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Fuel pressure S.O.S.

Discussion in '1994-2004 V6 Mustang Tech' started by 016banger, May 15, 2017.

  1. 016banger

    016banger New Member

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    Im a new guy here and have just bought a 01 mustang. It drove fine for a good 45 minutes then lost fuel pressure and died on me. It cranks after sitting and runs, Obd II is reading low 20s when it starts choking on me. Im thinking it's the regulator or fuel injectors. Anyone had this issue?
     
  2. pixapusho

    pixapusho Member

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    Would really start with fuel filter and inspecting for kinks (have had both cause a similar issue). I would do a mechanical test at the schrader valve in the rail. If i didnt have a fuel injection test kit, i would just replace fuel filter and report back.
     
  3. 016banger

    016banger New Member

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    Replaced the fuel filter which definitely helped with the fuel pressure but it is still reading mid to high 20s. Then it drops drastically and nearly cuts off if i don't hit throttle hard. Thank you for your help, any advice is appreciated
     
  4. 016banger

    016banger New Member

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    Update, i took it for a test run after letting it idle for fifteen minutes. It ran well for half a mile tip the local store. I went in for fifteen minutes and came back out. Lo and behold my little car full of fun does the same dann thing. Cranks, idled horribly then died. I came back to it around thirty minutes later and revved it to about 4000 rpm for a few seconds before driving it home. I'm gonna try and clean the fuel injectors next. This car sat for a while before i bought it, possibly just clogged. Any advice would help
     
  5. 6 Shooter

    6 Shooter Well-Known Member

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    Would also consider replacing the fuel rail sensor which can go bad. I have replaced mine multiple times over the year. The main problem that the sensor goes bad is because the files that Ford uses to control the fuel pump are lousy. Fuel pressures can swing from 20 to 90 and it's the high pressures that cause the fuel rail pressure sensor to get confused and out of calibration, even though not leaking. The only fix for the pump files is to change them in the tune and have found through experimentation the numbers which control the fuel pressure to within + or - 2 psi from 40.
     
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  6. 016banger

    016banger New Member

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    Thanks shooter, I'll be looking into that next. Would a tune in a can change/help the problem after the initial fix? Also I've noticed you're pretty prominent on here, thank you for all the help you give.
     
  7. 6 Shooter

    6 Shooter Well-Known Member

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    Only way to change the tune in the area of the returnless fuel pump is with an SCT tuner and providing him with new/different returnless pump specs which I have. If you have switched out the fuel pump to one with higher flow than the stocker, the fluctuating fuel pressure is even worse.
     
  8. 016banger

    016banger New Member

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    Ok cool, thank you for the advice. I'm very new to tuning and custom tunes.
     
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  9. Captain Max Silver

    Captain Max Silver Captain Max Silver

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    That Was A Big Help Here!! Thanks
     

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  10. 6 Shooter

    6 Shooter Well-Known Member

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    Captain Max, have you switched out the stock fuel pump for a higher flowing pump?
     
  11. Captain Max Silver

    Captain Max Silver Captain Max Silver

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    No Not Yet, Installed This One Last Year, ( I Know That Doesn't Mean Anything They Go Bad Anytime ) Just Replaced K&N Fuel Filter 3 Days Ago, Just To Make Sure No Block In Line. Have 5.0 4 Pintel 19# Injectors Installed At Moment, Have 24# 12 Pintel Injectors To Install But Want To Get Pressure Up First. Have Intake Spacer To Install At Time Of Change Of Heads And Injectors. Any Thoughts On Adding Inline Secondary Pump To Get Pressure Up. Also Was Reading About Fuel Rail Sensor Problems With Ford Software. Should I Swap That Out First?
     
  12. 6 Shooter

    6 Shooter Well-Known Member

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    You can change the sensor, change the FPDM, and change the fuel pump and will get the same results. Never seen the FPDM go bad so changing it is a waste of money. The fuel rail pressure sensors do go bad quite often when the fuel pressures spike up into the 90 psi range. Will say that that sensor is the identical to the ones on the Cobras and GTs.

    Best suggestion is to locate a local SCT tuner and ask them how much to change the fuel pump value files that you will provide them. If you find one you can trust/afford, send a private message with your email address. You will want to change the fuel injectors and the fuel rail pressure sensor at the same time of making the tune change. The tune change which will take about 1-2 minutes. The Ford value files for the stock fuel pump are lousy and cause huge swings in fuel pressures which you are noticing. The value files will control the pressure swings and a change to the voltage table will accommodate the 24s. One last issue will be that the PCM will probably make all fuel settings rich due to switching to the 24s. The tuner can then adjust the MAF transfer function (think air fuel ratios at all throttle settings) which will take a little dyno time, maybe 1 hour. The 24s will increase the fuel flow at all throttle settings and engine loads by 21%. The MAF transfer function table can be changed by the tuner to accommodate the extra fuel flow.

    Suggest you first switch out the heads, the fuel rail pressure sensor, and keep the 19s. Then, when ready, switch to the 24s and do the tuning.
     
  13. Captain Max Silver

    Captain Max Silver Captain Max Silver

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    Thank You, Heads Are P&P Lower Intake Ported Pretty Good, Upper Intake Ported As Much As I Can Without Cutting It Up. Have Manifold Spacer To Keep Upper Intake Cooler As Well, Running Scorpion 1.73 Rockers As Well, Shorty Headers. Anyone Make 11mm Studs For The Head Assembly?
     
  14. 6 Shooter

    6 Shooter Well-Known Member

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    ARP. But, not as a kit. You would first have to pull your head bolts (two different lengths) and measure the lengths of the shafts in both inches and milometers. Then, determine the 11mm thread pitch in metric numbers. ARP head studs will be taller than Ford head bolts due to the washer and nut thicknesses. You will need 4 separate ARP parts, two separate lengths of studs, the washers, and the nuts. So, call ARP tech and ask them for the thicknesses of the washers and nuts. Those thicknesses will need to be added to the lengths of the Ford bolt shafts. Next, ask the tech guy the length of 2-3 threads on their studs. Add in those lengths to the thicknesses of the nut and washer. You want, when installed and torqued down, about 2-3 threads sticking up past the top of the nut. One other point, the ARP head studs are to be screwed into the block to where they bottom out, BUT ONLY FINGER TIGHT. You can do the measurements by pulling you Ford head bolts with the heads still on and inserting a long smaller diameter bolt down into the hole and marking the bolt at the top of the head with a Sharpie marker. You now have the ideal length of the stud needed plus the thickness of the washer, the nut, and 2-3 threads. With that known lengths, the ARP tech guy will give you the part numbers.
     
  15. Captain Max Silver

    Captain Max Silver Captain Max Silver

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    Thanks.
     
  16. Captain Max Silver

    Captain Max Silver Captain Max Silver

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    Changed Out FUEL PUMP DRIVER MODULE And Replaced New Fuel Rail Pressure Sensor, Key On Pressure 35lbs. Running Pressure Same About 22Lbs. Found Out My ELM 327 OBD2 Interface Was Junk Ordered New One For Ford. (I Hope) So I Can Log In Some Data.