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  #1  
Old 05-01-2020, 05:00 PM
Redkliney Redkliney is offline
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Default Truck won't start unless primed

Ok need some help diagnosing. Did cp3 and injectors last week. Truck ran awesome for 4 days. Took the wife and kids to pick up the car at the garage for inspection and gave the gogo pedal a good push. Fell on its face and shut off. Figured a fuel line collapsing. I had to reprim the truck to get it to start ever since then. Put clear line from cp3 to the junction block and not getting air. Put on a vaccum gauge and with the truck idling will pull 2inhg at idle and 4inhg full throttle parked. Shut it off and let the rail pressure bleed down. Recrank and the rail pressure doesn't even budge. Prime it up and if fires right off lickity split. Tried unplugging the fpr and at idle will run about 25.5kpsi. Its an lbzsupersport pump. Was retuned and the fuel pressure desired and actual follow suit. Just does not seem to be drawing fuel to start unless its primed.
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2002 ccsb lb7. cat oil filter. homemade lift pump with cat fuel filter and extra water separator. ported turbo horn. sac45 injectors. Lbz sportsman pump.
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  #2  
Old 05-01-2020, 05:31 PM
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torqued2dmax torqued2dmax is offline
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Is your lift pump not putting positive pressure to your filter head ?
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Old 05-01-2020, 05:40 PM
Redkliney Redkliney is offline
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I had to bypass the lift pump. Caused my rail pressure at idle to go to 11500. The truck won't strat till i prime it to 10 psi though. Was told to regulate my lift pump to 4-5 psi so I'll have to find a regulator.
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2002 ccsb lb7. cat oil filter. homemade lift pump with cat fuel filter and extra water separator. ported turbo horn. sac45 injectors. Lbz sportsman pump.
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  #4  
Old 05-01-2020, 05:47 PM
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torqued2dmax torqued2dmax is offline
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I hope you did not hurt your new cp3 with too much pressure on the low pressure side before you realized it and removed it ! Do you know what the pump was putting out ?
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05 CC/LB DRW LLY Allison
AFE Blade Runner,AFE Momentum CAI,DHD Big Air intake Y pipe, DHD fuel block,DHD pcv reroute,MBRP 4 inch exhaust,DHD 3 inch downpipe,BD driver's side manifold,DHD pass side up pipe,DHD 3 inch intercooler hot&cold pipes, ATI damper,Empire pin kit by Big Foot on & off road shop, FASS fuel system,5/8 inch pickup, FASS fuel filter delete, EFI live,V2 & lap top , 5 position switch 250 hp big tune, shimmed fprv by Crank it up , built SunCoast Allison 1078 converter aftermarket trany mount by Limitless Diesel,ARP head studs,grade C gaskets,tig-welded water pump,T stats by Blackout performance,MA t case brace , Kriptonite motor mounts,MA pump rub kit,HD drive shaft 1480joints by Greensburg machine,BDS Recoil traction bars, PPE finned deep pan , Mike L trany cooler, PSC pump, 5100s, Sulastic Shackles, Curt com 2.5 hitch
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Old 05-01-2020, 06:08 PM
Redkliney Redkliney is offline
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The first time i started the truck i saw it was at 11500. Saw my desired and actual Ma for the regulator way off. Thought about it and remembered the lift pump thing so i pulled the fuse and it ran with desired perfectly. Ran it for a few trips over a few days. When it fell on its face and i saw the line wasn't kinked i figured the extra pull through two filters and a off pump did it. So i removed it. Its still on the truck but no fuel lines hooked up. I still have my test gauge hooked to the test port line so i may hook it up just to see what pressure it was running at. If it was high what does it damage in the pump? I've been reading up about the cascade overflow valve and am wondering if it could have stuck open causing too much fuel to go to the return and not the fca?
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Old 05-01-2020, 06:57 PM
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DAVe3283 DAVe3283 is offline
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I don't think you can hurt the CP3 with too much inlet pressure. Well, maybe something extreme like 25+ PSI could cause the seals to leak, but you're probably going to be pissing fuel out of your FICM (assuming you didn't bypass it) first.

When you crank it without priming first, what does rail pressure do? If you unplug the regulator and crank without priming, what does rail pressure do?
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Old 05-01-2020, 07:06 PM
Redkliney Redkliney is offline
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Rail pressure doesn't budge. After i shut the truck off it drops to around 200psi, will stay that way even over night. Go to start the truck and fuel rail pressure doesnt budge. Gonna get some clear 5/16 hose to put from the junction block to cp3 to make sure there is definitely fuel there. Honestly seems like for some reason it's just not sucking like it should till its at full running speed. Haven't checked cranking rpm but it sounds healthy.
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Old 05-03-2020, 07:52 AM
Redkliney Redkliney is offline
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So hooked lift pump back up. Pressure gauge at port reads 5 psi. Really starting to thing the cp3 itself is a dud. Put 10 psi to it starts and runs like a champ. Gonna try a clear return line yet to see if a seal in the pump is bad yet. From what I've been reading a cp3 should pull at least 12inhg while cranking. With a vac gauge on just the cp3 inlet its only drawing 4.
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Old 05-03-2020, 02:46 PM
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4" is the restriction in that factory setup with new filters. Unless you pinch off a hose or have old filters you won't see more then that.

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  #10  
Old 05-03-2020, 03:38 PM
Redkliney Redkliney is offline
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Thats why i hooked the vaccum gauge into the cp3 feed hose. Only got 4. Put all clear lines on today and i have no air in the fuel entering. But it sure is coming out.
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