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  • Hard starting kick backs and back fires

    I have recently installed a pro Flo 4 #35690 on a new 383 stroker in my 77 C3 Corvette .I had the wrong injectors for my horse power changed out injectors to the 35psi injectors part#3636 . Reloaded correct matrix map 5024.even before doing all this I've had kick backs on starter engine would only run for short periods of time back fires cuts out .called tech support followed distributor installation to a tee enginge runs rough if at all .Found out if I set my distributor on 0 degrees tdc on compression stroke on #1 cylinder then start engine then Advance to 12 degrees tdc with timing light then unlock timing on tablet it will run for awhile not long enough to get idle adjusted .Engine starts running rough back fires dies kicks back on restarts I am at a loss with out anymore Ideas to try

  • #2
    Recheck Dist install timing.

    Use a TDC checker, balancer ring may have slipped?
    Maybe timing tab is for a different engine?

    If timing is on the money ......Engine will start & run & can give gas & rev.....
    If it wont do this??? Then timing check needs to be investigated.

    Note: one owner found the Timing chain/gear off a tooth......Stated ran good with the carb.



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    • #3
      I have verified with enging builder and photos from my engine build timing is correct tech support wants me to run a wire to the battery on the pink and black wire I have that wired to my positive wire from my old HEI distributor and they want me to wire up a fuel pump relay

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      • #4
        I had these very same issues with initial run in of my PF4 on a mild small block Chevy. Turned out to be that my timing chain and gears were installed 1 tooth off and retarded. The solution for me was to reinstall the timing chain assembly properly, reinstall the distributor and verify base timing to be at 12 degrees btdc. The Edelbrock PF4 immediately started and all software functions were instantly spot on. My engine now idles like a Swiss watch and all tablet function adjustments occur instantly.

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        • #5
          I have verified that my timing is correct I've spoken to the engine builder and verified by the photos of my engine build I've been in contact with tech support just rigged up a wire from the battery and a toggle switch to the pink and black stripped wire so I have a unadulterated 12volt source installed i a new aeroflo electric fuel pump and relay just started it,it backfired so hard I'm amazed I still have mufflers left on this car this engine ran fine with a Fitech Throttle body 3008 I went through 2 ECU's on the Fitech thought I would give edelbrock a try it was supposed to be plug and play it's been all plug and no play I'm about to get another ECU for my Fitech and scratch this Edelbrock off as a learning lesson I've even tried to find anyone who deals with these in the greater salt lake city area Nobody knows anything about them

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          • #6
            The firing order for a small block chevy is 1-8-4-3-6-5-7-2.
            The plug wires are installed in a clockwise order on the distributor, with the #1 being at the rotors tip position. When the timing marks are at 12 degrees BTDC.
            The initial timing is set at 12 degrees Before Top Dead Center. That's at the 12 mark on the timing indacater, before the crankshaft gets to 0, when you rotate the motor clockwise, when viewed from the front of the motor, and the intake valve of the #1 cylinder just closed.
            In my neighborhood, if you open your hood to check your oil, and the vehicle still runs after you close it.......Then your labeled the Neighborhood Mechanic.

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            • #7
              I am aware of all that . That still doesn't explain why this engine wont run unless you set distributor on 0 degrees tdc then Advance it with a timing light to 12 degrees before tdc. If you followed the installation instructions it wont even run kicks back back fires I've pull all spark plugs double checked triple checked that the sparkplug wires are in the correct order . Setting distributor on 0 degrees and setting timing with timing light to 12 degrees before tdc and unlocking timing on tablet it will run, runs rough acts like its miss firing cant give it any throttle or it backfires then dies almost an act of Congress to get it to start again this engine has less than 2000 miles on it, it ran fine before installing this system only reson I changed out the Fitech is because they have design flaw putting the ECU in front of the throttle body its susceptible to heat damage I went through 2 ECU'S

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              • #8
                we understand that your engine builder showed you pictures of the timing set up. with what you tell us of the problem it is related to timing please check your self. remove the spark plug for # 1 cylinder and tap starter till you hear air coming out of the hole then look at the dampener and turn crank slowly to see it the dampener lines up to your 0 /zero timing mark use a screw driver in the hole to feel the piston come to t d c then remove distributor cap and check that the rotor and the small square tang is pointed at # 1 . if you will do this your self it will help anyone hear and tech line to fix your problem. dont trust anyone's word check it your self.

