Cummins QSF3.8 mechanical injection conversion and swap (1 Viewer)

[19931fz]

So ever since I bought my cruiser back in 2015 I've wanted to put a Cummins in it. The 1fzfe has a rod knock and blown head gasket and back then I didn't have the money or time to fix it so it's been sitting since like 2016. But no longer. I recently picked up a pile of parts that was once a qsf 3.8 and I plan on rebuilding it converting it to mechanical injection, building the automatic transmission adapter and then shoving the whole thing in and praying it all works out.
So first thing on the list before I build the motor is to deal with the fuel system. The qsf is common rail and the motor was out of a telehandler but I didn't get the ecm for it. So after a lot of searching I found out that the ecms are $1200 used and then I would have to pay on top of that to get it programed to the engine and then to get the emissions equipment deleted off of it. So I decided at that price I would go where no man has gone and convert the common rail injectors to mechanical and then run a VE pump off the gear drive in the back of the motor.

 

[19931fz]

And so after some digging I found a good cutaway of the injector and how common rails work. The basic gist of it is that the high pressure fuel is what keeps the nozzle closed. If you remove the fuel pressure from the control port you can then run the injector purely off of spring pressure like a traditional injector. On this one that means blocking a small port above the control rod.

 

[19931fz]

And so the butchery begins. I did a full step by step process on how I managed to take a $300 injector and basically make it worthless for anything other than this Frankenstein motor.

First things first we remove the solenoid off the top. It just unscrews

 

[19931fz]

Then you take the valve assembly off and are greeted by the nut. I made a tool to remove it and the tool broke inside the 3 holes and so I was forced to remove the nut like a heathen with a punch. I ordered a new nut they're cheap it was only a $40 mistake. I'll use this destroyed nut to make a tool for the other 3 injectors.

 

[19931fz]

Once you get the nut off there is the control assembly. This was where the real magic of this conversion comes together. You take the control orifice and just flip it over. That's it for the top of the injector. Now we no longer can get fuel to the top of the control rod and the injector just runs off the spring in the needle assembly.

 

[19931fz]

Put the top back together and then flip it over for the nozzle assembly. The nozzle just unscrews nothing special about it. Once the nozzle is off you get this nice stack of parts.

 

[19931fz]

Here's the control rod, shims, spring, nozzle opener and holder thing. The problem is that the stock spring only delivers a couple hundred pounds of pop pressure. Not nearly enough for what we need. So the control rod goes back into the injector body and then the slotted shim goes in next.

 

[19931fz]

Heres the assembly without the control rod. So I needed to up the spring pressure so I went to my bin of parts and grabbed a unit injector from a 1.9 TDI. I got the TDI injector apart and the spring is much more stout but it was too big around for the nozzle. So I just put it in a drill and ground it down to the correct size and height. I wanted maximum needle lift so I removed the non slotted shim from the stack. Once I get it dialed in I'll figure out what spring I need exactly so I can have something more reliable than a ground down spring.

 

[19931fz]

So assembly is pretty straightforward just line up the pins and put the cap on. Then the testing begins. I made a pop tester out of a hydraulic grease gun. Filled it up with diesel instead of grease and I was off to the races. So I actually just got really lucky with this spring it pops off at 3800 psi which is a little higher than stock for the VE pump I'm using.

 

[19931fz]

And that ends the first segment of this build. Now I gotta go get my injection pump and see what I need to do to make it work with these injectors.

 

[William839]

Cummins 3.9 ISB and ALLISON TRANS - auto parts - by owner - vehicle...

3.9 ISB Cummins (2004)and Allison transmission for sale 5500 for the pair OBO Can start and run engine before sale

denver.craigslist.org

 

[19931fz]

Ran the ve pump with the injector hooked up and it performed as expected. So I am now probably the only person in the world to have ran a common rail injector with a rotary pump.
Next I need to figure out my gear drive setup for it which is gonna take a while I'm sure.

 

[chondamx]

Did anything ever come of this? I have access to a 3.8 and the wheels are turning

 

[PIP]

I wonder if he got stalled at finding the RGT engines spin the injection pump backwards.

Cummins made 3.9 and 4.5 RGT engines with VE pumps. Hyster used them in Forklifts.

As for injectors, my understanding is needle/rod inside the CR nozzle won't work right mechanically. The CR nozzle works with the needle from a mechanical injector though. This has been done a few times.

 

[19931fz]

I wonder if he got stalled at finding the RGT engines spin the injection pump backwards.

Cummins made 3.9 and 4.5 RGT engines with VE pumps. Hyster used them in Forklifts.

As for injectors, my understanding is needle/rod inside the CR nozzle won't work right mechanically. The CR nozzle works with the needle from a mechanical injector though. This has been done a few times.

I ended up getting a hino WO4TC with 300 hours for free and since the qsf needed rebuilt the choice was obvious. But the the injection pump drive was also a dilemma I was going to have to spin it off the aux on the gear train with probably a pulley and belt from a Tdi.

 

[mjosoba]

I ended up getting a hino WO4TC with 300 hours for free and since the qsf needed rebuilt the choice was obvious. But the the injection pump drive was also a dilemma I was going to have to spin it off the aux on the gear train with probably a pulley and belt from a Tdi.

What’d you do with the Hino?

 

[19931fz]

What’d you do with the Hino?

It's going in the 80 cruiser whenever I get some time. I've got the flywheel and Bell housing sorted out for it now I just need to put it in.

 

[mjosoba]

It's going in the 80 cruiser whenever I get some time. I've got the flywheel and Bell housing sorted out for it now I just need to put it in.

Interesting. Stock transmission? I’ve always been interested in that one, too.