.I have a 1994 F-Super Duty with the 7.3idi Non Turbo that we recently rebuilt the engine in. We did a full rebuild pistons and everything put it all back together and now when we start it, it idles great nice and smooth no issues. But as soon as we touch the throttle to rev it up it runs away. We have all new injector lines o rings everything it doesn't smoke like a stuck injector when its idling or show any signs of stuck injector. We have tried using 2 injector pumps that were known good when we removed them off the other motors. Timing is all in check just don't understand why it runs away once we hit the throttle. Any help would be appreciated.

 

Explain runs away, you have to stop it by shoving something in the intake, or it shuts off with the key? If it goes away with the key, its fuel related, and in the pump. If you have to choke it down, has to be getting oil from somewhere

 

Have to choke it out it does not shut off with the key. I agree on itd be getting oil from somewhere if it was smoking when it ran away but its not. Its normal white smoke when it takes off for the rpm its running. No blue to the smoke at all.

 

That likely just means that it's burning oil efficiently. No power to the pump, no flow to injectors.

 

Is it puking oil out of the cdr into the intake?

I would think if it were cylinder related it would be a pita to start and idle rough

 

21.5:1 compression, it will burn oil just fine. I used to run 80/20 WMO / diesel in my 79, minus a very slight haze at cold idle, and the slight smell, you would never know it was mostly oil. That said, raw oil in the cylinder is different than injected oil, or vapor oil from the cdr. Bigger question is if it is oil, where is the oil coming from. Being NA its valves, rings or head gasket. Given that it runs fine, pretty much rules out rings, unless the heads are completely shot, we have to assume valve guides are fine. Only other path for oil is head gasket or CDR. Cant be the CDR unless the drain passages in the lifter valley are plugged, and theyre big, also, that would likely cause a very bad runaway, or hydrolock even and given that the engine is together, we can assume thats not the case. Its a small enough amount of oil that it doesnt surface at low rpms / low oil pressure. Thats my theories and im stickin to em.

Edit: If the covers have been off the pumps, they can be put on to cause a runaway / failure to shutoff with key condition im told. I personally dont see how you can do it, but apparently its happened.

 

It doesnt puke oil or even smell like its burning any oil, its a fully rebuilt engine sent the heads off had them pressure checked milled valve job done new valve seals everything bottom end had the block pressure checked new pistons and rings new rod main bearings new cam new cam bearings literally everything has been rebuilt on this motor its a tight motor if its picking up oil from somewhere how? and where? a new motor shouldnt have these issues. The injector pump has not been taken apart at all we had it running on another motor a couple days before putting it on this one same with the other injector pump we tried both we had running on other motors shortly before installing them on this one

 

That is one hell of an anomaly... from what youre saying, id say it has to be fuel / vehicle related then. Sticking throttle cable and FSS not shutting off? With air cleaner off, throttle cable off, move the lever by hand, let me know if it still tries to run on ya. Try disconnecting both wires to pump as you try to shut it off. You probably know, the pump does not have a return spring, so it has to manually go back to idle if the cable is off.

 

All this has been done with the throttle cable unhooked and moving the throttle lever by hand. Checking fuel return line for any blockage now everyone we have look at it says it seems fuel ralated becouse it doesnt smoke and shuts like a run away on oil does. the Cdr valve is not hooked up and front cover is off the engine so iv taken crank case pressure causing it to push oil or anything like that out of the picture

 

Does it shut down if you pull off the FSS connector?

 

I haven't tried pulling the wire off when it goes just jump to chocking it out next time i try it i will try puling the wire when it goes and see if that shuts it off. it shuts off fine with the key when idling but no affect when it starts to take off. trying to figure more out before i start it again feel like m pushing my luck on getting it to shut down

 

is it runnin the mechanical or a electric fuel pump?

 

Mechanical

 

well that rules out what i was thinking then.

 

does it have a c6 behind it. If so it could be drinking tranny fluid.