Anyone with a Holley carb on fc
10-01-13, 02:44 PM
#1
Senior Member
Thread Starter
Anyone with a Holley carb on fc
I have a Holley carb on my 89 gtu and im having issues with fuel pressure,i have a fpr but no matter how i try to adjust it ,it stays at only 3psi any help would be greatly appreciated..car still using stock fuel pump ..just tell me what i gotta do
10-01-13, 09:32 PM
#2
Rotorhead
Join Date: Feb 2001
Location: Charlottesville, Virginia, USA
Posts: 9,136
Likes: 0
Received 39 Likes
on
33 Posts
The stock high-pressure EFI fuel pump is completely inadequate for use with a low-pressure carb. Whoever converted the car is clueless, so I suggest that you go to the Racing Beat website and read their guidance for their Holley intake kit so you can see what else you need to fix.
http://www.racingbeat.com/RX7-1986-1...its/18045.html
http://www.racingbeat.com/RX7-1986-1...its/18045.html
10-01-13, 10:17 PM
#3
i'm curious how they managed to even drop the pressure that low to the point of still getting sufficient fuel.
why anyone would bother with the stock EFI pump on a carb, well.. no. buy a carbed pump and figure out how they restricted the system and remove it.
why anyone would bother with the stock EFI pump on a carb, well.. no. buy a carbed pump and figure out how they restricted the system and remove it.
10-02-13, 06:34 AM
#5
Some fuel pressure regulators are designed to work in applications like this...I think the Aeromotive one? They can regulate 30-40psi down to whatever you need for the carb.
Or maybe its the Mallory 4309 that I have?
Damn FC fuel pumps lol. I would get a Mallory fuel pump and Mallory 4309 reg. They're both cheap and work great.
Yeah your fuel pressure is too low. Holley recommends 5 psi minimum and 7.5 psi max.
I am going to put a Holley on my 13B swapped FB incase your wondering.
Or maybe its the Mallory 4309 that I have?
Damn FC fuel pumps lol. I would get a Mallory fuel pump and Mallory 4309 reg. They're both cheap and work great.
Yeah your fuel pressure is too low. Holley recommends 5 psi minimum and 7.5 psi max.
I am going to put a Holley on my 13B swapped FB incase your wondering.
10-02-13, 08:33 AM
#6
Some fuel pressure regulators are designed to work in applications like this...I think the Aeromotive one? They can regulate 30-40psi down to whatever you need for the carb.
Or maybe its the Mallory 4309 that I have?
Damn FC fuel pumps lol. I would get a Mallory fuel pump and Mallory 4309 reg. They're both cheap and work great.
Yeah your fuel pressure is too low. Holley recommends 5 psi minimum and 7.5 psi max.
I am going to put a Holley on my 13B swapped FB incase your wondering.
Or maybe its the Mallory 4309 that I have?
Damn FC fuel pumps lol. I would get a Mallory fuel pump and Mallory 4309 reg. They're both cheap and work great.
Yeah your fuel pressure is too low. Holley recommends 5 psi minimum and 7.5 psi max.
I am going to put a Holley on my 13B swapped FB incase your wondering.
Trending Topics
10-02-13, 11:55 AM
#8
Senior Member
Thread Starter
called racing beat they told me i can pull the fuse for the stock fuel pump and use the return line to put a mallory or holley fuel pump..anyone disagree?
10-02-13, 12:02 PM
#9
Senior Member
Thread Starter
if there is such a product there shouldn't be. it would be like putting a turbo on a car and then putting a restrictor in the exhaust so that the turbo produces no boost, blocking up the exhaust flow and creating excessive heat in the engine from the additional work. the fuel system is the same way, the fuel will get hotter, boil quicker when shut down, possibly vapor lock, burn out the pump, etc, etc, etc. do a peak pressure test on an EFI pump and tell me if that sounds like it is good for the pump to be doing that much work ALL the time.
