Dynod the L. 15-1 A/F! 2nd pump not coming on?

[04gtstang]

Well I took it to see where it stood before the 3# lower and tune. It made 332RWHP and 450RWTQ...bone stock minus K&N filter and bypass mod (soon to be removed for tune).

problem is A/F starts @ 13.5 @ 3400RPMs, and the pretty much slowly rises to nearly 15-1 by 5200RPMs. :dw:

SO I go home and datalog it. Just do a quick 2nd gear WOT pull to 3800RPMs. I logged the "secondary fuel pump ON" flag along with "pressure drop accross injectors" and also "Fuel pump flow rate".

Secondary pump command was never given :shrug:

Fuel pressure remained a CONSTANT 39.699 throught the entire datalog (147 seconds)....so obviously thats not REAL...but is it Normal? I would figure the EEC would like to know fuel pressure.

Flow rate starts @ .05 at idle and goes to 3.07 by the top of the shortish pull.

So what do you guys think? Isnt it supposed to kick on the 2nd fuel pump, or if its fried will it not even allow it to try? Im sortof thinking the pressure sensor is bad and the computer doesnt know actual pressure and its just going off the base voltage tables :shrug:

thanks for any help....really need to figure this crap out before the dyno tune on the 11th

 

[Hollywoood]

I had a similar issue awhile back, and it was the high speed fuel pump relay that controls the second pump........

 

[FordFanStan]

Alot of the Ford sensors fail often. It sounds liek it could be your fuel pump hi/low relay though. I would suggest I would suggest checking fuel pressure via another way, like a gauge, replacing the relay, and replacing the sensor as well. Depending on what you find when you replace the sensor or check the fuel pressure will let you know if you need to replace the fuel pump. Another recommendation is if you have to replace that pump, while your in the tank, replace both pumps and the Y and the hose. Stan

 

[04gtstang]

Thanks I appreciate the help! Do any of you know when your second pump comes on? Like as soon as you go WOT or high in the RPMs?

So its normal also for the EEC to have no idea what fuel pressure is?

 

[Hollywoood]

By watching my fuel press gauge, it appears that the 2nd pump comes on about the time the truck goes from vac to boost....

 

[FordFanStan]

Correct, I think one of the scenarios is when it switches to a vacuum state to a boost state. But is all in the EEC and or tune. I also believe there are prescribed commands so it will switch to hi during certain load settings, tps settings, etc. Stan

 

[svtsilverback]

i had the same problems and Modular Depot found the problem to be a factory power was damaged so the pumps were not getting enough power. they ran independent power wires and relays to each pump. fuel pressure issue fixed.

 

[04gtstang]

Thanks for all the help...we are going to replace that relay first.

 

[Fade 2 Black]

The secondary pump (hi flow) comes on under whatever load and/or TPS value is reached to go into open loop (WOT) as prescribed within the tune. Vacuum or boost has nothing to do with it, it's airflow (Mafv) or TPS reading that does it.

Without a fuel pressure gauge to look at it will be difficult to pinpoint the issue. Check the 620 ohm resistor located at the top left of the heat exchanger behind the front bumper. When was the last time you replaced the fuel filter?

 

[throttle jockey]

I met Cody (04GTStang) and his father at PSI Motorsports last Friday. We literally spent all day at the shop while Patrick worked his magic on our trucks, then followed each other on the ride home (until we had to part company). Great guys and I look forward to taking-up their invite to meet up with them at the track next Wednesday.

As it turns out one of the pumps on their truck had crapped-out completely. Once on the lift the guys at PSI had the problem diagnosed and cured in about 40 minutes... even threw in a fuel pump that was lying around in the shop free of charge. IIRC, final numbers were in the area of 385 RWHP/470 RWT with only a CAI and 3# lower pulley.

 

[04gtstang]

^Hey Allen! Man good to see you on here!...cant wait for this weather to clear up as well, so we can all get out to SAR!

PSI definatly knows what they are doing....they got us fixed up...saved the trucks motor as far as im concerned.

Between Allen and Patrick sharing thier knowledge, me and my dad (Larry) LEARNED A LOT about these trucks.

 

[Blk04L]

Good to hear that they fixed the problem.

 

[throttle jockey]

^Hey Allen! Man good to see you on here!...cant wait for this weather to clear up as well, so we can all get out to SAR!

PSI definatly knows what they are doing....they got us fixed up...saved the trucks motor as far as im concerned.

Between Allen and Patrick sharing thier knowledge, me and my dad (Larry) LEARNED A LOT about these trucks.

:thumbsup:
Just trying to pass on a little bit of what I claim to know :-D. Can't wait to hit the track... hopefully we'll see you guys on Wednesday.