Need a little help

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  • Crankyolman
    350 Buick
    • Sep 27, 2017
    • 891

    Need a little help

    I hope some of you FI guys can help me out here


    The short version of the story is my truck sat for the better part of 3 months while being repainted. It was started and ran every week or two during this period but never run for long because the tank was very close to empty. It ran fine when parked but now that it is back together it starts when cold but as soon as it gets warm it starts having issues and will only stay running at about 2000 rpm. If I let off the gas it sputters and dies and is very difficult to keep running. This morning I warmed it up and made a data log at idle. It took numerous attempts just to get it to idle, you can see the restarts in the log, I let it run for a bit then gave it a little gas and let off and it sputtered and died, which is at the end of the log. Can anybody tell me what's going on and how to fix it?


    Here are the details of my engine
    Stock 1972 AMC 360, TH400 transmission, Fitech 39001 (2 barrel), a Fitech 40102 fuel pump mounted in the fuel tank, (not in a fuel command center), No timing control, No fan control


    Here is a link to the log

    Thank you in advance for any help
    '72 J4500
  • Heep-J4000
    350 Buick
    • Feb 09, 2014
    • 865

    #2
    Can't open the log , but could be because that the fuel tank was almost empty that the carb is clogged with some residue from the bottom of the fuel tank!?

    Or because the warming up is playing a part , maybe a intake leak below the carb or some gasket from the carb is letting air into it.
    Jeep "because mother nature hates flat roads to"

    http://www.ifsja.org/forums/vb/showthread.php?t=180974

    99' Dodge ram 2500 4x4 crew cab 5.9 Cummins ,backup work truck for now
    73' Jeep J4000 (named Heep or Desert Dragon) amc 360 V8 converted to LPG with T15/D20 (was my daily work truck for thirteen years and is getting major overhaul at the moment!)
    80' Jeep cj5 350 V8 Chevy/sm420/D300 project
    70/71 Jeep J4000 parts truck with Buick 350

    Former vehicles:
    85' Volkswagen caddy mk1 1.6 diesel.
    83 Toyota land cruiser BJ42 3.4 diesel.

    Comment

    • Crankyolman
      350 Buick
      • Sep 27, 2017
      • 891

      #3
      My first thought was the fuel filter clogged and I am about to go check that/


      For those who might not be able to see the One Drive stuff here is a snip of it running badly



      and another of it when it was running well



      The differences I see are
      Good / Bad

      I (AFR TRIM) =a little higher. 11-12 is normal, in some it was as high as 40


      K(IDLE FUEL L)=120 / 129.7


      R(SPARK ADVANCE)=14 / 18 I'm not using timing control so shouldn't matter


      U=13-15 / In this section it is in the low 30s but in other areas it's -7 to -9 (that's negative 7 to negative 9)


      V(FUEL PUMP)=97 / 84 This varies normally from 80 to 100


      X(AIR TEMP)= 96 / 68 I assume this is the air temp under the hood. when the 2nd one was taken the hood was open.


      Y(CYLINDER TEMP)=154 / 132 This is some sort of wild guess on the fuel injectors part.


      Z(BATTERY)=12 / 14 The before was with the under powered Motorola Alternator, after is Powermaster 150 amp.
      '72 J4500

      Comment

      • rang-a-stang
        Administrator
        • Oct 31, 2016
        • 5472

        #4
        Have you measured your voltage to the computer? Or grounds from the computer? I am wondering if some of those values are off because of bad/missing grounds or low reference voltage.
        Chuck McTruck 71 J4000
        (Chuck McTruck Build Thread)
        79 Cherokee Chief (SOLD, goodbye old buddy)
        (Cherokee Build Thread)
        11 Nissan Pathfinder Silver Edition 4x4
        09 Mazdaspeed3 Grand Touring
        00 Baby Cherokee

        Comment

        • Crankyolman
          350 Buick
          • Sep 27, 2017
          • 891

          #5
          I haven't done anything yet, wound up having to do the weekly running around today instead of working on the truck.


