VP head on Common Rail Questions

weazel

weazel

5th gear killer
Well, I guess I’m going backwards with this, but working on an 03 common rail that dropped a valve seat. A VP44 head was purchased and I stuck it on the common rail block. Got everything adapted and now the engine won’t fire up.

I’m getting 0 rail pressure. It’s commanding 5800psi, but 0 is the actual.
I’ve swapped out the FCA, rail sensor, blocked the relief valve, and still no fire.
If I try to use ether, it only makes the engine spin faster, it doesn’t fire up and run like normal.

I’m using common rail injector tubes in the VP head. They touch the injectors, and I’ve torqued them down 2-3 times.

I’m at a loss why I have no rail pressure. Anyone have any ideas to try next?
 
If you have zero rail pressure, maybe the CP3 shit the bed? Whether the head will work or not, you should have rail pressure.
I can't say 100% for sure, but the head should be alright. We've gone the other direction before by using a CR head on a VP engine, so logically thinking...
 
There’s all kinds of info about that swap, vp to common rail. But none the other way lol.

When I was swapping out the rail sensor, I cranked the engine over and it had fuel at the rail. Whether or not it was enough, that I do not know.
The only part I haven’t tried swapping is the relief banjo bolt on back of the head. Would that be worth a shot?
 
I'd try an external guage and make sure rail pressure is actually zero first.

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weazel said:
Ok. I’ll see if I can fix something up to check this
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Be careful how you do that. If by chance it gets fuel pressure for even a second, it's enough pressure to fuck you up. A good data reader should do the job. Also, have you tried it with the FCA unpligged.
I would assume you're not seeing fuel in the oil? If the tubes don't seal it'll fill the fuel oil sump pretty quick. As far as the check valve on the back of the head goes, that would not keep it from making rail pressure. The rail relief valve would if it's stuck open. In that case the return line from the rail would be wicked hot.
 
Snedge said:
Be careful how you do that. If by chance it gets fuel pressure for even a second, it's enough pressure to fuck you up. A good data reader should do the job. Also, have you tried it with the FCA unpligged.
I would assume you're not seeing fuel in the oil? If the tubes don't seal it'll fill the fuel oil sump pretty quick. As far as the check valve on the back of the head goes, that would not keep it from making rail pressure. The rail relief valve would if it's stuck open. In that case the return line from the rail would be wicked hot.
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Ok, I don’t think I’ll do any hard part testing then lol.
I’ve been using the scan tool through HP tuners.
I have tried starting with FCA unplugged on two different ones while watching rail pressure on HP. Both resulted with 0 psi.
Gotta tell a little bad on myself, of all the Cummins injectors and motors I’ve rebuilt/installed parts on, this is the first one I accidentally installed an injector backwards. When I went to retorque the tubes, that’s when I found the problem. So swapped out the mushed tube with a spare one I had.
When the injector was in backwards, I was able to build 89psi for rail pressure. But now that everything is as it should, it hasn’t gotten over 0… and I’ll check again, but oil level hasn’t risen above what it was when I changed it. oil doesn’t smell of diesel..
 
Cp3 pumps a lot of fuel, if you had a big enough leak to make 0 psi, you should notice pretty quickly.

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weazel said:
Gotta tell a little bad on myself, of all the Cummins injectors and motors I’ve rebuilt/installed parts on, this is the first one I accidentally installed an injector backwards.
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See, we always get the whole story after the fact. LOL

I don't know that that has anything to do with your current issue. I'm betting the CP3 is the problem. Unless the truck is out of fuel. ????
 
Snedge said:
See, we always get the whole story after the fact. LOL

I don't know that that has anything to do with your current issue. I'm betting the CP3 is the problem. Unless the truck is out of fuel. ????
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LOL yeah true true haha
And it’s got plenty of fuel in it..
I may just have to pull the cp3 off of my truck and swap them around just to see if it’ll start.. will for sure determine if it is the cp3 or not lol
 
weazel said:
LOL yeah true true haha
And it’s got plenty of fuel in it..
I may just have to pull the cp3 off of my truck and swap them around just to see if it’ll start.. will for sure determine if it is the cp3 or not lol
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Absolutely.
 
Is there a ton of fuel going to the return on the back of the head? Do you have caps you can put on the rail and isolate say 3 injectors to see if it builds pressure? I would make sure the feed tubes are making good contact with the injectors. Maybe put dykem or a sharpie on them and then torque them to see if they have 100% contact.
 
I’m glad you mentioned that Tobin.
I have a messed up tube so started grinding off the balls and smoothing the shoulders the common rail tubes have.
I believe I found the issue, yes the tubes touch the injectors, but they’re not seating in the opening. When I pulled one of the tubes to start this, fuel was all over it up to the oring.
So stuck some grease on my ground tube and sure enough it’s barely going in the orifice of the injector.
 
Why would u put a vp head on a common rail in the first place
I see no way it will ever work
I don't see how the Cross tubes will ever seal properly
 
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I'm sure there is a reason cummins put the locators on the common rail tubes. If you ever get them to seal, I foresee them loosening up over time.
 
It was the tubes. Modified them and now truck starts and runs. Will mess with it more tomorrow and see if it clears all the stuff off the pistons from all the work.
 

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