anyone know any really good GM diesel mechanics?

**0rion** · 03-10-2014, 04:13 PM

Trying to help a buddy of mine with his 06 duramax. He's had trouble with that truck going on 3 years now. It's throwing the p0087 low rail pressure code. Started doing it only when hauling during the summer but now it does it anytime he goes past half throttle whether there's a load or not. I've searched all the diesel forums and we've tried just about everything out there and he's still throwing the code. I'm just curious if anyone has had any luck fixing the 0087 trucks that aren't fixed with the obvious stuff. He's at around $4k in parts/labor right now and it's no better than when it started.....it's actually worse.

What's been done:
CP3 was replaced and a couple injectors by a diesel mechanic up by where he lives that's supposed to know these trucks inside and out. I have my doubts. Problem went away for a short time but came right back.
We've replaced all the rubber sections of the fuel feed line.
We pulled the bed off and replaced the module in the tank thinking maybe there was an obstruction.
I looked at the balance rates for the injectors and they all were in spec.
We did a bottle test on the fuel pressure relief valve and it's not leaking.

I'm just at a loss and have no idea where to tell him to look next. He basically has a completely new fuel system from the tank to the injectors and it's still throwing the code.

**Cutlass** · 03-10-2014, 06:15 PM

Fuel filter? lol I'm sure you guys didn't overlook that.
Questions for you, any mods to the fuel system?
Does the CP3 come with a new fuel pressure regulator or does that get swapped over from the old pump?

**0rion** · 03-10-2014, 07:04 PM

fuel filter has been changed several times. I've kinda wondered about his filter head but he's not having any leaks, prime issues, or anything like that. I'm not sure on the regulator. I'd have to ask him if it was on the parts list when the guy did the work on it. For what that CP3 costs I'd hope you don't have to swap shit over. The only mods to the fuel system have just been replacing the rubber lines to rule out those collapsing and we put a new fuel cooler on last weekend due to a return line leak.

I did a log of the truck over the weekend and went over it where it limped and it's definitely a low pressure problem. Desired is ~25k psi and actual is ~10kpsi. That to me would rule out a sensor problem and point more towards a mechanical issue in some form or another. I really thought it was going to fail the bottle test and show that the relief valve was bleeding off the pressure but no such luck. The valve is holding. He's to the point of starting to shop for a new truck. He's put an ass load of money in it trying to fix it. I just don't know where to tell him to look next. The guy that worked on it only replaced 2 injectors so maybe he has another injector failing or something....not sure if they always show bad on the balance test. They were all within spec though. That's a $400 per injector guess which is never good. I'd thought about swapping the injectors out of my truck into it and see what it did but part of me don't want to take a chance of his truck ruining my injectors.

**Cutlass** · 03-10-2014, 07:29 PM

Jeez, with numbers that low, you'd think it be obvious.
I bet the fuel pressure regulator comes with the injection pump...but who knows.
There is an injector return flow test that actually measures the return flow volume of each injector. Theoretically I'd think it would be that as reading the balance rate on a scan tool but...don't know.
How long was the problem "fixed" with the new injection pump? I'm kinda wondering if its initial failure sent debris into the system. That debris could hang up the fuel pressure relief valve or maybe an injector intermittently.

**5.0THIS** · 03-10-2014, 09:20 PM

I cant fathom someone throwing 4000$ in parts at a vehicle (with no success), when honestly, they're in over their head to begin with. wow.

Hope he gets it figured out though

**0rion** · 03-11-2014, 03:51 AM

Originally Posted by Cutlass

Jeez, with numbers that low, you'd think it be obvious.
I bet the fuel pressure regulator comes with the injection pump...but who knows.
There is an injector return flow test that actually measures the return flow volume of each injector. Theoretically I'd think it would be that as reading the balance rate on a scan tool but...don't know.
How long was the problem "fixed" with the new injection pump? I'm kinda wondering if its initial failure sent debris into the system. That debris could hang up the fuel pressure relief valve or maybe an injector intermittently.

I think we can rule out the fprv because of it not letting fuel bypass when it did it. In the back of my mind I've kinda wondered about there being trash in his injectors because the cp3 shit the bed after the injectors were put in. I know the cp3 went out while the guy had it that was putting the injectors in it and I believe it did it on the test drive AFTER the injector install. To me that makes as much sense as anything.

Originally Posted by 5.0THIS

I cant fathom someone throwing 4000$ in parts at a vehicle (with no success), when honestly, they're in over their head to begin with. wow.

