the frame painted an doesn't have star washers where it'll dig to bare metal......grounding issues, possibly. Possibly a restriction on the suction side????????????? Wish I was there to help.....but.....thats what Roddin' is all about though..........

On a lighter note........it once took me 2 1/2 weeks to find a short in a ignition system.........I had people from the factory come by and couldn't find it!!!!!! Ha!

Know what it was??????

Someone had reworked the distributor and the whole system.....when they bolted down the ignition module, a human hair had fallen off someones head, got bolted down to the metal shell under the ing.module, and when they plugged it in, it got tangled in the connectors terminals.............it was a dead short cause by a hair that is pure protein.............go figure.....................:rofl:....................:toast::lol::lol:...........though at the time I didn't think it was funny.......ha!

 

[Hotrod46]

[quote name='Screamin' Metal'] Wish I was there to help....[/quote]

Yeah, trying to diagnose problems over the net is tough. An extra set of eyes can be all it takes. Sometimes with frustration and fatigue, you can actually keep overlooking the problem. It's happened to me before.

[quote name='Screamin' Metal']a human hair had fallen off someones head, got bolted down to the metal shell under the ing.module, and when they plugged it in, it got tangled in the connectors terminals.............it was a dead short cause by a hair that is pure protein.............[/quote]

Now that's one for the books!:rofl: Something like that will add plenty of "colorful" words to your vocabulary!!:toast::lol:

Mike

 

[Screaming Metal]

Yea HotRod........a bunch of folks were laughing over that one..........I couldn't believe it.......I asked someone from a college or university about a hair conducting electricity..............they said if a furry animal leans agianst a electric fence....they'll get shocked......its a extremely good conductor..............:rofl:

 

[engine24355]

Well, I set up a bench top fuel pressure test using my old pump first per the experts advice. Taking hotrod's advice, I used 12 ga. wire from the battery to the supplied carter connections. I am getting 4 lbs out of a 6 lb max pump which is an improvement with the bigger wire. I will try my new pump in the morning to see what pressure it yields. Seems like I should get at least 6 lbs out of that one as it is a carter 8 lb max pump. So, it looks like maybe the wiring size is at least one of the culprets. I have a fuel pump relay kit coming in tomorrow and from the results I have seen so far with the test, the relay should be an improvement. As usual, stay tuned for the next installment of the "Fuel Pressure Horror Show". Thanks again for all of the help guys!

 

[engine24355]

Okay, time for the latest installment. I tested the bigger carter pump and I only got 4.5 lbs after sever attemps. So, I went to one of my local parts stores that I have visited many times (so much that they ask me for pressure updates) and picked up a oem type Airtex 4.5 - 9 lb pump. Brought it home and hooked it up to my bench top testing station and got 9 lbs of pressure right off and it was still trying to inch up a little when I stoppeed testing (assume it would not keep building on a real application). This Airtex pump is a canister type similar in appearance to a metal fuel filter (does not hang down like the carter). After all of the issues with the carters I was pretty impressed that this little pump was cranking out some good pressure and doing it very quietly. The only problem is that the fittings are different than the 1/4 I am already set up for. The fittings are smaller so I would not be able to use the AN6 fittings with my braided line. So, the good news is I think I have finally isolated the issue to the pump itself. The question now is, do I try another carter pump or try to make this Airtex work with some adapters to fit AN6 fittings. What do you guys think?

 

[Screaming Metal]

Well Engine.....what I would do is ask the guys for a pump that'll achieve the pressure you want with the fuel lines your gonna be running...........since your already setup for the carter......that would be the way to go........I beieve the Sun Superpump.....which looked extactly like the Carter, bracket and all, would be a great substitute, IF, they can get you one.........I don't even know if these folks are still in business......I run checks on these pumps all the times cause we used them on our race engine stands.........unregulated......those puppies cranked out about 25PSI........if you didn't have your fuel line on right......it WOULD leak.

Go with something your already setup for.........NOW, if they'll let you bring up your little test rig.........see if another carter.....one of the hi Perf pumps would get to the nessary PSI........if they've got one.........

 

[Wild Mango]

I have a Carter GP 4070 rotary vane universal pump here for my son's bucket. Its rated at 6psi / 72gph- 267LPH. This is 4.4litres/minute, so if your sweet revvin' babe outstrips the pump it probably belongs on a B29.
So this pump, if it pressures somewhere over say 4psi and delivers more than 3 1/2 litres/minute into my measuring jug at that pressure (or close) is plenty good enough for me.
Don't forget;
1/ The fuel in the carburettor float bowls is not under pressure at all. It must never be at pressure over ambient atmospheric. The line pressure is on the supply side of the float valve.
2/ The float valves in the carb(s) are an on/off control. That is to say, the valve turns "off" when the float bowl is full, and turns "on" after the level has dropped a certain amount, about 3/16". This is called dead band. Effectively what it means is, sometimes the pump is against a static block (floatvalve shut) and sometimes it pumps flow (float valve open while the bowl(s) top back up.)
So, flows the thing that gets the job done, pressure is what encourages the flow.

