392 tbi sluggish starts, lacking power

Discussion in 'Injection Tech' started by 'Mater, Apr 24, 2019.


  1. 'Mater

    'Mater Binder Driver

    Joined:
    Jun 18, 2015
    Messages:
    556
    Likes Received:
    110
    Trophy Points:
    43
    I'm running affordable fuel injection (Chevy based) on an international 392. It acts like it's not getting enough fuel. It eventually starts after 8 seconds of cranking. It sounds okay but it doesn't make good power. Once it's hot it will not start at all. I pulled a plug and it looks white hot like the engine is running lean.
    I had some issues with water in my fuel system last winter. If my injectors froze would that damage them?

    Any ideas on where to start looking for a problem? It is not throwing a check engine light/code
     
  2. Bill USN-1

    Bill USN-1 Moderator Staff Member Moderator

    Joined:
    Dec 25, 2002
    Messages:
    17,058
    Likes Received:
    251
    Trophy Points:
    83
    Location:
    Whidbey Island, WA
    I would start with a data logging cable.
    Log data and BLM so we can see what it's doing.
    I have the cables if you need one.
    Just email me.
     
  3. 'Mater

    'Mater Binder Driver

    Joined:
    Jun 18, 2015
    Messages:
    556
    Likes Received:
    110
    Trophy Points:
    43
    Update:

    I noticed that my exhaust had a leak at the collector right before the O2 sensor. I tightened it up thinking that it could be part of my problem. It probably wasn't. Nothing has changed.
    When the engine is cold, it fires after extended cranking. When it's hot, it will not start. I can see the injectors spraying fuel but I wonder if my spray is weak. It's not steady, there's a pulse to it.

    Just so everyone knows, I'm a complete newbie with TBI. I tried to plug in my car scan tool into the wiring harness for the fuel injection but it's the wrong plug. Bill is going to get me the proper cable and hopefully he'll have a suggestion that gets me back on the road 20190424_180606.jpg
     
    MrKenmore and jeff campbell like this.
  4. Bill USN-1

    Bill USN-1 Moderator Staff Member Moderator

    Joined:
    Dec 25, 2002
    Messages:
    17,058
    Likes Received:
    251
    Trophy Points:
    83
    Location:
    Whidbey Island, WA
    Make sure you have a new filter installed before the pump.
     
    'Mater and jeff campbell like this.
  5. MrKenmore

    MrKenmore High Wheeler

    Joined:
    May 19, 2013
    Messages:
    2,628
    Likes Received:
    649
    Trophy Points:
    113
    Location:
    Long Island, NY
    Nice pic! I think with an exhaust leak, the O2 sensor gets confused that the engine is running lean so it richens up the mixture.
     
    'Mater likes this.
  6. 'Mater

    'Mater Binder Driver

    Joined:
    Jun 18, 2015
    Messages:
    556
    Likes Received:
    110
    Trophy Points:
    43
    I got this motor second hand with the fuel injection already installed. Supposedly it ran good when pulled. I cobbled it into my pickup and have not been able to get it tuned correctly.
    I'm used to it starting when it's cold, but this morning I have a little spray and no fire. I hooked up a fuel pressure gauge to my supply line and when I primed the pump it bounced up past 15 psi which pegged out my gauge. Is that an issue with starting? 20190508_092655.jpg
     
  7. 'Mater

    'Mater Binder Driver

    Joined:
    Jun 18, 2015
    Messages:
    556
    Likes Received:
    110
    Trophy Points:
    43
    I have not done anything with timing or touched the distributor in any way. I did put a new fuel pump on it this spring because the original one froze with water in it and broke.
    I got a data logging cable in the mail

    THANK YOU BILL

    I'd like to try it out but I'm under the impression that I need to be able to start and drive before I can make a data log
     
  8. Bill USN-1

    Bill USN-1 Moderator Staff Member Moderator

    Joined:
    Dec 25, 2002
    Messages:
    17,058
    Likes Received:
    251
    Trophy Points:
    83
    Location:
    Whidbey Island, WA
    Based on your pic I can tell you with absolute certainty that your system will not operate correctly even if it does start.
    You have the system wiring intermixed with the plug and coil wires.
    This is just like connecting a timing light when it reads the 40,000 volts through the skin of the wires.
    So you are shooting 40,000 volts directly into the ignition module and the ECM.
    This can and will damage the electronics.
    It will change the rpm signal to the ECM every time it gets shocked.
    So instead of 800rpm it will see 6300rpm.
    You need to properly route all the wiring to have a good air gap from the plug wires.
    The plug wires should be routed and loomed so they are above all wiring.
    As for the fuel, Inlet is 11-13, rtn is 0
    If there is no spark/tach signal from the ignition module, there is no fuel pump or spray.
    If it's flooded you can unplug the injectors or simply hold your foot to the floor.
    If it's lean you can add a little in the top of the TBI.
     
