Engine/Transmission (1994 - 1998) P-Pumps, Fuel and Mileage

[Rams-n-Hogs]

No issues with mine in 155K. No additives. I get 17-20 on the highway, depending on how I'm driving it. I've seen as high as 21-22, but not very often. When ULSD first came out, I noticed a mileage drop, of about 2 mpg. Had the timing turned up, and got it back.

 

[HPSimpson]

155K on truck no lift pump or p-pump problems all factory original, using ULSD no additives get 13-21, depending on load and right foot.

 

[Texis]

328,000 on the 97's original injectors and P-pump. Basically no consistant additive program, will stick in some Lucas when it's handy. The truck gets 18-20 mpg.

 

[Hootguy]

450,000 km's,,and still running good,,my truck has run on everything you could imagine,350,000 km's on all kinds of alternative fuels,,,regular diesel,,Jet fuel,,homebrewed bio-diesel,,diesel/veggie oil mix,,diesel/transmission oil mix,,biodiesel/veggie oil mix,,
All my fuels are carefully blended in barrels not in the truck,,,settled for about 1 week,,then fine filtered before going into the truck's tank,,gotta love that P pump,,
I would have new trucks many times if this thing wasn't so insanely cheap to run,,

 

[CCiatteo]

223,000 miles on the stock fuel supply system. No additives since I have owned the truck, which is about when ULSD hit here in NJ. No problems I am aware of. Mileage is 20+ during the summer months and 18+ during the winter months running empty mostly. Fuel filter gets changed twice a year, using NAPA Gold.

 

[SRath]

140K miles. I buy my No. 2 at walmart since they started selling it there cheaper than the truckstop last fall. I use Penray for anti-gelling in the winter.

But I also use synthetic (amsoil or mobil1) 2-stroke racing oil in my fuel just to keep my pump as lubed as possible. I know for a certain fact how effectively it protects our screaming, hot, high performance motocross bikes, and it is the ONLY lubrication the crank, rod, and piston get, and in very small 40:1 amounts. I also know for a fact it leaves behind a very slippery surface for long after it is gone and that it is designed to mix with fuel, stays mixed, and it burns super-clean with ZERO carbon or ash left behind.

Never any pump problems.

Our semis at work started dropping like flies when ULSD first came out. It definitely causes fuel system problems in vehicles that were built before it's introduction.

 

[LVJUNIOR]

I have 120k on my 98 and have never gotten more than about 12. 5mpg running ulsd or any combination of additives despite throwing thousands of dollars into it to improve mileage. If it wasn't for all of the customization I have it would be gone. I would never buy another one.

 

[SRath]

"98 12v 2500 CC 4x4, DD2 inj, #10 plate, georend converter, ported fire ringed head W/ 60# V. S. , PDR cam, II 62/14, Detroit locker rear, Detroit trutrack front, 4" exh, 4" lift, 35" BFG mudders, lukes link, DSS steering brace, ATS exh. manifold, Road armor bumper, ViAir compressor, PosiLok, 4w discs"

I don't see much there that is intended or likely to improve fuel economy, except the 4" exhaust, LVJUNIOR.

 

[LVJUNIOR]

"

I don't see much there that is intended or likely to improve fuel economy, except the 4" exhaust, LVJUNIOR.

I was told the injectors would improve mpg, Then they said timing would help, then I was told my sloppy converter was the culprit, then it was You don't have enough turbo to be efficient, next it was oh you need sinthetics in trans motor and diffs, then it was ulsd you need to buy additive, Then ohh use this fitch fuel catilist it will give you 1. 5mpg, and last a cam would give me 2mpg, and then it was you are not running enough plate.



Everything I have done to this motor has been strictly to gain fuel mielage and try to get this thing to tow my #3900 fifth wheel up a 6% grade at more than 60mph without going over 1300 degrees on my EGT. I have read and read and then read some more. I have asked as many questions as I can. My last truck was only 360hp and 660ftlb at the flywheel and with all the mods I have done to this one it it performs almost identical when empty as my last one did towing a trailer and grossing #20,000



Srath, I just can not get near the performance out of this truck as everyone else and I am just frustrated to all hell.



My appologies to the original poster. I had no intention of high jacking your thread.

 

[Texis]

LVJUNIOR. . I once heard of one like yours, made no sense. It wouldn't pull a turd out of a commode and lost speed up most grades without any load. Dodge couldn't figure it out and after a frustrating year or so the guy sold the truck.



On this P-pump Q&A it appears the pumps do just fine without additives. I do hate to speak about it much more, it might make mine lock-up tomorrow.

