Improve fuel efficiency in my M1009

[lindsaym]

I recently purchased a '85 M1009 and I absolutely love the truck! However, when I read forums and blogs, it seems that most guys get 18-25 mpg. I get around 13-15. Granted I do commute part of the way up a mountain each day (I live in Chugiak, Alaska), but I wouldn't think that could account for such a disparity. I'm not a natural-born "car guy" but I'm trying to teach myself everything I can and this will be my first major project. Anyone have some ideas on what I could look into? Thanks guys!

Mike
U.S. Special Forces

 

[maddawg308]

Subscribed - I'd be interested in seeing any recommendations. My local neighbor joediveguy has a M1009 that he says gets only about 15 mpg, want to see if there's anything I can recommend to him.

 

[SandBar]

I am no expert but from what I read a worn injector pump accounts for poor MPG at times. Secondarily, bigger tires and lift do as well. My IP needs replaced, when you shut the truck down do you see diesel dripping from the bottom of the bell housing?

 

[Cucvnut]

I do on mine!

 

[lindsaym]

Actually, there have been a few times where I notice some fluids beneath the truck but wasn't sure if it was mine or the previous vehicle that parked there. I laid out some cardboard the other night but it came away with only a single drop.

 

[sierrajcharlie]

I'm in the same boat. I'm getting 14-16 mpg on my normal 8 miles to work. Every now and then I'll go 20-25 miles on a trip but the mpg stays the same. I don't have any dripping from the ip but it does look damp under the intake on the pump. I want to try tightening those connections up without removing the intake but that hasn't gone to well. Of course the worse looking ones are on the bottom side of the pump. I've been thinking about having it rebuilt but is the cost worth it. It's still in the stock form, no big tires etc. I've got a buddy with a couple of 1009's also and he's getting over 20 mpg. So, I'm open to ideas also. Thanks!

 

[lindsaym]

I sounded like an idiot in this post so I'm changing it! lol

 

[lindsaym]

I've also noticed in the past few days that she was pretty sluggish starting up so I went under the hood and discovered that the NEG connector on battery #1 had popped off. I've read that batteries can adversely effect MPG, but I'm not sure if that holds true for a vehicle with two batteries. To be honest, I'm not completely clear on why the M1009 has two batteries. Yeah, I know that's probably sacrilegious and all, but I'm trying to learn here!

Mike
U.S. Special Forces

 

[cpf240]

Not "private" as in only you can see it, but "Private" as in rank. It says "Private" because you only have a few posts. It will change what it says at certain posts counts.

 

[Skinny]

Leaky IP is probably the throttle shaft seals

 

[on1wheel01]

**** 14-16 is good in my book. Mine is almost back together and with 35's and a 6"+ lift that would be great

 

[MarcusOReallyus]

To be honest, I'm not completely clear on why the M1009 has two batteries. Yeah, I know that's probably sacrilegious and all, but I'm trying to learn here!

Nothing wrong with trying to learn something you don't already know!


And there's nothing wrong with not knowing everything, either.


The stickies are a good place to start. (BTW, you have two batteries because these beasties have a 24v start system.)

 

[MarcusOReallyus]

I'm in the same boat. I'm getting 14-16 mpg on my normal 8 miles to work. Every now and then I'll go 20-25 miles on a trip but the mpg stays the same.

Hmmm. On a computer controlled gasser, short trips like that are murder on gas mileage because you never get the engine warmed up enough for the computer to kick you out of cold-engine mode. It runs a lot richer in that mode.

I have no clue if that concept applies to diesels, especially non-computer diesels.

But I DO know that having nothing but short trips like that is hard on batteries, engines, and exhaust systems. You don't get a full charge, and you don't burn off the moisture that collects in the engine and exhaust system. You need to make some longer trips on a regular basis to burn things out.

 

[wayne pick]

Both engine and ambient temperature is a big factor in how a diesel performs. Cold ambient air and a warm engine equals good performance. Cold air, cold engine, not so good. Ever notice how well you can breathe after a rainstorm? The air is saturated in oxygen. Cold air has more oxygen in it also. A warm gas or diesel engine will always run better in cooler temps with higher humidity.

 

[lindsaym]

Do you think that having one of them separated from the connector could account for some of my problems?

 

[Barrman]

The M1009 has 3.08:1 axles in it. Any start stop driving you do will kill the mpg's because there just isn't much mechanical advantage to get a 5,000 pound truck rolling. If you include a hill or mountain climb in there, 14-15 mpg is good. Take it for a long highway run at 55-60 mph and you will be amazed at how high the mpg's get.

 

[sierrajcharlie]

I agree the short trips are not good overall on any vehicle. Short trips and having the plugs on the 12 volt only, is harder to keep a full charge (imo). My son ended up killing the front battery about a month ago. So I put the 24 volt back into service along with a voltmeter on the load side of the glow plug relay. The "afterglow" was registering 18 volts! (Bosch Durotherm's rated at 11 volt) That scared me and I went back to the 12 volt only. I'm thinking about getting a 12 volt solar charger and laying that on the dash to help that battery. So, all in all, maybe the mileage I'm seeing is just what it's going to be. Thanks for the thoughts!

 

[lindsaym]

The M1009 has 3.08:1 axles in it. Any start stop driving you do will kill the mpg's because there just isn't much mechanical advantage to get a 5,000 pound truck rolling. If you include a hill or mountain climb in there, 14-15 mpg is good. Take it for a long highway run at 55-60 mph and you will be amazed at how high the mpg's get.

My commute looks like this: Drive down the mountain about 3 miles, hit the highway, coast about 15 miles to the base, and then roughly two miles to work. Then of course the opposite at the end of the day. Not too much starting and stopping overall. Except for a few months of the year, I'm usually in 4-wheel drive going up the mountain because of snow, and riding the transmission down for the same reason.

 

[MarcusOReallyus]

Except for a few months of the year, I'm usually in 4-wheel drive going up the mountain because of snow, and riding the transmission down for the same reason.

There it is. 4WD is not kind to fuel economy.

 

[rivcrazy2000]

I only get about 16 on long trips but I've only ever driven long distances in the winter so far with it with mixed hubs locked/unlocked. I will be going to Fairbanks next week taking the 09 for the first time since February so I am hoping I will see a slight increase with the warmer air/2wd combo.