Still going lean with FM clamp

[Matthew]

i have my FM clamp hooked up and im still running lean. sometimes i can get it to stay at --- (rich) but mostly thats boosting at 80mph on the freeway...

i can hear the clamp clicking...it clicks a whole bunch of time when i hit boost (almost like a whirrring noise cause it clicks so much) and then it shuts off...

i guess my question is (its dark so i cant fix tonight), could it be bad wiring or something else? and is it supposed to just click once or click for a while and shut off or should it click the whole time youre in boost?

 

[Matthew]

i am at 6.5psi and the gauge is pegged at 100psi, which seems to me is odd because it used to bury itself in the gauge (fuel pressure)...

anyways, i went out there with a flashlight because this is driving me crazy, and checked all hte wires. i disconnected each one and reconnected. for testing purposes only i wrapped the living s*** out of them and then put pieces of elec tap over them just to trouble shoot. while this is obviously not a good way to keep the wires, they were all conneected and wrapped around each other like mofos.

i still hear the clamp whirr on at 1psi or so, but it shuts off shortly after. im starting to think the ECU really has learned around the clamp.

1) fuel i think should be a higher pressure than 95-100psi but its not
2) should the clamp shut off at all?
3) should the clamp make one click or many?
4) what the **** else could it be?

here are my vacuum lines:

1) fm clamp runs to the vacuum line that goes to the cruise control
2) begi vacuum line t's off the line from the brake booster to the wastegate
3) boost gauge with own line to brake booster
4) BPV with own line to brake booster

i dont know what else it could be? please help

 

[ddogg777]

Sorry Matt, I know nothing about the voltage clamps...I don't even know what they look like.

 

[Matthew]

damn. im kinda at a loss...i dont know what else to do.

 

[mp5jeff]

pmed ya, sounds like either a) short in the wiring, or b) the clamp itself is ****** up...

 

[mp5jeff]

im not familiar with the clamps, are they supposed to click at all, im curious myself....

 

[Matthew]

yes when they turn on and see boost. im not great with wiring, BUT there is only a few wires and like i said i completely disconnected them and reconnected them without butt connectors. they are each COMPLETELY wrapped around each other tightly for the time being to try to isolate the problem....hmmm

 

[changedman]

the fuel gauge only goes to 100psi, so you wouldnt know if its over....

 

[Matthew]

no but it doesnt bury itself and really its at like 95psi but then creeps to 100psi where the old mech gauge would shoot straight to 100psi

 

[Matthew]

my AFR is like 13.5 at 6.5psi with 100psi of fuel.

 

[changedman]

aim

 

[Matthew]

:wtf:

youre already talking to me on AIM you postwhore

 

[Matthew]

would a bad o2 sensor cause this problem? the reason i ask (my CEL light is uh, broken..or removed lol) is because i had a CEL for low voltage or whatever on the bank one o2 or whatever, but someone said that when their TM was bad with the mpi they got that CEL as well. since i took out the TM i never checked again to see if the CEL went away, i guess i could..

i was just thinknig that if the clamp is between the o2 and the ECU, why does it matter what the o2 reads if the clamp just tells the ecu 14.7 as soon as it sees boost?

 

[505zoom]

The several clicks at the transition from vac to boost is normal... or at least mine does it and I am running good. How are you coming to the conclusion that it is staying off after it stops clicking? The only way I can tell is that my WBo2 drops at least 2 full points as soon as I hear the clicks.

...i was just thinknig that if the clamp is between the o2 and the ECU, why does it matter what the o2 reads if the clamp just tells the ecu 14.7 as soon as it sees boost?

I don't think it works quite like that. The clamp doesn't just tell the PCM 14.7, it lowers the voltage by a set amount.

These aren't real numbers but this is just to give an example of how I understand it. If 5v on that line = let's say 10:1 AFR, and 2V on that line = 14.7:1 AFR, then what the FM clamp is doing is lowering the incoming voltage by 3V and then sending that new signal to the PCM. The reason I say this is because there is an adjustment screw on the clamp that I believe might help you out here. I read a little about it when I first got mine and it said that you could use that adjustment screw to fine tune the clamp for the AFR you want to hold.

Just my .02

 

[daKiNeP5]

Did your clamp ever work or did it just suddenly crap out on you? Mine just started acting funny and I get really similar a/f ratios to you at 4psi. A couple weeks ago my a/f used to be low 12s.

 

[LinuxRacr]

Guys, the way the clamp works is that a pressure switch is activated when you reach 1 PSI of boost (the click). This switch activates a voltage limiting circuit that keeps the O2 sensor voltage around 365mv. The reason I know this is because I've monitored this before with a scantool hooked to the OBDII port. If you look at this on the MPI tuner, you will notice that the A/F ratio is stuck at about 13.7 when the voltage clamp activates. With a separate wideband, you can see the real A/F ratio when this happens.

The clamp is not 100% at all. From what I've observed, the FM clamp works good up to about 6 PSI at keeping the A/F ratio consistantly close to 12. Above that boost level, it is possible to start leaning out a little after the ECU learns. The stock ECU is just too ******* smart.

 

[Matthew]

well it used to work at 8psi no problem. this is a brand new clamp. rich im not saying the clamp is "off" per se, im simply saying that the clicking turns off.

 

[Matthew]

I read a little about it when I first got mine and it said that you could use that adjustment screw to fine tune the clamp for the AFR you want to hold.

can you figure out where you saw that, i saw nothing of the sort....

 

[YP5 Toronto]

Matthew....I dont have any first hand experience with the clamp.

Outside of double checking wiring... I am not sure.

Are you running an INLINE fuel pump or upgraded in tank pump?

 

[Matthew]

walbro intank. i dont think its the BEGI or pump cause im getting 100psi of fuel...