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j7l2
03-09-2011, 11:35
On my last 2 tanks of fuel I only got about 14.5 to 15 mpg. I have always gotten 18 mpg or better. My truck is a 1995 K2500 4wd, ext cab short bed auto trans 6.5 td with 256,000 miles. It starts and runs fine. Injectors are the original ones from new. Will worn injectors cause this sudden drop?

Thanks for any input.

Regards,
JimO
trbankii
03-09-2011, 12:03
Based on other comments, that is a lot of miles for a set of injectors. But I doubt that you'd notice that much of a change that suddenly.

I'd check the fuel filter first.
scot5146
03-09-2011, 17:53
:confused:

I agree start with the fuel filter (I change mine every 3 thousand miles), and yes 200k + miles is alot on injectors, read the article on the diesel page members section about injectors it may be helpful...

Oh and is there a loss of power? Is it still running ok? how does it start?

let me know
mike;)
j7l2
03-10-2011, 06:30
Mike,
Power still seems normal, starts normal and runs fine. Fuel filter has 5000 miles on it. How would a fuel filter cause more fuel useage?

Thanks for replys,

JimO
DmaxMaverick
03-10-2011, 07:54
Mike,
Power still seems normal, starts normal and runs fine. Fuel filter has 5000 miles on it. How would a fuel filter cause more fuel useage?

Thanks for replys,

JimO

It can, but it is usually negligible or unnoticed. Under some conditions, it can be significant. Throttle position affects fuel injection timing. A fuel restriction, such as a bad filter, can require more throttle input for a given power level. This will affect combustion efficiency, which will affect economy, to some degree.

Any time there is a drivability or fuel related concern or issue, the fuel filter should always be the first to address. Whether it makes sense or not. If it doesn't cure the problem, nothing is damaged, the expense and time invested is minimal, and you've eliminated one possibility. It's an important step in an effective diagnostic process.
j7l2
03-10-2011, 08:04
DmaxMaverick,

That makes sense. I will get a new filter and see what happens to the fuel mileage. I appreciate the responce.

Thank you,
JimO
scot5146
03-11-2011, 12:59
Hey Jim-

I was thinking about your original posting and I was curious if you or any owner prior that you know of has ever changed the timing chain?

I have had bad experience with the chain stretching over time and miles making a loss in power and performance due to the cam timing being off...

just and idea... But Dmax is a very good resource for questions and very knowledgeable, so ask questions!

also does your rig have a cat converter and a EGR value? If your engine temps are rising even a little the cat may be plugged up causing a decrease in performance.

Let me know
Mike:D
j7l2
03-12-2011, 15:20
Mike,

Timing chain is original, I bought the truck new in 1995. Cat has been gutted. EGR valve has been bypassed and truck is running the F eprom.

Regards,
JimO
DmaxMaverick
03-12-2011, 17:57
At 256K, injectors and timing chain are due. Neither will normally cause a sudden issue, but stranger things have happened. On MFI engines, the injection timing tracks the cam timing, while EFI's track crank timing. It is possible the pump is nearing the TDC offset limit, with an overdue, sloppy timing chain. Compensating for it increases the departure between the cam and injection timing. This creates a condition for inefficient combustion, which can only be corrected with a new timing set. 256K mile injectors aren't doing you any good, either. If your engine is healthy otherwise, just addressing these 2 (simple) issues should get it back to running like new.
suburbanK-2500HD
03-13-2011, 02:53
WB Air filter ?
16gaSxS
03-15-2011, 12:47
Mike,

Timing chain is original, I bought the truck new in 1995. Cat has been gutted. EGR valve has been bypassed and truck is running the F eprom.

Regards,
JimO

JimO; We have the same truck except mine is 2 wheel drive. If you plan on keeping it for several more years I would consider spending some bucks and doing some up grades. Timing chain is behind the water pump I would do the 1997 cooling up grade new high volume water pump and dual thermostats. You will have most the work done. New Injectors and Glow plugs, I'd use JK Quick Heat.
Take your Radiator to a shop or replace it. If you tow I would also get a Fan clutch from JK. I would also consider a Turbo Master so you can get rid of the bloody vac pump. I did most of this at 158,000 miles with my truck some before some after and I really enjoy the truck more since.:D
16gaSxS
03-16-2011, 09:24
One other thing that could be contributing to your lower MPG is winter blend fuel. Winter Blend is a blend of #2 & #1 Diesel. #1 has less BTU's per gallon so your MPGs will be less.
j7l2
03-18-2011, 10:10
As recommended I replaced the fuel filter. I used a stock GM brand 6.5 filter. I am pleased to report that after my first full tank my mileage was back to 18.3 mpg. This was from a low of 14.5 mpg on my previous tank. The filter I removed had approx. 5000 miles useage.

This was an eye opener for me as far as filter life.

Thanks to all who replied and for the many helpfull suggestions.

Regards,
JimO
scot5146
03-18-2011, 18:12
As recommended I replaced the fuel filter. I used a stock GM brand 6.5 filter. I am pleased to report that after my first full tank my mileage was back to 18.3 mpg. This was from a low of 14.5 mpg on my previous tank. The filter I removed had approx. 5000 miles useage.

This was an eye opener for me as far as filter life.

Thanks to all who replied and for the many helpfull suggestions.

Regards,
JimO


hey jim-

i replace my fuel filter every oil change, it may be a bit excessive but it runs great all the time, and its cheap insurance to get the most possible from the fuel system! food for thought...

Glade to hear its working better!

Mike:D