LB7: Rail pressure issue with dual cp3

[bluecollar]

Hey guys having a lil issue. Ill start with details on the truck, 2001 lb7 it got a lml bottom end, built trans, dual fueler, 100% injectors, s463, airdog 200 (11psi) and some other stuff over the winter all work done by me except trans. Got it running last week and im very pleased with how it runs, makes 45psi of boost and a max egt of 1400° on a 1500us tune.

now for my only issue is when i let off throttle to slow down and stop, rail pressure will start to climb to 10k while desired is 5k and it will stay there and lope/rattle till im almost stopped then calm down. Actual and desired are great besides when im off throttle and slowing. Dual cp3 is a ats kit with 2 used stock pump that ive never had a issue with before. Curious if anyone has had this issue? I have no problem putting new regulators on but hate wasting money, or could it be from to much lift pump psi? thanks for any input

 

[IOWA LLY]

Turn your lift pump down or start tuning the regulator voltage table.

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[Muff]

Turn your lift pump down or start tuning the regulator voltage table.

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X2

 

[Porno Joe]

I had a very similar issue with my truck and it was the regulator table needing tweaked for the dual fuelers

 

[bluecollar]

Thanks guys! That is as low as my lift pump will go, looks like ill be cutting the spring a lil.

 

[bluecollar]

I had a very similar issue with my truck and it was the regulator table needing tweaked for the dual fuelers

Ok thanks.. ill start with the lift pump then look into the voltage table

 

[PACougar]

I can understand the regulator table needing to be changed, but when did 11 psi from a lift pump become a problem? Mine runs at 12 psi and so does my buddies and I've never seen this problem.

 

[Porno Joe]

I can understand the regulator table needing to be changed, but when did 11 psi from a lift pump become a problem? Mine runs at 12 psi and so does my buddies and I've never seen this problem.

I would guess its NOT the lift pump but the regulator tables needing adjusting. How i understand it, on my truck the "stock" voltage table used for one regulator was not letting dual regulators close enough (or is it open I can never remember). In my case, my truck was commanding a lot less rail psi at idle, but the regs could not close far enough to get that low.

I'd start by doing some logging to see if the regs are closing enough first.

 

[Muff]

11psi should be more than ok. Tune the reg current table and you'll be golden. I would start with the tuning.

 

[PACougar]

I would guess its NOT the lift pump but the regulator tables needing adjusting. How i understand it, on my truck the "stock" voltage table used for one regulator was not letting dual regulators close enough (or is it open I can never remember). In my case, my truck was commanding a lot less rail psi at idle, but the regs could not close far enough to get that low.

I'd start by doing some logging to see if the regs are closing enough first.

My thoughts exactly!

 

[05smoker]

Start with tuning.

Could also be a regulator going bad.

We had a similar issue when we kinked our return line to the tank when we welding under the truck. Forgot we had moved the line to weld and it would hold 18k as idle.:spit:

 

[bluecollar]

This is what you guys are helping with. Thanks 2 everyone in advance!!!!

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[bluecollar]

Thanks for all replys!! I will look into this all along return line. It idles great only when slowing down. It was my understanding that the springs in the fpr's might be weak and cant clamp down enough and turning lift pump down may help.

 

[IOWA LLY]

Watch how much fuel the engine is consuming while idling stopped, versus 0% throttle coasting to a stop and you will see why it idles fine when stopped.....

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[duramaxzak]

This is what you guys are helping with. Thanks 2 everyone in advance!!!!

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Looking good Travis! You need to update your signature!!!

 

[bluecollar]

Looking good Travis! You need to update your signature!!!

Thanks alot zak! Ya i do :hug:

 

[bluecollar]

If anyone has a couple low mileage lb7 regulators let me know. Id like to make a hook this weekend in richland center wi. Would be great to find a couple just incase

 

[bluecollar]

Pulled spring on lift pump and cut it.. now have 8psi and all seems well:woott: time for bigger tunes thanks everyone!