Hope he gets it figured out though

most of that money went to the cp3 and injector R&R.....that cp3 is like a $1000 part by itself and injectors are $400 a pop. Doesn't take long for that kinda money to add up plus the guy had a ton of labor on replacing that cp3. The guy that did that work came highly recommended because he's supposed to be some kinda diesel genius. My buddy said when he told him what problem he was having the guy said he new exactly what it was (injectors). When he was telling me this I was skeptical because I've read too many threads where injectors didn't fix the problem. Anyhow.....the guy works on it, calls him, and tells him after the injector install and on the test drive the cp3 ate itself to death. He only replaced 2 injectors I think but still....that's $800 in injectors. The thing that gets me though is I would think if injectors were clogged it would show up on the balance rate check or you would hear injector knock or something. He has nothing like that going on. Truck starts and idles perfect.....it's only when you put it under heavy load that it runs out of fuel. I've tried to look at everything I know about and nothing. I guess I need to read on how to test that cp3. I've read where people have had luck adding a boost a pump but that's another expensive guess. He started truck shopping yesterday so he's pretty much done throwing money at it.

**cpop98ws6** · 03-11-2014, 07:45 AM

Are you using an A/C delco Fuel filter? I Just had a 5500 in out shop the other day with the same code, it had a fram fuel filter on it so i swapped it out with an A/C delco and problem solved.

**0rion** · 03-11-2014, 09:10 AM

he runs wix filters on it I believe the same as I do. Those are quality filters so I just can't see that being his issue. I actually think early on he tried running an ac delco but had the same issue still.

**5.0THIS** · 03-11-2014, 12:17 PM

Originally Posted by 0rion

most of that money went to the cp3 and injector R&R.....that cp3 is like a $1000 part by itself and injectors are $400 a pop. Doesn't take long for that kinda money to add up plus the guy had a ton of labor on replacing that cp3. The guy that did that work came highly recommended because he's supposed to be some kinda diesel genius. My buddy said when he told him what problem he was having the guy said he new exactly what it was (injectors). When he was telling me this I was skeptical because I've read too many threads where injectors didn't fix the problem. Anyhow.....the guy works on it, calls him, and tells him after the injector install and on the test drive the cp3 ate itself to death. He only replaced 2 injectors I think but still....that's $800 in injectors. The thing that gets me though is I would think if injectors were clogged it would show up on the balance rate check or you would hear injector knock or something. He has nothing like that going on. Truck starts and idles perfect.....it's only when you put it under heavy load that it runs out of fuel. I've tried to look at everything I know about and nothing. I guess I need to read on how to test that cp3. I've read where people have had luck adding a boost a pump but that's another expensive guess. He started truck shopping yesterday so he's pretty much done throwing money at it.

That's the thing with guessing on your own or having an independent person guess at it. If they're wrong, the answer is oh well, let's try something else and you can spend more money on it. For all the hate out there for dealerships, a good diesel tech isn't going to guess at it by throwing parts at it. And if they do, it's on them to fix it after that when they've already told the customer what's wrong and what should fix it. The irony about getting advice on the internet is that so often people end up spending more on a vehicle than if they just would have taken it in for a professional diagnosis in the first place

**0rion** · 03-11-2014, 09:20 PM

Originally Posted by 5.0THIS

That's the thing with guessing on your own or having an independent person guess at it. If they're wrong, the answer is oh well, let's try something else and you can spend more money on it. For all the hate out there for dealerships, a good diesel tech isn't going to guess at it by throwing parts at it. And if they do, it's on them to fix it after that when they've already told the customer what's wrong and what should fix it. The irony about getting advice on the internet is that so often people end up spending more on a vehicle than if they just would have taken it in for a professional diagnosis in the first place

you should do some reading on the 0087 code......many many dealerships have done just that. Thrown injectors and cp3's at it to not have it fix anything and then the guy is screwed because the injectors didn't have good balance rates or the actual rail pressure wasn't following the desired. The best I can tell from the hours and hours of reading I've done on it that no one knows exactly what the issue is.....not even the dealerships. For some the cp3 fixes it, for some injectors, collapsed fuel lines, filter heads, fprv, ect ect. I've read so many threads where guys have poured money into their trucks, just like my buddy has, and still not figured it out. I'm trying to keep him from putting anymore money into it that he doesn't have to. It's like no other car problem I've ever ran into. Normally there are only so many things you can point at and it has to be one of them. With this damn thing no one knows and it can be anything or evidently nothing. I think next on the list are trouble shooting his injectors. Balance rates I can do but return rates are something he'll probably have to have a dealership do. It involves hoses and graduated cylinders and knowing what the returns should be. It would still probably be cheaper in the long run to pay a dealership to test them and for us to only replace the injectors that need it but I have a feeling the dealership will come back that all 8 need changed. As a matter of fact I almost guarantee it because dealerships are fucking crooks and they think they'll be the one's installing the injectors.

