Fuel Pressure Problems

[1QUIK6]

Seems the GN is running lean on the top side down the track. With old combo (Stock Intercooler) I was mph'g at 114.8 O2's 783-Boost 24#. New combo (PTE Intercooler) I have done a best of 111-112.4 mph O2's 742- Boost 24#. No matter what fuel pressure 43-52 static It just won't richen up. Seems the new PTE intercooler is flowing a tremendous amount of air. I did notice that my fuel pressure at WOT is only 69# (static 51 boost 24#). Shoudn't it be 75#. In 3rd gear easing into WOT it only goes to 69# & stays. In 3rd gear if I go instantly to WOT its only 69#. I was hoping to pick up 5-6 mph with the PTE. Is the Walbro 340 just not going to flow the amount of fuel the car needs at that high of pressure? Frustrated.

 

[Jerryl]

Seems the GN is running lean on the top side down the track. With old combo (Stock Intercooler) I was mph'g at 114.8 O2's 783-Boost 24#. New combo (PTE Intercooler) I have done a best of 111-112.4 mph O2's 742- Boost 24#. No matter what fuel pressure 43-52 static It just won't richen up. Seems the new PTE intercooler is flowing a tremendous amount of air. I did notice that my fuel pressure at WOT is only 69# (static 51 boost 24#). Shoudn't it be 75#. In 3rd gear easing into WOT it only goes to 69# & stays. In 3rd gear if I go instantly to WOT its only 69#. I was hoping to pick up 5-6 mph with the PTE. Is the Walbro 340 just not going to flow the amount of fuel the car needs at that high of pressure? Frustrated.

I am no expert, but ......If the pressure stays constant at 69# in 1st, 2nd with the same boost level, it may be the gage. Does the gage EVER go to 75#? .......... or O2 sensor heats up enough where readings drop, or gage is off ............you may not have a pump problem. I have come the realization that one really needs a WB to accurately define mixture.

 

[SPOOLFOOL2]

1quik6

I've got almost the same combo as you, and am haveing the same problem. Starts going lean at about 90 mph with 24 lbs boost with 91 oct and meth. As soon as I see my o2s hit 760s I lift. Make sure you have at least 1/2 a tank of gas in the tank, to rule out sucking air. Would like to hear from others on this.



Not trying to hijack your thread, Just saying that your not alone and lets figure this thing out.

Mike

 

[1QUIK6]

I mounted another FPG at the rail & at static pressure (51#-70#) it was reading right on with the hood mount gauge. Seems if the gauge was off, I would be running rich with that amount of WOT FP. Maybe 820-800. I'm running at the track w/Red's chip & C16. I was told yesterday the the Walbro 340's were only good for around 70#? Would the MAF sensor have anything to do with WOT FP on a race chip? Double Pumper?

 

[1QUIK6]

Any others having trouble with their Walbro 340 flowing the fuel needed at 75# WOT FP? Could my 340 be bad? Been having this trouble for a year now. Any suggestions greatly appreciated!

 

[SPOOLFOOL2]

Ttt

 

[SHADOWII]

Going from ....

memory, I think it was about 73#s w/the 340. are you maintaining your voltage to the pump, or is it starting to fall off by the time you are hitting 3rd gear? how about the tps? could be worn on the top end.

spoolfool2 your alchy should make up the difference in low fuel if your using meth, it's just not the cure.

 

[Mad_Trbo]

I think the voltage might be the place to look, do you have hot wire and good ground???

My thoughts on TPS are probably not, but it wouldn't hurt to check TPS voltage key on engine off and see what kind of reading you get. If you don't get between 4.7 - 4.8 volts shadowII could be right.

But again first place I would check is the pump voltage, I would look for around 13 volts - right??

 

[1QUIK6]

TPS- is set at .48-4.65 volts.
Voltage at the pump (at idle) is typically 13.64v, but it does jump around. The voltage on the scanmaster seems to jump all over the place also, 12.01v-13.9v. They don't seem to be at a fixed voltage. I haven't checked the voltage at WOT. I'm in the process of looking for a Quad Air voltbooster. As far as the ground is concerned, it seems to be fine, is there any other additional grounding that can be done at the fuel tank? I am using a hot wire kit.

 

[Jerryl]

TPS- is set at .48-4.65 volts.
Voltage at the pump (at idle) is typically 13.64v, but it does jump around. The voltage on the scanmaster seems to jump all over the place also, 12.01v-13.9v. They don't seem to be at a fixed voltage. I haven't checked the voltage at WOT. I'm in the process of looking for a Quad Air voltbooster. As far as the ground is concerned, it seems to be fine, is there any other additional grounding that can be done at the fuel tank? I am using a hot wire kit.

On my car, I ran a ground from the tank top the frame, just to make sure. You probably should verify voltage @ WOT. If that is OK, you should be good on the charging system side.

Do a search on volt booster. While it may increase voltage (to the pump) it is not the right fix. Some have stated problems with the booster as well (as in burning up a few things, but I can't remember).

 

[Lee_Burough]

This is a link to a graph showing fuel pressure for the 340....It will go plenty high according to this graph, depending on your voltage and amperage.

 

[1QUIK6]

Should the alternator be putting out a constant voltage (13.8) or should this voltage fluctuate? I am going to run an external ground from the gas tank to the car frame. Looks like the new HW kits have additional ground wires on them. My kit doesn't have any other ground wires besides the system ground in the connector along with power & fuel level wires.

 

[brian]

How fast is the car? Mid to low 11`s?
I thought the old way of thinking was that once you crossed 50psi static pressure, it was time to upgrade injector sizing? As the pumps were not designed to see much over 70psi.
This is what old school thought was anyway. I use a T+ and Extender chip so I do not ever touch fuel pressure.

Brian

 

[1QUIK6]

Old combo (Stock Intercooler) 11.92 at 114.8 mph
New combo (PTE Intercooler) 12.20 at 112.5 mph
Was looking to mph new combo at around 120.

 

[Fuelie600]

If you are using a hot wire to the 340, and you are running out of fuel, replace the pump. You might need more pump, or the 340 might just not be functioning properly and needs replacing. 51 is a high static # as far as I'm concerned. Once you get the pump replaced/figured out, and if you still need to run that static #, up the injector size. Brian

 

[Mad_Trbo]

When you guys say static are you calling static - car running with vacuum or car running without vacuum?

I am thinking the latter, because static won't change regardless of where the car is running in the RPM band or boost range.

 

[Fuelie600]

Motor running, vacume line disconnected and plugged.

 

[1QUIK6]

Looked at the alternator & seems when I last replaced the alternator I was given an Delco Remy 108A-12V neg. alt. The face of the alt. is stamped with 108A. This could very well be my problem. Weren't the stock alternators rated at 120A & upgraded alts. 140A?

 

[Cme2fly]

Do you have any way of controlling fueling at WOT through your chip? I doubt your pump is your problem..

 

[1QUIK6]

I don't have any way of controlling fueling at WOT. I am using a Red Armstrong 107 race chip. Same problems with a Neal Steward race chip.