          I know the Fitechs are sensitive to interference from spark plug wires and I haven't shielded the wire but up to now there haven't been any issues so I haven't worried about it. I'm really hoping it's something simple like the fuel filter but it starts acting up right at the temperature it goes into self tuning mode so I'm afraid it's something computer or sensor related.
          '72 J4500

          Comment

          • babywag
            out of order
            • Jun 08, 2005
            • 10284

            #6
            Start with basics...
            Check fuel pressure
            Check voltage @ fuel pump
            Check + connections and grounds.
            Tony
            88 GW, 67 J3000, 07 Magnum SRT8

            Comment

            • Crankyolman
              350 Buick
              • Sep 27, 2017
              • 891

              #7
              OK I pulled and cleaned the fuel filter, that wasn't the problem. There was a small amount of debris but not much.



              So then I moved the spark plug wires as far away from the tach wire as possible. No help.


              I checked connections, all of them seem good.


              Fuel pressure is strange. when I initially turn the key on it is 58PSI as it should be but drops to 40 or so at idle, then if I rev it it drops more. because this system feeds fuel back to the tank I don't know if this is normal or not because I've only ever checked the fuel pressure prior to start and at idle, but it seems a bit low. I'm currently trying to figure out how to set the fuel pump back to initial setting to get full pressure all the time. I wonder if I should cap the return line and see what kind of pressure I have while running.


              The popping through the throttle body is bothering me so my plan for tomorrow is to pull the plugs and check them and the compression, maybe new plugs as well. I like to change out the spark plugs ever year or two anyway.
              Last edited by Crankyolman; 07-26-2020, 11:39 PM.
              '72 J4500

              Comment

              • babywag
                out of order
                • Jun 08, 2005
                • 10284

                #8
                Pressure should not drop.

                If it is dropping either the pump or regulator isn't working properly.

                The popping through throttle body is likely because it is running very lean.
                Just looked @ AFR on bad running...it is WAAAAY too lean!!!
                18.3 18.6 17.9
                that's piston melting lean

                Last edited by babywag; 07-27-2020, 03:52 PM.
                Tony
                88 GW, 67 J3000, 07 Magnum SRT8

                Comment

                • DarkMonohue
                  Shakes hands with danger
                  • Jul 01, 2012
                  • 1145

                  #9
                  Lean AFRs aren't terribly dangerous at idle, but they won't help it run well.

                  You're seeing lean AFRs despite increased fuel trim and consequently longer injector pulsewidth. That does suggest a fuel pressure problem.

                  I'd be very interested in seeing what fuel pressure is like when it runs well and when it runs poorly, as well as voltage at the pump (measured directly with a voltmeter) under those conditions. It's possible that either the fuel pump or the circuit that feeds it are working well when cool, but failing after a few minutes of work.
                  '85 J20 Old Man Truck, bought @ 65K miles - not great, but better than walking.
                  Member, FSJ Prissy Restoration Association
                  High quality junk here: intro thread and slow build thread

                  Did you know? Willys is just Willis spelled differently, but pronounced the same. Neither Willy nor his apostrophe are involved.

                  Comment

                  • babywag
                    out of order
                    • Jun 08, 2005
                    • 10284

                    #10
                    most fitech(s) i have seen run pretty rich@idle.
                    16/17/18 AFR won't run worth a crap and if his pressure falls with throttle it will never drive.
                    he'll just get lean backfires out throttle body and stalling.
                    Tony
                    88 GW, 67 J3000, 07 Magnum SRT8

                    Comment

                    • DarkMonohue
                      Shakes hands with danger
                      • Jul 01, 2012
                      • 1145

                      #11
                      Agreed. It's definitely not going to be happy idling that lean.

                      My limited experience is that most engines idle a little better just on the rich side of stoich.

                      Fuel pressure at the rail needs to be verified. This could be as simple as a dodgy pump or a poor connection that transmits less and less power to the pump when it gets hot.
                      Last edited by DarkMonohue; 07-28-2020, 09:11 PM.
                      '85 J20 Old Man Truck, bought @ 65K miles - not great, but better than walking.
                      Member, FSJ Prissy Restoration Association
                      High quality junk here: intro thread and slow build thread

                      Did you know? Willys is just Willis spelled differently, but pronounced the same. Neither Willy nor his apostrophe are involved.