**5.0THIS** · 03-11-2014, 11:25 PM

Originally Posted by 0rion

you should do some reading on the 0087 code......many many dealerships have done just that. Thrown injectors and cp3's at it to not have it fix anything and then the guy is screwed because the injectors didn't have good balance rates or the actual rail pressure wasn't following the desired. The best I can tell from the hours and hours of reading I've done on it that no one knows exactly what the issue is.....not even the dealerships. For some the cp3 fixes it, for some injectors, collapsed fuel lines, filter heads, fprv, ect ect. I've read so many threads where guys have poured money into their trucks, just like my buddy has, and still not figured it out. I'm trying to keep him from putting anymore money into it that he doesn't have to. It's like no other car problem I've ever ran into. Normally there are only so many things you can point at and it has to be one of them. With this damn thing no one knows and it can be anything or evidently nothing. I think next on the list are trouble shooting his injectors. Balance rates I can do but return rates are something he'll probably have to have a dealership do. It involves hoses and graduated cylinders and knowing what the returns should be. It would still probably be cheaper in the long run to pay a dealership to test them and for us to only replace the injectors that need it but I have a feeling the dealership will come back that all 8 need changed. As a matter of fact I almost guarantee it because dealerships are fucking crooks and they think they'll be the one's installing the injectors.

Some of them certainly are crooks. I have a friend who is a great GM tech. I know if such a problem came into him, it would be fixed the first time. If it wasn't, then I know that dealership would make sure it is fixed on their dime, especially if they tell you x is the problem, and y is the solution, and neither one or both end up being the right answer.

**Cutlass** · 03-14-2014, 03:32 AM

Not every diagnosis is black and white. There is a lot of gray area diagnosis because you can't physical test everything. You can just rule some stuff out and point at the most likely cause. Sometimes you just have to try something and see if it fixes it. Good techs get gray area diagnosis correct 80% to 90% of the time. When you don't get it right, you have to have a good service writer who can translate the technical jargon into something they are comfortable with. Even then, some customers still think you're BSing them.
0rion, there are several GM service bulletins on this code. Most of the stuff you guys already tried it seems like, but PM me if you want more info.

**0rion** · 03-14-2014, 04:49 AM

Yeah....I've read all those bulletins. Most talk about the collapsing hose, cp3, injectors, fprv, ect ect. We've pretty well knocked out everything on those bulletins minus the injectors. Do you have access to the return rates for the injectors? I know how to test the return rates.....I just don't know what the acceptable range is. I've read 5-8cc but I saw like 2 oz which would be 60cc's. No way we're replacing injectors unless I can for sure point to them as being bad or at least have them fail a test. I did a balance rate check and all were within spec. 2 of them were out further than the others but still within spec.

**Cutlass** · 03-15-2014, 04:06 AM

Fuel Specific Gravity Testing

Use a J 38641-B Diesel Fuel Quality Tester to measure the fuel specific gravity (API Rating). Follow the instructions on the tool to obtain the proper temperature-adjusted value. This information must be accurate for the proper diagnosis of the fuel system.

Fuel Injector Return Flow and Fuel Pressures

The fuel return from the fuel injectors to the tank will vary based on the API value of the fuel. Measure the Fuel API with the Diesel Fuel Quality Tester. For this reason the Fuel System Diagnosis – High Pressure Side values will vary for identifying a fuel injector or fuel pump concern. Use the following tables when referred to by the diagnostic. The first table is to be used during the initial diagnosis to identify the worst fuel injectors. After the fuel injectors that fail the first part of the test are capped off, the return flow from each uncapped fuel injector must be measured again, (not applicable to LLY). This is because the fuel system is returning less fuel to the tank, and thus the fuel pressure is higher during the retest. Failure to use the correct table may result in the replacement of good fuel injectors.