10-02-13, 12:17 PM
#10
Senior Member
Jesus its 10 minutes of work to take the pump out. Do it right the first time and also check the inside of your 25 year old fuel tank.
10-02-13, 05:32 PM
#11
Senior Member
iTrader: (3)
Join Date: Oct 2008
Location: Glenwood, Iowa
Posts: 447
Likes: 0
Received 0 Likes
on
0 Posts
Wouldn't regulating from 40psi down to 6psi actually be less work on the pump? The way I understand a return type fuel system is that the more it flows back to the tank the lower the pressure. So basically it'd be a regulator all the way open. Close the return on the reg and the pressure increases.
Unless of course the regulator is before the injectors/carb and is return-less. I don't know carbs so maybe they don't run return type fuel systems. Which then I'd feel like an idiot for opening my trap.
Unless of course the regulator is before the injectors/carb and is return-less. I don't know carbs so maybe they don't run return type fuel systems. Which then I'd feel like an idiot for opening my trap.
10-02-13, 11:37 PM
#13
Senior Member
iTrader: (3)
Join Date: Oct 2008
Location: Glenwood, Iowa
Posts: 447
Likes: 0
Received 0 Likes
on
0 Posts
No, just trying to educate myself, not trying to start anything.
Why would you use the return? I think you misunderstood my questions. I'm saying the standard efi flow direction with efi pump, the carb, a return type regulator set open far enough to go that low, something like this maybe, and back to the tank through the stock return line. Again, I don't know if carb setups run return type or return-less fuel systems.
If this is plausible, how would a wide open regulator put more stress on a pump? Like I said before, according to my knowledge, a regulator set that low would be more open to drop the pressure that much. I haven't played with aftermarket regulators yet, waiting on my Aeromotive so I can finish my fuel setup.
Why would you use the return? I think you misunderstood my questions. I'm saying the standard efi flow direction with efi pump, the carb, a return type regulator set open far enough to go that low, something like this maybe, and back to the tank through the stock return line. Again, I don't know if carb setups run return type or return-less fuel systems.
If this is plausible, how would a wide open regulator put more stress on a pump? Like I said before, according to my knowledge, a regulator set that low would be more open to drop the pressure that much. I haven't played with aftermarket regulators yet, waiting on my Aeromotive so I can finish my fuel setup.
10-03-13, 02:00 PM
#14
you can use both hardlines for feed and return but i would remove the stock EFI pump and run an extension to a strainer to where the stock pickup sits.
run an external pump below the fuel level suitable for a carb.
then your regulator should work the way it is supposed to.
problem with the thought that running the EFI pump without any restriction is it moves way too much fuel at low pressure, if the regulator can even bypass that much fuel and keep the pressures regulated well is another story. fuel gets hot in being circulated, too much pump and it becomes a fuel warmer.
run an external pump below the fuel level suitable for a carb.
then your regulator should work the way it is supposed to.
problem with the thought that running the EFI pump without any restriction is it moves way too much fuel at low pressure, if the regulator can even bypass that much fuel and keep the pressures regulated well is another story. fuel gets hot in being circulated, too much pump and it becomes a fuel warmer.
Last edited by RotaryEvolution; 10-03-13 at 02:03 PM.
10-04-13, 10:45 AM
#15
Senior Member
iTrader: (3)
Join Date: Oct 2008
Location: Glenwood, Iowa
Posts: 447
Likes: 0
Received 0 Likes
on
0 Posts
Didn't take heat into consideration. But, unless OP is planing on tracking the car, I don't think fuel temp is going to be an issue. I'm currently driving around on an Aeromotive 340 Stealth with a stock regulator, now that's gotta to circulating quiet a bit and warming up but I've had no issues.
