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Old 04-01-2014, 03:32 AM   #26 (permalink)
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Originally Posted by 79chevy39.5's View Post
Does pressure drop right away and stay down for a bit? Thats rail plug. Can you see balance rates? Id check return rates too......another thing id check is maybe some clear tubing after filter head.
Sometimes it stays down all the way to 100 MPH, sometimes it pops back up. If the rail is plugged, why does it run fine on the run after that?
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Old 04-01-2014, 03:33 AM   #27 (permalink)
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Here are two videos from this morning. On the first run, you'll see FRP hit 26, then drop all the way to 4.5, then slowly creep back up. I've never seen it drop that low before. The next run it hits 26 and never drops.

https://www.youtube.com/watch?v=N1jG...ature=youtu.be

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Old 04-01-2014, 06:10 AM   #28 (permalink)
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I dont run and additives, maybe I should...
not stepping on any toes, but just a comment....

ran my '02 lb7 without additives up to 140k with no issues and sold it for my '07. have 100k on my '07 lbz and zero additives used as well. only thing I use is power service in the winter so it doesn't gel up.

my lb7 was a 450rwhp truck and the lbz is a 520rwhp truck (both with lift pumps)

I have several friends who run them and several (including myself) who don't.

I do have an airdog 150 and a water separator filter

not saying don't do it, but just a comment from someone who doesn't.
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Old 04-01-2014, 07:38 AM   #29 (permalink)
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Sometimes it stays down all the way to 100 MPH, sometimes it pops back up. If the rail is plugged, why does it run fine on the run after that?
He is talking about the FPRV (fuel pressure relief valve) at the end of the rail I think. Google bottle test and you can see if its popping open (sounds like it is) and releasing rail pressure.I installed a plug in place of mine on my 06 LBZ in the process of chasing similar problems. Finally found out the other day that i have 3 injectors with higher then desirable balance rates causing my P0087. I'm going to try the GM injector cleaner though before dropping the coin on new. Mines at 180k miles and I have run additive most every tank since 08 when i bought it.

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Old 04-01-2014, 07:55 AM   #30 (permalink)
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He is talking about the FPRV (fuel pressure relief valve) at the end of the rail I think. Google bottle test and you can see if its popping open (sounds like it is) and releasing rail pressure.I installed a plug in place of mine on my 06 LBZ in the process of chasing similar problems. Finally found out the other day that i have 3 injectors with higher then desirable balance rates causing my P0087. I'm going to try the GM injector cleaner though before dropping the coin on new. Mines at 180k miles and I have run additive most every tank since 08 when i bought it.

Brian
Thanks for the help.

My Edge says balance rates should be +/- 4 at idle or +/- 6 in gear. So looks like I'm good there. I'll check into the bottle test tonight.
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Old 04-01-2014, 08:05 AM   #31 (permalink)
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Sometimes it stays down all the way to 100 MPH, sometimes it pops back up. If the rail is plugged, why does it run fine on the run after that?
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Originally Posted by knaffie View Post
Thanks for the help.

My Edge says balance rates should be +/- 4 at idle or +/- 6 in gear. So looks like I'm good there. I'll check into the bottle test tonight.
I'm not sure if a tech 2 uses the same measurement of flow as an insight (it should?) but I was told over 3 in drive would be enough to cause my issues by my friend who does this stuff every day at a diesel shop. My "bad" injectors are 3.4ish.

By his words, your number 4, 7, and 8 would be returning too much fuel.

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Old 04-01-2014, 09:49 AM   #32 (permalink)
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Quote:
Originally Posted by raptorider01 View Post
He is talking about the FPRV (fuel pressure relief valve) at the end of the rail I think. Google bottle test and you can see if its popping open (sounds like it is) and releasing rail pressure.I installed a plug in place of mine on my 06 LBZ in the process of chasing similar problems. Finally found out the other day that i have 3 injectors with higher then desirable balance rates causing my P0087. I'm going to try the GM injector cleaner though before dropping the coin on new. Mines at 180k miles and I have run additive most every tank since 08 when i bought it.

Brian
This. Check the fprv

Quote:
Originally Posted by raptorider01 View Post
I'm not sure if a tech 2 uses the same measurement of flow as an insight (it should?) but I was told over 3 in drive would be enough to cause my issues by my friend who does this stuff every day at a diesel shop. My "bad" injectors are 3.4ish.

By his words, your number 4, 7, and 8 would be returning too much fuel.
+/- 4 is the magic number
Do the gm injector cleaner to pull those numbers back to normal.
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Old 04-01-2014, 09:56 AM   #33 (permalink)
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Balance rates are fine, an '06 should be between -4mm≥ to +4mm≥ and have nothing to do with returned fuel. Its how much is added or taken away to make the engine run smoothly.

Check the pressure sensor and the connector terminals. Sometimes when they will spread from engine vibration. The connector will rattle when unplugged and tapped.

A relief valve will act up but not "fix itself" in the same drive cycle.

I have seen a few with high return rates, but that is only after driving a long time (heat), and with double/triple the miles.
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Old 04-01-2014, 10:56 AM   #34 (permalink)
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Balance rates look fine to me...if in gear in nuetral could show there is some wear going on. I would check return rates....if the frpr is weak it can release fuel differently than designed and just slip fuel by (speculation)

Ill resay it check return rates i bet there are a couple that are high
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Old 04-02-2014, 08:39 AM   #35 (permalink)
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https://www.pirate4x4.com/forum/chevy...l#post25001106

Shim your FPRV to stop it from releasing the pressure as easy as indicated in the link?
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Old 04-02-2014, 08:49 AM   #36 (permalink)
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https://www.pirate4x4.com/forum/chevy...l#post25001106

Shim your FPRV to stop it from releasing the pressure as easy as indicated in the link?
Yup. I did some more reading on that last night. Didn't do the "bottle test" yet. I was going to take my truck to Merchant next week, but he said give this a try first, since he's a few hours away and I would have to rent a car while he has my truck. Part is on the way.

