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Thread: Help Needed !!!!

  1. #1
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    Help Needed !!!!

    Ok, I'm stumped I have a 347 stroker with Mass Flo FI, I thought closing off the front of the air cleaner would solve my issue with bucking and hesitation as speed and rpm increased but it's back. It happens in 2nd, 3rd and fourth gears. The engine runs fine till about 3,500 rpm or so but as it approaches 4,000 it starts to buck and sputter and refuse to rev anymore like it's starving for fuel. Anyone an expert with this Mass Flo thing? ANy suggestions? Help a newbie.

  2. #2
    Boydster's Avatar
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    Could be a timing issue...
    ---Boyd---
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    any idea where timing should be?

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    Senior Member cv2065's Avatar
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    Quote Originally Posted by caesarmascetti View Post
    any idea where timing should be?
    Do you have a timing light? Have you verified TDC? Even if its not related, I would at least get a baseline of where you are for future reference.
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  6. #5
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    Off timing, usually feels like the engine is sluggish or has a low peak rpm. Your issue sounds like lack of fuel. Popping can be a lean backfire, also related to lack of fuel. I would check your fuel pressure, filter, heated fuel lines, etc.
    Fuel inj engines are not too sensitive air flow interference.
    Is this a problem that just developed or something occurring with your build?
    A picture of your CAI, MAF sensor location. Check for air leaks in your CAI. If unmetered air is getting in the engine, your ECU cannot read how much fuel you need. If you have a TB FI, same for vacuum leaks.
    Give us all the info you can, easier to diagnose.
    Engine ign timing cannot be ignored. What distributor and ign are you using?
    20th Anniversary Mk IV, A50XS Coyote, TKO 600, Trunk Drop Box, Trunk Battery Box, Cubby Hole, Seat Heaters, Radiator hanger and shroud.

  7. #6

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    In the early models of the Mass-Flo systems they were having problems with the converter from corvette mass air meter to Ford electronics. Also I would check fuel pressure. should be around 40 PSI and timing at 10 degrees below top dead center.
    Call Chris Richards at Mass-flo if you cannot get it figured out.
    mike

  8. #7
    Not a waxer Jeff Kleiner's Avatar
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    I've encountered this on a couple of cars. Check fuel pressure UNDER LOAD while the problem is occurring. Watching pressure when just revving it in neutral won't tell you if the problem is fuel starvation. Put enough hose on the fuel pressure gauge so that you can run it out the back of the hood and tape the gauge to the windshield so that you can see it from the seat then go out for a drive and watch for the pressure to drop while the stumble or hesitation is happening. If so start with the easiest item first---the fuel filter. If that doesn't get it you'll need to pull the pump to check the sock, the transfer hose from the pump to hard line or the pump itself.

    Good luck,
    jeff

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    guys thanks for the suggestions, I have some work ahead of me

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    ok guys just contacted the original owner and he states he never had a problem with fuel starvation. I'm beginning to wonder if it's bad gas. The car sat since jan on consignment I got it with barely 1/4 tank of gas in it. I may trying having an FI service done at my local service center

  11. #10
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    Quote Originally Posted by caesarmascetti View Post
    I may trying having an FI service done at my local service center
    I would not be in favor of this. I will not list all of the bad things that can happen.
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  12. #11
    Senior Member karlos's Avatar
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    Had a similar issue with my car, which sat for a number of months while in the process of being transformed in the bat cave (injectors were gunked up and needed to be cleaned). I would agree that having a fuel injector service performed at a local service center may not be the best approach, as they likely won’t have any familiarity with the car and will probably try to service the injectors without removing them from the engine. I had good luck with Witch Hunter Performance, a dedicated fuel injector cleaning and testing facility. If you go this way you’ll have to remove the injectors and mail them off to be serviced, but this is the only way to really do it right. They will clean, test, rebuild as necessary, and provide you with a report showing the before and after performance of each individual injector. Link provided below.

    I also echo the suggestion to call Chris Richards at Pro-M. He’s been a great resource as I’ve worked through the little startup bugs with my Pro-M system. Best of luck in fixing the issue!

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  13. #12
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    very interesting my fuel pressure gauge shows 30psi at idle, thats 10psi lower than specified in the mass-flo user manual

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    ok so looks like when we set the fuel pressure regulator to show 40psi at idle and connect the vacuum hose it drops back down to 33 or so. Should it be 40psi at idle with the vacum hose attached?

  15. #14
    Not a waxer Jeff Kleiner's Avatar
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    Fuel pressureshould increase when vacuum decreases.

    Jeff

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    Quote Originally Posted by Jeff Kleiner View Post
    Fuel pressureshould increase when vacuum decreases.

