Bad MPG = Bad Pump?

[azcummins]

My 24V (BARF) has 42,000 miles on it and its already bad mpg (15 for all times) just went to 11mpg. I pulled the fuel filter and it was plugged, but even after a full tank with the new filter, the mpg still suck.

I'm wondering if this means that my pump is going out? I haven't seen a decrease in the non-existant power, but the sudden drop in mpg is just too odd.

What is even wierder is that my 12V did the same thing at the same time in the trucks life.

What are your thoughts guys?

------------------
Mark Callahan

1998. 5 3500 4x4 24V 5spd, Geno's Muffler Kit, Chrome exhaust, Western Hauler Headache Rack, Chrome Rocker Panels, A-Pillar Mounted Boost and Oil Temp Gauges, No Turbo Silencer Ring (Yeah Baby!)

 

[DHatfield]

I think it may be your pump. At first I was going to say that maybe you have blended fuel and colder weather and that would lower your mileage, but then I noticed that you are from AZ and I don't think your weather gets very cold in the winter. My truck has 26,000 miles and just lately my mileage has dropped by about 3 MPG as its been in the teens for temps and I am running blended fuel as well. DO you happen to have fuel pressure gauges to check the pressure your pump is putting out?

------------------
2001 2500HD Quad Cab SLT SB 4x4, HO Cummins, 6-speed, 3. 55 gears, LSD, brightwhite/driftwood, 4w ABS, camper and trailer tow packages, HD transfer case, snow plow prep, group, cab lights, Isspro Boost and Pyrometer gauges mounted on A-pillar, 4" JRE exhaust, BD exhaust brake. 22500 miles as of 11/11/00.

1980 CJ-5, Modified for off-road use, bobbed fenders, 350 TBI, NP435 trans, 4. 56 gears, Dana 300, Dana 44 front, Dana 60 reverse-cut rear axle, ARB air lockers front and rear, 15/35/15 Super Swamper TSL on 10X15 steel rims, Cobra CB, Warn 9000I winch, nerf bars, 1/4" steel rock crawler bumper front and rear, jerri can/spare tire rack, custom roll cage.

 

[azcummins]

Doug- I don't have a fuel pressure pump, but the truck is going to dodge (esch!) service on thurs. and I can have them check on that.

I think the our fuel is blended, but if it is that problem, then they didn't start blending it till dec. 1.

Thanks for your help.

------------------
Mark Callahan

1998. 5 3500 4x4 24V 5spd, Geno's Muffler Kit, Chrome exhaust, Western Hauler Headache Rack, Chrome Rocker Panels, A-Pillar Mounted Boost and Oil Temp Gauges, No Turbo Silencer Ring (Yeah Baby!)

 

[Jeff Clark]

Mark, when my pump went out, I didn't have a drop in mpg, I had problems with acceleration. It started cutting out starving for fuel. I replaced the pump with a new Carter from Jeg's. Only problem is that it has 3/8" fittings which will require some modification of the original fuel lines.

------------------
98. 5 3500 QC 4x4, Driftwood/Mist Grey, 5 spd, 3. 54, 19. 5 Alcoa's, Ranchhand bumpers, DeeZee toolbox, "Scotty Air", TST PowerMax2, VA, 275's, Autometer Gauges, Centerforce clutch, Upgraded fuel lines (JRE and Aeroquip), MagHytec Diff Cover, PacBrake, Cowl Induction Hood

 

[azcummins]

That is what puzzles me. My truck doesn't seem starved for power anymore than it already is (1st Gen, 24V... yuk). The only change is my MPG.

I'll be interested to hear what DC has to say about it since I'm taking it to a 5* dealer... .

------------------
Mark Callahan

1998. 5 3500 4x4 24V 5spd, Geno's Muffler Kit, Chrome exhaust, Western Hauler Headache Rack, Chrome Rocker Panels, A-Pillar Mounted Boost and Oil Temp Gauges, No Turbo Silencer Ring (Yeah Baby!)

 

[Jeff Clark]

If it's not under warranty (i. e. they won't cover it) then don't let them replace the lift pump. It's pricey. A new lift pump is available from Cummins for way less than Dodge. It's easy to install.

 

[azcummins]

Jeff- I still have the 100k mi warranty, but the 36k is gone. I think the lift pump should be under the 36k mi one, but knowing DC, it isn't. Is it under the 36k?

Also, if I get it from Cummins, how much will they charge to replace it? Less than DC? Is it hard to do yourself?

------------------
Mark Callahan

1998. 5 3500 4x4 24V 5spd, Geno's Muffler Kit, Chrome exhaust, Western Hauler Headache Rack, Chrome Rocker Panels, A-Pillar Mounted Boost and Oil Temp Gauges, No Turbo Silencer Ring (Yeah Baby!)

