I have inj pump for 84 6.9, I have 87 6.9 that needs a pump. Are they interchangeable? If not, what has to be changed in the 84 pump to work on 87. I've heard that the 84's used different inj. pressures. Is it higher or lower?

 

I think you'd be OK as long as they're both 6.9s. The earlier pumps just had less upgrades inside.

 

Upgrades?

Anything that would prevent me putting on a turbo? Supposedly the pump was redone a short time ago. Would they have done the upgrades as part of a normal rebuild or is it something that isn't doable?

Thanks for the help I appreciate it.

 

No, all you need for the turbo is the fuel screw under the little cover on the side, they all have that.

 

There were some timing/pressure changes from the original 84's thru till the DI introduction

To get optimum performance you should stick with the designated IP/injectors.
Will it work? Yes.
Will it be perfect? Prolly not

 

I think the changes you are refering to would be on the 7.3 pumps, they will run crappy on a 6.9. Been there, tried that.

 

Actually, there were numerous changes with the 6.9, also. I believe there were 3 (maybe more?) different Injector codes, and pumps tuned to those inj specs.

 

But all the codes are pretty much interchangeable.

 

They are interchangeable, but for optimum performance, they should be used in combonation. The calibration sticker on the engine explains the fuel system 'tune'.

Theres' a reason for suppliers asking for the year of your truck, when you order a new IP or injectors. They want to know what 'tune' you have.

 

My pump shop sells the same injector for all the pre-turbo IDIs, and only worries about pump model to make sure they get the same core back.

 

Thanks for all the help. I think I'll probably just spring the bucks for a rebuild unless I run across another good deal.

I just got a turbo, so I guess I better start planning for the pump and injectors and ,.....

 

Any ideas why the 7.3 pump runs bad on a 6.9? Is is something that can be fixed?

 

ok this is a relatively easy one. one of the main reasons they wont is simple mathmatics. 7.3 pump pressurizes more fuel than the 6.9 which means that the 6.9 fuel pump is probably still on it. im not sure if the fuel pumps are interchangable, but i believe the bolt pattern is the same. the 6.9 engine was a very reliable and dependable motor that saw lots of service in light and medium duty applications. when the IDI 7.3 was designed it was mearly an upgraded version of the 6.9. kinda like boring out a 460 big block to make a 502. when you upgrade stuff like that you gotta upgrade everything. putting a 7.3 pump on a 6.9 doesnt do much good if you dont make sure the fuel pump can keep up. the 6.9 and 7.3 were notorious for having fuel starvation problems. the injectors on the 6.9 are rated at about 1800 psi per injector. thats a lot a pressure. if the injector pump doesnt recieve the proper amount of fuel its gonna have problems running right. like a lean running carb on a 460. got lots of power but if there isnt enough fuel it aint gonna work right. if i was installing a 7.3 pump on a 6.9 id upgrade the fuel pump, injector pump, and injectors to the 7.3 specs. they should be the same size since its the same block.

jason

 

Hmmm, notorious for having fuel starvation problems?? Funny, I've NEVER heard of anything like that.

 

Like I keep saying, the injectors are all the same. The 7.3 pump will go right on the 6.9 and run. It's just set a little too high fuel wise for the smaller displacement. We ran one for maybe 6 months, but it always smoked gray or darker. We tried backing of the fuel screw to compensate for it and it just lost power. We asked our local pump shop about it and they said there would be no way to tune it in, so we finally got a 6.9 pump back on it and it's been happy ever since.