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New motor not running well.

Discussion in 'Truck & Equipment Repair' started by theguynextdoor, Feb 12, 2010.

  1. theguynextdoor

    theguynextdoor Senior Member
    Messages: 307

    I just put a new motor in my 98 dodge ram 2500. 360 V8 gas. I have checked everything over and over again, but I can barely get it running. It will run with my foot on the gas, but very very rough. I don't even know if you could call it running. It backfires a little bit. Is it possible that I have it timed backward so it is firing at TDC for the exhaust stroke and not the intake stroke? Or would it not run at all this way. I want to get some input before I turn the distributor around because its a pain since its located behind the motor. I have checked all my connections. All of the wires, plugs, most sensors, distributor cap and rotor, distributor, gaskets are all new.

    How can I tell if its on TDC for the exhaust or compression stroke?

    I would really appreciate some input.
  2. ahoron

    ahoron Senior Member
    from here
    Messages: 422

    Take the #1 spark plug out, cover the hole with your finger and rotate the motor by hand the compression will force air out when near tdc. Remove dis. cap and check rotor
  3. theguynextdoor

    theguynextdoor Senior Member
    Messages: 307

    I didn't have a person to check for air in the cylinder before, but my buddy will help me today. Thanks for the info. I know the rotor points to the #1 plug terminal at TDC, but wasn't sure if that was on the compression or exhaust stroke.

    Thanks for the help. Hopefully I ccan figure it out today since I just got word that my Ford transmission is toast and apparently they only made that tranny for 1 year so there aren't used ones any in the area and a new one is 2300 plus install.
  4. cubicinches

    cubicinches PlowSite.com Addict
    Messages: 1,412

    Have you put a timing light on it? It won't run with the distributor 180 degrees out. You could be way off on the timing though. Put a light on it and double check the firing order.
  5. theguynextdoor

    theguynextdoor Senior Member
    Messages: 307

    I have not put a light on it. I can't even get it to run without being on the gas pedal.

    I checked the timing today. It is definitely firing on the compression stroke. Lots of pressure coming out the the spark plug hole. The distributor rotor is perfectly aligned with the #1 terminal with the 1st piston at TDC as my books says to do. I put the old injectors back on, but have not ran it yet. I wasn't happy with the fit of the new injectors. They kept leaking.

    I'm running out of ideas.
  6. cubicinches

    cubicinches PlowSite.com Addict
    Messages: 1,412

    Put a light on it. Or at least just advance it some and see if it improves.
  7. ontario026

    ontario026 Senior Member
    Messages: 228

    did you verify the firing order?
  8. theguynextdoor

    theguynextdoor Senior Member
    Messages: 307

    Yes, I was very careful putting the motor together and checking all my wiring, torques, etc. I'm going to adjust the firing time slightly tomorrow. If that makes a difference, I'll get someone to put a light on it to get the timing just right.
  9. bchurch05

    bchurch05 Junior Member
    from NH
    Messages: 29

    did you check all your vacuum lines and wiring? is your o2 sensor hooked up with exhaust? not saying nothing is wrong but most computer controlled motors have a learning curve and will take a few minutes to figure it all out. also do you have enough or the right fuel pressure?
    just some ideas. good luck
  10. theguynextdoor

    theguynextdoor Senior Member
    Messages: 307

    I have checked all of the wiring and vacuum lines. I replaced all questionable vacuum lines and made sure they were all connected. All of the sensors are new (oxygen, crankshaft, camshaft/distributor, temp, etc.) I Kept getting leaks on my fuel rail so I put the old injectors back in because I wasn't happy with the fit of the after market ones. I have not run it yet, but will find out if the injector situation helped tomorrow. After that I'll try the timing and then take it to my mechanic.

    Thanks for all the input. Any other ideas are appreciated.
  11. lotec25

    lotec25 Member
    from Florida
    Messages: 47

    that can be a huge issue, if your leaking at the rail your not going to have enough fuel pressure. Witch will keep it from running correctly.
  12. theguynextdoor

    theguynextdoor Senior Member
    Messages: 307

    I may need a new fuel rail since its rather rusty. I decided to rid myself of this project and have it towed to my mechanic tomorrow. I have had this thing in my shop for 3 months and since the ford is 4000 dollars shy of running (which I'm not spending) I need this truck running yesterday. I can't deal with it anymore. It need brakes and inspection anyways before I can drive it. I'll let you guys know what the problem(s) end up being. I'm guessing its a combination of fuel leak/vacuum leak/ timing.

    Thanks for all the advice.
  13. theguynextdoor

    theguynextdoor Senior Member
    Messages: 307

    Well, my mechanic found out that the crankshaft sensor that napa gave me was no good so he put a new one on. It is running now, but the computer is shot. I am so pissed. I can't keep putting money in this thing. Another 500 bucks for the computer plus all the labor figuring the problem out.
  14. the_experience

    the_experience Member
    Messages: 75

    How did he determine that the PCM is bad? They very rarely go bad. The fact that it was running before on the computer, but isn't now makes me suspect that there might not be anything wrong with it. Service manuals suck...a lot of them have diagnostic flowcharts with two steps. 1. Does t work? 2. Replace the expensive part and see what that does for you. I'd discuss who is responsible for the cost if it's a misdiagnosis before going any further.
  15. sjcolwell22

    sjcolwell22 Junior Member
    Messages: 7

    Doesn't sound like an ecm. Sounds like to distributor is 180 degrees out. What was the reason for replacing the motor in the first place?
  16. theguynextdoor

    theguynextdoor Senior Member
    Messages: 307

    PROBLEM SOLVED! Lots of time and money later, the truck runs like new. The crankshaft sensor from napa wasn't putting any signal out. With the new sensor, the waves shown on the computer seemed to be causing a double spark. I remember that the driveplate was slightly bent when I put it back on the motor. I bent it back with pliers, must have been dammaged in the garage somehow. I told the mechanic this, so he looked at it since we were out of options. Every hole in the driveplate had a slight dent in front of it, hardly noticable. This was causing the motor to spark twice per cycle for each cylinder. New drive plate installed and the truck runs like new.

    My mechanic said "my specialty is diagnostics and this one was challenging to figure out"
  17. toptech72

    toptech72 Member
    from 21078
    Messages: 61

    If his specialtly is really diagnostics then he should have caught the bad signal from the crank sensor when he was checking the sensors with a scope. The basic diagnostic should have been check for any codes and if any were present run diagnostics for said code(s).If no codes present a check for fuel pressure and volume. Then check compression and cranking vacuum. Then if those checked out the scope should have been hooked up to check for crank signal compared to either the cam signal or injector pulse to check for sync.
  18. theguynextdoor

    theguynextdoor Senior Member
    Messages: 307

    He was aware of the crank sensor issue right away. They just couldn't figure out why even the new sensor was putting out a wierd signal. I can't believe these tiny indentations in the drive plate made the truck run so horribly. You can barely notice them if you are not looking for it.