Initial Fuel Injector Return Flow Values

API Rating_ _ _ _ _ _ Maximum Single Fuel Injector Return Flow

30-34 _ _ _ _ _ _ _ _ _ _ _3 ml

35-39 _ _ _ _ _ _ _ _ _ _ _4 ml

40-44 _ _ _ _ _ _ _ _ _ _ _5 ml

Retesting Fuel Injector Return Flow Values

API Rating_ _ _ _ _ _ Maximum Single Fuel Injector Return Flow

30-34 _ _ _ _ _ _ _ _ _ _ _4 ml

35-39 _ _ _ _ _ _ _ _ _ _ _5 ml

40-44 _ _ _ _ _ _ _ _ _ _ _5 ml

**0rion** · 03-15-2014, 05:05 AM

Thanks for the info.

I knew about the API rating. The whole ordeal sounds like a pain in the ass really. He was supposed to call around up there where he lives and see how much the dealerships would charge him to check those injectors so I guess we'll go from there. I have no doubts that I could check his returns it's just a matter of how much time it's going to cost me versus how much the dealership will charge him to do it.
The price of those injectors is crazy. The price of most things on that motor is crazy. You could sink $10k into that motor in a hurry. That boggles my mind. I can buy a stroked LS motor for what injectors and a cp3 cost on a duramax.

**Cutlass** · 03-15-2014, 03:08 PM

Fuel Injector Return Flow Test

Note: Perform this test on both right and left bank of fuel injectors.
1. Remove the fuel return hose from the fuel injectors of one cylinder bank. Refer to Fuel Injection Fuel Return Pipe Replacement - Left Side or Fuel Injection Fuel Return Pipe Replacement - Right Side.
2. Clamp off the appropriate fuel return hose to prevent leakage.
3. Install the J 45873 and J-45873-30 on the bank of fuel injectors.
Note:
If the engine does not start, crank the engine in 15 second intervals, with 1 minute cooling time between intervals, until fuel starts to flow into all of the graduated cylinders.
The engine cranking speed must be more than 150 RPM during the cranking portion of this test.
4. Start or crank the engine until fuel starts to flow into all 4 graduated cylinders.
5. Elevate the 4 yellow hoses to retain the fuel in the hoses, and empty the 4 graduated cylinders into a suitable container and reinstall the hoses.
6. Crank or start the engine for 15 s
7. Measure the quantity of fuel in each of the graduated cylinders. Refer to Fuel System Specifications for the initial fuel injector return flow values.
=> If greater than the specified amount
Note: During replacement of the injectors, inspect the inlet and outlet fittings for corrosion or contamination.
7.1. Replace those fuel injectors that had high return flow and retest.
7.2. Repeat the return flow test and replace any additional injectors that measure greater than the specified amount. Refer to Fuel System Specifications for the retesting fuel injector return flow values.
=> If less than the specified amount
Refer to High Pressure Fuel Pump Test.

Fuel Injector Return Flow Test — Enhanced

Important: Do not perform this testing unless the vehicle has the following symptoms.
DTC P0087 sets in memory
DTC P0087 only sets during high ambient temperatures and while the vehicle is under a heavy load
If the vehicle does not have the above symptoms, refer to Circuit/System Verification.
Engine must be at operating temperature 83–87°C (181–189°F) for proper diagnosis.
Perform this test on both the right and left bank of fuel injectors.
1. Engine at normal operating temperature, 83–87°C (181–189°F).
2. Remove the fuel return hose from the fuel injectors of one cylinder bank. Refer to Fuel Injection Fuel Return Pipe Replacement - Left Side or Fuel Injection Fuel Return Pipe Replacement - Right Side.
3. Clamp off the appropriate fuel return hose to prevent leakage.
4. Install the J 45873 and J-45873-30 on the bank of fuel injectors.
5. Place the 4 yellow hoses into a suitable container.
6.Engine running until fuel flows from all 4 yellow hoses.
7. Engine at idle, command the fuel rail pressure to 120 MPa (17,400 psi) with a scan tool.
Note: It may be necessary to exit command after each cylinder to ensure commanded state does not time out.
8. With the rail pressure commanded to 120 MPa (17,400 psi), place each of the 4 yellow hoses one at a time into the 4 graduated cylinders for 30 s each.
9. Ignition OFF.
10. Measure and record the fuel return volume in each of the graduated cylinders.
11. Repeat Steps 1–9 on the opposite bank of injectors.
12. Add together the recorded injector return flow volumes of all 8 fuel injectors to determine the total injector return flow volume.
13. Verify the total injector return flow volume is greater than 144 ml
=> If the total injector return flow volume is less than 144 ml
Refer to High Pressure Pump Test.
=> If the total injector return flow volume is 144 ml or greater
Replace any injector with an individual injector return flow volume of 18 ml or greater.