                      Comment

                      • Tripwire
                        AMC 4 OH! 1
                        • Jul 30, 2000
                        • 4656

                        #12
                        even though i have 3 rigs with howell FI the only problem i had ever with running poorly and dying was a bad TPS, why do your readings indicate zero at idle - there should be something there IIRC is like 1 volt closed throttle and Wide open 5 volts more or less?

                        alot of guys here are experts on FI, i am only a humble beginner who installs pre-made kits

                        steve
                        Abort? Retry? Ignore? >

                        86 GrandWag. Howell fuel Injected 360. MSD Ignition + Dizzy. 727/229 swap BJ's 2" Lift and 31's

                        88 Wrangler 4.2, Howell TBI and MSD - Borla Headers w/ Cat-back + winch and 31's AND a M416 trailer (-:

                        Comment

                        • babywag
                          out of order
                          • Jun 08, 2005
                          • 10284

                          #13
                          tps in log is probably a %
                          modern systems tend to auto-zero
                          so 0=idle and anything above is a calculated % based on pcm/sensor reporting
                          Tony
                          88 GW, 67 J3000, 07 Magnum SRT8

                          Comment

                          • Tripwire
                            AMC 4 OH! 1
                            • Jul 30, 2000
                            • 4656

                            #14
                            thanks tony....wow thats new, ok so how can the tps voltage be above 6 volts? or is this FI a non GM based system?

                            steve
                            Abort? Retry? Ignore? >

                            86 GrandWag. Howell fuel Injected 360. MSD Ignition + Dizzy. 727/229 swap BJ's 2" Lift and 31's

                            88 Wrangler 4.2, Howell TBI and MSD - Borla Headers w/ Cat-back + winch and 31's AND a M416 trailer (-:

                            Comment

                            • Crankyolman
                              350 Buick
                              • Sep 27, 2017
                              • 891

                              #15
                              Wow, getting a lot of discussion and I'm learning a lot. Thank you everybody. Fitech tends to have less than stellar customer service and I don't know a lot about EFI so I have to rely on the generosity of others.


                              So there is a story about PWM and AFR. PWM is supposed to come pre set to 74.9 but for some reason mine came pre set to 80 but at the time I got the setup their website said 74.9 was for the frame mounted pump but to reset it to 40 if you are using the fuel command center. Since I am using the the same pump as the command center but in the tank I asked Fitech what I should set PWM to. They sent me 3 different emails about completely different things and FI systems and none about PWM. and they eventually just quit answering my emails rather than actually answer my questions or actually read my emails.


                              Driving it in the beginning it became apparent PWM at 80 was far too high and was causing some issues so working with some people we eventually worked it down to 66. It ran really good at that.



                              The preset fuel mixture was also far too rich and eventually I got that adjusted so it was 13.5-13.8 at idle and low to mid 14s at speed but it always had a tiny lean tip coming off idle but never long enough or severe enough to matter.



                              You can adjust the target mixture and I've always kept them a little on the rich side but never as rich as the factory settings.



                              Now one thing many people have run into is whatever it is that controls the fuel pump in the Fitech system has been known to fail and cause issues and people often have to go to some kind of fuel pressure regulator instead of the factory controller but I don't even know the first thing about setting something like that up but that kind of thing seems to be the direction this thread is heading. Hopefully someone can nelp me out if it comes to that.


                              I did set the PWM back to 80 and it helped make it run better. Fuel pressure at idle is only 35-37, which seems low and pressure rises when the throttle is moved instead of dropping. The pump is running at 99% all the time but there is still a severe lean spike, hesitation, popping back when I hit the throttle quickly. I think they have an adjustment to increase the fuel when you accelerate but I'll have to research that. I'm also considering the possibility of buying a frame mounted pump and or a fuel pressure regulator if I can figure out how to make such a thing work correctly.
                              '72 J4500

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