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Thread: "F" 250 as the ultimate tow rig! Can it be?

  1. #31
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    My stock fuel pump had a check valve and held pressure, even when the pump was only pushing 12psi. The new pump didn't and immediately went to 0 when the car was shut off.

    I think the newer pumps just don't use them.
    Quote Originally Posted by jcassity
    I honestly dont think you could exceed the cost of a new car buy installing new *stock* parts everywhere in your coug our tbird. Its just plain impossible. You could revamp the entire drivetrain/engine/suspenstion and still come out ahead.
    Hooligans!
    1988 Crown Vic wagon. 120K California car. Wifes grocery getter. (junked)
    1987 Ford Thunderbird LX. 5.0. s.o., sn-95 t-5 and an f-150 clutch. Driven daily and going strong.
    1986 cougar.
    lilsammywasapunkrocker@yahoo.com

  2. #32
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    I think I found the problem. The regulator is not working well. Under load the fuel pressure drops off. Not sure if it's the regulator seat or plunger. Appears the diaphragm is still fine but something else is not working correctly. I have a stock fuel rail and regulator and I'm gonna try that with the 24# injectors.

  3. #33
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    Hope that is part of the problem but dips in pressure also indicate lack of enough volume.

  4. #34
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    Quote Originally Posted by Aerocoupe View Post
    Hope that is part of the problem but dips in pressure also indicate lack of enough volume.
    I agree, but feel some of the volume is being limited possibly by the regulator returning needed fuel. I will cross that bridge once I determine if replacing the regulator makes a difference. There may not be an issue after that. After all, these pumps also fed 460 powered trucks, they should be enough for a 351 with heads and a lightning intake.

  5. #35
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    The key to this one as Aerocoupe said, the fuel pressure is fluctuating all over the gauge as well as the rail did not hold pressure after the key was off. These trucks have issues with the 1 way check valve on the fuel supply side that normally causes issues. This was not the case for me as it was not filling from tank to tank, which is the usual characteristic.

    So I did find the issue. The regulator was hanging open. I pulled the rails and 19# injectors out and blew through the inlet and air was coming out the return. That should not happen until the adjusted pressure is reached. Since I did this by mouth, I doubt I reached 40ish lbs.

    I replaced the rails with a stock 1994 set with a factory regulator as well as I crawled underneath to look at the fuel filter. It had a cheap Chinese duralast filter, so pitched it in the trash and installed a Motorcraft. Bang! Easy 30 hp and 100 foot lbs of tq. Now it's impressive! I'm excited to tow with it again!

  6. #36
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    Finally got a code! 38, Idle tracking switch.... Assuming the IAC is taking a dump. Gonna try to clean it and see what happens.

  7. #37
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    OK, so I've had enough of this Speed Density system. Its impossible to tune out the issues since I changed the heads and cam. It's gonna get real for the truck cause I'm going 1993 Cobra X3Z computer and Mass Air. I am sick of the erroneous computer codes and Full rich check engine lights. There is nothing left to replace or eliminate.

    I'll post pictures and a write up as to why some things are the way they are! I am not using a 302 HO or 351 camshaft, so gonna have to move some injectors in the harness and consolidate the placement of the O2's.

  8. #38
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    BTW, using a Painless harness I had left from another project, so I'm gonna have to make it work.

  9. #39
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    OK, so I was screwing this up. The truck has 3 digit codes and that would make it another test on the scanner. Codes 33, 25, 38 turned out to be 332 and 538. EGR and rack the throttle open. That turned into 332....which is no issue since EGR is not installed. Then I pulled the memory codes. Appears that 128 is an issue (Not sure of the code but think that was it), damaged or inoperable MAP sensor hose.....That's telling me that the computer is not getting the correct vacuum signal and is outside of calibration.

    I'm going Mass Air this weekend! 1993 Cobra X3Z computer and factory MAF. Will work well with 5 speed and 24# injectors. I'm in the process of cutting up a harness and making a few things to make this work. Decided to go with a "Layover" harness, that lays on top of the existing one to get the job done now. I just need it to work correctly and be able to tow my race car. I'll take some pics of the harnesses and install. I have already pulled the required harness pieces out of my gacked 88 Bird harness to get what I need.

  10. #40
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    Ok, I suck. I did not get any pictures of the harness and the install this far. I will go snap a few tomorrow morning, but I'm almost done. I did fire it up today. Here is the list of stuff I did.
    1. Made an injector harness from an old 88 bird harness, pinned out each injector and moved the 7,3 and 5,4 injectors to work with my Tbird SO camshaft firing order.
    2. Made an O2 harness from the same old bird harness. Placed both O2 sensors in the same place on the 4" exhaust since the injectors are shuffled around. The computer may have been confused if I left them for each bank and it would be controlling the wrong injectors. This made them read all of the O2 total but would see changes.
    3. Removed upper intake and cutout injector harness from truck existing harness.
    4. Placed the "layover" injector harness in the truck and moved pin 8 to 19 and 11 to 32 and 51 to 38 to start. I then pulled all the original truck pins cooresponding to the new harness and plugged in each pin.
    5. Placed the O2 harness in the truck and the sensors, plugged in the pins and ran a chassis ground as well as a +12 volt to the O2 heaters. The +12 can only be hot when the key is on or it will burn up the heater leaving it on all the time.
    Lastly, I dropped in the MAF and harness, plugging in the pins 50 and 9 and piggybacking 37 and 40 to get the MAF up. I then had to cobble together an air intake using some of the existing piping and the factory elbow.
    I was so excited to hit the key, kind of expected it not to start, but it fired right up. Adjusted the idle and tps in the ball park and drove around the block.
    I did notice the motor revs so quick now, timing and fueling must be way different on the MAF computer vs the truck speed density. The idle is so nice and smooth as well as the drivability is way better.

    I need to install the computer in the holder and cut back some of the removed pins as well as clean up some of the wiring tomorrow. I'll shoot some pics, I promise, and upload them. I'm also gonna drive it on the road tomorrow and see how it goes.

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