Boost Leakage and Compression test results

[JMM776]

Hello everyone,

New to the forum as a member but have been reading posts on here for a couple years. Need some sound advice as I am still quite the diesel novice.

I have been chasing a boost leak for quite some time now as I have been trying to improve fuel economy. Long story short, I recently narrowed it down to the crank case (I believe). Bought a diesel compression tester and tested cylinders last weekend. Results below by cylinder. I did read somewhere that the spec is no more than a 10% delta from cylinder to cylinder and realize both cylinders 6 & 8 are a bit low. I was impressed with how much compression I saw overall across the board though. The truck is a 2004.5 LLY with just about 240K miles.

As a side note, I added a 60hp economy tune to it late last year and recently my tranny has slipped 5th gear when pulling hard up mountain with roughly 7500lbs of weight. I suspect but of course can't prove its a result of the tune. Anyways, I know I will have to do a tranny rebuild but is it possible with that mild of a tune that its caused valve or piston ring issues too? Obviously trying to not spend on a tranny rebuild and engine rebuild all at once but need some advice from the experts.

Should I leave the engine be for a while or tackle now?

Cylinder Press
1 365
2 380
3 365
4 390
5 380
6 330
7 380
8 350

Thanks in advance for the help!

 

[Ron Nielson]

If it were me, I wouldn't use the 60 HP economy tune pulling trailers. Find something in the 30 HP range. Much easier on the engine and the trans. The engine and trans will live longer if you take it easy when pulling hard.

 

[2004LB7]

other then fuel economy, how does the engine run? does it start in the cold ok?

if it runs good then save your money and do the transmission first. then save up for the engine. but don't forget the little things like that boost leak you mentioned.

also, please describe how you did your compression check. did you have it on a charger? all glow plugs removed? FICM disabled? crank time, etc

 

[JMM776]

If it were me, I wouldn't use the 60 HP economy tune pulling trailers. Find something in the 30 HP range. Much easier on the engine and the trans. The engine and trans will live longer if you take it easy when pulling hard.

Thanks Ron. Yes, in hindsight I may have done things differently. Didn't think that small of a bump would be too much for the Allison but might have been wrong. To be fair though, the tune being the reason for failure is just my hunch. For all I know, the guy who had the truck before me may have beaten it to hell.

 

[JMM776]

other then fuel economy, how does the engine run? does it start in the cold ok?

if it runs good then save your money and do the transmission first. then save up for the engine. but don't forget the little things like that boost leak you mentioned.

also, please describe how you did your compression check. did you have it on a charger? all glow plugs removed? FICM disabled? crank time, etc

Yes sir. Was running great in every other respect. Cold starts just fine. The only reason I went down this path is because I am getting about 12.5 mpgs and a lot of guys were saying they get much better economy. I checked boost about 6 months ago and found a leak. Turned out to be a quarter size hole in my egr valve body underneath! Naturally deleted that. Also deleted the PCV, cleaned the turbo blades and put an upgraded turbo mouthpiece in. Still not much improvement so performed the boost test again. Still losing some. Could not figure out where it was leaking until my son noticed bubbles coming up from standing water I had on the engine in the vicinity of the passenger side valve cover (was trying to clean away some of the old soot from the EGR hole from the valve covers before I ran the test). Then checked and verified pressure was coming out of the hose where the PCV reroute discharges as well so must be in the crankcase. Thats what lead me to a compression test.

I pulled all the glow plugs to do the test. I unplugged the glow plug module and removed the 25 amp fuse for the FICM. I cranked each cylinder consistentently for 7 cranks. Battery on charger. The only thing I didn't do is run the test with the engine hot as I didn't want to burn the hell out of myself removing the glow plugs.

 

[2004LB7]

id try again hot and see if anything improves. not normal to rely on cold numbers

 

[Bdsankey]

Have you thought about maybe contacting your tuner about your mileage or even trying a different tuner? If the truck runs fine its very possible that whomever is tuning the truck has things set where it is not very efficient. I've seen that happen with every tuner where something will be off and the truck will get poor economy. It happens, but if they don't know about it they can't possibly correct it.

Your compression isn't ideal BUT I don't personally believe it is a smoking gun as my truck got better economy on a 10mm/60%/68mm turbo/6 tweaked rods/1 visibly bent rod.

 

[JMM776]

Have you thought about maybe contacting your tuner about your mileage or even trying a different tuner? If the truck runs fine its very possible that whomever is tuning the truck has things set where it is not very efficient. I've seen that happen with every tuner where something will be off and the truck will get poor economy. It happens, but if they don't know about it they can't possibly correct it.

Your compression isn't ideal BUT I don't personally believe it is a smoking gun as my truck got better economy on a 10mm/60%/68mm turbo/6 tweaked rods/1 visibly bent rod.

Yes. I actually sort of did that when I started having tranny issues but the poor fuel economy pre-dated putting the tune in and I have the ability to restore back to my factory tune if need be.

I used the EZTuner (powerupdiesel.biz). Just tried to search and can't find their website any longer. They may have gone out of business but there is a post in this Forum where someone asked about them. They had pretty decent reviews and really emphasized that their tune was designed to maximize the low end of the engine curves to improve fuel economy more than it was designed to get some mega racing horsepower. That is what I was looking for as I really just wanted better fuel economy and a little more low end torque for when I pull my camper through the mountains. Not doing any racing or burn outs.

As a matter of fact, I spoke directly with the owner and designer of the tune for a good hour or so as I had some technical questions. He gave me his personal cell phone number and told me to call or text with questions any time. I felt like this was good customer service so proceeded with buying the product. I knew there was risk it wouldn't do much for my fuel economy but it certainly did add some low end torque. Not unhappy with the overall performance.

The module literally took months to arrive and when I started having tranny issues, I tried to text the guy to ask some questions or see if this was a common issue. No response whatsoever.

All that said, it is still only a hunch that the tune has anything to do with any of these tranny issues as they started just a few months after installation. Could just be coincidence. Confident the tune has nothing to do with the fuel economy numbers though as they were poor prior to installation.