    Jeff
    I ordered a new fuel pressure regulator lets see what happens

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    Quote Originally Posted by caesarmascetti View Post
    I ordered a new fuel pressure regulator lets see what happens
    The regulator is maintaining different fuel pressure between the manifold and fuel supply, and the gauge is simply connected to the fuel supply, the measured pressure will drop when the engine is started or the vacuum hose is connected. The gauge needs to measure the differential pressure between the manifold and the fuel supply to know what is really happening when the engine is running.

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    the pressure drops off very quickly once the engine is turned off, going to 0 this is also a symptom of a fuel pressure regulator problem. Im not going to spend lots of $$$ trying to get what is now an antiquated FI system to work properly. If this doesn't work Im converting the whole thing to a carb

  19. #18
    Senior Member CraigS's Avatar
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    Fuel pressure dropping when vac is connected is normal. Connecting and disconnecting the vac hose and looking for a FP change is a common quick diagnostic procedure. I don't know the specs of the MassFlow system but some quick googling says stock efi Fox Mustangs FP is 38-40 w/o the vac hose and 33-34 w/ the vac hose connected. I don't know if Mass Flow was set to run at those same pressures or not but, at least you are in the ball park. FP dropping when the engine is off is fine as long as it builds immediately when the key is turned on. The pump should run for maybe 6-8 seconds when you turn the key to on. Then the pump will shut off until the ecu sees that the engine has started.
    FFR MkII, 408W, Tremec TKO 500, 2015 IRS, DA QA1s, Forte front bar, APE hardtop.

  20. #19
    Senior Member Joel Hauser's Avatar
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    I was having similar problems with my EFI 4.6 L engines. I changed the fuel pressure regulator, MAF sensor, IAC, and a bunch of other parts, but to no avail. Then I bought a fuel pressure gauge. Sure enough I had very low fuel pressure, it pressure dropped to zero as soon a the car was turned off. It turned out that the short "Z" shaped hose that connects the actual pump inside the tank to the solid line that exits the tank had come loose. The check valve at the output end of the pump, which I think is intended to prevent rapid pressure drop when the engine is turned off, so you have pressure when you restart the car, had popped out and was stuck inside the hose! I bought a new pump assembly on ebay, and that fixed my pressure problem.
    With my MK4, I was able to remove the pump without dropping the tank by removing the oval access panel in the trunk.
    good luck

  21. #20
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    Quote Originally Posted by Joel Hauser View Post
    I was having similar problems with my EFI 4.6 L engines. I changed the fuel pressure regulator, MAF sensor, IAC, and a bunch of other parts, but to no avail. Then I bought a fuel pressure gauge. Sure enough I had very low fuel pressure, it pressure dropped to zero as soon a the car was turned off. It turned out that the short "Z" shaped hose that connects the actual pump inside the tank to the solid line that exits the tank had come loose. The check valve at the output end of the pump, which I think is intended to prevent rapid pressure drop when the engine is turned off, so you have pressure when you restart the car, had popped out and was stuck inside the hose! I bought a new pump assembly on ebay, and that fixed my pressure problem.
    With my MK4, I was able to remove the pump without dropping the tank by removing the oval access panel in the trunk.
    good luck
    thanks I'll have them check this as well.

  22. #21
    Not a waxer Jeff Kleiner's Avatar
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    Caesar,
    You have not yet told us the results of a fuel pressure test under load as I suggested a couple of weeks ago. This will go a long way to helping answer what is happening. As Craig said your fuel pressure regulator is behaving as it should.

    I got a good chuckle out of this:

    trying to get what is now an antiquated FI system to work properly. If this doesn't work Im converting the whole thing to a carb
    Seems to me that is going to something that is even more antiquated...but hey, that's just me

    Jeff

  23. #22
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    Quote Originally Posted by Jeff Kleiner View Post
    Caesar,
    You have not yet told us the results of a fuel pressure test under load as I suggested a couple of weeks ago. This will go a long way to helping answer what is happening. As Craig said your fuel pressure regulator is behaving as it should.

    I got a good chuckle out of this:



    Seems to me that is going to something that is even more antiquated...but hey, that's just me

    Jeff
    Hi Jeff the fuel pressure test showed 34psi under load. It was set to 40psi before connecting the vacuum hose, so it dropped to 34 and stayed there even under load. LOL yeah but sometimes antiquated is just easier.

  24. #23
    Senior Member CraigS's Avatar
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    "...it dropped to 34 and stayed there even under load". Just to be sure I understand, how did you apply a load? Did you have the gauge connected while driving the car?
    FFR MkII, 408W, Tremec TKO 500, 2015 IRS, DA QA1s, Forte front bar, APE hardtop.

