Poor mileage?

[TX Gooseneck]

The fuel mileage on my 93 d350 has fallen severely. I'm getting consistently around 15. 3 (x-cab, 2wd, auto, 3. 54's).



Offboost and full boost fuel are turned up, and the truck is straight piped - only mods.



Truck currently has 227,000 miles on it.



Any suggestions or tips to pick it up? I'm seeing 19. 8 on my 91.

 

[BCaldwell]

Do something with your air filter, after market i. e. AFE or K&N or big honking filter, or cut lots of holes in your air box. let it breath. Bill

 

[CDegner]

I also noticed a pretty drastic drop in my mileage at about 225K miles. I ended up changing my injectors. I don't know how my truck was running witht he ones that were in ... OK actually, it was not running very well. On 3 of the injectors, they wee so carboned up that I could not even see any of the nozzle holes. On 2, I could see one of the holes and on one, I could actually see 2. The engine also had a noticable knock which I suspect was due to the uneven fueling of cylinders.



Just a thought.



Carl

 

[cerberusiam]

Started seeing the same drop on mine about 220k. If everything else stays the same its probably injectors. To keep them in top shape and operating efficiently it has been suggested checking them every 100k to 120k. In that case most of us are way over due for a little maintenance on a fairly important part of the fuel system.

 

[JLEONARD]

When I changed out my original injectors last month they had 132 K on them.

They were pretty well carboned up... . the holes were all open, but the carbon "extended" the opening by quite a bit... this no doubt changed the sray pattern..... probably delivering an inefficient pattern... at the incorrect time.

The truck started and ran fine... I didn't have any hint that they were not "perfect" other than past experience.

The engine runs sooo much better with the new injectors.....

Try it... you'll like it!

 

[JDMills]

Ok, Dim whit of a question. Do injectors need to be changed every 175/200 K or can they be cleaned? (it is not in the budget at the moment)

Jason

 

[dpuckett]

Most shops can clean and recalibrate the injectors for fairly cheap, IF you dont need new tips. I know a guy in Sikeston MO that charges $15 a piece; $35 for a new tip/ needle valve. Bosch certified. In-tank injector cleaners can clean the injectors fairly well, but the wear from 150-200K affects the pop pressure, which in turn has a net effect on timing and fuel atomization and duration. That can kill your MPGs.



MOre on MPGs.

Fuel filter

Air filter

Overhead adjustment

Timing

Fuel quality

Weight of right foot

transmission efficiency- i. e. worn TC

tire perssure, though it isnt so critical in our load range D and E tires



Daniel

 

[JLEONARD]

Yes they can be cleaned/rebuilt/adjusted.

I've had that done on other diesels.

But do the math yourself... if they need new tips, adjustment, yada, yada, the price can easily be 70% the cost of new... then it's a no brainer in my opinion... . UPGRADE!

Jay

 

[dpuckett]

I figured if I came up to 60% of the cost of upgraded injectors, I'd be sending the stockers away..... Hmmm... . didnt quite make it, but then, I can say I was one of the first to get EDMs in a nonIC truck.



On a related note- When Mom had her injectors cleaned and recalibrated, one needed a new tip. I dont think the new tip was flowing EXACTLY the same fuel as the other 6 old ones, as they had 190K of wear and use on them. IT never idled quite the same, had a bit of a miss, and never got the 20mpg I got when I bought it with 140K. My theory is, the new tip was a hair smaller, and if the shop didnt have the stuff to measure how much fuel was being flowed per pop open, they may not haev been balanced as closely as they could have been, but we are in SE MO, and cheaper is ALWAYS better; If a diesel starts and runs, it's a miracle, dont mess with it; close enough is good enough, etc, etc. Hence, my opinion of "if it needs one new tip, it needs six. "



-DP

 

[TX Gooseneck]

How much is a set of aftermarket injectors? I'm trying not to put to much more into this truck as I want to sell it (new powersteering, front end rebuild, new transmission, new tires, and new radio).

