• Welcome to The Truck Stop! We see you haven't REGISTERED yet.

    Your truck knowledge is missing!
    • Registration is FREE , all we need is your birthday and email. (We don't share ANY data with ANYONE)
    • We have tons of knowledge here for your diesel truck!
    • Post your own topics and reply to existing threads to help others out!
    • NO ADS! The site is fully functional and ad free!
    CLICK HERE TO REGISTER!

    Problems registering? Click here to contact us!

    Already registered, but need a PASSWORD RESET? CLICK HERE TO RESET YOUR PASSWORD!

Fast idle.

valyidol

valyidol

Active Member
Messages
316
Reaction score
112
Location
Russia, Moscow
Hi!
DB2. The engine has fast idle. 750 rpm. The screw of single turns is twisted to the end. How can I make the low speed of idle?
 
Check that nothing is binding, throttle cable, fast idle cyl that is mounted towards the front top where the cable attaches to the pump lever.
 
750 is high for most applications. the screw is the only idle adjustment.
make sure there is no power to the high idle electrical wire - the one that connects to two locations on the pump.
Also check inlet pump fuel pressure, high pressure advances timing and the electrical raises rpm for cold start up.

put Clear tube in place of the rubber one on the return fuel line to ensure no air is in diesel fuel. it is about 5" long and 1/4"
 
X2 for what @Will L. said. Air or lack of fuel will have the pumps do weird stuff. Like Knock, surge, etc. You know the sound of a 6.2 that is about to run out of fuel right?

Cruise control cable holding it open? Bent bracket? Can you manually close the throttle? Is the high idle solenoid locked up?

Remove everything attached to the throttle but the return springs to see if it still has 750 RPM. This includes the TPS or Vac switch on the passenger side of the pump. The passenger side of the pump stuff can be so far out of adjustment it holds the throttle open. Or switch or TPS is binding...

Is your RPM tool is accurate? Using the dash tachometer with the wrong "gas engine" pulley on the alternator will screw the RPM reading up.
 
I know this is an old thread but I would like help on this as well. I have a turbo swap set up on my 6.2, pump is turned up a half turn. In the video it sounds about 1000 rpm which is way high. It is advanced slightly, that was done pre turbo install. The idle screw is back out all the way as well, no high idle solenoid on it, that was removed. I do have an electrical pump from a 6.5 feeding the IP, could this be causing too much fuel pressure to build up?
 
Max pressure at the ip (injection pump) should be 5 psi.
Remove the throttle cable temporarily to ensure that isn’t holding it up any.
Clear tubing on the ip return to verify no air bubbles.
Check you aren’t sucking oil.
 
Will L. said:
Max pressure at the ip (injection pump) should be 5 psi.
Remove the throttle cable temporarily to ensure that isn’t holding it up any.
Clear tubing on the ip return to verify no air bubbles.
Check you aren’t sucking oil.
Click to expand...
Clear tube, got it. I do not have a psi gauge after the filter, but that is an easy fix. lets say psi is too high, I wonder if the only fix for that would be a lower psi fuel pump? the one i got is for a 93 6.5, I figured that would be adequate.
Where would it be sucking oil from exactly? it has a small amount of haze out of the pcv, but i have always known these engines to have that a small amount.
Also forgot to mention it did get a new head gasket (.005 thicker than stock) with ARP head studs. Not that it has anything to do with the idle, I just figure the more info the better.
 
Oil feeding as fuel through intake from turbo, or cdr are the two common supplies.
This is really rare- but needs to be eliminated because if it is- that leads to a run away.
 
I can see the throttle cable is broken just above the IP likely from laying on it working on something. Replace it before it hangs at WOT and gets "interesting".

If the above doesn't get your idle speed down the pump needs to go to a shop to adjust the min-max governor in it. The military manuals in the reference section here may cover how to do this.

IMO get a better paper air filter box. That one is a hot air intake costing you MPG and it's poor filtration can dust the engine's rings.
 
WarWagon said:
I can see the throttle cable is broken just above the IP likely from laying on it working on something. Replace it before it hangs at WOT and gets "interesting".

If the above doesn't get your idle speed down the pump needs to go to a shop to adjust the min-max governor in it. The military manuals in the reference section here may cover how to do this.

IMO get a better paper air filter box. That one is a hot air intake costing you MPG and it's poor filtration can dust the engine's rings.
Click to expand...

Warwagon thanks for the input. I think you are correct with the min max governor spring. I was able to find some info on another forum saying that is the likely cause of the high idle. It was when I turned up the IP and when I reinstalled the governor spring I must have done it a little wrong. I will report back when I have a chance to mess with it this weekend.
As for the intake, I agree with you... that was a quick fix just so I could start the thing.
 
You must log in or register to reply here.
Back
Top