 

[Gohon]

My first question would be your source of fuel. What was it plugged with and why? You've always had low fuel milage, and your 12 valve did the same thing. Have you always fueled at the same location? 15 mpg is not great fuel milage but with your set up (much the same as mine) 17 to 17. 5 is pretty much going to be your top milage for city and highway driving, all depending on your driving habits and conditions. I know there are super claims of high mpg with some of these trucks but take most of them with a grain of salt. If you did get trash in your fuel it will take several filter changes to get all of it out. Just my thoughts.

Jerry

 

[azcummins]

Jerry-
I was fueling at the same station (a 76 Cirlce K) when I began to notice that my mpg was dropping. The Filter was plugged, but I couldn't tell with what. It looked like dirt and brown gook.

I'm running Power Service fuel and injector cleaner right now. I've changed fuel centers and I'll probably pull the current filter again after 3k miles to inspect it.

I'm expecting at least 17. 5 mpg out of this truck as my 12V got this and the 24 V is supposed to be a better engine. I know it takes diesels some time to break in and this one has only towed a boat 2x for about 20 miles. Maybe things will come together in there and I'll stop eyeing those trucks with model F- so closely... .


------------------
Mark Callahan

1998. 5 3500 4x4 24V 5spd, Geno's Muffler Kit, Chrome exhaust, Western Hauler Headache Rack, Chrome Rocker Panels, A-Pillar Mounted Boost and Oil Temp Gauges, No Turbo Silencer Ring (Yeah Baby!)

 

[Evan A. Beck]

Hmmm...

Does it have a Prime-Loc on it?

*LOL*

Seriously, I bet your truck has one of two things wrong... Maybe both:

--Boost leaks
--Dirty air filter

I doubt your injector pump is going... Usually there are other signs such as hard starting, or low power. Bad mpg can be a symptom, but it is uaully not the only one.

Check your air filter... And I mean physically check it. That Filter Minder thing is a piece of sh*t and belongs in the trash.

As for the boost leaks, they can really kill your mileage. Tighten all of your clamps, and check them frequently. You might even want to go to Cummins and have them do a boost leak test, you may have a bad intake gasket or something. My guess is your clamps are all loose, and you are loosing boost, thus killing your mileage.

Also, you might want to check your fuel pressure. If your lift pump is bad, that could effect your mileage in a negative way.

Hope this helps!

BOMBED #ad

------------------

 

[Jeff Clark]

Mark, I don't think it is your injector pump but it could be the lift pump. Cost from Cummins is very reasonable although I don't know what they would charge to install it. It is easy to replace. Remove the old fuel lines, unplugg the switch, and remove the three nouts holding it on. They are all on the top of the unit. You can buy the replacement from Jeg's if you want to install the Aeroquip lines. You will need two additional fittings that will not come with the kit that Vaughn MacKenzie sells. E-mail me if you want some more info on this.

 

[Mopar-muscle]

i thought i read on here that the lift pump is under the 100k mile warranty ???

 

[Vaughn MacKenzie]

I think most of the aftermarket pumps suitable to replace the lift pump have 3/8" NPT ports. I can easily send a fuel line kit with the fittings to go with the new pump. I was talking to HVAC a couple weeks ago and he feels the Mallory pump he is running now may hold up longer in the long run due to the pump design than the vane-pump design of the Holley he was using (and the Carters our trucks come with stock). The mallory (if I understand correctly) is more like an oil pump with meshing gears, actually a single 4-point gear in an offset spinning 5-tooth ring like older Chrysler oil pumps. I don't recall what model he said it was but it's over $200.


Vaughn

 

[Steve St.Laurent]

According to the warranty books at the dealer the lift pump should be covered under the ~70K emissions warranty believe it or not! I looked at it with my own eyes. A stock lift pump from Cummins is around $130 and it takes about 2 hours to install it. It's an easy job, could be done by anyone that can turn a wrench.



------------------
-Steve St. Laurent - President of the Great Lakes TDR
'98 QC LB (CMNSPWR), 4x4, ISB, 5sp, 4. 10 LSD, TST Powermax, 275hp RV injectors, SW fuel pressure gauge, BD exhaust brake, Isspro turbo temp monitor, front Draw-Tite receiver, rear Draw-Tite class V receiver, BFG 285/75R16 AT KO's, (all the common stuff clipped)

 

[azcummins]

Thanks Steve! Hopefully it will be covered under the warranty as my truck only has 42k miles on it.

------------------
Mark Callahan

1998. 5 3500 4x4 24V 5spd, Geno's Muffler Kit, Chrome exhaust, Western Hauler Headache Rack, Chrome Rocker Panels, A-Pillar Mounted Boost and Oil Temp Gauges, No Turbo Silencer Ring (Yeah Baby!)