My 1996 2WD 2500 Quad has got to get better than 12 MPG, please. It had Bosche 370's in it when I got it a couple months ago but since morepoweritis hasn't fully infected me (yet) I swapped them out for the stockers. It also had a K&N air filter on it which I replaced with a BHAF and added a new fuel filter, just for fun. I'm the third or so owner and the PO had a raging case of morepoweritis and was the one that added the 370's and K&N so he may have tried other things to tweak out some more power. Any ideas on what I should check next? Should I check the smoke screw or star wheel? Can I tell if he shifted the plate any? Could my fuel pump be weak or is that a post 98.5 issue? My teenager's driving this rig so I really don't need (or even want) extra power but really need to boost the MPG's a bit (or a bunch!) Any help would be appreciated as I don't know how I'm going to feed this beast...

 

You got me beat, mine gets 10mpg.
A couple things to check are fuel pressure, automatic transmissions' torque convertor efficiency and what your gearing / tire size is.
clogged filters, bad lines, bad injectors, bad pump timing will all affect your economy.
Ive got 4.10 gearing (theres a sticker under the hood that tells you what was originally in the truck) and 265 tires which dont offset the difference much.
If youve for 3.55 youre a bit better off.
Check the fuel pressure first and if youre not seeing ~24psi at 2500 rpm no load Id say something is going on in there. Then Id start looking at other stuff like pump timing. Youll probably want to advance it to 16.5 or so anyhow for a bit more top end.

 

I have the fuel pressure gauge already and was going to install it this weekend. It's a an electronic model and I have one of those 1/8" NPT tapped banjo bolts from Geneo's and a snubber. Where's the best place to locate the sender on a '96? Should I use a grease gun tube to protect the sender from vibration? ~24psi at 2500 rpm no load? Is the 15psi number I've read here for the 98.5+ models?

 

You might want to go with a half way from stock to 370s , becouse it seem from reading other post that a little more power/fuel gets better MPGs , but at 12 , my guess is that you got some issues , brakes draging , maintinace , valve adjustment , ect.
Do you know what your gear ratio is ,3:54s vs 4:10s , thats a biggy , but then you mentioned that the kid was driving , that is also a biggy , light foot on brake & throdle.

 

I'd say something ain't right.

I average 15 in the city with mine, and 18 on the highway (empty of course), and normaly around 13.5-14.5 loaded.

 

I just posted about this same problem. The thing that's killing me is i can smell fuel ... but i can't find a leak ...

I was getting ~ 400 miles to a tank (i hate that puny 26gal tank) ... now i have to drive careful to get 300 ... gonna have to back off some of this new found power to gain back some of that economy.

 

Heck I got 19 mpg with a 40 mph head wind. Thats with 4.10 gears and the 35" tires off set it a bit. Pump might be turned up too much to cope with the 370. Back off that a bit and it will give you some MPG.

 

Well I can rule out dragging brakes as I redid those last weekend and none were dragging. In fact I'm not sure the back were even dragging with the pedal applied before I did 'em

anyone care to offer any fuel gauge sender unit positions? What about the banjo bolt on the output side of the fuel filter unti?

 

I tapped the banjo bolt on the input to the IP and put the needle valve there. Then I ran polyethylene hose and compression fittings to the sender which I mounted up near the hood hinge using a plumbing pipe standoff. Looks pretty good.
If you can smell fuel under the hood youve got a leak someplace. Id check the rubber feed and return lines first. Then the lines and banjos.
Ive heard the pump can get wet around the throttle shaft seal and that those arent hard to replace.
Hm, 35" tires, thats equal to a 315? Im not even sure Id be able to clear the fender let alone keep if from spanking the wheelhouse. I might try squeezing them in with a 2" levelling kit up front. Im trying not to lift the truck since it really hurts visibility close to the truck.

 

Before you get too far---
I am almost 100% certain that the tapped banjo bolts Geno's sells are only for 24 valves. As far as I know no one sells them for a 12 valve, you have to tap it yourself.
The 15 psi number is for 24 valves also, a 12 needs 17 - 22 psi at idle and 25 - 35 psi at 2500 rpm (no load).

Good luck with the electronic gauge, I've never had one last more than a 1000 miles on a 12 valve and would only use a mechanical.

 

My '96 with 4wd and automatic, with 4.10 axels and 385 tires is getting a solid all around 15 MPG with 18 or 19 on long highway trips. I'm pretty stock for the moment. Try switching to synthetic fluids, at least in your drivetrain. Also a little bit of Power Kleen and Marvel or 2cycle oil pays for itself in better mileage and performance. O yeah lighten up on that push pedal !

 

where you puttin the 2 cycle oil?

 

Right in the fuel tank...

 

Smoke = unburnt fuel. Are you getting alot of smoke all the time or when you load the engine?
Don't use #1 fuel thinking you'll get better milage.
Winter blend fuel will get less economy and performance.
Check for fuel leaks, if you SMELL raw fuel, you have a leak. Common place for a leak is the hoses to/from the injection pump. Replace them with diesel rated fuel line, don't use the standard gas fuel hose.
Check pump timing.
Check valve lash.
Turbo or wastegate could be bad, or AFC incorrectly adjusted... you need plenty of air to go with the fuel for power and economy.
Check for exhaust restrictions. I would guess the cat has already been removed.
Is the transmission shifting through all the gears properly and the torque converter locking up?

 

I had economy problems with my 12V at first and come to find out the previous owner was not very good at keeping his truck. The intercooler boots were all loose. Tightened em up and it made all the difference. Went from 15 mpg on the highway to 18.5-19 constant. I still maintain that with the mods in my sig.