High Pressure Fuel Pump Test

1. Attempt to start the engine.
=> Engine cranks but does not start
Replace the high pressure fuel injection pump
=> The engine starts and runs...continue to step 2
2. Engine at idle.
3. Command the fuel pressure control to 145 MPa (21,030 psi) with a scan tool.
4. Verify the Actual Fuel Rail Pressure is the same as the commanded fuel rail pressure.
=> If the engine does not start or the actual fuel rail pressure is less than 145 MPa (21,030 psi)
Replace the high pressure fuel injection pump.
=> The Actual Fuel Rail Pressure is 145 MPa (21,030 psi)...continue to step 5.
5. Engine speed above 1000 RPM.
6. Command the fuel pressure control to 180 MPa (26,106 psi) with a scan tool.
7. Verify the Actual Fuel Rail Pressure is the same as the commanded fuel rail pressure.
=> If the actual fuel rail pressure is less than 180 MPa (26,106 psi)
Replace the high pressure fuel injection pump.
=>The Actual Fuel Rail Pressure is 180 MPa (26,106 psi)...continue to step 8.
8. All OK

**0rion** · 03-15-2014, 09:16 PM

wow....thanks for taking the time to post that up. The J 45873 tool is on ebay....for $250. The other one is ~$75. Still cheaper than an injector. I sent him a text today....he still hasn't called the dealership to see what they charge to test the injectors. I'm just waiting on him at this point to see what he wants to do.

**Cutlass** · 03-16-2014, 03:33 AM

Yep and you can always just resell the tool so in the end it doesn't cost anything. Looks like the 1st test is looking for individual injectors that flow too much return volume, and the second test look at the total return volume. So it could be possible for all the injectors to be in spec, but if they are all on the high end of the spec, the total return volume could be out of spec.
The third test is a good way to test the CP3. Since you have everything you need to run that test, maybe you could do that one first.

**0rion** · 03-28-2014, 03:43 PM

small update.....after showing him all of this info and what all we'd have to do to check the return rates he took it to a dealership to have them check the returns on the injectors. There's supposed to be 2 or 3 dedicated diesel guys at this dealership. He took it in and told them what was going on and what had been done so far. They swore the injectors were fine that it was probably the fprv (even though he told them we checked it) and they kept it to look at it. Called him the next day and said the fprv was fine, pump was fine, and they were going to check the return rates on the injectors. Checked them and couldn't get the return line off of 8 so they only tested 7 and 6 of those were showing high returns. I told him to get the actual readings. He had them check another noise he had which was a whining noise. I heard it a month or so ago and to me it really didn't sound like much but I didn't pay that much attention to it. Sounded like maybe a power steering pump or something whining a little bit. They called him today.....they said it's the tranny whining but wasn't sure what it was. I'm thinking pump as that's the only thing I've ever known in a tranny that will whine like that. So the allison is known to be a good tranny for the most part and the 06's are supposed to have the most reliable injectors and evidently he has problems with both. Feel sorry for the guy. He's going to decide this weekend what to do. I told him I would help him replace the injectors and save a shit ton of money doing it ourselves but the tranny (if in fact it is the tranny) is something I'm not comfortable tearing apart because my experience with those are just doing converters. I *think* that pump isn't a huge job but I'm not sure and not sure I'd want to learn on someone else's vehicle. If I tear my shit up it's just a learning experience but if I tear someone else's shit up I'd feel 10 times worse about it.

**Cutlass** · 03-28-2014, 04:28 PM

My buddy went through the same thing with his 2004. Needed injectors (well known issue with the older LB7) and the Allison needed attention. Trans was a beefed up rebuild gone wrong. The triple disc torque converter failed internally and during the trans tear down he found the previous owner made a few minor mistakes on the rebuild. Expensive stuff, no doubt about it.
The Allison trans is actually relatively easy to work on...except it being REALLY heavy. You can just set it on a bench and pull half the internals out the front. Or mount it to an engine stand via the PTO cover like this picture. I helped my buddy out a bit on his. He did it with the truck on jack stands and used an ATV/Motorcyle jack to lower it out.

Its stories like this that make me gun shy on buying a Diesel truck. I can do all the repair work myself, but the risk of dropping $2000 to $4000 on parts all at once is something that would hurt. Guess I'd favor a 6.0 gas 2500 HD. Scary thought there.