Fuel System Problems

Ok so I have a cobra tank with dual cobra pumps not sure if my fpdm was ever upgraded. My problem is I am constantly blowing fuel pressure sensors now like 1 a month at least!


I started blowing the sensors after I got a tune. The KB tune was much better with stock pumps and a BAP. the dyno guy said i was out of fuel with BAP and stock pumps. So a random guy walked in and was getting work done on his cobra and happened to be selling his tank and cobra pumps so i bought them off of him. had the shop install it and then tune it again.


Now I have been driving around for a year with the car like this. Makes great power runs strong at WOT. But i continue to blow these sensors. Probably spent close to a grand on sensors now.

So my question is if I upgraded my FPDM would this help? I have the stock injectors that come from KB. I believe they are 36lb or 39lb. Not sure if that could be a problem meaning trying to increase fuel pressure to push the injectors a little bit further.

I do not have a fuel pressure gauge as of right now but will be getting one here soon.

The car surges under a very slight amount of throttle but runs hard when out of VAC or into Boost. I also have the KB burst DISK but didnt seem to help since after i put it on I blew another one 2 weeks later.


If there really isnt gonna be much of a fix to this problem then i am just going return style. Yes i take a big hit initially but heck at 120 dollars a sensor and If i keep popping them at this rate then heck within a year i would have spent just as much money as i did on a return style system and be problem free!


any knowledge would be greatly appreciated!


EDIT: and I literally just changed the sensor. Fired the car up after having the battery unplugged drove it a bit and still kicking and surging like crazy! So that is why I am unsure of what the heck is going on now cause It couldnt have just popped a brand new sensor in less than 5 minutes otherwise that is definitely a reason to go return style.

Ya I get a cel but it just runs terrible even without the cel. Constantly bucking at very very little throttle. And I mean very little. It runs best when you tap the gas and get it out of vac then it runs smooth. But I can't imagine blowing these things driving it easy. The last one literally went as soon as I started the car. Got down the street good then started driving up the street and bucking again. And I keep getting po190. All this crap happened after I had the guys tune it. The kb tune was worlds better than this tune. Its like the idiots didn't tune at all for part throttle and just left it go

I also dont want to throw more money at a retarded returnless system that will always blow sensors. Kinda dumb when you think about it. 2200 for the MMR return style setup. or at my rate of 1 sensor a month and I have blown 8 at 120 a pop thats 960 dollars already wasted on this crap system. heck in another year i would have already bought the return system and i would still continue to pop these. just doesnt make sense to even bother with that setup anymore. In the long run i would come out on top with a return style cause heck then i know i at least have the capability for much more than the returnless can provide.

trinity_gt said:

Where is the pressure sensor getting its pressure reference? That is, where's the vacuum line connected?

Click to expand...

it is Teed Into exactly where KB shows in the manual. Same line the Bypass valve is connected into.


It is more than likely the tune because I never blew a single FRPS in the 2 years I had the KB without a tune. So more than likely what happened is the tuner installed my dual cobra pump setup noticed my injectors were struggling up top and then increased fuel pressure to try and stretch them out a bit more but who really knows.


I will check a few more things though when i get the chance this weekend. I am just getting tired of spending money on a lost cause fuel system. So next ill go with larger injectors because i will need them anyways very soon. If that doesnt take care of it for me then its off to get a return style fuel system.

I dont really want to spend the money on a return style system cause I know there are plenty of high hp cars on returnless but blowing a sensor a month is kind of ridiculous if you ask me. It is not even a daily driver anymore so i am not too worried about gas mileage being terrible on return style. I just want the car to work nicely when i do get in it and drive it. Not bucking and kicking like crazy down the street for all to hear. Kinda embarassing when your nice looking stang sounds terrible. makes the borlas sound like poop

trinity_gt said:

My setup is a bit "less" than yours -- 1.7L KB with a 9-psi pulley making ~400 at the wheels -- and after three years running the KB "chip" I've never had an issue with mine. Your problems started with the new tune and so you should focus on that.

A return system shouldn't give reduced mileage. Returnless systems are attractive to manufacturers because the architecture eliminates running fuel up to the engine compartment and back again which will heat the fuel in the tank and heated fuel will increase vapor emissions to be dealt with. The plumbing is somewhat less cumbersome too...

But there's no reason to go return when the OE returnless system is more than capable of delivering the fuel you need (especially with the Cobra tank.) You simply need to find out what's going on with the current tune (i.e. why is it apparently driving the FPDM incorrectly?) The car runs like **** down low which suggests to me that the fuel pressure is too high. Get a gauge on it, even if you need to just rent one for the Schrader valve, and check it.

It's almost like the new tune is set up for a return car (say, a pre-99) and is just driving the fuel pump at 100% duty cycle...

Click to expand...

yea thats what im saying. I know its the tune cause i never had a single problem with the KB tune. then i decided to go be safe and get a dyno tune and it went to hell after that hahaha. i mean when you step on the gas even just a little bit it smooths out but when you try and cruise and are just trying to maintain speed its bucking like crazy.

Do you think I should go get some new injectors and then go back for a tune?

trinity_gt said:

I don't know if I'd go back to that shop. I doubt you're maxing the KB injectors at this point. I'd consider getting a second opinion on the tune causing your issues first.

If you still want to go with larger injectors and a tune then you should consider upping the MAF (I assume by "stock intake" in your sig you mean the MAF is also stock GT...) to a Lightning unit and getting the whole combo re-tuned at once.

Click to expand...

oh no sorry just havent updated that. I have the KB big tube kit with 90MM MAF. the only thing stock now on the intake is the airbox. I just never really liked the KB cold air tube.


Yea I will try and find someone around the area thats better. If you know of any good stang tuners around PA, VA, WV, or MD or even NC let me know. Yea i know from the start i was blowing these sensors but only like 1 every couple months but still i never had a problem with the KB tune. Guess I should have listened to KB hahaha