10-04-13, 05:36 PM
#16
sometimes it is unavoidable but i always worry about fuel temperature and it affecting fuel volume through the pump. less of an issue in this case but it still seems like a cheap workaround that can cause issues if it isn't monitored.
on one car i have set up on ethanol it runs nearly 800litres per hour through 1/2" line, so far it hasn't had any issues but that is a ton of fuel moving around..
on one car i have set up on ethanol it runs nearly 800litres per hour through 1/2" line, so far it hasn't had any issues but that is a ton of fuel moving around..
10-05-13, 12:26 AM
#17
Rotorhead
Join Date: Feb 2001
Location: Charlottesville, Virginia, USA
Posts: 9,136
Likes: 0
Received 39 Likes
on
33 Posts
Also, as you have noticed, the regulator has a difficult time dealing with it.
10-05-13, 01:38 AM
#18
Senior Member
iTrader: (3)
Join Date: Oct 2008
Location: Glenwood, Iowa
Posts: 447
Likes: 0
Received 0 Likes
on
0 Posts
I'm sorry to contradict Evil Aviator but, how is that a lot of strain? Just trying to learn. In school we learned a pump doesn't make pressure, it makes flow and supports pressure. A regulator is just a restriction, which in turn increases pressure, but with a regulator set to bypass at ~8 psi for a carb'd application, given the regulator will flow enough, I just don't see how that is more strain.
I know my regulator isn't up to the task which in turn, I'm assuming, is raising my fuel pressure because it can't bypass enough. But, I've got an Aeromotive in the mail right now so that'll be a non-issue.
RotaryEvolution, I've recently switched to E85 and have noticed that it needs quite a bit more fuel. I'm glad I went with the 340 stealth, which is probably more pump than I need. Luckily, I'm still getting the same mileage I was on just regular super unleaded but at almost $1 cheaper a gallon, though 15mpg isn't great either way. I should probably keep my foot out of it a bit more... HAHA!
I know my regulator isn't up to the task which in turn, I'm assuming, is raising my fuel pressure because it can't bypass enough. But, I've got an Aeromotive in the mail right now so that'll be a non-issue.
RotaryEvolution, I've recently switched to E85 and have noticed that it needs quite a bit more fuel. I'm glad I went with the 340 stealth, which is probably more pump than I need. Luckily, I'm still getting the same mileage I was on just regular super unleaded but at almost $1 cheaper a gallon, though 15mpg isn't great either way. I should probably keep my foot out of it a bit more... HAHA!
11-02-13, 07:26 PM
#19
Dragons' Breath
Join Date: Sep 2010
Location: Pump Handle, SK. Canada
Posts: 1,129
Likes: 0
Received 2 Likes
on
2 Posts
Holly Carbs ,Fuel Pumps +Regulator:
Holly Fuel Pumps with Regulator:
This is a very common combination and it has alot of problems. The pump puts out too much pressure so you have to buy a regulator for it. The Regulator is just a restrictor that inhibits flow. This causes a huge loss of Volume and overloads the pump causing alot of noise and premature failure. This results in the float bowl going low or empty under hard acceleration and causes cornering problems with the pump still working it's guts out because you have RESTRICTED it's flow .
I can't think of a carb that demands high pressure . I'm sure there is but not the ones being discussed here .
Get a high volume low pressure pump , Many different sizes to choose from . The difference is in how the pump moves the fuel flow , vane or what ever that determines the flow and pressure combination .. these guys are right 88na
Have a good one . JMO
This is a very common combination and it has alot of problems. The pump puts out too much pressure so you have to buy a regulator for it. The Regulator is just a restrictor that inhibits flow. This causes a huge loss of Volume and overloads the pump causing alot of noise and premature failure. This results in the float bowl going low or empty under hard acceleration and causes cornering problems with the pump still working it's guts out because you have RESTRICTED it's flow .
I can't think of a carb that demands high pressure . I'm sure there is but not the ones being discussed here .
