HELP! Need more miles, not more power.

Armed Partisan

Registered User
Joined
Aug 21, 2013
Posts
16
Reaction score
0
Location
Cocoa, FL, United States
Hey gents. I drive like an old lady. I got a 87 F-250 6.9 idi, brand new Delphi injectors, a rebuilt injection pump (of unknown age; was on there when I got the truck about 5k miles ago. Truck has just shy of 120k), a C6 auto, and 3.55 gears. I'm getting 10 MPGs. HO-LEE-HECK. Diesel is $4.20 a gallon right now, and my goal has been to get to some usable level of fuel economy with this truck since I got it. There's about a million different places where fuel can leak, but I think I've plugged most of them. I read about people with nearly the same set-up getting 13MPGs while pulling trailers, and I'm getting 10mpgs UNLADEN, in FL (which is to say, on flat roads). I would be satisfied if I made 13 empty, thrilled with 16, and ecstatic if I could get 20mpgs with this truck.

What should I do? Keep turning the injection pump DOWN until it sputters when I rev? How do I know when I've gone too low? Will choking down the fuel flow with the injection pump harm my MPGs by reducing power too much? I can't imagine I could harm my MPGs at my current rate. Also, I remounted my injection pump when I installed new injectors, and the truck is now MUCH more powerful and it certainly runs better, so I know that I didn't screw it up, but the previous person who "fixed" it certainly had something wrong (pump timing was WAAAAY far to the advanced side, and the truck barely ran). However, I need to do better on MPGs, or I'm gonna be forced to sell this thing. Suggestions?
 

Saskredneck

Full Access Member
Joined
Dec 27, 2013
Posts
128
Reaction score
1
Location
Saskatchewan, Canada
That low of MPG I'd be checking the engine timing first, then looking into the fuel system if it is timed properly. 10mpg seems really low to me, I get 15-18 pulling 7,000lbs at 60mph with my 6.9 4 speed.
 

FordGuy100

Registered User
Joined
Apr 1, 2006
Posts
8,749
Reaction score
282
Location
Silverton, OR
Timing, injectors, IP, transmission.

I would go in that order. Those are some of the bigger things that contribute to poor fuel economy.
 

Armed Partisan

Registered User
Joined
Aug 21, 2013
Posts
16
Reaction score
0
Location
Cocoa, FL, United States
What on Earth could possibly be so out of tune as to cause results like that? Like I said, I'm fairly certain that the fuel injection pump is mounted properly, and the injectors are brand new. Could it be the differential fluids need to be changed? I already flushed and changed the transmission fluid and filter. It's got good oil, and a newish filter. What I need to know is: what could possibly be causing such losses?
 

OLDBULL8

Good Morning Ya'll.
Supporting Member
Joined
Feb 12, 2009
Posts
9,923
Reaction score
338
Location
Delphos , Ohio
Fuel leaks. Wasted fuel.

Timing of the IP. Very Important.

Injectors, uneven popping pressures. Even new, doesn't guarantee they are all set up correctly.

Rebuilt IP. This is the last I would suspect, besides timing it.

C6 trans. Only 3 speed, no Overdrive.

Truck has just shy of 120k), a C6 auto, and 3.55 gears.

I wouldn't believe that, unless it can be proven. With a 5 digit odom, it can be way more.
 
Last edited:

franklin2

Full Access Member
Joined
Feb 24, 2009
Posts
5,156
Reaction score
1,382
Location
Va
How much black smoke comes out when you get down on it? If you get a lot, you could turn the fuel down some.
 

ToughOldFord

The Cold Glow-Plug
Joined
Sep 30, 2007
Posts
663
Reaction score
1
Location
City of Shasta Lake, Ca.
You won't get 20 out of a C6, as mentioned already no overdrive, but it'll easily get 15, possibly one or two mpg more if the stars are aligned.

As everybody already mentioned, check that timing, the IP "being mounted correctly" has nothing to do with timing, it just means it was installed properly. And most shops do not have nor know how to set the timing on an IDI. They "set it by ear" which means they guess.

Another item to look into is check if your brakes are dragging, a stuck caliper and/or over tightened shoes will reduce mileage.

Or it could just be your odometer is bad and you're getting better mileage then it shows.
 

chris142

Full Access Member
Joined
Apr 15, 2012
Posts
3,007
Reaction score
353
Location
SoCal
how fast are you driving? @65+ mine will suck fuel and get 12-13. if i slow down to 55-58 and i dont power over hills but let it slow down i can get 15-16. never more than that no matter how hard i try
 

Knuckledragger

blowing chunks and grabbing porcelain
Joined
Nov 7, 2008
Posts
2,338
Reaction score
232
Location
Payson, AZ
I get over 18 with the same setup. I am not shy about gunning it, but mostly drive in a sane manner. It is very true that driving between 53-58 will garner immense improvement in MPG over 65-75. What size tires do you have? Correct IP timing is very helpful and air filter cleanliness could be an issue. Health of the transmission could be hurting MPG, too.

