mpg improvements

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I have a 93 W350 4x4 with 4. 10 gears #ad
. I have done a valve adjustment, had the timing set to 1. 35mm, and do not drive with a heavy foot. I can still only get 14-15 mpg out of it in town, 19 hwy if I go 60-63. (Would not recommend that in CO on I25). I bought some Stanadyne Performance formula, and that has seemed to help more than anything. The previous owner NEVER put any additives of any sort in the tank (140K), and was quite proud of that. I was wondering if it may be time for a new pump? It takes a while to turn off (2-4 sec), and the solenoid looks new. EGTs run 450-550 on the flat at 5 psi boost and 60 mph. Hard acceleration up a hill will bump 850 with 20-22 psi. I have my starwheel up 5 full turns from bottom, smoke screw backed out all the way; diaphragm pin at 90% max, full power at stock (turning in only made it rougher and idle faster), no perf difference. Last tank with Stanadyne got 16. Any ideas will be greatly appreciated. I can post more info as you all need it.

Daniel Puckett

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1993 W350 club cab, 5 speed, treadplate aluminum flatbed, 4. 10 rear end, straight pipes, K&N, "slightly" tweaked pump. IRBCTS.

 

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Sorry to hear about your troubles. Sounds like you may have a bad injector from what you are saying. Bad injectors/air in the system are characterized by rough idle. Be sure your idle is set correctly @750 rpm's. These engines will shake if the idle is down near 600. You mention that just off idle the truck studders/stumbles etc. this almost always defines an injector problem. I've fooled with enough of them that if they stumble just off idle it is usually a leak or bad injector. Try cracking the fuel lines to purge air.
Ususally they will smooth out near 2000 rpm's if they aren't too bad. Sometimes if you're driving and decellerating (such as slowing up on an off ramp or at a red light) the engine will act almost like you have an exhaust brake on it like it is trying to decell quickly or when you change gears you may notice rpm's drop off fast when you let off the acclerator. Wnet thru this with my turck due to installing som erebuilt injectors from a local cummins certified shop. they were real a@@holes about it. They explained to me that i was not Cummins Certified and could not tell them what was wrong. I brought the truck home cause they refused to help and bought 6 more injectors(new) and it solved the problem. Granted I'm not cummin Certified, but I ain't no fool.

good luck
Don

 

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I have the same model truck with 4. 10's and get 13-13. 5 mostly stop and go and 14. 5 at 70 mph and 2500 rpm. Boost is 10-12 psi at 70 mph. Even when the truck was bone stock the mileage was not any better. I have some performance goodies that give a lot more power and did not hurt the mileage. My injection pump has been serviced and it didn't make any diference. I know I could get a little better mileage, maybe 16, by driving slower with 4. 10's but can't seem to do that.

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'93 W350 Club Cab, Bright White, 5 sp. , 136K, Factory Options: LE package, 4. 10 Limited Slip, 7600 lb. rear springs, tachometer, front stabilizer bar. Mods: Banks stinger plus, Linex bedliner, 25,000 lb gooseneck ball, 10,000 lb receiver, Tekonsha brake controller, POWER WAGON injectors-WAY faster than stock!.

 

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Big Don,

The roughness is at higher rpms or heavy throttle, idles smooth as any other. That leads me to think that it may be timing. Before the reset, it was as smooth as my 92, that has had a reman pump at some point, (no mopar tag), and which gets 20+ empty. My 93 starts good (2 turns at +5 deg, no plug in), but just sucks fuel. I originally thought injectors, but $$$ is so tight right now, I want to be sure (wedding this sumer, saving for down on house and land, etc). Next $300 I get may well go toward some Power Wagon injectors, unless there is something I have not thought of that someone here suggests, which is the purpose of this site, right? You all are a great bunch of guys, and I hope to bum much more information off you guys in the future #ad
And of course, I will share my personal experiences.

Daniel

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Daniel's current truck: 1993 W350 club cab, 5 speed, treadplate aluminum flatbed, 4. 10 rear end, straight pipes, K&N, "slightly" tweaked pump. ISSPRO color coded pyrometer and 50psi boost guage. IRBCTS.

 

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Sorry to hear about your woes. My 93, CC, auto 4x4, 3. 54 gets 19MPG at 75-80. I think your timing may be off

 

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Seems like your mileage should be much higher than you are getting considering that you are empty and have relatively mild mods. to the motor. I run 3. 53 in the pumpkin and get between 18 and 22mpg depending on the driving conditions and how heavy my right foot is. ushually around 20mpg at 70mph here in the mountains. I would follow up on Big Dons post then check out the pump as well. Are your rear brakes adjusted correctly? Sometimes in winter moisture can create drag on parking brake cables and prohibit full release.

 

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19 highway in a 4x4 sounds pretty good to me, at those speeds with that gear ratio.

My 92 2wd 5spd with 3. 54 does 21mpg kept at 60-65, but going up to 75 (I25 in Colorado South of you a bit, but just as insane) gets the mileage down to 19mpg or so. Accounting for the gear ratio difference, seems OK to me.

The other replies about roughness seem right on to me, but I wouldn't expect a bunch of mileage improvement once you fix whatever that is.

