I have been getting what i think is pretty poor fuel economy in my 1996 ram. The truck has been converted to a 2 tank system - sunwizard style. I have been getting only about 10 miles per gallon around town and some highway. This seems really low to me. these trucks are supposed to get 19-20 on the highway right? but I have never found the city mileage. So I don't know if this is really bad or not. It seems like the mileage was better before conversion. I admit i do have a low tire.

I have not changed the stock waterblock filter yet. and I am not looking forward to it- it's waaaay down there and now covered with wvo components. My Idle was pretty low and the truck was dying in parking lots - so i adjusted it back up to about 800 rpm and it runs great.

if the filter is plugged up that would probably drop the idle rpms. right? and if i adjusted the rpms up that would be sidestepping the problem.

could someone please explain why a clogged filter reduces the fuel economy? lift pump working harder is all i can think of.

thanks

A plugging filter will cause stumbling and low power under load before anything else. It won't change idle RPM.

Low MPG could be due to many things like air filter, injectors, almost anything that makes the engine smoke or not run properly.

I get around 18mpg with a mix of city/highway. 15 worst, 20 best.

Are your mileages on VO or D2? If you purge too long you get some D2 in your VO tank.

Its hard to get accurate mileage figures, tell us in detail your process to compute it? and over how many tanks full?

Something is definitely wrong - I don't think I can get my mileage down that low dragging a Ford (and all it can carry, and all it can tow...) up a mountain. I typically get 20-24 mpg out of my '96, depending on speed. Pump up the tires (for Obama! ), swap out the fuel and air filters - and pull the injectors and inspect/test them. Maybe it's time for new injectors.

My veg mileage went up when I changed to a 195 termostat.
Now you know why I moved my diesel filter to the passenger battery. Not to mention that the stock filter is expensive and small.

Lots more info to give a good answer ?
What gear ratio ?
What tire size ?
You should have gauges on your truck , and then know fuel pressures ?
Do not let things go , low idle , low tire ect .

Any idea how long injectors are good for? I have 174,000 on a 12v and was thinking I am getting close to new ones but do not know how long do they last. The truck still has good power but does smoke more than it used to.

You mention that you are low on mileage, how about power? There are a bunch of things that will affect power as will as mileage. If your mileage suffers but not your power, it is a different issue.
Do you smoke under load or hard acceleration?
What color?
Do you accelerate the same as the past?
Do you have any gauges to measure boost, fuel pressure, EGT's? If not you should install them, they give you a bunch of information.
Have you modified the engine? How?
All of these bits of information will help.

Since I move to the city my millage sucks. Cold starts suck up lots of fuel and so does starts and stops. Driving my truck to work was costing me $80 a week. I could do about half my trip each way (20k, 12miles) on veg.

The worst milage I get with my 92 Dodge Cummins is 15 MPG around town in the winter, lots of stop/starts and battery charging going on. Get 17 to 19 MPG at freeway speeds when burning 70% veg in a cold blend and weighing 22,000 pounds gross, 22 to 23 MPG on any fuel with the truck weighing around 6,000 pounds.

I had experianced slow idle and bog on acceleration/deacceleration due to the small stock fuel lines and thick cold blend fuel. I also had a very slow idle and stalling when my lift pump developed a air leak, if I kept it revved up it would sorta run but at idler the air was enough to cause stalling.

Auto trans with overdrive, low stall converter (this gained 1 MPG), 3.50 rear axle ratio.

I was consistently getting 19-20 on my 94. Started running centrifuged oils (tranny, hydraulic, veg, and mineral) and noticed it dropped back to 15 when I next checked it. Smoke on start up. Last time I had the Catalytic converter removed and ran some power service through it. Returned to 20+. Now waiting to see it it will come back with power service treatment. Plugged a filter with less than 50 gallons so probably need to centrifuge for longer. As Dana would say. Fuel economy is an indicator. Like smoke at startup and thick engine oil. Have to watch it closely to aviod trashing the motor. Catch it early and adjust the sytem or it will deterioate rapidly. I found a 205 thermostat. Gonna install that as I have no FPHE and the filter coolant wrap is not staying above 160. I don't think in my application the 205 will be to hot becasue I never tow anything with the truck. If I was towing, I would not try above a 190-195. I will spend this afternoon swapping the veg filter and thermostat and give it another run. I agree with DieselBurps, I would have to do somethng really bad to my truck to get 10 MPG on diesel. I have 269,000 miles on my truck and it probably does need new injectors. I put in one pressure guage after both the filters and it runs 15 psi on diesel at 70 mph and 18 at idle. Veg runs 10 psi at 70 mph and 21 at idle. Makes me curious what the pressure is on the ohter side of the filters. I also use injector line heaters. Reggie came up with the design I use and it is cheap and efficcient.

