Walbro relief valve mod?

[scot w.]

What Jeremy is saying makes sense, if the alt isn't putting out enough volts no matter if you have a hot wire kit or not it will only take what the alt is putting out. My fuel pressure is set at 43 (line off) and at 20lbs boost my fuel pressure gauge shows 63.

SW.

 

[TR Custom Parts]

http://www.vortexbuicks-etc.com/basics.htm#Fuel Pump Sizing This is where I got my info from on the 1 to 1 deal.


Fuel Pumps

Fuel pressure must increase one pound for each pound of boost increase. In other words, if the base fuel pressure is 43 psi at idle with the vacuum hose removed from the regulator, then, with the hose reconnected, we must see 68 psi of fuel pressure when the boost gauge reads 25 psi of boost. This is critical!

 

[87GN_70GS]

There is one more test to diagnose fuel pump flow rate under load. With the engine off, disconnect the fuel return at a convenient point
(at the frame by the motor mounts for ex.). Don't lose the o-ring. Slip a hose over the line and have it empty into a can of known quantity (half-gallon, gallon, etc). May have to attach a battery charger so the pump volts are close to what they would be during a run. Adjust the regulator to the pressure you would expect to see for your setup (i.e., 43+25 = 68psi). Using a stopwatch, time how long it takes to fill your can. Divide the fuel amount by the time (using the proper units) to calculate flow rate in gph. Either look on a graph of pump performance or use your actual fuel demands (60 pph times 81% dc times 6/6 = 49 gph in your case) to see if your pump flow rate is adequate enough.

 

[TR Custom Parts]

Got a really dumb question. I have been measuring my fuel pressure at the inlet to the stock fuel rail, would this skew my readings? Wouldn't think so but just putting it out there. Both my transducer for the power logger and the mechanical gauge are in the same place.

 

[jdpolzin]

Nope I use that spot sometimes too. It's always the same either side.

 

[Pronto]

How about a small split in the hose from the pump to the sending unit. Seen that happen on a brand new install on a S/C 3800 Fiero conversion. As pressure went up the split opened more and pressure was lost.

 

[TR Custom Parts]

How about a small split in the hose from the pump to the sending unit. Seen that happen on a brand new install on a S/C 3800 Fiero conversion. As pressure went up the split opened more and pressure was lost.

Will know soon. Might drop the tank next Friday.

 

[TR Custom Parts]

Just an update. Love throwing parts at this car! Dropped the tank installed a new hanger/pump for shlts and giggles, did not go with the DW pump though, added a KB boost a pump set at 16v at 3lbs of boost. Have a volt meter hooked up to verify boost apump is working too. Guess what? Same results. Then even hooked the vacuum line to a different vacuum steel line, same result. At this point I am thinking it still has something to do with boost reference, wondering if the vacuum block fittings themselves have something to do with it. Going to put one of the ones we sell on and plumb up my own vacuum lines. If that doesn't work it is up for sale.

 

[Heg87t]

Just an update. Love throwing parts at this car! Dropped the tank installed a new hanger/pump for shlts and giggles, did not go with the DW pump though, added a KB boost a pump set at 16v at 3lbs of boost. Have a volt meter hooked up to verify boost apump is working too. Guess what? Same results. Then even hooked the vacuum line to a different vacuum steel line, same result. At this point I am thinking it still has something to do with boost reference, wondering if the vacuum block fittings themselves have something to do with it. Going to put one of the ones we sell on and plumb up my own vacuum lines. If that doesn't work it is up for sale.

Is the vacuum block gasket on wrong?

 

[turbobitt]

Just an update. Love throwing parts at this car! Dropped the tank installed a new hanger/pump for shlts and giggles, did not go with the DW pump though, added a KB boost a pump set at 16v at 3lbs of boost. Have a volt meter hooked up to verify boost apump is working too. Guess what? Same results. Then even hooked the vacuum line to a different vacuum steel line, same result. At this point I am thinking it still has something to do with boost reference, wondering if the vacuum block fittings themselves have something to do with it. Going to put one of the ones we sell on and plumb up my own vacuum lines. If that doesn't work it is up for sale.

For diagnostic purpose I would tee off the turbo WG port. It won't pull vacuum but for troubleshooting it will be OK.

Also have to ask, did you verify your boost gage reading ? Maybe it is reading higher than normal and making you expect higher fuel pressure.

Allan G.

 

[TR Custom Parts]

For diagnostic purpose I would tee off the turbo WG port. It won't pull vacuum but for troubleshooting it will be OK.

Also have to ask, did you verify your boost gage reading ? Maybe it is reading higher than normal and making you expect higher fuel pressure.

Allan G.

Yeah, we talked about that the other nite, will give that a shot as well. Have tried two different boost gauges as well.