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    yes the shop had a gauge tapped to the widsheild of the car while they drove it

  26. #25
    Senior Member CraigS's Avatar
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    This is getting weirder by the minute. I am surprised that the pressure will vary at idle depending on having vac or no vac but then it doesn't do the same while driving. Is there a way to tap into the MassFlow and connect a laptop to watch mixture while driving and reproducing the problem. BTW what have you done w/ the gas in the tank? Had a boat w/ a Yamaha 4 stroke outboard w/ similar problem. Started misfiring at higher rpms and over a few months the rpm where it started got lower and lower. Pulled the boat out of the water in Oct and decided to chase the problem in the spring. Long story short, by then the water in the gas had sat in the tank and efi system for 6 months. Replaced the gas and finally took it to the local Yamaha shop. They cleaned corrosion out of the fuel reservoir in the engine, replaced the high pressure pump, had the injectors cleaned, replaced both fuel filters, and finally $2400 we later had a great engine again.
    FFR MkII, 408W, Tremec TKO 500, 2015 IRS, DA QA1s, Forte front bar, APE hardtop.

  27. #26
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    Quote Originally Posted by CraigS View Post
    This is getting weirder by the minute. I am surprised that the pressure will vary at idle depending on having vac or no vac but then it doesn't do the same while driving. Is there a way to tap into the MassFlow and connect a laptop to watch mixture while driving and reproducing the problem. BTW what have you done w/ the gas in the tank? Had a boat w/ a Yamaha 4 stroke outboard w/ similar problem. Started misfiring at higher rpms and over a few months the rpm where it started got lower and lower. Pulled the boat out of the water in Oct and decided to chase the problem in the spring. Long story short, by then the water in the gas had sat in the tank and efi system for 6 months. Replaced the gas and finally took it to the local Yamaha shop. They cleaned corrosion out of the fuel reservoir in the engine, replaced the high pressure pump, had the injectors cleaned, replaced both fuel filters, and finally $2400 we later had a great engine again.
    yeah well going to look at one last thing then converting it to a carb. replacing the fuel pressure regulator and if that doesn't work, the whole FI system is going being replaced with part's from Mike Forte carb, intake etc....

  28. #27
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    Quote Originally Posted by CraigS View Post
    This is getting weirder by the minute. I am surprised that the pressure will vary at idle depending on having vac or no vac but then it doesn't do the same while driving. Is there a way to tap into the MassFlow and connect a laptop to watch mixture while driving and reproducing the problem. BTW what have you done w/ the gas in the tank? Had a boat w/ a Yamaha 4 stroke outboard w/ similar problem. Started misfiring at higher rpms and over a few months the rpm where it started got lower and lower. Pulled the boat out of the water in Oct and decided to chase the problem in the spring. Long story short, by then the water in the gas had sat in the tank and efi system for 6 months. Replaced the gas and finally took it to the local Yamaha shop. They cleaned corrosion out of the fuel reservoir in the engine, replaced the high pressure pump, had the injectors cleaned, replaced both fuel filters, and finally $2400 we later had a great engine again.
    put in injector cleaner VP, also have filled the tank twice since the problem started, driving it under 3500rpm to avoid the stuttering etc

  29. #28
    Senior Member frankb's Avatar
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    Caesar:

    Years ago, I had an ignition coil fail on my Mustang and its symptoms were the same as you describe. You may want to check it to eliminate it as the issue...

    Frank B
    FFR MK4 #8317, 393 Cleveland, Lunati VooDoo solid roller, CHI 3V heads and intake, TKO 600, Std roadster seats, 8.8 3.55 diff, 17" Halibrand replica wheels, Ford "Magnetic Metallic", silver ghost stripe. (Sold 10/16/21)

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    Quote Originally Posted by frankb View Post
    Caesar:

    Years ago, I had an ignition coil fail on my Mustang and its symptoms were the same as you describe. You may want to check it to eliminate it as the issue...

    Frank B
    thanks will do

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    well the saga continues, had my shop check out the coil, as well as replace the fuel pressure regulator, no change the ignition coil checked out fine they used a meter and everything was within spec. I've thrown in the towel, and just ordered a Holley Sniper and new manifold

  32. #31
    Administrator David Hodgkins's Avatar
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    Quote Originally Posted by caesarmascetti View Post
    well the saga continues, had my shop check out the coil, as well as replace the fuel pressure regulator, no change the ignition coil checked out fine they used a meter and everything was within spec. I've thrown in the towel, and just ordered a Holley Sniper and new manifold
    I'm very tempted to do the same. I'm going to replace my I-squared chassis harness too.
    IMO some mid-aught products many of us installed were just not ready for prime-time. And FFR coming up with their chassis harness made building one of these cars a TON easier!


    FFR 5369 Pin Drive, IRS, Trigos, Torsen, Wilwoods, FMS BOSS 302 "B" cam , Mass-flo. CA SB100 (SPCN) Registered
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