Wow. thanks for all the replies. Sorry it took so long to get back to this thread. If anyone has read my other threads I've had some polymerization problems. clogged fuel heater screen and nasty steel tank. changing the tank.

quote:

Originally posted by SunWizard:

Low MPG could be due to many things like air filter, injectors, almost anything that makes the engine smoke or not run properly.

I get around 18mpg with a mix of city/highway. 15 worst, 20 best.

Are your mileages on VO or D2? If you purge too long you get some D2 in your VO tank.

Its hard to get accurate mileage figures, tell us in detail your process to compute it? and over how many tanks full?

I have been calculation mileage with d2. fill up with 10 gal and go until the fuel light comes on and stays on and used the odometer. I've done this about 6-7 times.
I've been running through a new cimtech filter 10 micron and not much change. tires are good now. they are a little over stock size. 305/70/r16. this will cause the odometer to read a little less than acutal miles but shouldn't affect it all that much.

quote:

DieselBurps
Member
Posted 13 August 2008 01:09 PM Hide Post
Something is definitely wrong - I don't think I can get my mileage down that low dragging a Ford (and all it can carry, and all it can tow...) up a mountain. I typically get 20-24 mpg out of my '96, depending on speed. Pump up the tires (for Obama! ), swap out the fuel and air filters - and pull the injectors and inspect/test them. Maybe it's time for new injectors.

I've got the K&N filter so i will clean that and see if it helps. I have never pulled an injector. I could probably do that but have never attempted it. I did have a mechanic check out the engine before conversion and he seemed to think it was sound.

quote:

JohnTF
Member
Posted 14 August 2008 10:15 AM Hide Post
Lots more info to give a good answer ?
What gear ratio ?
What tire size ?
You should have gauges on your truck , and then know fuel pressures ?
Do not let things go , low idle , low tire ect .

94 dodge ram 4x4 , Cummins 5.9
need to get an other vw diesel
the others rusted away long before the engine

John,

don't know the gear ratio, it's an automatic w o/d. probably needs that bands adjusted too.
tires are 305/70/r16
No pressure/vacuum gauges yet will look into that.

quote:

Baja 1
Member
Posted 14 August 2008 12:48 PM Hide Post
You mention that you are low on mileage, how about power? There are a bunch of things that will affect power as will as mileage. If your mileage suffers but not your power, it is a different issue.
Do you smoke under load or hard acceleration?
What color?
Do you accelerate the same as the past?
Do you have any gauges to measure boost, fuel pressure, EGT's? If not you should install them, they give you a bunch of information.
Have you modified the engine? How?
All of these bits of information will help.

96 Dodge 4x4,5sp, not stock

Baja,
power seems to be a little less than before conversion (hadn't had the truck long though). While pulling a small-med trailer the truck would have trouble maintaining speeds on hills (I'm in OK ---HILLS). acceleration seems a little sluggish. the engine is stock, it starts strong, runs smooth and no smoke. I did the "refridgerator" polymerization test on my last lube oil and it was fine after 5k flowed nice @ 35 degrees.

I have only put about 2k veggie miles on this truck. Mostly at about 165 degrees just before the iP. drove a little with the temp at around 150. and it died a quite a few times on veg due to the low idle mentioned on the 1st post. but was immediatly restarted. Always used centrifuged oil.

thanks again,
Daniel

Halleleuja,

Just wanted to update on this thread. This problem has been in the back of my mind for months now. I replaced fuel filter, air filter, got new tires and no change. I was starting to think my engine was messed. but yesterday I spent about an hour going though my fuel system. I have checked for leaks several times but it must have gotten worse because yesterday i stuck a sheet of wood underneath and sure enough...drip, drip, drip. That explains the 10 miles per gallon i have been getting for the last few months. It was leaking out of my fphe. so i removed the threaded barb and reinstalled it and the problem is fixed. It's great that I finally figured this out but not so great that i have been wasting half of my fuel for a few months. Im sure i will recover the cost in the future.....
thanks.
DAn.

Thanks for the update. I have been curious about this thread. When mine has a leak, it pisses everywhere. Easy to see even if I am parked on gravel. Glad you got it fixed.

With the mileage you have there a few things I would check. One is the solenoid switch. It is on the left side of the engine, just behind and below the IP. It is right next to the AFC. There is a rubber bellows and rod that hangs below a cylinder. With the engine running try to push the rod up, push hard. If the rod moves the solenoid is dirty and you are not getting full fueling. Remove the solenoid, clean the cylinder, make a new bellows out of a bicycle inner tube or buy one from Fostertruck.com.
Next would be your overflow valve. This is on the right side of the engine. There is a spring and ball interior. This spring can get compressed over time. It should be 1/2" long and you can stretch it as a temporary fix, but a new one should be installed if the old is not to spec. I would check both of those, they are common problems that come up with long term ownership or mileage.