Get a high volume low pressure pump , Many different sizes to choose from . The difference is in how the pump moves the fuel flow , vane or what ever that determines the flow and pressure combination .. these guys are right 88na
Have a good one . JMO
11-02-13, 10:45 PM
#20
Rotorhead
Join Date: Feb 2001
Location: Charlottesville, Virginia, USA
Posts: 9,136
Likes: 0
Received 39 Likes
on
33 Posts
Yes, but hopefully you also learned that low fuel pressure + high fuel temp = cavitation and vapor. Since fuel is used to cool and lubricate the pump, this condition will start running the pump in a semi-dry condition, creating strain, and possibly burning it up.
11-03-13, 09:52 AM
#21
Engine, Not Motor
iTrader: (1)
Join Date: Feb 2001
Location: London, Ontario, Canada
Posts: 29,789
Likes: 0
Received 108 Likes
on
91 Posts
It seems beyond a number of posters that there may be a design difference in a pump designed for high pressure vs. one for low pressure. For example, vanes vs. gerotors.
11-03-13, 02:34 PM
#22
Senior Member
iTrader: (3)
Join Date: Oct 2008
Location: Glenwood, Iowa
Posts: 447
Likes: 0
Received 0 Likes
on
0 Posts
Evil, I know high temp can cause vapor lock, but last time I checked specs on most pumps, they flow better at lower pressures, so how would that cause cavitation?
Gerald, if you read what I had said, fuel pumps do not put out pressure, they put out flow and support pressure. If it put out too much pressure, how would a regulator bring it back down??? Try this, take a fuel pump, hook a pressure gauge onto the outlet, bypass the regulator, and run a return back to the tank. Tell me how much "pressure" shows up and what amount of fuel it moves. Now, grab an adjustable regulator and slowly bump up the pressure and tell me how much more noise it makes at lower pressures compared to higher? Noise seems to be a decent metric on how hard a pump is working, right?
Gerald, if you read what I had said, fuel pumps do not put out pressure, they put out flow and support pressure. If it put out too much pressure, how would a regulator bring it back down??? Try this, take a fuel pump, hook a pressure gauge onto the outlet, bypass the regulator, and run a return back to the tank. Tell me how much "pressure" shows up and what amount of fuel it moves. Now, grab an adjustable regulator and slowly bump up the pressure and tell me how much more noise it makes at lower pressures compared to higher? Noise seems to be a decent metric on how hard a pump is working, right?
11-03-13, 03:05 PM
#23
Rotorhead
Join Date: Feb 2001
Location: Charlottesville, Virginia, USA
Posts: 9,136
Likes: 0
Received 39 Likes
on
33 Posts
I suggest that you try it and see for yourself. Some people learn better by experience. Indications will be fluctuating fuel pressure and increased noise from the pump. Try it on a hot day with about 1/8 to 1/4 tank of fuel if you want a faster manifestation.
11-03-13, 04:21 PM
#24
Senior Member
iTrader: (3)
Join Date: Oct 2008
Location: Glenwood, Iowa
Posts: 447
Likes: 0
Received 0 Likes
on
0 Posts
I have tried this, it was part of a demo I did for a project in school to explain the very concept of pumps supporting pressure, not making pressure. There was no increase in noise, except when we slightly pinched off the return line to demonstrate a regulator. Wide open there was very little, if any fuel pressure, showing on the gauge and flow did not fluctuate as it came out of the return line back into the test container.
11-03-13, 05:57 PM
#25
Rotorhead
Join Date: Feb 2001
Location: Charlottesville, Virginia, USA
Posts: 9,136
Likes: 0
Received 39 Likes
on
33 Posts
I have tried this, it was part of a demo I did for a project in school to explain the very concept of pumps supporting pressure, not making pressure. There was no increase in noise, except when we slightly pinched off the return line to demonstrate a regulator. Wide open there was very little, if any fuel pressure, showing on the gauge and flow did not fluctuate as it came out of the return line back into the test container.