 

[engine24355]

I have a Carter GP 4070 rotary vane universal pump here for my son's bucket. Its rated at 6psi / 72gph- 267LPH. This is 4.4litres/minute, so if your sweet revvin' babe outstrips the pump it probably belongs on a B29.
So this pump, if it pressures somewhere over say 4psi and delivers more than 3 1/2 litres/minute into my measuring jug at that pressure (or close) is plenty good enough for me.
Don't forget;
1/ The fuel in the carburettor float bowls is not under pressure at all. It must never be at pressure over ambient atmospheric. The line pressure is on the supply side of the float valve.
2/ The float valves in the carb(s) are an on/off control. That is to say, the valve turns "off" when the float bowl is full, and turns "on" after the level has dropped a certain amount, about 3/16". This is called dead band. Effectively what it means is, sometimes the pump is against a static block (floatvalve shut) and sometimes it pumps flow (float valve open while the bowl(s) top back up.)
So, flows the thing that gets the job done, pressure is what encourages the flow.

The Carter 4070 is the same pump I have (old one) that I replaced with the next step up (8 lb model). When running the test I did notice that the carters seemed to push much more fuel than the Airtex, but the pressure was much less. So, are you saying that I need to just stick with the carter for the flow over the pressure?

 

[Wild Mango]

Yep, I would go for flow. Thats what we need, delivery at the carb connection.

I should have said, most pumps are rated for open flow, no pressure, but I like to test them with a bit of pressure to pump against. That Carter I talked about might struggle to give me 3 1/2 LPM at 4 psi but I would expect it to go close. (and draw about 4 1/2A)
Pumps to feed carburettors are rated for open flow because thats what they are pumping in real life when the float valve opens.(of course the float valve has some restriction). Feeding a carburettor flow is the important consideration. Pressure is a secondary consideration.
So if you disconnect the carb connection and pump into a measure container you should expect close to the pump rated flow.

 

[Mike]

Guys, guys, guys, why are we making this harder than it has to be?

If you have a motor stalling at full throttle with 4.5 lbs of pressure, it is a volume issue. Plain, flat and simple. How much pressure do you think you are going to get by trying to run in the first place? I've seen off-brand needle/seat assemblies for Holleys that wouldn't seat at 5 lbs and I never ran the pressure over 7 lbs. on the race car.

If you were originally using the 12-804 Holley regulator, then 4 lbs. was all you were ever going to see out of it. The 12-803 is the high pressure carburetor regulator.

The number of carburetors on an engine does not dictate how much fuel pressure you need. At 6,000 RPM, a 350 inch motor is capable of pulling 608 CFM. If you have one 750 CFM carb or two 1150 CFM carbs, the motor is still only capable of pulling 608 CFM.

The determining factor on how many lbs of fuel that 608 CFM can carry is the density altitude. But if that variable can be controlled, the combination with the two 1150 CFM carbs can actually survive on a lower fuel volume than the single 750 CFM carb, because there are a total of four float bowls feeding the motor. Why do you suppose so many single 4 bbl racers use a fuel log?

Back in the dark ages, when they were unheard of, we put a Don Hardy V-8 kit in a Vega. It went about 3 hours before we shelled the rear end, so in went a Dana 60 and a set of ladder bars. The next problem was tossing the rear window out of the hatch when it would get hold of the ground. I digress. We had a fairly decent 331 inch motor that maybe made 1.5-1.6 (gimme a break, this was back in 1976) with an old Brandywine tunnel ram and a pair of 660 carbs. Note - I have not mentioned ever changing out the stock fuel system. At about 1,000 foot, the fuel pressure gauge would lay down on zero, but the car still had enough volume in the float bowls to pull through to the finish line. We changed out the pump with a Holley blue pump, installed bigger lines and the car ran the same ET and the same MPH.

How much fuel pressure do you need? Enough to overcome the weight of the fuel column leading to the carb/s (ever wonder why a Pro Stocker has the fuel cell up front?) and keep the float level above the power valve (or jets, if no power valve is used). Remember, if you increase line size to the front of the car, then the fuel column also increases in size and weight. Under hard acceleration, that weight will require more pressure to keep it moving.

Bigger rarely equals better.

 

[Screaming Metal]

Guys, guys, guys, why are we making this harder than it has to be?

If you have a motor stalling at full throttle with 4.5 lbs of pressure, it is a volume issue. Plain, flat and simple. How much pressure do you think you are going to get by trying to run in the first place? I've seen off-brand needle/seat assemblies for Holleys that wouldn't seat at 5 lbs and I never ran the pressure over 7 lbs. on the race car.

If you were originally using the 12-804 Holley regulator, then 4 lbs. was all you were ever going to see out of it. The 12-803 is the high pressure carburetor regulator.