I go over 330 miles on my front tank (mostly freeway miles), usually needing only 17 gallons to refill. That is about 19MPG.
 

Agnem

Using the Force!
Supporting Member
Joined
Jan 10, 2005
Posts
17,067
Reaction score
373
Location
Delta, PA
The key to great fuel milage, is low RPMs, a clear exhaust, and lightest weight. Efficiency of the fuel system means the right amount of fuel at the right time, under the best possible conditions. Things to check that haven't been mentioned.... is your truck free rolling? One man should be able to push it on a flat and level surface. If your brakes are dragging, or your tire pressure is too low, that will effect economy. Were your injectors tested? Just because they are new, doesn't mean they are right. Was the IP timed precisely? And even if it was, is it working right? We dynamically time these engines at 2000 rpm, but just because it is timed right at that speed, doesn't mean it is right at other speeds. The timing advance in these pumps will wear with miles, and it can drift or be wrong at other speeds if it isn't working correctly. Ditch the C6. Those things give away MPG all day long at any speed. Change your air filter too.
 

ToughOldFord

The Cold Glow-Plug
Joined
Sep 30, 2007
Posts
663
Reaction score
1
Location
City of Shasta Lake, Ca.
He hardly has to "ditch the C6", the OP isn't trying to hyper-mile, he's trying to get the mileage he should be getting out of his setup. He should be getting 50% more mileage with his combo than he has.
 

PwrSmoke

Full Access Member
Joined
Jan 2, 2007
Posts
807
Reaction score
22
Location
Northwest Ohio
Check odometer accuracy first! Ours are notoriously INACCURATE. Run several measured miles (mile markers) on a straight road. If you are clicking over exactly 1 mile for every mile run, great. If you are running less (say 9/10s or .9) then mulitply you tank milage by that. Say 220 miles indicated x .9= 198 miles actually traveled. Or, if you show 1.1 miles then multiply that 220 miles x 1.1= 242 miles actually traveled.

Second, take care fulling up. You probably know about foamy diesel fuel and how hard it can be to get the last few gallons in. Until you get this figured out, fill up slowly to the same level every time... not when the nozzle clicks off (which could be a couple of gallons off in either direction).

Once you have the MPG testing accurate, THEN you can start determining what the problems are... if any. Wouldn't you feel stupid if you went out and bought a reman IP only to find out your odo was off and that was your only problem?

FWIW, with my odo accurized, my '86 truck (I am the original owner, Banks kit installed in '87) can seldom break 15 unless I am driving under 60 mph. Over the years, I have seen it so many times: 70 mph= 13-14 mpg, 60 mph= 14-15+ mpg and 55= 16+. My truck has 4.10s so my 55 is like a 3.55 trucks 65.Those numbers are in good conditions with an empty truck. It's been the same whenever the truck is running good. When I had a pump going south, it would go down from there.

Finally, where the truck is driven can tell a lot. If it's driven on a lot of short in-town hops where it never gets fully warmed up... mpg will suck. Only long runs at speed will get you the upper mpgs. In town, my truck never gets more than 12-13 or so and never has done better.

Anyway good luck. All the above suggestions are valid, it's just that you want to verify the problem first with accurate mpg numbers. Then eliminate the easy, free and cheap stuff first.
 

92F350CC

Ford Man
Joined
Oct 7, 2006
Posts
3,479
Reaction score
15
Location
Las Vegas
You should definitely be getting better. That IP could have been rebuilt by some **** addict for all you know.

Fwiw, my F350, crew cab, long bed, 4x4 gets 14-16 mpg doing 75 on the freeway. That's with a 351 gasser, so I should think your truck could do better.

Sent from my Nexus 4 using Tapatalk
 

Armed Partisan

Registered User
Joined
Aug 21, 2013
Posts
16
Reaction score
0
Location
Cocoa, FL, United States
Well, thank you all for the responses, and Happy Easter! I Suppose I should answer some of the questions asked of me here.
1)IP: The Injection Pump is a reman from Stanadyne, and has a Stanadyne badge which is marked "Remanufactured".

2)Mileage: I know the truck has 120k, and not 220k, because the original owner, who screwed up the wiring, took otherwise excellent care of this old beast. He wrote down the date and mileage of every oil change up until he sold the truck in 2009, at which point it had about 98k on it. I bought it in 2013 with X14,***.X miles on it, so I doubt it got over 100k miles put on it in about 3 years, which took 22 years to reach previously, especially if it was only making about 10mpgs!

3)Tires: Tires are 235/85-16. I was an OTR truck driver for a while, so I'm keenly aware of tire pressures. The drives are filled to 80 psi, and the steers are 55 psi (door specs are 80/51psi), filled at a truck stop, checked with my trusty gauge.

