LB7: P0093/return rates question

[AKlowriderZ71]

Did some testing yesterday for my P0093 (finally). I just have a couple of things I'd like your input on.

At idle, FRP was around 6000 psi. When commanded to increase, it just laid there dead on/around 6000, no change. Weird. Anyways, diagnostics led me to the high pressure side testing, and the bottle test.

Left bank & right bank both returned 8ml in 15 seconds. Looks like the injectors are okay, right? Still doesn't explain my problem though. Tested again, same results. Hmm. So I measured the return on the injector pump, and it returned 28ml. I looked for a spec on this but didn't find one.

I did find a "total return" spec, which I think was 26 or 28ml? Does this sound right? I believe I have a bad injector pump. Just wanting to know if you guys agree before I spend the cash.

 

[adeso]

does it keep 6000 when you try to drive it? I would think FPR replacement first. Not sure what the return rates are off the top of my head. The other quick thing you can try is unplug the FPR while it is running, should open the FPR then. Would tell you quick if it was some sort of wiring issue

 

[AKlowriderZ71]

When I'm driving it, the pump can achieve 11-12000 psi just fine. After that it struggles, and sets the P0093.

I unplugged the FPR at idle and expected the rail pressure to climb. But it stayed at around 6000 psi.

 

[adeso]

I would think bad FPR, they are cheaper anyways. If you have EFI you can go to the LBZ FPR with a simple tune rewrite, or just put athother LB7 one on there (LBZs flow a tiny bit more fuel but until you get max effort lift pump tune you wont notice). That and maybe check the FPRV, some cheaper things to do before you replace the CP3. How many miles on the CP3? FPR are not the cheapest, but I would put a new one on the new CP3 anyways so you are not really wasting money. The FPRV shim is a little of a PITA but cost less than $1.00

 

[AKlowriderZ71]

I was thinking bad FPR also. So I did the test on it and it passed. Then checked to see if the valve was leaking, and it wasn't.

CP3 has 135k on it. I'll probably never do anything more than a ~75 hp tune and a lift pump on this truck. Should I be considering anything besides a stock LB7 CP3?

 

[adeso]

No, that will work just fine, are you sure it is getting all the fuel it needs? that a filter isn't plugged or a line is bad? what test did you do on it? I would think you should have change messing with the FPR at idle even with a bad CP3
And I'm just throwing ideas out there to try before you spend money on it, good chance it is just the cp3

 

[AKlowriderZ71]

Did the vacuum test to make sure there was no restriction in the supply side. Replaced the fuel filter on day one of ownership, along with a bunch of other preventive maint.

I'm hoping that somebody can verify that my CP3 return rates are too high, and condemning the pump is the right move here.

And if so, should I just get a stock LB7 CP3? Or should I do something different or better?

Thanks for helping guys!

 

[adeso]

for a stock trans no, that is fine

 

[AKlowriderZ71]

Okay, so new question.

Where's a good place for me to buy a new/reman CP3? Of course, a good price would be nice, but I'd pay more to have a better quality pump. I'd like the seller to have a good track record, and stand behind their part. Any sponsors on here that can help me? Or is this a part better purchased at the dealer?

 

[blk smoke lb7]

Ive got a brand new gm pump for 600 plus the ride,its an lbz pump and it has no
fpr on it

 

[AKlowriderZ71]

But I have a LB7, and I want some type of warranty.

Do the pumps interchange? Is there a reason to use something different than a LB7 pump? I've been trying to find these answers myself, but haven't found good answers.

Sorry for all the newbie questions, but I'm a newbie.

 

[adeso]

LBZ pump is a little better, but at your power level you won't tell a difference

 

[blk smoke lb7]

But I have a LB7, and I want some type of warranty.

Do the pumps interchange? Is there a reason to use something different than a LB7 pump? I've been trying to find these answers myself, but haven't found good answers.

Sorry for all the newbie questions, but I'm a newbie.

lbz pump will make more presure and all you have to do is bolt your lb7 fpr up to it and away you go and i will stand behind any part i sell.

 

[AKlowriderZ71]

Does the tune have to be tweaked to run the other pump?

 

[rgullett83]

with an lbz regulator yes, lb7/lly reg no. Its a very simple change, I can help as can several others here as well

 

[AKlowriderZ71]

Bump!

 

[chevyburnout1]

Injector return flow is high but not near as excessive to cause that drastic of a fuel pressure drop. Max return per bank usually runs about 4-5ml.

 

[AKlowriderZ71]

Injector return flow is high but not near as excessive to cause that drastic of a fuel pressure drop. Max return per bank usually runs about 4-5ml.

According to the test procedure on Mitchell, and GM's bulletin, with my fuel API at around 40, it says max return is 40ml per bank. Is this info incorrect? This is the "crank engine for 15 seconds without starting" method, here's a pic of the chart.

 

[AKlowriderZ71]

Here is the "meat" of the test procedure I followed guys.

 

[AKlowriderZ71]

No tech help here? Did I post this in the wrong section or something?