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Old 02-07-2017, 02:48 PM   #1
Procharged2k3
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I keep popping the FRPS!!

I posted this at SVTP as well, but thought I'd see if the pros here have any idea too.

So my Mach keeps popping the fuel rail pressure sensor every few days after my latest upgrades. It's got a Cobra short block and is Procharged, with an 03/04 Cobra tank swap + KB BAP (40 amp) and 60# injectors. Making 486 rwhp right now, can't seem to get any more out of the P1SC.

The most recent upgrades I'm talking about specifically include smaller blower pulley, larger crank pulley, and an alternator underdrive pulley to keep that from overspinning.

The strangest part is that it only pops the sensor at idle... it happened once as I shut the car off, and the second time it happened 2 seconds after I started it.

This is driving me nuts.
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Old 02-07-2017, 03:09 PM   #2
DSG2003Mach1
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Re: I keep popping the FRPS!!

its a bandaid for sure but have you looked into the burst disc KB was making for a while? It popping that quick after startup is tough to get any kind of useful datalog going. Hopefully it would last a bit longer and you could get a log of what might be causing it
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Old 02-08-2017, 12:07 AM   #3
01yellerCobra
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You shouldn't need the BAP at that power level. If you still have the dial turn it all the way down. If you don't I'd remove it from the circuit for now.

My guess would be the BAP is over driving the pumps which is causing high pressure.
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Old 02-08-2017, 09:38 AM   #4
Mach828
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Re: I keep popping the FRPS!!

^^ Agreed

Tune issue might be contributing to it as well. The tuner might not have the fuel pressure tables dialed in. So it thinks it needs to send let say 8 volts but by the time the computer realized that is way too much fuel the FRPS has popped.
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Old 02-08-2017, 10:19 AM   #5
Procharged2k3
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Re: I keep popping the FRPS!!

It's true I probably don't need the BAP at this power level, but my tuner believes something else is the culprit since there are thousands of Cobras running around with this same fuel setup. I was also using the BAP and these dual pumps on the same settings with the previous tune for months at 448 rwhp before the upgrade with no FRPS problems.

I think he's going to take a look at the tune, since a new tune was also part of the latest upgrades of course... maybe he'll see something in there. He's a great tuner though, one of the best Ford guys in the midwest.

I've actually got the car at his shop right now and he's trying to pin down the issue, but was seeing if any of you guys had any ideas as well. The collective knowledge here is awesome.

DSG2003Mach1: Yeah I was thinking about a KB burst disc, I'm going to see if we can figure out the real cause as well though... then add one of those for extra protection.
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Old 02-08-2017, 10:46 AM   #6
Procharged2k3
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Re: I keep popping the FRPS!!

Maybe we went a little too big with the alt underdrive pulley and voltage is too low at idle, causing the BAP and computer to do weird stuff to compensate for fueling... like too high a duty cycle when the voltage is low and when the voltage goes back up a bit it spikes before the computer can stop it?
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Old 02-08-2017, 10:48 AM   #7
TKat13
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Re: I keep popping the FRPS!!

When I had a BAP making similar power and a single 340lph pump, I had to turn the BAP down to 25% just for the computer to be able to control the fuel at the normal driving loads, idle , etc. Never killed a pressure sensor but my tune had me turn it down after the first pull on the dyno. Ultimately, I ended up removing it completely. I was also running E85 which requires more fuel as well. Just my 2 cents.
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