fuel pressure question

[jerritt]

my car is ideling at about 60 psi of fuel and i have the tt340 fuel pump with 60lb injectors. the adjustable fp regulator i have seems to have no control over it so how could i test to see if thats working properly first? with this pump it says that you may have to do some work to the return line for high fuel pressure so im aware of that but what is the cheapest way of going about this. i heard somewhere that you could just make the connections on the return line bigger rather then increasing the size of the whole line has anyone done this and how did you do it? thanks alot
jerritt

 

[earlbrown]

Sounds like you might have a pinched return line.

 

[Ttype6]

Another victim,although you were warned that this might happen on the sight that you bought the pump from,you bought it anyway. Why? Biggest problem in this forum currently,but you were warned. Another vender who sells a big pump doesn't tell you that this might happen. You'll have to drill out the Saginaw fittings in the return line. There are two of them. It's likely that a different regulator might also be needed. This could have been avoided if you would have bought a Walbro 255 LPH pump.

 

[jerritt]

well i went against the walbro becuase there were a few post about them failing quickly idk i just went with this one becuase i bought the injectors from them as well nothing wrong with the pump and its great i just clearly made a mistake and went a little to big but im trying to figure out whats the best solution just buy the walbro or increase the return lines? if i just drill out the saginaw fittings will that be enough im trying to hear from someone that has already gone through this. it seems to me that it will still be backed up in the return line at the sending unit on top of the tank because that would be thee same size? idk just a thought what do you think i need to fix this fast before i break the pump.... thanks again
jerritt

 

[we4Mateo]

... If you can get it down to 43 lbs,your good. If you can't you'll need to drill the two Saginaw fittings to a larger diameter on the return line. One is located where the return line connects to the regulator. The other one is located where the return line connects to the steel line where the line sticks out of the frame by the steering box.

search

 

[Ttype6]

well i went against the walbro becuase there were a few post about them failing quickly

Again,those people who spew this crap have caused you a problem that you should never have had. By the way,the pump you bought is a Walbro. It's just a bigger Walbro. You'll have to drill out the fittings to find out where that gets you. If that doesn't get you all the way to where you need to be,you could then try a Red Armstrong regulator as it has a larger diameter orifice in it. If these things don't work,you'll have to buy a smaller pump or replace the return line.

 

[pmoore4321]

Ttype6 is right. You are going to have to either drill out your Saginaw fittings or run another return line. I installed a high-flowing pump about 2 years ago and could never get the fuel pressure to go below 42#. The vacuum line had no effect on fuel pressure. This resulted in all sorts of problems. Soot at the tailpipes, a "hunting" idle, slow spool, poor economy, low BLMs, etc. After running a new return line, my car is running better than it ever has. I went back and reviewed all the "problem" threads I started on this board over the past 3 years and just about all of them were related to this issue.

http://www.turbotweak.com/forum/showthread.php?1968-Fuel-Return-Line-mods-for-bigger-pumps

 

[87GN_70GS]

What you can do to verify if the problem is the return line is to disconnect it. Disconnect the return line at the bottom of the regulator. If you can move it out of the way, attach a fitting with a length of hose and have it discharge into a can or fuel container. Or you can disconnect the line connection where it disappears into the frame and attach a hose there and discharge into a can. Run the engine at idle to see if fuel pressure drops. If so, it's the line. If not, it's prob the regulator.

 

[Ttype6]

What you can do to verify if the problem is the return line is to disconnect it.

I hate to even say that the problem is the return line because the real problem is the pump. There's nothing wrong with the return line. Many people have supplied and are supplying gasoline to their 1,000 hp motors with the stock feed and return lines. How can they feed their motors all the fuel it needs without overcoming the stock return line? They use two smaller Walbro pumps. The second pump comes on at a certain boost level so the return line never gets overwhelmed. People in the turbo Buick world have been doing this for many years. Then comes a new fuel pump that is larger and the proponents of this pump will tell you that the other pump is junk to help sell you the new pump but they never want to warn you of the problems that it creates. That is so wrong. Many people have been misled and have incurred more labor and expense and heartache than needed. However Eric is one who does warn people about the problem that might be created and that is to his credit. He gives complete information so the buyer can make a more informed choice. In this case and others,the warning was dismissed. Why? Because the buyer is motivated buy fear. Good job again guys.

 

[Ttype6]

my car is ideling at about 60 psi of fuel and i have the tt340 fuel pump with 60lb injectors. the adjustable fp regulator i have seems to have no control over it so how could i test to see if thats working properly first? with this pump it says that you may have to do some work to the return line for high fuel pressure so im aware of that but what is the cheapest way of going about this. i heard somewhere that you could just make the connections on the return line bigger rather then increasing the size of the whole line has anyone done this and how did you do it? thanks a lot
jerritt

Do you have the pump hot wired? If so,you could return the wiring back to stock. Having it hot wired just makes the problem worse. Drilling the lines always helps because it is a substantial restriction. Another reason to do it is because it costs almost nothing.

 

[nonosv6]

You could regulate the voltage to the pump then at a set boost level with. a hobbs give it full voltage ...

 

[nonosv6]

I mean lower the voltage

 

[earlbrown]

I wouldn't starve a DC motor for power. It'll drastically shorten it's life. If this pump is so badass it's inflating the return line I kinda want to assume it needs some serious current.

I guess I've never heard of this pump as I've got a hot wired Supra pump and the only mods to my fuel lines are opening up the feed line. I've even got a modified stock FPR and can pull the pressure down into the low forties. (no idea how far down it will go as I set it at fotey5)

 

[nonosv6]

What does a pump controller do then like the one weldon and aeromotive have? Not being a wise ass earl ,jus wondering...Have u checked the return line for some kind of blockage ?

 

[nonosv6]

Just checked weldons sight, its a pwm ,so basically it interrupts the voltage to the pump 12000 times per second to bring down pump rpm. Could go that route too.

 

[Ttype6]

Just checked weldons sight, its a pwm ,so basically it interrupts the voltage to the pump 12000 times per second to bring down pump rpm.

Yes,the controller turns on and off full voltage.

 

[Ttype6]

I guess I've never heard of this pump

Walbro also makes one that flows 430lph.

 

[Ttype6]

Have u checked the return line for some kind of blockage ?

This is a very common occurrence in this community lately. The pump is too big for the unmodified return line.

 

[pmoore4321]

When I bought my car I thought I better change the fuel pump not knowing its history. I removed what was probably a perfectly good Walbro. There was no issue with the Walbro and the pressure could be adjusted as normal. The Supra pumps move some fuel for sure.

The orifice on my return line at the Saginaw was 11/64"...measured with a drill bit. That's crazy small!

More of the same:

http://www.turbobuick.com/forums/threads/modifying-stock-fuel-lines.382334/

 

[earlbrown]

What does a pump controller do then like the one weldon and aeromotive have? Not being a wise ass earl ,jus wondering...Have u checked the return line for some kind of blockage ?

Without putting my hands on the controller I would guess it sends either variable voltage or a PWM signal to the pump. I'm no expert on varying speeds on motors but I believe the norm is to vary the voltage on DC motors and PWM or square wave pulses on AC motors.

Since our pumps are designed for 12V you can't go much lower than that without harming the pump. Much in the same way you can smoke a starter trying to crank an engine with a dead battery.

Going down on power wire size to slow it down would be using the small stock wire as a resistor and relying on voltage drop to slow the pump down. As the wire heats up the resistance will go up slowing the pump down even further, which heats the wire more... You'll get a closed feedback loop of heat and our iffy connectors don't like that either. 80's GM didn't use the best plastics on some of our electrical connections.