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HELP: AFPR + Wally400 + BM1650 = cant get fuel pressure below 58 psi

3K views 10 replies 4 participants last post by  kmetiuk 
#1 ·
So as the title states, my final issue followed this path:

1. Installed Aeromotive AFPR: Car starts, no issues.
2. Installed Wally 400LPH: Stock wiring still, car starts, turn down the base pressure a bit, no issues.
2. Installed FIC BM1650's: Getting the car going was rough. Took a bit to figure out the deadtimes. I could get it running but was having issues at WOT. If I changed some of the sliders to weird values I could get the WOT pretty decent but then if it stalled or I stopped I couldn't get it started again till I set the sliders where they needed to be (at the cost of WOT again). So I researched and read that the alternators are kind of shit...
3. Installed Saturn Alternator: Used a relocation kit which wasn't half bad. The brackets had to be modified and one of the belts needed to be replaced with a shorter one as the one supplied caused the alternator to hit the subframe under load. Also needed about 4 washers to shim the kit for the power steering pump part...so i guess it was kind of a crappy kit haha. Meh...moving the alternator made a shit ton of room up front so all in all im happy. The saturn alternator packed a punch too, got a solid 14.4V right at idle and at all the low potential spots from before. Had to reset the deadtimes again to get it running but it seemed to help a lot overall. WOT and idle were both decent, but now I had a studder at about 2.2K and could not get over 4.5K at all. More research lead to the 1650's being weird about deadtimes and draw and voltage and other drains in the system...
4. Installed FIC Easytune box: Immediate difference, set all the deadtimes the same and it fired right up. Multimeter shows 16V at the injector resistor right at idle...huge jump! Still could not get over 4.5-5K... now the logs showed that the injectors were getting decent duty but the WB showed lean ass hell. More research turns up the stocker pump needs a rewire as theres huge voltage drop in the stock wiring....
5. Fuel pump rewire: Straight forward, car starts but really rough. Check the fuel pressure and it shows 60+ psi. I think sweet, lots of voltage and flow now, so i back the screw out until its at 0 and it still shows 58 psi. I cannot turn it down enough now...reverse problem....too much fuel! I check the voltage at the pump and it shows 14.4V...so about 2.3V gain but right where you want it to be. I research more and figure that it could be the stock fuel lines restricting flow...
6. Installed tank to rail return/supply -6AN: Installed was a bit challenging....those lines were way beefier than the stockers. Does not help the issue. Still waaaay to much pressure. So I took the AFPR apart to check for a blockage....nothing. So i figure it must be the gauge, installed a new one....no dice. Same high ass 58psi. So i was thinking maybe the little orifice in the AFPR was too small (reaching for straws here I know) but I drill it out an extra .22mm and reinstall with the same preset. I figured if that was the issue then there should be at least a small change in the pressure. Nothing....

So thats where I am at. WB shows Lean but I believe that to be rich knocking causing puffs of missed unburnt cylinder air causing high O2 readings. Tons of pump (pressure and flow), injectors to flow them, and an AFPR that appears to be sized right. I am not gonna upload logs cause they're useless....the DSMLink thinks everything is running fine except for the WB...

I am totally out of ideas now....anyone have some fresh ones out there?

Second set of "eyes" needed....
 
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#2 ·
34 reads and not one new idea?
 
#5 ·
Thats the response i got from Tuners as well...I will perform the syphon mod this morning.

As an aside what exactly does this syphon do and why would it restrict flow? As I understand it, it is simply the fuel syphon from one side of the tank to the other.
 
#9 ·
Thats the response i got from Tuners as well...I will perform the siphon mod this morning.

As an aside what exactly does this siphon do and why would it restrict flow? As I understand it, it is simply the fuel siphon from one side of the tank to the other.
On a 1g car the fuel tank is just one large container so no siphon exists, the fuel returning to the tank simply gets deposited in a baffle system near the fuel pump. On a 2g awd car the driveshaft divides the lower half of the fuel tank so below half a tank, with the fuel pump being on the passenger side of the car the drivers side of the tank would normally never get used thus effectively reducing the capacity of the tank.

So the designers used a system that used the fuel returning to the passenger side of the tank to draw a vacuum in another line and that line crosses over to the drivers side of the fuel tank, thus drawing the fuel over, to make sure that there is always fuel at the pump on the passenger side. The siphon however is designed around the fuel flow of the stock pump and by increasing the flow substantially the fuel cannot get through the siphon quickly enough and the entire return fuel line system basically winds up getting pressurized at fuel rail pressure or above.
 
#10 ·
Think of the siphon as a Y vacuum fitting. 1 leg is the return from the rail, the other is the dump back into the tank, and the 3rd is line from the driver's side to be siphoned. The siphon is there because the tank is a saddle due to the drive shaft running through the middle of it, so when cruising down a straight road, the right side where the pump is will empty, while the left side of the tank remains full, thus the siphon to pull fuel to the pump side.

The problem with this siphon is that the leg that dumps back into the tank has a restriction in it, sorta like an oil restrictor for ball bearing turbos. It needs to be drilled out to allow for the greater flow of the larger pump. Most drill it out to..... 1/4" if I remember correctly. It'll be fairly straight forward and obvious what I'm talking about when you pull it out and take a look at it.
 
#11 ·
FIXED! Worked like a charm. Drilled the syphon out to 1/8" which brought the base pressure down to about 30psi. Woot Woot.

Still seem to have the weird studder at 4-4.5K then after it "clears its throat" it digs in and goes. Nothing on the logs in the way of knock or anything else that might cause this. At least it gets over 4.5K now...hopefully its just tuning issues now.

Thanks for the help. :)
 
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