Merchant Automotive - ALLIGATOR RACE VALVE

Now I gotta read up on how to install it.
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Old 04-12-2014, 06:54 PM   #37 (permalink)
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Well, its not the FPRV. I put a plug in today and it didn't help.

Sent from AutoGuide.com App
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Old 04-12-2014, 07:59 PM   #38 (permalink)
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Interesting

Fca on the CP3?
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Old 04-12-2014, 11:37 PM   #39 (permalink)
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Have you checked that its not collapsing the fuel line where the soft line is down by the transmission, or any other rubber line for that matter? Buddy just found where his has collapsed. Was only able to find it by trying to squeeze the line in various spots. You could feel where it was soft in one spot (about an inch long right by the connection). It sat for about an hour, came back out, felt hard again like the rest of the line. Sounds like its a common problem with these trucks, but hard to diagnose because it "fixes" itself when you are not using it.
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Old 04-13-2014, 07:43 AM   #40 (permalink)
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This. Check the fprv



+/- 4 is the magic number
Do the gm injector cleaner to pull those numbers back to normal.
stupid question time.


+/-4 from each other

or +/-4 from zero.
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Old 04-13-2014, 08:29 AM   #41 (permalink)
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Interesting

Fca on the CP3?
What is fca?
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Old 04-13-2014, 08:30 AM   #42 (permalink)
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Have you checked that its not collapsing the fuel line where the soft line is down by the transmission, or any other rubber line for that matter? Buddy just found where his has collapsed. Was only able to find it by trying to squeeze the line in various spots. You could feel where it was soft in one spot (about an inch long right by the connection). It sat for about an hour, came back out, felt hard again like the rest of the line. Sounds like its a common problem with these trucks, but hard to diagnose because it "fixes" itself when you are not using it.
Have not, but I will.
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Old 04-13-2014, 12:45 PM   #43 (permalink)
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FCA: Maintains a constant fuel pressure for fuel that is supplied to the fuel rail.

http://www.amazon.com/gp/aw/d/b00bhk...&robot_redir=1

http://www.dieselpowerproducts.com/p...928400653.aspx
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Old 04-13-2014, 01:38 PM   #44 (permalink)
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stupid question time.


+/-4 from each other

or +/-4 from zero.
+/-4 from zero. Balance rates are the amount of fuel that the computer adds/removes from the "standard" injection amount at idle to try and get a smooth running engine.
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Old 04-14-2014, 07:45 AM   #45 (permalink)
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I reserved a rental car and made an appointment at Merchant Automotive for Monday next week and told them to keep it until they know for sure it's fixed, including putting a lift pump on it if necessary. That will be $1200 I really don't want to put into a truck I probably won't have another year.
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Old 04-14-2014, 03:57 PM   #46 (permalink)
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100k is not a lot for injectors, but I have seen high return rates cause similar problems. Does it ever go into reduced engine power?
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Old 04-14-2014, 04:57 PM   #47 (permalink)
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100k is not a lot for injectors, but I have seen high return rates cause similar problems. Does it ever go into reduced engine power?
From what I understand, that's not a lot for LB7 injectors, but very few LBZ need injectors that soon. Never went into reduced power mode.
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Old 04-14-2014, 05:56 PM   #48 (permalink)
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FWIW: I know GM has had some problems with some of their injectors. Mainly the fuel return that is in the injectors themselves. They stop sealing correctly and they will return fuel to the tank instead of injecting it into the engine. If you have a Tech2 you can command the fuel pressure to maximum (I think is 26K for this test but can't remember) and watch where each cylinder reaches. If the fuel pressure doesn't reach maximum on the bad injectors then you've found your problem. If they all reach the maximum then I got nothing
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Old 04-15-2014, 05:33 AM   #49 (permalink)
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FWIW: I know GM has had some problems with some of their injectors. Mainly the fuel return that is in the injectors themselves. They stop sealing correctly and they will return fuel to the tank instead of injecting it into the engine. If you have a Tech2 you can command the fuel pressure to maximum (I think is 26K for this test but can't remember) and watch where each cylinder reaches. If the fuel pressure doesn't reach maximum on the bad injectors then you've found your problem. If they all reach the maximum then I got nothing
If they all reach maximum it will sounded like a pissed off Cummins at idle, its awesome!!!
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Old 04-15-2014, 10:14 AM   #50 (permalink)
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From what I understand, that's not a lot for LB7 injectors, but very few LBZ need injectors that soon. Never went into reduced power mode.
I have put just as many lbz injectors in as lb7 (granted I work a dealer and have only been here 2 years) so a lot of lb7 work goes elsewhere or have already been done

balancing rate is just an observation of if the injector is leaking into the cyl.(but often times goes hand in hand with body wear) where I see most wear on them is in the body returning fuel to the tank and too much flow for the injection pump to make full pressure, that's why I keep suggesting return rate testing anything over 5 mil. (iirc) is too much if you have even as little as 2-3 around 10 mil it will cause low rail pressure but typically the truck will set a code and go into reduced power.

that being said any news from yesterday?
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