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289 dies after starts, runs happy when warm

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    289 dies after starts, runs happy when warm

    I'm not sure anyone can help me on this, because I have an aftermarket electronic fuel injection (Retrotek Speed) that isn't supported anymore, company is gone, which makes normal diagnosis hard... but I'll give this a try:

    The car starts well and runs well, but about 30 seconds after starting the revs drop off until it cuts out, the only way to keep it going is to feather the accelerator, and then rev the nuts off it... then when it settles down it might idle. Once she is running/hot it's very happy (idle is a tiny bit high). I can't remember a time when it wasn't like this.

    Other info: I'm replacing the rotor arm and the distributor cap at the moment and it is a '68 286 with Petronix ignitor and MSD 6AL electronic ignition

    If it runs fine then dies off I would look at fuel supply / pressure / flow.
    I am guessing a fuel injection system will need consistent fuel pressure
    Current Mustang Red 1965 Coupe - Previous Mustangs 2008 S197, 1965 Coupe


      A description of it's connections I found;

      Add positive and ground leads from the battery, an ignition lead, a lead from the coolant temp sensor in the intake, and snap in a wide-band O2 lead, and you're ready to go. Everything else is pre-wired, and the injector body is an all-inclusive EFI system. No fuel rails to plumb, no extra wires to run or sensors to install, and no headaches. Hit the ignition and the basic tune will get the motor started. At that point the STT System will start checking air/fuel ratios 60 times per second, until it creates it's own fuel curve. Drive around the block and the system will continue to learn, until engine operations reach peak efficiency. As your driving style changes, the STT will continue to adapt.

      Just a thought.
      It uses an input from the coolant temp sensor.
      I wonder if that's U-S and it's seeing the water temp as normal (or defaults to normal if the sensor has failed) and not richening for cold start but running O.K for normal running.
      2014 GT/CS
      88 LX 5.0 Coupe, sold.


        As Scaf says I think you need to check the fuel pressure against what is required and ensure an adequate fuel supply. I would also check the sensors in the coolant and exhaust. I doubt if these parts were made by Retrotek so I would assume they may still be available. I think if the system itself had bust it would not run at all.


          Does sound fuel pressure related on a EFI system.
          Last edited by rider; 11-01-2019, 01:07 PM.


            Found this into text on the system from 2006 for reference:

            Thank you for your interest in the all-new RetroTek BossEFI system. The
            story in Hot Rod magazine came out a little early and our site was not ready
            to go up so we will be adding info daily.

            To answer some basic questions, the system is set to target the $2000.00
            price range for the 930cfm body and comes as a complete package. The
            Throttle body bolts in place of a Holley or similar 4 barrel and has the
            same overall dimensions, so the air cleaner will remain in the same

            The computer is the first self-tuning system available and is a speed
            density ,closed loop system . We use a PLX wide band (included) and the
            system delivers hands free tuning at all loads and RPMēs. The key to our
            system is its VE SYNC which reads the air fuel of your engine and re-writes
            the base fuel table to deliver the exact Target Air Fuel ratio desired for
            your engine. This can be done while viewing the info on a laptop, or without
            one. The system re-programs itself so the oxygen sensor does not have to
            work to correct an inaccurate calibration each time you run your engine.
            Once this is done you can leaved the O2 in place to compensate for various
            fuel and elevation differences. A video demonstrating a system being tuned
            will be posted on the site shortly so keep checking it out.

            The kit comes with a high pressure fuel pump that mounts on the chassis at
            or below the fuel tank . For over 500HP and larger applications, an
            ultra-high performance pump is required for an additional charge. Also there
            is no need for a return fuel line although one may be used along with an EFI
            bypass regulator. The return-less system is included in the kit but the
            bypass style system is not included and can be purchased separately.

            ECU & WIRING DETAILS
            The computers dimensions are 6-inches long, 4.5-inches wide, and 1.65-inches
            high; and it can be mounted either under the dash or in another dry
            location. All wiring features weather pack connectors and are completely
            terminated although you are required to install an o2 sensor bung in the
            exhaust pipe. This can be done in one side only by any muffler shop and the
            bung is included.

            There BossEFI comes in 2 sizes, 930 & 1200 cfm ratings. The 930 will handle
            up to 650hp and the 1200 is good for 900+hp with the correct size injectors.
            There is a simple formula to size the injectors. We use 4 so the math is:

            HP divided by 2 /4 = injector size.

            The computer is capable of very small pulse widths so it is better to be a
            little large in this area. An example of this is 500hp/2/4 = 62.5lbs. In this
            case we would use 63 lb injectors.For Dual Quad systems we would have 8 injectors so HP/2/8= injector size. 500hp/2=250/8=31.25. We would supply 8 32lb injectors in the kit. You can use this simple math to work up any HP combo you have. This is a Quick tip only,call us if you are un sure. All necessary sensors are included so
            this is a true bolt on system!!

            We will be sending out periodic emails with more details about the BossEFI
            system up to the Spring 2007 release date. Please stay tuned, as THE MOST

            Thanks for your interest,
            RetroTek Speed


              As well as the HP pump pressure it'd be worth checking out the O2 sensor. You can easily check out the integrity of the heater circuit by a simple resistance check across the sensor, checking the sensor output will be somewhat harder with no OBD port to access but it is possible with a blow torch, multi-meter and 12v source. These sensors are recommended to replace every 50,000 miles or so. If you remove it and it looks dirty then some claim they can be cleaned with oven cleaner or 24hrs sat in lemon juice. Best would be to replace if there is a sensor available with the same boss fitting.