Engine/Transmission (1994 - 1998) Over fueling. 12mpg

[Windwalker]

I have followed this forum for years but just joined I have a 98 qcab, 5spd, 4x4. Mods are 4 inch exhaust and bhaf truck quit running so I replaced fuel lines and lift pump but that didn't help, no fuel from the p7100. I had a 175hp pump from another engine so I tried it and truck started right up. 98 used to get 21mpg and the 95 that donated the pump got 25mpg. Now it gets 12mpg, smokes black even on light acceleration, power is down and after 500 miles black soot in tailpipe. I am reading about9 pounds boost at 2000 rpm and 8-900 degrees exhaust temp. I did not check pump timing other than to align the pins. Starting is great as is idle. Does anyone have an idea?



Unrelated to the above, does anyone know a guy from Denver, he used to go by max torque on the diesel ram forum?

Thanks in advance for ny and all help.

 

[BarryG]

cant help with the truck but I know who Max is and have used his shop services in the past with no issues.

 

[Windwalker]

cant help with the truck but I know who Max is and have used his shop services in the past with no issues.

Thanks for the reply. Can you tell me the name of his shop?

I am from Montana but in Denver right now.

 

[BarryG]

here is his website should have all the contact info

http://www.maxtorqdiesel.com/news

 

[surfbeetle]

Check the timing, the AFC and the boost hose going to it. Also at 2000 rpms, I would think that you should have a little more boost than just 9 psi. Good Luck.

 

[Sticks]

Check the turbo (both ends), wastegate, and boots.

I have concerns that the old pump went Tango Uniform. They are generally bulletproof. Might be that you have injectors that are going out, or caught some debris from the old pump.

 

[Missouri Mule]

On the 98 pump if the overflow valve was stuck open you have no fuel pressure, also the ball mite get stuck in the valve not letting fuel out which will stall the engine and won't restart (this happened on my Mule a new overflow valve solved the problem). (Lucky for me when the lift pump quit and a few weeks later the overflow valve Mule died in my driveway. The bad thing it cost me $88 dollars both times to have it hauled to my Mechanic.)

On the 95 pump you probably did not set the timing right. I think you need to advance it.

If you have 3.54 rear 9 lbs is just a little over what my boost gauge reads (6 to 7 lbs loaded heavy it is 8 to 9) your egt temp is little higher than mine ( Mine is 750 in hot weather 700 in cooler weather).

Check your fuel pressure.

 

[Sticks]

Improper timing would cause a lot of smoke (black or white), but should not obliterate his MPG and still start and idle with no issues.

 

[CChinman]

I have a '97 3500 and am also getting poor mileage with some white smoke on start up which goes away within a couple minutes. The mileage is a concern however, the previous owner had a FASS fuel system install, not sure why as he has since passed but could that be part of the poor mileage? Grasping at straws - thank you..

 

[The patriot]

How bad is it?

 

[CChinman]

About 10-12 mpg, it's a combined mpg however not a whole lot better on highway.

 

[The patriot]

Need more info.
Got a tool box? Is it loaded? Extra fuel tank, how big, if so, is it typically full? 2wd, 4wd, auto, manual, gearing?
Is it turned up? Star wheel adjustments will kill mpg's driven locally in my experience.
My truck did about as bad as you're until recently. I went over the fuel system after the fuel and air filters, still no good.
I happened to adjust the valves and timing and it went to around 20 all the time. Last tank was almost 22. I'm still trying to figure that one out.
I have a 1998 12v 5 speed 4x4. It has a big tool box full of tools and 60 gallon aux tank. Truck weighs right at 10K lbs with me NOT in it. 3.55 gearing. 265 Michelins.
Mine is stock except for 370 injectors and star wheel adjustments. Oh, and I have a BHAF.

If youre doing that much better on hwy, I'd be thinking the star wheel. jm.02

 

[SSage]

Your in Denver, CO? So your over 5,000' in elevation? That will cause smoke issues just in elevation. Whats the timing set at? Was it set correctly or the rough dirty way?

If the injector pump is set up right and timed properly then I would look hard at the turbo and the associated pipe and intercooler. Test it for leaks. Plus, where is the fuel plate set? Stock plate?, AFC ever removed? Is the tamper screw all original or is the plate slid forward and the AFC adjusted beyond OEM? How about sliding the AFC housing full back, adjust star wheel for minimum fuel.

I don't see any 22 mpg with my 2wd whale anymore, not the way I drive. My 3500 2wd dually with heavy fueling still gets 15 mpg mixed. At 70 mph I make 5 to 10 pounds of boost with an auto 3.54 and high-rise camper shell with ladder rack and I carry a substantial tools all the time. When I check it I see 15.4 on two lanes, 16.2 and sometimes 17.0 if its mostly highway. I got 19 average and 22 plus mpg highway stock, but I only kept it stock for the first 28K. 12 mpg is pretty bad...

 

[CPO]

I had a similar problem and come to find out the rubber boot on the outlet side of the inter cooler blew off lol! Too much boost I guess.

 

[CChinman]

Need more info.
Got a tool box? No Tool Box
Extra fuel tank - No Extra Fuel Tank
2wd, 4wd, auto, manual, gearing? - 4WD Automatic
Is it turned up? Star wheel adjustments will kill mpg's driven locally in my experience - I didn't turn it up and didn't ask previous owner. Is there a way for me to tell?
I went over the fuel system after the fuel and air filters, still no good. - Air and Fuel filters are new within the year
I happened to adjust the valves and timing and it went to around 20 all the time. Last tank was almost 22. I'm still trying to figure that one out. So I guess I will see about getting that done as I do not know how to do that myself.
I have a 1998 12v 5 speed 4x4. It has a big tool box full of tools and 60 gallon aux tank. Truck weighs right at 10K lbs with me NOT in it. 3.55 gearing. 265 Michelins.
Mine is stock except for 370 injectors and star wheel adjustments. Oh, and I have a BHAF. I do have a BHAF and believe my '97 3500 is 4.10 Gearing, I believe.

If youre doing that much better on hwy, I'd be thinking the star wheel. jm.02

Thank you for the input.

 

[The patriot]

Yea, you should be getting better than 10-12, depending on how you run her, fuel, conditions etc.
You should monitor your gauges.
Fuel pressure should be at least 18 psi. Should REALLY be about 25 psi.
Going down the road @ 55-65 you should have low boost on level ground (2-10 psi I'd guess)
EGT's should be low in this condition. I'd guess about 700-900 deg.
Maybe someone else can check these numbers for me. Could be off a little. I only run mine 3K miles per year anymore. Not nearly as much as I used to.