I'm about ready to unsrew the FP guage and start it up and put a match to it!

I've got the usual 255's pumps and 60# injectors. KB built motor, heads, cams, and all. I have a 97 F150 rail with an aeromotive adjustable regulator.

I set it to the standard 39#'s with the vacuum line off and it runs wayyyyy lean. So, I bump it up to about 45#'s vacuum line off and can get the A/F into check, and had it there with a Eaton on top of the motor. When I put the KB on now I am going lean again(leaner than the program commands for by about .5~.8 a/f)

Well; this whole time I have been having one side read richer and one side leaner. Say the program commands a 11.7 the drivers side will ready about a 11.0 and the passenger side will read about a 12.1~12.2 At first I thought it was the wideband on the rich side(I have two dynojets running at the same time) So, I put both in the same side and they matched so that puts that out. I have swapped all injectors side to side and that made no change. WOT I see over 60#'s of preassure more like 65#'s It will actually be lean 1st and 2nd then goes into 3rd and boggs a little then the A/F goes into check and is actually richer than it should be. There is never less than 1/2 tank of fuel. The exhaust tips are BLACK! Back when it was running good and correct(old motor) they would stay a goldish color.

Anybody have any clue wtf is wrong with this truck???

Only think I could possibly thing of being wrong is at the "y" connector in the fuel tank the "y" crushed when the pumps were installed, and is causing a lack of volumn. Since the drivers side(the rich side) gets fuel first then the passenger side gets it second. But, I see pleanty of preassure....

 

If you are not seeing a pressure drop, then it's not your fuel system. It sounds to me like your x-fer is off. Hard to say without seeing it in person. Big fuel trim differences bank to bank usually indicate an air leak of some sort. What's your PCV and valve cover vent line setup?

 

I would say it's the maf x-fer if both were doing the same thing, but they arn't!

The PCV system is completelly blocked off on the intake and it has breathers on both valve covers. I have small breathers on the small holes on each, and a regular screw in breather on the filler.

I mean the high FP and program says it should be running very rich which it is on the drivers side. If I had an vacuum leak pre blower it should make it lean on both sides true? After the blower(say at the lower intake manifold to head) it shouldn't change a/f when under boost because a leak would be pushing out; not sucking in correct?

 

How lean is real lean? What a/f do you have in 1st, second, and third gear at wot?

Jody

 

It's just on the passenger side, but looks like it wants to do upper 12's in 1st gear, and mid to lower 12's in 2nd gear then it boggs going into 3rd and the A/F will drop good into the mid 11's into 3rd.

It revs quite a bit faster threw 1st and 2nd; is the fuel catching up going into 3rd?


This maybe be farrr of, but is there a possibility that my engine builder has the timing off half a tooth and it's screwing everything up on one side?

 

O yeah; sometimes it drops the A/F off into the 11's in 2nd gear. It seems to vary up a lot.

 

I can say that the a/f will drop each gear you go up. If mines mid 12's in 1st gear it'll be about 11.8 in 3rd. That is normal and not a problem. I can't say why the two sides are so different as I've never had the wideband on the passenger side, always the drivers side. I thought that the drivers side is the leaner side, but maybe that's wrong.

Jody

 

Well; I know it's the first side to lean out if you pumps go dry. But, it gets fed fuel first from the pumps. #7 rod on mine broke, and I've had #7 burn a plug before(actually the only plug my old motor burned)

Only thing really different with this motor is I did do the modular cooling mod where the drivers side head now has a coolant exit just like the passenger side and they both equally "T" and go into the heater core. I don't see that causing that big of a difference.

 

I dont know what I'm talking about so hopefully Sal will come back in with the correct way of saying what I'm about to.

I understand that the factory pumps and the 255's work differant,
meaning the factory pumps will both work at the same time to meet your fuel flow needs, HOWEVER with the 255's only ONE PUMP is used for normal driving, and only when the system demands more flow does the 2nd pump kick in.

I also believe that there have been situations such as yours with big HP Built Motor/KB combo's. SOMETIMES that one pump operation just dont cut it.

I also believe there are "2" differant type of 255's available for us,
but either way the issue I speak of DOES have a fix. I believe Sal once told me something about adding a resister, or altering the voltage or amps,
OR SOMETHING.
They somehow change the flow rate or maybe it was that they have a way of fooling the other pump to kick in quicker ???

I of course asked if I needed this mod, but the answer was NO,
I also believe it's usually only a problem on big HP trucks with atermarket Fuel Rails and oversized Fuel Lines, BUT it's worth talking to someone about
THAT KNOWS WHAT THE HELL I'M TALKING ABOUT, hehehehehe

Good Luck Bro

 

Your kindof correct. Both pumps run all the time factory or 255's; The are wired togeather. Just there is a drop down resistor that under normal conditions you only get "half ground" to the pumps so they only run at half speed. Then at a certain load I beleive a relay kicks in and goes to full ground and they both go to full power. Mine are doing this just fine; you can see the guage kick up. I have even tried the wiring in the extra resistor. A while back I verified the pumps to be the correct part number too.

This is getting very discusting; I can sure see why a lot of people sell there built motor L's not long after they get a built motor

 

Something else I will say that has be still thinking it's a fuel system problem.....


It will NOT hold fuel preasure when it primes (turn the key on, but not start the truck). Turn the key on, it goes into the prime cycle then instantly the FP starts dropping down. Which I have not found any external leak from tank to injectors. And cannot smell fuel even after priming it for 10 or more times. But it ALWAYS leaks down. I have even changed the FP sender on the rail thinking it might be bad.

 

Your FP will drop if you just cycle the pump.


I agree with Sal, it's most likely your MAF X-fer function. If you've never had your short trims dialed in, you will have this problem.

 

Other people say there's holds steady FP after the key cycles for a long time.

On the MAF, I would think this also IF it was both sides. Why just one side???

 

Casey, have you logged fuel trims to see the bank to bank difference, or are you just going by the widebands?

 

The return line going into the tank has a small, rubber piece on the end that acts like a valve. Under pressure from the pumps it is forced open and the gas returns to the tank. With no pressure it shuts. The more it relaxes or stays open (it's rubber I think), the faster the pressure will bleed off once the priming cycle is complete. I wouldn't think this is your problem at all if you have pressure when it's running.

Do like Sal says and check the short term fuel trims for both banks with adaptive learning off just to verify what your WB shows. At idle or in closed loop do you trip an SES or is the PCM able to keep up?

FWIW, mine is the same way - bank 1 runs about 5-6% leaner than bank 2. I tried swapping injectors directly over (1 to 5, 2 to 6, etc.), swapping the injector set and even doing a smoke test looking for a leak. Nothing. My PVC system is OEM now, as well. No unmetered air on bank 1 THAT I CAN FIND. I didn't put my WB in bank 1 but I can see it in the trims. I've just been running it a bit richer to satisfy bank 2 and, yes, my pipes are black as soot. I'm not looking for it anymore, though. I haven't fouled plugs or anything. I'll just clean the pipes more. I have wondered about the head to header flange gasket, though. I re-used the Percy's aluminum gaskets and even though I re-tightened them I wonder if they are leaking.