One thing I have been hearing about mileage is to remove bug-shields, visors, etc. that change the stock wind footprint. And, keep your tailgate UP. Down, it will throw rocks all over it and ruin the paint, provide more surface area for the wind to pass over, and reduce your mileage - lockheed martin did some wind tunnel tests on trucks and proved it.

Best of luck on the rough idle, I'm chasing gremlins in my spare time too!
jon

 

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Thanks for everything guys. I may get my timing checked,(elsewhere) if it aint too pricey. What should it cost? I paid $240 last time, and found out I got scr#wed bad enough to be smiling into the NEXT millenium. I had a feeling about my injectors, and sent an email to Ted Jannetty (hope I spelled it right) and he basically said the same thing, try injectors and maybe pump. I had thought the same thing about the mileage- high teens/low 20s. And 60 is the "ideal" rpm range. But in my 92, I can drive it to about 80 before I notice a slight decrease in mpg. Maybe a splitter? I want one, anyway, just so I can go 80 and not be too emarrased by PSDs trying to prove something. Smoked a 99/00 model with Mom's 92 last week. Got up to 55 on College Ave in Ft COllins before I backeout of it. He was in front of me, and I kept up with him under light throttle. Now wishing I had kept it, but the shifter is in the wrong place (column instead of floor)

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Daniel's current truck: 1993 W350 club cab, 5 speed, treadplate aluminum flatbed, 4. 10 rear end, straight pipes, K&N, "slightly" tweaked pump. ISSPRO color coded pyrometer and 50psi boost guage. IRBCTS.

 

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Nordby,

Where exactly do you live? I have a cousin who lives across from the AF academy, and my dad lives in Calhan.

I have no bug shield on my truck yet. With the stuff the hwy dept puts on the roads, I am still looking to get one. Made no difference in my 92, except I clean the windshield every WEEK, not daily like before.

I just had another thought- could a bad lift pump affect performance? It is leaking a little oil down the side of the block, and I plan on replcing it this wknd ($35). Seems like I saw something on this subject a few weeks ago.

Daniel

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Daniel's current truck: 1993 W350 club cab, 5 speed, treadplate aluminum flatbed, 4. 10 rear end, straight pipes, K&N, "slightly" tweaked pump. ISSPRO color coded pyrometer and 50psi boost guage. IRBCTS.

 

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I'd guess on a torque motor like a cummins, a bug shield/etc would make very little difference mpg-wise. On an hp motor, I'll bet it does make a difference, just a guess though.

I'd suspect the lift pump would make more of a power difference, and be related to your rough-running. Running smoother should help mpg, shouldn't it? The pros here would have to answer this one!

I live west of I-25, off Mt Herman road, right on the Pike National Forest. If you look west of monument for the large sandstone rock sticking out of the trees, my house is in the line of sight between the interstate and the rock! Just north of your cousin it seems.

Jon.

 

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Daniel,
I own a 91 W-250 with 4. 10's and a 89 D-250 with 3. 54's, both have the 5 speed trans.
I will consistantly get 21-23 MPG on the '89 and only 16-18 MPG on the '91. I guess its just the nature of the beast when you are running low gear ratios, your milage will also be much lower. I plan on running a much larger diameter tire size the next time I purchase tires for the '91. I figure with the larger wheel size, the final drive ratio should be closer to the 3. 55's and hopefully the milage will improve.

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89 D-250 LE 5 speed 3. 55 Limited slip, K&N, straight piped, Boost/Pyro. & 16cm2 215K and still going. 91 W-250 5 speed, 4. 10 Limited slip, 16cm2, 6" Skyjacker lift, RS9000, Dump bed, 18K original mi.

 

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my 93 duelly ext cab 4x4 get 19 hwy
somewhere 15 -16 combined 3. 55 rear
i wish more o/drive have np 4500 5 spd

today got bk fr reno nv there and back
total trip 260 m over sierra nevada's
from west side used per gauge 1/2 tank
mileage s/b appx 17 on that trip

gets 14 with 4k lb camper on it

bill

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1993 w350 ex cab, banks,nv 4500 in
open exaust, pw Injectors are in. Big rig flaps,tach soon to be in. Its loud and goes ok, for a 93,only beat 1 pwr strk furd. 2 optimas,
love driving it!

 

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Bill,

That's about what I expected out of mine, with a 1-2 mpg adjustment for 4. 10s.

Engine has sounded a little "off" past couple days. Something in its rattle is a little different. Could be different fuel I put in today, or cold weather. It is a little eratic, sometimes idles alright, sometimes a little lower. Drops about 2 volts, but no oil press. This is not a defintie sign, since the alt is due to die in next few months (92 went out at 155K, mine has 148K, and not as religiously maintained as I like, but for $9000..... )
Beggars cant be choosy, especially since I can put in a new pump, injectors, and a used splitter, and still be ahead of NADA value.

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Daniel's current truck: 1993 W350 club cab, 5 speed, treadplate aluminum flatbed, 4. 10 rear end, straight pipes, K&N, "slightly" tweaked pump. ISSPRO color coded pyrometer and 50psi boost guage. IRBCTS.

 

[Archive]

My '90 seems to always get about 16 combined and I spend a lot of time sitting in traffic. I haven't had a chance to take it on a long trip though.

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'90 LE W250, 727, 3. 07, Line-X bedliner, 140k miles,