Horrible Mileage...STILL...after alot of work/troubleshooting

[Rabbit on Roids]

nobody has went over this posibility since its a new pump, but possibly the input shaft seal got messed up some how installing it or the shaft through it? thats the first place i usually think of an air leak, and if not that much air is being fed into the pump, and tons of air is being fed back out of the pump, something is getting past the seals, and the front seal is the only one under suction im pretty sure. and everything past the vain pump is at a high pressure.

[Giles@PerformanceDiesel]

"Guess Giles just goofed on something? maybe something was forgotten and wasn't torqued down on/inside the pump?"

not saying that i can't make a mistake sometimes but every pump is test on the test stand before it goes out and
i would know if a pump was sucking air because we force feed the pump with about 2 psi of fuel pressure and it would
leak fuel and drip on the test stand.

Andy the Doakster has a supply problem if he has Air in the system.

Giles

[Vincent Waldon]

... and I'm gonna lock this thread (temporarily) so that we can keep our help focused in the thread with the correct title... less confusing for all involved:

http://www.vwdiesel.net/forum/index.php?topic=22625.0

[Vincent Waldon]

....temporarily unlocked for an update...

[Doakster]

To update on the my mileage issue, I ended up getting another rebuild pump from Giles and got it installed. Based on what we've discussed in this thread it would have seemed my previous ECO pump was the cause of my poor mileage.

Unfortunately I did a small mileage run today and my mileage didn't increase a bit with my new Giles pump, still at 32mpg.

To Recap, the car has....

-New Giles Pump and Injectors, timing set to .95mm
-New Fuel and Air Filter
-Completely New Brakes Front and Rear, which are not dragging at all.
-New Front Hubs with new bearings
-New Rear Wheel Bearings
-Verified my Odometer and Tachometer against a GPS and nearly dead on
-Verified compression, which was very good and in spec
-Car makes good boost numbers underload, plenty of boost present on my boost gauge
-Verified no turbo intake boot leaks
-Installed, 2.25 DP, and exhaust, no Catalytic converter installed
-Trans, ring and pinion was changed from ECO 4.25 to 3.94

The only other issue i can think of is a bad CV joint, but you would think i would notice that with such poor mileage.

Any other ideas are appreciated, I've dump thousand of dollars into this car to try and get the mileage up to what it should be and upgrade the car, but I've had horrible luck so far.

[rabbitman]

Could the odo work fine and then at say, 300 miles, fail to roll the hundred over again?

Something is badly wrong to get such poor mileage.

[rabbitman]

The best thing to do would be get a gps and let it get connected before driving, use it for a whole tank and see if it and your odo are close to the same. Check your mileage with it too.........

[Doakster]

I've verified my tachometer and odometer against a GPS, on a 125 mile run (with the GPS), the tach and the odometer were only below by a few miles, maybe 121 or so, not nearly enough to cause the poor mileage.

You can more or less account the difference in mileage to my larger tires...205/45/16

So....my tach and odometer are not the issue. I know what you guys are getting at....the frequently found chipped or cracked gear that runs the odometer in the gauge cluster.

My tire pressure is good....I've had this issue for a long time now...regardless of where my tire pressure is at.

Plus over a year ago after I replaced just about everything on the front end, (still had the ECO pump and AVX 4.25 R&P in the trans) and the car got 43mpg consistently. Then it just dropped to low 30s.

To me it CAN'T be anything with the motor or trans, the trans is freshly rebuilt, had the low milege before and after. Motor compression is in good shape, injectors and pump are all rebuild by Giles, had the low mileage before and after that too.

I'm REALLY REALLY stumped.

[Doakster]

I don't mind recaping....any advice is appreciated.

Don't know what T-Stat is in there...but it's the original one when i got the car, I haven't touched the coolant system, and I was getting 43mpg with it...then the sudden change. I don't trust my in dash gauge (like everyone else), but it usually runs no more than 1/2 when cruising, plus I periodically shoot my head outlet line with a laser temp gun, it doesn't run more than 170F

Engine oil is and always has been Rotella T, 15W40, got 43mpg with it before

Engine has 113,000 on it, like I said, compression test was excellent, around 450psi on all cylinders if i remember correctly.

Trans has less than 2k on a fresh rebuild, done last fall, the rebuild is when I installed the 3.94 R&P and the Peloquin LSD, i was getting the poor mileage before and after the rebuild, no change. I thought this would help me at least some, but not change going from the AVX 4.25 to the 3.94

I'm not a lead foot, far from it. Most of the mileage tests/run that I'm going on are all highway mileage at not more than 65mph. I've always driven the car the same and even when I'm somewhat hard on the car I only see a few MPG decrease.

Back when I got 43mpg, I could drive it highway, city, somewhat hard, or easy, didn't matter and I always got 40-43mpg

My other ideas of things to check are the preload on the front bearings, maybe there is too much? But then you would think that would cause premature failure.

Or my CV joints, I have no audible/clicking noises in them now, how would I check if one is bad?

[Doakster]

Anyone?

[fatmobile]

Tires are too fat,.. maybe.
 205s are pretty wide, I have them on my Golf but haven't checked the mileage lately.

[burn_your_money]

What RPM do you normally upshift at?

[truckinwagen]

has the front end been aligned recently?

poor front end alignment can wreak havoc on your mileage(as well as tires, tie rods, bearings etc...)

[Runt]

I'm assuming that your odometer is correct, which is a big assumption.  That is the first thing I would confirm, over a long drive.  Either that or I would test mileage against a gps, or over a premeasured ~200 mile trip, and ignore the odo.
The way I see it, you are either burning the fuel, or leaking it. 
Burning enough fuel to drop mileage to 30 mpg should result in a fair amount of black smoke, more soot than normal out the exhaust (and in the pipe), and higher than normal egts.  Do you have an egt gauge?  If so, did it change with the mileage change?  With a close to stock engine, even putting one in now might help, as there are lots of people with knowledge to give you a baseline to compare to.
I'd test for leaking fuel by parking over a big white sheet (flea market/second hand store/wife's linen closet) and running the car for at least a half an hour, running the engine up and down in rpm, and holding steady somewhere around your cruise rpm for at least 5 minutes.  I'd also (when the car is NOT running, before the test) loosely wrap the I.P., and injection lines, and injectors, with strips from the sheet to catch finely atomised spray from a leak somewhere there.
Last thoughts, I only read a couple pages, but I didn't see where you've commented on how the car runs?  Does it run like a bag, or go like a scalded cat, or is it just about normal?  I think that they'd have to be pretty bad (think melted precups and pistons) to make that much of a difference, but have you checked for leaky injectors?

[BlueMule]

Doak, time for old school solutions and basepoint. You will need a one gallon gas can full of Diesel, a five gallon gas can full of diesel and someone in another "known good vehicle" that does not have larger than factory tires etc. Drive your vehicle till it runs out of fuel, or rather till it just starts to sputter and die. Pull to a safe side of the road, and add one gallon of fuel. Have your chase vehicle set their Odometer to 0, then turn off all accessories in your vehicle and keep the windows closed, restart and drive until you run out of fuel again. If you can do this on a flat stretch of road and keep it a 55 mph it will really, really help the mileage. Now you also want to take note of the turbo PSI and see exactly what it is doing at this speed. So you drive it and when you run out of fuel again see how far your chase vehicle has traveled. Now if the mileage is still bad, do the same procedure only this time take your fuel from a one gallon container instead of the fuel tank, this eliminates the feed system from the tank. Again take good note of what the Turbo is doing during these drives, it might not be working quite right. Also, guess what the 5 gal can is for, hehehe.