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                • #9
                  " cant give it any throttle " .... == Timing is not correct.

                  " Backfires " ..... == Check firing order/ spark plug wires ( burnt boot arcing )

                  Stay away from E3 sparkplugs.

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                  • #10
                    I have personally completed all procedures you have advised at least 25 times with no success

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                    • #11
                      Have you found your engine's TDC utilizing the threaded rod stop method and witnessed that your zero mark on the balancer coincides with the true TDC? My engine and EFI had similar startup issues to yours before I found that my car's previous owner had installed timing tape on the balancer about 20 degrees off since the timing chain gear assembly had been installed 1 tooth off and no one before me knew it. I put 8000 miles on that retarded timing chain and it ran strong with a carburetor and HEI distributor. I finally removed the timing chain cover to inspect possible excessive timing chain slack being a culpret. Only then did I discover that that the timing gear installation witness marks were 1 tooth off. Installed a new chain with proper phasing and all of my problems went away. My engine would not idle for more than 1 minute, died every time I attempted to put it in gear and IAC tuning was erratic prior to the proper timing assembly. It now runs like a Switch watch and my tablet changes occur instantly. A true joy to tune and drive now.

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                      • #12
                        Also forgot to mention that I experienced hard starting and backfire issues as well. Engine now starts and stops with precision. My experience with this leads me to believe that ignition integrated EFI requires precise engine assembly in order to utilize the precision built into the complete EFI software system. My ECU was attempting to compensate for my engine's flaw but could not so it shut itself down.

                        Did your previous FiTech system utilize integrated digital ignition control too ..or was it just a throttle body?

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                        • #13
                          Sorry to hear of the problems that you are having. I don't know your engine builder or reputation. There is one sure fire way to determine if the pictures that you have are how it was finally buttoned up. As has been mentioned before, check TDC mechanically and see where the timing mark is on the balancer. When I built my engine, I had the option to retard, straight up, or advance the relationship between cam and crank. I chose straight up in my build. 71 Corvette LS5. I had that plug and play result you are looking for but I was also the one who put it together and knew what I had. The fact that you can start it lined up to TDC definitely points to your cam being advanced, especially since it runs like poo when you advance it to 12 degrees and lock it down. Essentially, if 0 degrees is really 12 degrees, when you add in another 12 degrees you are at initial of 24 degrees and that is without mechanical kicking in. When you unlock you timing on the tablet it will look to add the mechanical advance in also. Your fuel on the other hand is not in time with your advance. Like they said the ecu needs to know 12 degrees is 12 degrees for injector timing, otherwise it is like opening the throttle on your carb and having the accelerator pump shoot 2 seconds later. No one would be happy with that. The difference with the carb setup is it doesn't give a crap about ignition timing. It simply takes vacuum and flows appropriately for the vacuum conditions. The PF4 takes multiple inputs and works to orchestrate the timing, injector timing, and advance for a smooth running engine. The problem is that it needs a known reference point to do it all correctly.

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                          • #14
                            Originally posted by 77 C3 Corvette View Post
                            I have personally completed all procedures you have advised at least 25 times with no success
                            so you took it apart 25 times to check cam gear alignment ? or you have remover the #1 spark plug 25 times to check for t d c ? somehow you are missing something wish i new what to tell you but we are lost as to help you.

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                            • #15
                              I have pulled # 1 spark plug put my finger over the hole had my girlfriend bump the starter until air starts coming out of that hole the front drivers side cylinder if you are looking at engine from outside lined up the mark on the harmonic balancer the big 8" round thing at the end of the crank shaft to the 0 degree mark on the timing tab at least 25 times now I'm taking it apart and sending the distributor Wiring harness tablet and ECU back to Edelbrock to be bench tested acts like the pick up coil in the distributor has failed it is progressively getting worse the company who built this custom crate engine is also in contact with Edelbrock

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