Unexpained MPG drop

[Ozymandias]

I think you broke the cables at the actuator by touching them now, they are prone to break at some age, that's probably the reason for the returning P0243.

 

[TSimonson]

Update - Yep, Dave, I should have used a test light instead of the voltmeter. I'll try that tomorrow night.
Wires at the harness aren't broken, still have ~11 ohms, not an open circuit. Plus, when I started the truck after work, DTC cleared, only the third start since P0243 showed up.
I'm still curious why I had to run the compressor up to 45 psi (max recommended by the Holset manual) before I could get the wastegate to move. I'll probably try that again tomorrow night when I put the test light on.
The saga continues. Thanks again to all. More tomorrow.

 

[lpennock]

I'm still curious why I had to run the compressor up to 45 psi (max recommended by the Holset manual) before I could get the wastegate to move.

Drive pressure plus boost pressure is fighting against the spring. Up to about 35psi the drive pressure is about equal to boost pressure. If the surface area of the gate valve is exactly 1 square inch the contribution from boost and drive is the same or about 22 psi each hence the reason you didn't see movement until 45psi since you had no drive pressure.

 

[TSimonson]

So based on all of the great advice from fellow TDR members, here are is an update after some tests...
There is no problem with the wastegate (now). It may not have been working, mechanically or electrically, a week ago when I started on this turbo saga. After the recommended Holset tests described above left me with more questions than answers, I pinched off the hose going to the mechanical wastegate actuator to see if I could get above 23 psi boost. Yes, I did. Managed 28-29 psi in-town driving with no load.
Took the vise-grip off the hose, hooked everything back up - stock - and got 30-31 psi, so the mechanical wastegate and command valve are working as far as I can tell. This is completely different from the high EGTs and low boost described starting in 2014. So that change I can attribute either, or combined, to the few times I had to apply 45 psi to the mechanical side of the wastegate to get it to move, and tightening the exhaust leak off the down pipe.
So it's too early to tell if the poor "unexpained" efficiency drop has been corrected, but the truck sure as he!! responds better.
Before I end this thread as "solved" I still observe what I thought was normal rail pressure, but after cerberusiam's post, it gives me pause. After closer observation, I'm still seeing 19k+ psi at the rail at cruising speeds on the freeway ~60-70 MPH.
Does anyone have the ECM mapping for environmental vs. rail pressure? That still may be the problem with fuel efficiency, but power/EGT/responsiveness is back to stock.

 

[TSimonson]

So the "maybe" stuck wastegate wasn't the issue. I have to retract my above statement that the truck is responding better. I was excited about seeing 31 psi boost, but really no change at normal throttle. And again, 13.88 hand-calculated MPG this fill. So I would like to explore cerberusiam's rail pressure idea before going for a tuner or ECM. I'm seeing ~7kpsi at idle (in drive) with 500+ psi rail pressure fluctuations. I consistently see 19 kpsi+ at 55 MPH consistent cruise.
Can't upload data logging since I haven't done the homework on custom PIDs for data logging software. Anyone have the Cummins PIDs for the 2004.5?
And there's still the HUGE delta between ECM reported efficiency (24 MPG) and hand calculated (13.9 MPG). Maybe it's an FCA? Any thoughts?

 

[TSimonson]

So I never did find anything on custom PIDs. I guess that's how Smarty, Edge, etc., stay in business So I pulled the data logs from my Edge and converted the time stamp to something useful, then graphed EGT, RPM, Boost (actual from the banjo bolt on the intake, not ECM calculated), MPH, and fuel rail pressure. Two things stick out to me:
1) Consistent rail pressure above 17 kPSI at "cruising" speeds (55-60 MPH)
2) Changes of > 500 PSI while idling

I can't find either as hard data points in the factory manual, but reading through posts here and elsewhere, these seem to "problems" that point to a faulty FCA or ECM (or ECM connection). At any rate, I think the graphs are of more value than the logs I posted earlier. Top graph on each page is drive data, bottom graph is a subset of one period of idling from that drive period. If anyone can confirm either the above as "issues" I'm all ears.

 

[cerberusiam]

Both of those look pretty much normal. That is what I see on an analog gauge also.

 

[TSimonson]

Thanks cerb. Just curious, what kind of mileage do you get empty with the 3.73?
I found a TSB that debunks my 500 psi criteria. For everyone's info, it's +/- 500 PSI from set point, not 500 total variation. All mine are within that 1 kPSI range at idle.
Guess I'll keep looking for an answer - maybe one of the return lines. I'm going to make some runs with both OBDII gauges and see if I can merge some data. Thanks again.