The number of carburetors on an engine does not dictate how much fuel pressure you need. At 6,000 RPM, a 350 inch motor is capable of pulling 608 CFM. If you have one 750 CFM carb or two 1150 CFM carbs, the motor is still only capable of pulling 608 CFM.

The determining factor on how many lbs of fuel that 608 CFM can carry is the density altitude. But if that variable can be controlled, the combination with the two 1150 CFM carbs can actually survive on a lower fuel volume than the single 750 CFM carb, because there are a total of four float bowls feeding the motor. Why do you suppose so many single 4 bbl racers use a fuel log?

Back in the dark ages, when they were unheard of, we put a Don Hardy V-8 kit in a Vega. It went about 3 hours before we shelled the rear end, so in went a Dana 60 and a set of ladder bars. The next problem was tossing the rear window out of the hatch when it would get hold of the ground. I digress. We had a fairly decent 331 inch motor that maybe made 1.5-1.6 (gimme a break, this was back in 1976) with an old Brandywine tunnel ram and a pair of 660 carbs. Note - I have not mentioned ever changing out the stock fuel system. At about 1,000 foot, the fuel pressure gauge would lay down on zero, but the car still had enough volume in the float bowls to pull through to the finish line. We changed out the pump with a Holley blue pump, installed bigger lines and the car ran the same ET and the same MPH.

How much fuel pressure do you need? Enough to overcome the weight of the fuel column leading to the carb/s (ever wonder why a Pro Stocker has the fuel cell up front?) and keep the float level above the power valve (or jets, if no power valve is used). Remember, if you increase line size to the front of the car, then the fuel column also increases in size and weight. Under hard acceleration, that weight will require more pressure to keep it moving.

Bigger rarely equals better.

Mike????? A BRANDYWINE Tunnelram??????? oh oh......I haven't heard o that in a bunch o years my friend!!!!!!!

Hey.......I know engine is probably anxious to drive his rod,,,,,,as long as he can get about 6 PSI and then regulate it to about 4.5....he can bolt it up to the fuel line in his car....does a really hard launch, and he doesn't hurt for fuel and start missing..........I'd call it good.......I don't think he's gonna be linin' up agianst good ole Nanook anytime soon! Ha!...............

 

[engine24355]

Correct me if I am wrong, but it seems like the advice now is to go back to what I started with even though my pressure is not where holley says it needs to be. I understand the flow etc. and it does make sense. However, holley says more pressure. So I should not even consider the Airtex at all?

 

[Screaming Metal]

Correct me if I am wrong, but it seems like the advice now is to go back to what I started with even though my pressure is not where holley says it needs to be. I understand the flow etc. and it does make sense. However, holley says more pressure. So I should not even consider the Airtex at all?

Hey Engine.......I know your having trouble with your fuel system.......and I want to see you get it right! I wasjust saying to Mike that I kinda agree with him about not getting too overly complicated.....

I'd go with what Holley says.....ehy.....they're the guys that designed this thing!!!! Ha! I'm sorry Engine.....I didn't mean to make you think you were messing up, my friend.

Your on the right path.....we need to get where the folks say we need to be...........with enough pressure.

 

[RPM]

I'd say buy a Holley blue pump and set the regulator at 6 psi and you won't have to look back. How long have you been messing with this?

 

[Screaming Metal]

I'd say buy a Holley blue pump and set the regulator at 6 psi and you won't have to look back. How long have you been messing with this?

Yep....thats what I'm thinking......the fella needs to be driving.....not wrenchin at this point...............

 

[Mike]

Actually, I would recommend a Holley red pump. I've no explanation for why, but it seems the red pump will outlive the blue pump in a street-driven application. I've never been a very big fan of the blue pumps, as it seems they are always in need of freshening or replacement. And when it comes to race pumps, the big Mallory pumps are hard to beat.

Yeah, an old Brandywine intake. Years ago, they did up one of their fiberglass tunnel rams for the V-6. We had a top made up for a Dominator and a split. The split sat up-front in a fore and aft positioning and the full carb sat in the rear in a side mount positioning. (Talk about an SOB to hook a throttle cable to!) The intake never worked very well. We made the same top up for one of Hogan's intakes and it helped.

When we went back to running a pair of 4150's, they were a pain to make linkage for, as well. The front carb sat with the linkage off the front of the intake and the rear carb with it's linkage off the rear. We had to mill the choke side of the baseplates and the choke attachment bosses off, in order to get the carbs close enough on the plenum. The float bowls had to come off to get to button-head screws bolting the choke side of the baseplates down. We would then make up slugs to fill the dead throttle bores. Racing a V-6 is not for the faint of heart.

 

[engine24355]

One of my first thoughts was to try a holley blue, but then read that the blue is more for racing and not street driving as Mike mentioned. I was just thinking that I should probably try a red as mentioned by hotrod and see what happens. My only concern (really just more trouble) is changing the mount etc. since carter uses a different mount and inlet / outlet size (1/4). The holleys use 3/8 if I remember right, but nothing a good adapter will not fix I guess.