4) IP Timing: I bought a Snap On MT480, which came with the Luminosity Probe for $150 on Ebay. It came with the remains of the original box, instructions, and the meter itself looked like NOS, barely used. I cannot, however get the damned thing to give me a reading. The RPMs fluctuate wildly at times, and the top needle pegs to the far right as soon as I connect it to the terminal. When I re-installed my IP based on the fine instruction tutorials provided by numerous fine folks online, I am certain that I did it correctly. After the re-install, the IP was timed to the timing mark, and then...

5) Smoke: I would say that I have very little smoke. When I started the truck at the timing mark setting, I had a very small amount of white smoke, which I believed indicated incomplete burn. Thusly, when I would put the hammer down for brief road tests, it would expend white smoke, according to my buddy who was there on the ride along. I then advanced the timing slightly, about 3/32 worth, until I got black smoke during the same. The truck felt a bit more responsive (marginal) but my long term road tests netted horrible MPGs, which is why I'm here. Should the truck ideally produce NO smoke at all for best efficiency? I know Diesel fans pride themselves on their ability to "roll coal", but I am too cheap to be concerned with impressing or annoying anyone.

6)Driving: I really do drive like an old lady. My commuter car is a 97 Toyota Corolla base model with a 3-spd auto, 224k on the clock, and I get 37mpgs on it all day long. Personal best was 39.8mpgs, tank average. I drive that an hour to work everyday at 60mph on the interstate. I got used to being passed when I was driving rigs, and now I don't care about putting anyone in their place, and this car couldn't do it anyways. The truck is arguably less responsive than the car if for no other reason than sheer mass. Trust me when I say I drive it at 55mph on the highway and get 10mpgs, I'm not driving it like a teenager for that to happen.

7)Transmission: The C6 is a marvel of reliability, but I have wanted to dump it since I figured out it only had three gears. My old 2003 Mercury Marauder (which I sold, despite my undying love, because it was bad on gas!) had a 4-spd, which I thought was pathetic for a car built in the 21st century. My dream is to find a junked out F-series with a Gear Vendors six speed in it, but I apparently have bigger fish to fry before I worry about that.

8)Odometer: Accuracy was checked with a GPS AND my Smartphone GPS. I was shocked to discover that with these factory sized tires, the speedometer was within +/- 1.5 mph, and the Odometer is accurate to within about 1-1.5 miles. This truck was sold originally to a person who lived in the same town that it was built in, so he might have known something about this tire size. It is more accurate than any other vehicle I've tested in those two metrics. The Corolla, for example, has a speedo that's off by 4-5mph with the factory sized tires. The fuel gauges, however, are guesstimates. I go by a full tank in the front, and my Odometer. I tried using a GPS tracker on my phone, but it was too difficult to remember to turn it on and off everytime I went anywhere in the truck, wait for it to initialize GPS, hope it would never crash, etc.

9) Brakes: The rear brakes were non-existent when I bought this thing. They would lock up, and were softer than a new pillow. I put a new hardware set on the rears and drained the entire brake system with a vacuum pump. They're now much improved, and I don't think they're dragging, but I will try pushing the truck on the street to see if it rolls very far.

10) Bulk Weight: I have cut off the stupid, idiotic spare tire mount on the bottom, which took me around 2 hours of unscrewing and messing around with it, which should have reduced the weight by about 80lbs. Damn steel rims weigh 50+lbs. I would like to change those out for lightweight aluminum ones when I get the chance, just to improve my City MPG if for no other reason (but aesthetics are a big reason, too). I don't keep too much in the truck.

11) Aerodynamics: I took my CB antenna off (and promptly lost the little plastic insulator for it) and don't have much in the way of drag inducing items. When I heard these trucks could get 20+mpgs running WVO and B99, I dreamed of putting belly panels and an aerotopper on the back to be able to hypermile with it. Getting 25mpg with an ancient truck just to **** off people at the University I work at would be fantastic, but seems unobtainable at this juncture. "My truck is greener than your Prius, hippy."

12) Injector testing: I asked the folks at Pensacola Diesel to test these when I was buying them. They, along with my local Diesel Mechanic, both said that it was unnecessary to test Delphi injectors, as they were usually high enough quality that most companies that said they tested them had a larger variance than Delphis did from the factory. This was two different people, in two different parts of my state, who know more about diesels than I, only one of which had a vested financial interest in the advice. So, despite what I had read online, I did not bother to have them tested. I also changed the return lines, O-rings, and caps (which I then changed back, because the new ones leaked badly), and tracked down all the leaks I could find to try to get better MPGs. I do not think I have any serious enough leaks to warrant a loss of 1mpg, letalone 5-10mpgs.

13) Warm-up: I will say this truck gets HOT when I drive it. I drive it on the highway, and it's getting to nearly 220 degrees after a run. It's warmer under the hood than my gassers ever have been. This is one reason I wonder if it's getting too much fuel. All that unburnt fuel might be going into the exhaust and burning in there. I do have the awful, awful stock down pipe and exhaust setup.

14) THANK YOU ALL SO MUCH FOR YOUR HELP AND INPUT! :D ;Sweet
 
Top