 

[cerberusiam]

Average of all driving 15-16 mpg. I run a 33" tire all the time for towing so have a little better rpm leverage. At 70-75 it is consistently 15-16 in good conditions, good conditions that will go to 17-18 mpg in the 65-70 mph range and jump to around 20 at 60 or so in hot conditions.

Only thing I can think to check is how smooth idle is at 800, 1100, 1400 rpms. Watch your steering wheel and door with it open. If feel and roughness or either of those items bounce a little you have an injector that has been compromised.

Have you have a contribution test and rpm drop on kill done on injectors?

 

[TSimonson]

Injectors were all tested when replaced with the CP3 15k miles ago. No change in power, EGTs or mileage after replacing them and no change since.

 

[cerberusiam]

Injectors were all tested when replaced with the CP3 15k miles ago.

What did you use for replacement injectors and CP-3? Have you had a contribution test done on the installed injectors? Testing means nothing without seeing how they are performing in the engine at operating temp.

 

[TSimonson]

Replaced with new OE injectors and CP3: CP3 0986-43 7-304; injectors 0986-435-505. Contribution test done after the tank was drained, fuel system was flushed, and CP3, injectors, feed tubes, and fuel filter were replaced. I was told no issues with any cylinder, but I don't have any documentation. It was the first time I'd used this shop (or any work done except warranty and the transmission), but it was highly recommended by guys I trust, so I brought it there for the work since it was only a couple hundred bucks more for everything warrantied and installed than it was for me to buy the parts. Original diagnosis was from a dealer in town. I took it to these guys for a second opinion on the CP3. I did get a look at the old CP3 and there was play in the driveshaft. Maybe I was just lucky like I was with the 48RE that probably had <50 more miles on it until complete breakdown (took 3 days to flush the transmission cooler). Regardless, there was no change in truck performance after either of these major repairs, so I'm kind of back on square one.
I'm going make a few more runs to try and combine some data from the two OBDII loggers and see if that might shed some light. I think the results are going to show some goofy data with respect to ECM-calculated fuel consumption - overhead console used to show 18 MPG when hand calculated was 16. Now it shows 15-ish and hand calculated is 13-ish. OBDII reports 23-25. So we'll see what that gives me, but I'm thinking it's time to pivot back to the ECM.
Oh, and my turbo timer stopped working last week. All the wiring is good and everything reads out fine

 

[cerberusiam]

The 0986435505 are not new, those are remans. That may or may not be the problem but it just adds another failure point in the process. My experience with remans is they are not that great. New production Bosch injectors are +\- 3%, remans you are lucky to get that in at double the variance rate. That will mess with mpg numbers and introduce vibes and rough running.

Without contribution test numbers per cylinder, rpm drop on injector kill per cylinder, and a return flow test you are just guessing at the problem.

 

[TSimonson]

I should have been more clear in stating "reman" not "new". They were only "new" in the sense they weren't the ones installed when the old CP3 started crapping out and introducing metal shavings throughout the fuel system. I was only trying to point out that there was absolutely no change in low power, high EGT, or low MPG conditions from the old CP3/injectors to the new in June 2016. So to me it seems unlikely the injectors were the source of the low power, high EGT, and low MPG that came on suddenly in October 2014. Same as the fact that the 48RE did eat itself in March 2015, but after replacing it there was absolutely no change in performance. So it seems unlikely the 48RE was the source of the problem.
I absolutely need to do a return flow test, especially off the pressure limiting valve on the rail, because I know that wasn't done when the CP3 was replaced. If the pressure limiting valve on the rail has failed, I think that would explain A LOT.
I'm certainly no expert and sincerely appreciate all the advice. Now I have to fix a shower that's leaking through the ceiling into the kitchen

 

[cerberusiam]

Rail PRV failing would definitely make change things. Those are easy to test though so that can be done in driveway.

The sequence is kind of the point I am making that you are not back to what it was when you had good mpg. CP-3 failed and took out injectors, injectors were replaced with remans, CP-3 was replaced with reman or new? Rail and lines not replaced, PRV not replaced, hopefully cross over tubes were replaced. If you did not replace everything with NEW parts then you still don't have a solid basis for comparison.

 

[TSimonson]

CP3 was also a reman; feed tubes were replaced. The rest of the fuel system was drained and flushed before replacing parts - I stopped by the shop and saw the whole apparatus while it was on the truck. But I see your point, and I didn't realize the performance gap between new and reman.

