6.7 fuel system

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SuperSonic

SuperSonic

El Vato
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May 31, 2006
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I have a no start condition on a 6.7 that we put into a 99 F-350.
So far I have replaced the CP3, verified that the FCA is functioning, found that someone had swiped the guts out of the FPRV (it is temporarily capped for now) verified that the cascade valve is working, the co3 has 16.5 psi inlet, is producing low pressure fuel, is pumping out high pressure, but will not build enough rail pressure to allow the injectors to fire. If I unplug the rail sensor it will run them but I'm too chicken chit to try to start it with a capped rail and the FCA and RPS unplugged. There isn't much if any fuel coming from the return on the back of the head. From what I understand, the cascade valve regulates inlet and internal pressure of the cp3, but is the injector return pressure regulated or free flow back to the tank. I just can't figure where my fuel pressure is going, it's deffinately not getting to or through the injectors???
 
Can't say I'd try start it either without a relief if I wasn't positive the injectors were firing. The return to the tank can be just run free, no issue there. Little to no return while cranking would suggest the cross tubes are sealed up.

If I could see them firing on a scope while cranking I'd try it with the cap.
 
I have a noid light to check for signal. With the RPS unhooked (reading open) they get juice but with it hooked up it will not read higher than 500-1000 psi which isn't high enough for the ECM to allow the injectors to fire.
 
I sent a PM but also were the injectors calibrated to the ECM?
 
The engine didn't come with an ECM, so no. I have no way of doing this, but will that keep it from starting?
Got your PM, I know the 6.7 cp3 is different as far as fuel connections. I did install an AirDog on it. I believe it is hooked up properly. I double checked it against a customers stock truck.
 
The injectors need to be calibrated to the ECM for starting. You can usually get a dealer to calibrate very cheap. You can save yourself some cash by having all the codes written down off the injectors for each cylinder and numbered so they can just plug in the Star Scan and punch them in quick.
 
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Thanks to FIAT, the closest Ram dealer that has support for diesels is an hr away. Maybe I can get the Cummins Bridgeway Mobile service guy out here to do it.
 
I have drilled out the fitting on the back of the head on higher HP engines with no ill effects. I have never heard of having the injectors calibrated though, thats good to know.
 
That's what I was wondering. Right now it just has a standard open banjo bolt in the back of the head. I read somewhere that the fitting should have a regulator built into it to hold a little pressure on the return side of the injectors. Kind of like the overflow valve on a p pump.
 
Each injector in a 6.7 has a code on the upper body facing the intake side and that code must be entered into the ECM calibration in order for it to fire correct. If your mobile guy has the correct system and you have the injector codes written down in order for him its literally a 5 minute job for him to calibrate them.
 
SuperSonic said:
That's what I was wondering. Right now it just has a standard open banjo bolt in the back of the head. I read somewhere that the fitting should have a regulator built into it to hold a little pressure on the return side of the injectors. Kind of like the overflow valve on a p pump.
Click to expand...

The open banjo bolt is a new thing for the 6.7 from what I understand. The 5.9 had the restricted banjo bolt but not the 6.7. Thats according to a dodge mechanic so I don't know that for fact. I know mine was open.
 
Thank you, good to know.

Ordered a new FPRV and a S-67 to try and solve some of my issues.
Big thanks to Garrett @ PureDieselPower and Bob Wagner.
 
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When your really jacking pressure or injector leakage starts to get to the high side of service that small check can become a major restriction. Enough to blow the solenoids off the injector resulting in a 100% duty cycle.
 
Ben46a said:
Reread csnyders posts..
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I got them loud and clear.
Something that will be addressed ASAP. But after a lengthily conversation with the head of mobile service at cummins bridgeway, I won't need to change the trim codes just to get it to fire. It will be done very soon though.
 
SuperSonic said:
I got them loud and clear.
Something that will be addressed ASAP. But after a lengthily conversation with the head of mobile service at cummins bridgeway, I won't need to change the trim codes just to get it to fire. It will be done very soon though.
Click to expand...

Ive had just the opposite luck. I can always get them to pop and bang but not fire and run without doing the calibration. Hope you get it figured out.
 
At this rate it will probably be done before we try to fire it again, it's just that those mobile guys are very backed up right now.
I called the dodge dealer about it and after explaining exactly what I was doing, he laughed and hung up on me.
Took the valve cover back off last night and wrote down all the trim codes, hopefully learn more Thursday when the guy gets over this way.
 
when i had my injectors swapped they had to code the injectors also i remember cause my truck wasnt running right and the mech ended up having 1 number wrong on 1 injector guess it wasnt reading right
 
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