 

[MidwestMotorman]

What kind of mileage to people see on a truck with a nonIC, nonOD trans, and a non-locking torque converter? I got 10-11 with mine towing a 3500lb trailer at 65mph. I loaded another 6500lbs on the trailer, towed 10mph slower, and got 11-12mpg. With 256k, perhaps it is time for injectors. I already have new fuel filter, reman Cummins VE, and new lift pump.

 

[dpuckett]

Nathan,

Yeah, I'd say it's time to get them checked out at the very least. What gears do you have? If 3. 54s (top end of about 68-70) then that is about right, for gears, transmission, load. If you have 3. 07s (top apporaching 80), that may be a little low. I averaged 14MPG towing 4-10K with Mom's truck (when I owned it)- 92 D350CC, auto/OD, 3. 54, all stock (back then, anyway)



TX Gooseneck-

If you want to sell it, and it runs smooth, I wouldnt worry about it, then. Rebuilding/ recalibrating stock injectors is about $150 or so, no new tips, you do R&R; aftermarkets run from about $450 for PODs to $750 for Mach2 EDMs.

 

[TX Gooseneck]

It runs almost to smooth. Power feels good too, just sucks down gas.

Tank to tank, I'm getting 100miles less on the 93 than the 91 with 130k MORE miles on it (stock injectors, never been out of the truck)

 

[BushWakr - RIP]

Just pull the nozzles out and, send them in for a balance and spray pattern check.

They will work just fine. One of the guys noted that they wear as time goes by... that's exactly right... in fact they behave like an injector that has been extrude honed... well, by that I mean, they flow more and more fuel as time goes on because the diesel fuel wears the holes in the tip larger as time goes on.



Hmmmmmm... ... ... . lets see..... if I start with POD's then drive them for about 1,000,000 miles and have em retweaked, they'd be like... ..... Ooooooooo "Loon-'O- Mentals" or was that Moen's... .

something like that right... .



pastor Bob... .

 

[dpuckett]

"... ..... Ooooooooo "Loon-'O- Mentals" or was that Moen's... .

something like that right... . "



Some of us are already there at Loon-O-Mentals, waitin on ya, Bob.



-DP

 

[TX Gooseneck]

Is this something I can do myself? Grab the old dremmel and go to town hogging the stockers out?

 

[MRickard]

If it is just carbon buildup you can try an additive. You can get a gallon of Lucas upper cylinder lubricant with injector cleaners and fuel conditioners, which normally treats 400 gallons, but for tuneups, lucas says to fill the primary filter with it, and then put the rest in the tank. Got the gallon for 19 bucks at a Pilot travel station. Never done the tune up but only a little in each tank so I do not know how well it would help you out... but for just 19 bucks might be a good deal.



You should get it fixed though - a fouled injector can actually burn pistons and cause and early overhaul

 

[REldridge]

CDegner; I see you use Amsoil products. I am surprised you don't use their Diesel Fuel Modifer in your fuel. That probably would have prevented your injector problems. I have about the same mileage with 1oz or Modifier per 5 gallons of fuel all the time and have had not a problem. Try it!

Bob Eldridge

 

[southpaw]

I was getting 12. 5 on my 93 new afe,new fuel flt, new oil, ck tire pres. inspected turbo connections, then while looking for the turbo boost port I saw what appeared to be a casting dimple but with closer exam and good light it had threads painted black, wholly cow its a hole right thru the intercooler crossover base . now i have boost pressure and super increase in fuel milage. don,t know how much yet i just finished installing guages and everything works thanks to some great pics by SamsRam. also turned pump up as far as i could push it. Then on my 89 i had to replace the ve pump 130k mi . runs like a dream now its getting new paint. I need help locating ports and connection places on my 02 I posted a plea on the 2nd gen forum already. thanks for all your help . K. E. this 1gen forum is the best