    'Mater likes this.
  9. 'Mater

    'Mater Binder Driver

    Joined:
    Jun 18, 2015
    Messages:
    556
    Likes Received:
    110
    Trophy Points:
    43
    It looks like I'm not getting enough spray. The injectors pulse about 3 times every 5 seconds of cranking. Holding my foot to the floor or pouring gas down the gullet has no effect. I'm assuming then that my issue is timing signal from the distributor to the ECM. I looked at my spark with a plug out the last time it would not start and it seemed like there was little to no spark. It fired up on the other 7 cylinders so I just ignored the weak spark. I swapped on my backup coil to no effect.

    I hope that I didn't barbecue my computer with lazy wiring. I jumped pin a and b on the connector and turned the key. I get "code12" over and over again. I assume that means that it is functional?
     
  10. Bill USN-1

    Bill USN-1 Moderator Staff Member Moderator

    Joined:
    Dec 25, 2002
    Messages:
    17,058
    Likes Received:
    251
    Trophy Points:
    83
    Location:
    Whidbey Island, WA
    The ECM has NOTHING to do with spark.
    It only takes control of the timing above 400rpm.
    Clean up your wiring.
    Do you have 12v to the coil while cranking?
    run a jumper from the batt + to the coil + and try again.
    remove the ignition module and take it to a store and have it tested 3 times.
     
    'Mater likes this.
  11. 'Mater

    'Mater Binder Driver

    Joined:
    Jun 18, 2015
    Messages:
    556
    Likes Received:
    110
    Trophy Points:
    43
    Okay, I got my wires minimally separated, I had 12 volts to the coil with key on and only a slight drop with cranking. Not even the slightest cough from the engine while testing. I put the jumper wire from the battery to the positive side of the coil and the fuel pump immediately primed up (my ignition has a hot wire that goes to the coil so it was bypassing the key) I gave it a crank and it immediately started and idled for two seconds before dying. I never touched the throttle.
     
  12. 'Mater

    'Mater Binder Driver

    Joined:
    Jun 18, 2015
    Messages:
    556
    Likes Received:
    110
    Trophy Points:
    43
    I pulled the "brain box" out of my pickup and brought it to town. O'riley and auto zone will not test it. My local Chevy dealer would have helped me but they trashed the proper scan tool 15 years ago.
    Any idea who might be able to test this? 15573618934728256136977977698812.jpg
     
    Last edited: May 9, 2019
  13. 'Mater

    'Mater Binder Driver

    Joined:
    Jun 18, 2015
    Messages:
    556
    Likes Received:
    110
    Trophy Points:
    43
    The guy at my favorite local parts house listened to my tale of woe and he said that it sounds like I have a failed module in my distributor. The fact that it won't start hot, cools off and fires up is one of the symptoms of module failure. I'm going to recheck my spark and if it is weak in the slightest, it would seem that the distributor must come out of the vehicle to access the suspect module
     
  14. Bill USN-1

    Bill USN-1 Moderator Staff Member Moderator

    Joined:
    Dec 25, 2002
    Messages:
    17,058
    Likes Received:
    251
    Trophy Points:
    83
    Location:
    Whidbey Island, WA
    Reread what I said to do.....read it twice!
     
  15. 'Mater

    'Mater Binder Driver

    Joined:
    Jun 18, 2015
    Messages:
    556
    Likes Received:
    110
    Trophy Points:
    43
    Sorry for the confusion. You said module, I was thinking about the big grey aluminum box. My terminology is weak. No excuse.

    So yesterday I charged up the battery fresh. Separated my wiring a little bit, and sprayed some actual starting fluid down the intake. She fired right up, ran for 2 seconds and died. As it happened, I was watching the injectors spraying properly.

    WATER IN THE FUEL

    I flushed my fuel system and the engine started right away.
    I then followed the instructions included with Bill's data cable. I installed the software on an old laptop, plugged it into my 1967 pickup (didn't seem right at all) and was able to go for a drive and make my first data log.

    ...So easy a caveman could do it.

    I sent it to Bill for a guru interpretation. If anyone is interested, I can post it here as well.

    My pickup ran okay yesterday but it wasn't making the power I would expect. This fuel injected 392 is replacing an old 304. At the moment, the power output feels about the same.
     
  16. Bill USN-1

    Bill USN-1 Moderator Staff Member Moderator

    Joined:
    Dec 25, 2002
    Messages:
    17,058
    Likes Received:
    251
    Trophy Points:
    83
    Location:
    Whidbey Island, WA
    You don't need an old laptop. I use the software on every version of windows and I have customers that have ran it on apple laptops in a windows environment.
    If the data logging instructions are followed exactly as written in my manual, it works great.
     

Share This Page