 

[SRath]

With apologies to Kenny, there have been some recent threads about low and lost power and economy. There appeared to be some interesting information in the parts I read. Much about sneaky air leaks. Maybe you're way ahead on that, LVJUNIOR, but there really must be an explanation. I wish you luck, it sounds very frustrating.

 

[kenny61]

No need to apologize, I left most of my feelings back on Paris Island... . and lost the rest over the last 18 years. However I do still get the urge to scratch my rear every now and then.

LV my truck gets about 18. 7 with nothing in tow and averagng about 75mph. I have the 3. 55 pr 3. 73 rear I forgot which was stock back in 96. are you getting that bad mileage when unloaded or when towing???

 

[Chrisw]

Well I have only had this truck for about 15k miles so no clue before that. Its got 138,000 mi 90 hp edm injectors. 12 plate, 3. 55 gears timing bumped up, best ever 20. 8 one time trip cruse set at 2000 rpm and 67 mph, normal 17 mpg or so, towing 10,000 lb i get around 11.

 

[hsmith]

Mine may be a tad better, but you are in the normal range.

 

[LVJUNIOR]

With apologies to Kenny, there have been some recent threads about low and lost power and economy. There appeared to be some interesting information in the parts I read. Much about sneaky air leaks. Maybe you're way ahead on that, LVJUNIOR, but there really must be an explanation. I wish you luck, it sounds very frustrating.

I have checked and rechecked for air leaks and seems air tight with a test rig on the turbo input

No need to apologize, I left most of my feelings back on Paris Island... . and lost the rest over the last 18 years. However I do still get the urge to scratch my rear every now and then.



LV my truck gets about 18. 7 with nothing in tow and averagng about 75mph. I have the 3. 55 pr 3. 73 rear I forgot which was stock back in 96. are you getting that bad mileage when unloaded or when towing???

I am getting around 12 empty and have gotten as low as 10 towing #3900



I finally got this thing on a dyno and think the trans is an issue. I only had 293hp and 753ftlb but the curves were terrible with no real power at all below 1850rpm and above 2200rpm View attachment 74831

 

[Rogan]

My 96 SCLB (when it was with 47RE) got 21. 8 on a 498mi round trip, about 90% highway. Avg speed for the trip was 68mph, but most of the highway was 72-74mph, rolling with light traffic.

In normal daily driving, my truck got ~14mpg

It's now a 5speed, and I haven't tested MPGs. .
And it's a p7100 pumped, 106k mi 4x4.

 

[mfburns]

268000 miles, 19. 6 mpg over the last 200,000 miles. Better in the summer lower when I tow but hand calculated over the last ten years. 2WD auto, stock, K&N drop in filter, cleaned annually. Still running.

 

[Flinty]

'97 with 165k. Bone stock p-pump, never been opened up. Ran Stanadyn when I bought it with 130k in '06, then switched to Howe's when ulsd hit the pumps. I can bank on 18mpg but usually get 19-20. On one occasion I was in a hurry with a 11k fifth wheel; kept the truck right at the speed limit and pushed it hard up the hills (fourth of july pass, for those who know it). The truck pulled hard but only delivered 9mpg with a stiff head wind. With the wind figured in I was probably going 90mph.

 

[KB0OU]

96 with 415k miles. The only thing I have done to the p-pump is to put the plate in the govener etc. and to time it. Stock injectors. I get 20 mpg average on road and usually 16 or so around town. towing depends on the size of trailer.

I dump a little 2 cycle sythetic oil in the fuel on fillup.

Note: not all of the p-pump is lubed by engine oil, the plunger area is lubed by fuel.

Have been running bypass oil filter and extended oil change, engine uses very little oil between changes.

 

[RLHannink]

There's a station here in Reno that still sells LSD, or at least it's labeled on the pump that it's "not ULSD, can't be run in 2007. 5 and newer vehicles". I fill there as often as possible, but I can't really tell if it's any better, fuel-mileage-wise, than ULSD I get from other places. The truck seems to like it better, but that's not a real objective test



Usually put in about a half qt Winter PS when I fill. Can't tell any difference in mileage, but I can really feel the good feeling I get by "protecting and cleaning my fuel system"...



Haven't noticed any problems since ULSD introduction.



97 4x4 5spd with 3. 54's, mileage b/w 15. 5 and 21, highly dependant on city/highway, offroading, winter fuel, wind, load, speeds. All those factors kind of deteriorate my ability to do real scientific-like mileage testing. I just fill it when the guage goes down, write it down, then hammer down