 

[turbobitt]

Yeah, we talked about that the other nite, will give that a shot as well. Have tried two different boost gauges as well.

It has been a while since I had some of the stock equipment on my car but here is another suggestion.

Look at all the vacuum lines going to the block. Also look at the vacuum canister under the left front wheel well. Maybe a leak somewhere bleeding off boost signal. Maybe you will get lucky.

Allan G.

 

[Ttype6]

If the pump will put out 63 psi at 28lbs of boost what's keeping it from putting out 60 psi at 17lbs of boost?

The fuel filter. I've seen a 7 lbs increase in WOT fuel pressure switching from a brand new Perolator to a brand new AC Delco . Red Armstrong told me about this. If your pump was bad,the pressure would fall off more and more with increased boost. It doesn't. If voltage was the problem the same thing would happen. A bad hose would do the same thing. A restriction in the fuel supply line would result in a steady but low fuel pressure. The biggest restriction in the fuel supply line is the fuel filter.

 

[Ttype6]

Yeah, we talked about that the other nite, will give that a shot as well. Have tried two different boost gauges as well.

Your boost is correct because your Powerlogger gets its boost reference from the MAP sensor.

 

[TR Custom Parts]

The fuel filter. I've seen a 7 lbs increase in WOT fuel pressure switching from a brand new Perolator to a brand new AC Delco . Red Armstrong told me about this. If your pump was bad,the pressure would fall off more and more with increased boost. It doesn't. If voltage was the problem the same thing would happen. A bad hose would do the same thing. A restriction in the fuel supply line would result in a steady but low fuel pressure. The biggest restriction in the fuel supply line is the fuel filter.

Has new AC Delco filter.

 

[Ttype6]

Has new AC Delco filter.

It's not your pump and it's not your regulator. Again,if it was your pump your pressure would fall off as the motors demand for fuel increased. There is only one other thing that I can think of that would cause this,and that is making an adjustment to your fuel pressure by moving from a higher pressure than desired,downward to the desired pressure by turning your adjustment screw counter clockwise and stopping when you get to the desired pressure. If I adjust in this fashion,my pressures will act as you've described. If you are unsure if you adjusted this way,start the car and loosen the lock nut on your regulator. Then,while watching a gauge,take note of how far you have to turn the screw clockwise before the pressure starts to rise. If it takes a noticeably large amount of movement to get the pressure to rise,then this is an indication that the pressure was adjusted to its current setting from a higher pressure. If,after doing this,you note a lot of movement before you see some rise in pressure and you stop turning just as it starts to rise you'll be where you want to be if you are at 43-44 lbs of fuel pressure. In order for my pressures to act right I have to first turn my adjustment screw counter clockwise to a much lower pressure than desired. Then I approach my desired fuel pressure from there,turning my adjustment screw clockwise,increasing my fuel pressure until I reach my desired number. Never adjust your fuel pressure downward to your desired number. Always approach your desired number from a lower one.

I hope you can at least see that you've proven that your pump and regulator are not the problem.

 

[lrayzer]

What Vacuum block are you running, I am chasing a similar problem, dropping fuel pressure and will not build boost, all the goodies, Double pumper, new SST sender, -8 and -6 AN lines, complete staged hotwire kit.
Seems hit and miss, fixed bypassing pumps ( spraying fuel at low pressure ) a pinhole in a NEW -8 AN line, all new back to front, FP reg looks fine, have the rebuild kit, but it did not need it.
going to keep isolating vacuum lines until it goes away, can't get more than 14lbs of boost, which is thankfully safe considering the FP spikes to 65 then drops to 45 ( Mech Pressure on the hood )
Ah the joy !

 

[TR Custom Parts]

What Vacuum block are you running, I am chasing a similar problem, dropping fuel pressure and will not build boost, all the goodies, Double pumper, new SST sender, -8 and -6 AN lines, complete staged hotwire kit.
Seems hit and miss, fixed bypassing pumps ( spraying fuel at low pressure ) a pinhole in a NEW -8 AN line, all new back to front, FP reg looks fine, have the rebuild kit, but it did not need it.
going to keep isolating vacuum lines until it goes away, can't get more than 14lbs of boost, which is thankfully safe considering the FP spikes to 65 then drops to 45 ( Mech Pressure on the hood )
Ah the joy !

Different issue than mine. Mine doesn't drop, just doesn't go high enough. Have since used one of my vacuum blocks and replumbed all the vacuum lines and guess what.....................................














Still no difference. Did notice a very SLIGHT kink in the bend of the fuel supply line right before the fuel filter but don't think this would affect things. Pretty much have given up at this point.

 

[Ttype6]

You haven't replaced the pump have you?

 

[TR Custom Parts]

Replaced it with a new Walbro from Racetronix when I went with their new hanger/sending unit. Supposedly has the relief valve modified for higher pressure.