It's still hard for my little pea brain to comprehend this scenario: In one day, during one trip from Nevada to Nebraska in 2014, performance dives off the cliff - 17% from the average from the previous 115k miles which included car hauling across the Rockies. I drive the truck, no towing, for 2 years with the same 17% degrade. Drain and flush the fuel system, replace the CP3, injectors and feed tubes (albeit with reman parts) and performance improves 1% over the previous 2 years. To me that says 1 of 3 things:

1) The mechanical, physics part of the fuel system isn't the culprit (with the possible exception of the PRV)
2) Fuel system was still contaminated when reman parts were put in and that clogged injectors with < 7 micron particles as soon as it was started the first time
3) "New" reman parts are as bad as a wobbly old OE CP3 driveshaft and clogged old OE injectors

If it's 2) or 3) I'm right back where I was in 2016, so I'm going to start with 1) checking the PRV. With any luck I'll get home before 8 tomorrow night and have time to play with it in the garage. But it is opening duck down in Missouri this weekend so I might not get much else done

Thanks again for everything. I've seen almost this same problem a few other places with no resolution, so hopefully I can put this to bed and help some other folks.

 

[cerberusiam]

The reason you don't see a lot of resolutions is the truck gets traded, that is the resolution.

It is tough to find issues like this with complex tight tolerance mechanical parts and dynamic electronics. It is like your list, looks perfectly reasonable until you consider #1 is influenced by #2 and #3. None or all of the items could be either true or false, that is when it gets tricky to resolve.

 

[Tuesdak]

Step back a second. You appear to have solved something with the turbo waste gate testing. So all you did was test it and "thump it twice." And now it works better. Hmmmm...

I would be suspicious that it's intermittent. Sticking wg, sticking solonoid, intermittent electrical etc. Black smoke, boost numbers, etc can help you decide if it's acting up.

As hard as you are looking I suggest calling a turbo shop like Turbo Resource in Lake Havasu and run this by them. They may have more tests you can run.

 

[TSimonson]

So after some tinkering last night and today, I have a few more data points:

1) I took JD's advice and went back to the WG before looking more at the fuel. Solenoid still at 11 Ohms, wastegate pops open at about 40 PSI. Looking back, I don't think it works "better" now, I had really just never "tested" it. I've been babying the truck since this popped up in October 2014, no towing, no stomping on it on on-ramps, no really "working" the truck. Again, I don't have any log data from pre-October 2014, so it was all qualitative assessment on my part. But in investigating the WG, getting it out on the freeway and trying to generate stock boost, I can easily make 30-31 PSI. Worked the same last night. There's a pretty good turbo shop here in Plattsmouth that I called two months ago, they recommended the stuff you guys all recommended out of the Holset manual. Looking at my previous posts, I see I didn't mention that WG was in the closed position the whole time when I was looking at it (when I pulled the downpipe to fix the exhaust leak, I chalked the exterior lever) and that was probably important info I should have included. You can look at the logs, I think I'm generating about the right boost; I get no smoke of any kind, except a nice quick black cloud if I have to stand on it to get around someone driving like an idiot, and no codes of any kind from the ECM. The "non-clearing" code mentioned above was my fault - I had the engine on and that won't clear with the truck running. Probably should have posted that too. I appreciate all the help with the WG, but after making some mistakes, I'm pretty confident it's working.

2) Back to the fuel suspect: Just a general note from an old idiot (me): If you're going to go the shade tree mechanic path and not use "special tool 9013" to test the PRV, remember that the banjo at the PRV side of the fuel line is part of the full drain circuit, not just the PRV to the CP3. So unless your engine compartment and garage floor need a diesel bath, you need some way to catch the fuel coming from the CP3 to the PRV.

3) So after that mess was cleaned up (garage will smell like diesel for a couple more weeks), I did get a usable test on the PRV today. After unhooking the FCA, drying out the inside of the PRV, and zip-tying bags on to BOTH the PRV and the banjo, there was quite a bit of fuel (maybe 2 oz) in the PRV bag after 30 seconds of idle-to-1000 RPM. Most of that shot out when the truck was started, but there was still a dribble at 1,000 RPM. So I'm pretty sure the PRV weak, and most likely kaput.

I'm not going to go the route of capping it off. I'd like to have the protection if I ever get this issue fixed and start towing with this truck again.

So to avoid another parts debacle... Aside from $155, what's the difference between Geno's $280 Cummins PRV and Bosch $125 PRV? And what's the difference between either of those and a $28 ATS PRV? I'm sure the $28 part isn't as "good" as the $280 part, but if the only purpose of the part is to not exceed the max Bosch rail pressure, then I'd rather change out the $28 part as part of routine maintenance every 5 years instead of waiting for the $280 part fail every 10 years. And to Cerb's point, if the $280 Cummins PRV is the way to go, then it's probably smarter to replace the whole rail for $395. That's an easy fix.

 

[cerberusiam]

With the metal contamination you had the fuel pressure sensor could also be compromised at this point. One of the reasons to buy the whole rail is eliminate as many possible issues at one time.