03 Cobra hit 6500, it falls flat on its face

[Termi Mo]

I will post a pic of the engine bay as soon as possible, the one I have now is not that clear. It has the stock pulley's, stock charger, injectors are blue, and it does have a sc bypass mod (shouldn't affect a p0148, may cause a p0234 though). Maybe the pumps are maxed because if the pcm is signalling not enough fuel the duty cycle of the pumps should have increased, but I am possibly reading in 1/2 value percentage.

I was also logging in closed loop.

What sort of resistance should the fuel pumps measure? I am leaning towards the fuel pumps being maxed out as well.

If it is, what would the recommended repair be, stock pumps with a kb bap, focus pumps or gt pumps (I have another fpdm if needed).

 

[Termi Mo]

have you put the bypass mod back to stock and see if this still happens?

The pprv mod? if so, no. I removed it as an attempt to resolve the problem.

 

[hotcobra03]

LOL, donuts. Really man? Is this some new kind of racing or something?

First I would say it is how much fuel you have in the tank and really, 1/4 may not be enough considering what you are doing to that car. All the 1/4 level reports are in regards to launching at the track and the initial hit. Going around in circles you are forcing the fuel to one side and it will remain there, where the drag strip it is an initial thing and then comes back.

Second, it looks like your fuel pressure is low. Your base pressure stock should be 39psi and then for every pound of boost, you get a pound of fuel, so you should see about 47-48 psi at WOT with a stock boost setup.

you mention PPRV and you dropped the tank, I assume you checked the hoses? Have you logged FPDC?

if op`s problem is fuel pump related,,i like to follow along with reading datalogs to see if it shows up with numbers...

i always had a feeling 1 of my pumps went out years ago...i remember the sound of the pumps changed after a filter change...but havent had any issues...after what ive put this car thru things have got to be starting to go....

i see 37-41 lbs with predator tuner as to fuel pressure...

i did a short (wot) run and now want to see what a normal reading should say...

question....when loggind a (wot) run,,,is it done from 40mph in 4th gear,,,or a dead start ?

 

[hotcobra03]

The pprv mod? if so, no. I removed it as an attempt to resolve the problem.

you replied before edit...

i meant boost bypass mod...

the vacuum hoses were moved for this,,,maybe you did something other than what i know ,but you also have the vacuum hose for frps running in main vacuum harness,,,these hoses crack very easy,,just a slight bump is enough,,,worst in cold weather

 

[encasedmetal]

if op`s problem is fuel pump related,,i like to follow along with reading datalogs to see if it shows up with numbers...

i always had a feeling 1 of my pumps went out years ago...i remember the sound of the pumps changed after a filter change...but havent had any issues...after what ive put this car thru things have got to be starting to go....

i see 37-41 lbs with predator tuner as to fuel pressure...

i did a short (wot) run and now want to see what a normal reading should say...

question....when loggind a (wot) run,,,is it done from 40mph in 4th gear,,,or a dead start ?

WOT datalogging is best done in 4th since it is a 1:1 gear. you do not do it from a dead start since you will be in closed loop until past half load- so your base fuel command tables will be different. do a pull in 4th and disregard any maf counts below 550, to base your afr at WOT.

 

[beave]

Im having a similar problem with my car right now. 1st and 2nd gear are fine but in 3rd and 4th gear at about 5600rpm the car just falls on its face. I logged it and fuel pressure is about 42psi at the start of 3rd, it is at around 34psi at 5400rpm then when it hits 5600rpm it drops to 30psi and falls on its face. A friend of mine is telling me its the fuel pump(s).

 

[hotcobra03]

WOT datalogging is best done in 4th since it is a 1:1 gear. you do not do it from a dead start since you will be in closed loop until past half load- so your base fuel command tables will be different. do a pull in 4th and disregard any maf counts below 550, to base your afr at WOT.

what are suggested rpms? start at ...end at...

i do have a spot to get up 6500 in 4th...but really 135mph:shrug:

 

[Termi Mo]

you replied before edit...

i meant boost bypass mod...

the vacuum hoses were moved for this,,,maybe you did something other than what i know ,but you also have the vacuum hose for frps running in main vacuum harness,,,these hoses crack very easy,,just a slight bump is enough,,,worst in cold weather

I will double check this, but the vacuum going to the frps would cause an increase psi reading if the vacuum line is cracked or removed from the frps.

 

[TRBO VNM]

I will double check this, but the vacuum going to the frps would cause an increase psi reading if the vacuum line is cracked or removed from the frps.

Not sure I understand your statement. If the vac line is cracked, how would that cause an increase in psi? If you have a vac leak, the car may not(usually doesn't) run right and could cause a number of other situations/issues.

And if the FRPS is not getting boost, you can go lean and well, bye bye motor. The FRPS needs a boost source, not vac source.

 

[Termi Mo]

Not sure I understand your statement. If the vac line is cracked, how would that cause an increase in psi? If you have a vac leak, the car may not(usually doesn't) run right and could cause a number of other situations/issues.

And if the FRPS is not getting boost, you can go lean and well, bye bye motor. The FRPS needs a boost source, not vac source.

Are you sure thats correct, there is no way that a small vac line on the frps can withstand 10 psi without blowing off. But none the less I will just check the lines to make sure none are ruptured.

 

[encasedmetal]

what are suggested rpms? start at ...end at...

i do have a spot to get up 6500 in 4th...but really 135mph:shrug:

I would suggest going to your spot, getting to 4th gear at a relatively low speed and doing a pull until it falls on it's face as you described and not beyond. datalogging all of this of course. and when you look at your datalogs- you can disregard all maf counts below 550 or so- post up the rest.

 

[hotcobra03]

I would suggest going to your spot, getting to 4th gear at a relatively low speed and doing a pull until it falls on it's face as you described and not beyond. datalogging all of this of course. and when you look at your datalogs- you can disregard all maf counts below 550 or so- post up the rest.

had chance to look over the log i already had done with predator..

this was done in the WOT option and i logged all options given to log..

I was in 4th at 70mph start, ran from 3900rpm to 5600 rpm..

option---------start---------finish

rpm 3900 5600

IAT1 82* 80*

MAF V 3.72 4.13

FRP 33 34

SPKADV 25 25

LOAD 119.1 124.5

CLFDBK OPEN OPEN

ENGTMP 190* 192*

IAT2 120* 160*

STFT1 -18 -25

STFT2 -18 -25

TPS 4.63 4.62


if i switch to other options in datalog,,,,driveability,fuel,ign....

i see some of the other things suggested to watch...

when in those sections can a do a WOT pull as im doing in wot section ?

while reading data numbers do change,,, i noticed under normall driving my load was 30-40%,,,stft would balance 0..and would be in closed loop..

when i nailed it ,it went open loop,,load changed 80-125 and stft went
-18 to -25

fuel pressure was 32-45

 

[encasedmetal]

load is fine- disregard STFT as I said before cause they aren't active while in OL. your FRP is extremely low however. you should be at around 39 psi at idle and 1:1 gain per psi boost after that. fueling is your issue

 

[hotcobra03]

load is fine- disregard STFT as I said before cause they aren't active while in OL. your FRP is extremely low however. you should be at around 39 psi at idle and 1:1 gain per psi boost after that. fueling is your issue

thanks im going to do more testing...

ive had an issue with boost being lower than 10lbs for a long time..seeing frps is on the end of the line this could be my problem vs fuel pump...
with coooler temps i have seen it rise higher than its been

it is original...im going to cali next wk for sons graduation of marine corp basic trainning...i will see if i can find someone local with a good frps for testing...