Cylinder Fuel Balancing Quantity

Keith Browning · February 7, 2019

Does anyone know what the + or - limits are on cylinder fuel balancing quantity pids? I assume thse are similar to the sort term fuel trim pids we used to look at. Have a cylinder that was flagged for contribution so after the engine passed all of the fuel system tests I was watching the pids before and after replacing the injector. It wasn't too far out from the other cylinders but it was distinctly more positive. The odd thing is now the same cylinder has swung negative after replacing the injector - not sure if that is expected but I am thinking it is as long as it is not drastic. Cylinder 1 went from +.06gr to now setting in at -0.02gr.

kbomb2788 · February 8, 2019

So far Ford has not been specific whats the actual spec and their "are the cylinders fairly in line with each other". I remember on 6.4 where anything over 8 meant injector is going out. Also had couple of like yours when I forgot to input IQA number in, and injector would fire using old number causing a miss

8WA Sman · February 8, 2019

What year truck is this because what I am about to mention it makes a difference. I watch the balance rates along with the injector Mode 6 data.

Chad_Kelsoe · February 9, 2019

I was diagnosing a P0170 on a 2015 F-350 the other day, which lead to pinpoint test MX. When I got to step MX13, it asks "Are all the fuel balance quantity PID values within 6.4 mg (0.1 gr) of each other?" . If I perform pinpoint test M step M7 it asks "Are all 8 fuel balance quantity PID values relatively in line with each other?". I asked hotline a couple years ago about step M7 and they responded that anything above 0.1gr would be considered out of line.

Anytime I see injector balancing pid swing back and forth more than 0.2 grs either direction, I find metal in the LH fuel rail. Hotline had told me if no metal is on the VCV, then the high pressure pump is good and the metal came from machining of the fuel rail. But I've always been taught that on a common rail system no metal should be present. So who do I trust?

kbomb2788 · February 9, 2019

You did 16-0134 right...I noticed when they updated this trucks fuel system I haven seen the sparkle show like it used to show on vcv...and as some one said I was tought if any metal present is bad...I see they push more and more to acceptable...I had one was running ok before...then ford told me to replace PCV and could not get it to start after that...they told me to replace VCV....afte that had me taking fuel sample out of line coming from high pressure pump to rail and finding metal

Keith Browning · February 9, 2019

It's a 2013 F550 - sorry I didn't include that. The end determination was the engine has base engine concerns most likely valvetrain. The engine starts rough and improves once at operating temperature. Intermittently disappears completely. There is always a shudder on acceleration though. It has 9803 total engine hours and 7190 idle hours.

I suspect valvetrain wear. It passed all testing including relative compression. The diagnostics led to injector replacement which the customer agreed to try. No change at all except the fuel balancing numbers. At this point I wont know. It's a JCP&L truck that has been in two accidents and they have had it with the truck. I suggested pulling the head which would cost them some labor but considering the engine hours a long block was priced along with a fuel system kit. They decided to stick a fork in it.

As for the numbers aspect, 0.1gr would be significant. I looked at another truck and the numbers were all within .03gr from zero. I wonder now, how the wrong IQA number programmed to an injector in the PCM would look. I wish I had time to mess with this and I think I will have to make time.

8WA Sman · February 10, 2019

Page 30 in the OBDII theory and operation has some info on fuel balancing.

Page 28 gives more info on the mode 6 data I was referring to.

Steve Mutter · April 20, 2019

I had a truck that would set p0304 ran rough cold but would be fine hot, would show low in power balance and pass a relative compression test. I performed a manual compression test and found #4 was 45 psi different from the others. Took the engine apart and found a bent rod on #4. The truck had also had an injector replaced on a different cylinder a couple of months previous and they did not performed an injector IQA. The point of this story is that relative compression is not as accurate on the 6.7 as they where on the 6.0/6.4 just wanted to add to this post.

fergy12 · July 15, 2021

Sorry for reviving an old thread but does someone have the cylinder mass values of a good running engine? I’ve got a 6.7 right now threw fuel limit codes for 3 cylinders (5,7,8). did all the pinpoint test to no real conclusion, relative compression good, manual power balance has cylinders 4 and 6 slightly higher than the rest but those cylinders not tossing codes. No driveability issues. Did the TSB for clearing fuel values and crank position sensor. Vehicle returned to have injectors done, rechecked codes, now have codes for cylinder #2, #6 and #8. Cleared the fuel values again and 3 cylinders are up around that .03-.07grams range, the rest are in the -.03- -.06. No real evidence of metallic flakes in lower fuel housing.
vehicle does have bully dog tuner, IQA all correct, dyed diesel (farm fuel) that the customer states they use additives in at all times, latest programming I removed tuner, updated pcm, reloaded tune last visit.

im thinking the cylinder mass pids should be +-.05grams or less, more in the range of +-.03 as stated above but just curious as to what you guys are seeing. I tried to find another 6.7 to compare and unfortunately don’t have one at the moment. Thanks.

Keith Browning · July 28, 2021

I have the same problem in that I look at those PIDs so infrequently I have no idea what they should be on a healthy well running engine. I always am more concerned with differences between cylinders that are significant.