acceleration

[burb31]

I just got a 99 dodge cummins 2500 4x4 auto trans.....spoke to mopar man last night about my lift pump not working and I havent checked codes yet but Im sure the main pump is shot too....I tried accelerating and bad hesitation and a little white smoke.....one thing im concerned about though, before it did this yesterday,the day before I was at a dead stop and hit the fuel kinda hard....it jerked 4 or 5 x's really hard....didnt feel like hesitation...felt lke the rear end was gonna come out from under it....almost like the rear tires were slipping and then catching again.....could this be related to the fuel prob?....it just didnt feel right ....it was jerking pretty hard

[Mopar1973Man]

Did you see about those error codes?

[burb31]

Im going to today....I'll let ya know...I guess I'm gonna try autozone.If they cant read them I will try getting it into work and hooking up insight.

[JOHNFAK]

Im going to today....I'll let ya know...I guess I'm gonna try autozone.If they cant read them I will try getting it into work and hooking up insight.

You have a 99 - won't the key trick work to pull codes ??? Check for fuel line restrictions. Not sure about at those low speeds - but I had a badly pinched fuel supply line (will killed my vp44) - and at certain speeds on thottle the whole truck shook around like I was on some bad magic carpet ride. Enough to give me a headache quick. You can also use MM vp44 diagnostics flow test http://mopar.mopar1973man.com/cummins/2ndgen24v/lift-pump-diag/lift-pump-diag.htm basically bump starter with fuel supply line going into bucket. Measure fuel. Should be greater than 1.33 liters.

"Bump the starter to activate the transfer pump. Look for air bubbles. If no air bubbles are present, proceed to step 10. If bubbles are present, check the lines/connectors between the fuel tank and the transfer pump for conditions allowing air to be drawn into the fuel system. Correct the condition and repeat steps 6, 8, and 9. 10. Measure the amount of fuel in the container after the pump shuts off. If the amount of fuel in the container is GREATER than 1.33 liters (45 fluid ounces) and the fuel is bubble free, then the low-pressure fuel system is OK, the cause of engine performance problem lies elsewhere. No further testing of the low pressure fuel system Is required. If the amount of fuel in the container is LESS than 1.33 liters (45 fluid ounces), proceed to step 11

[guesswho512]

You have a 99 - won't the key trick work to pull codes ???

the key trick doesn't work on 99s

[burb31]

Just got back from autozone.....their reader said NO CODES....Not sure what my next step is at this point.....I might try and hook up to cummins insight at work but not sure if I can....I know the stock lift pump don't work. Im going to install a raptor 100....I don't know if my vp44 is bad though...I guess I'll see how it acts afterwards.....

[Mopar1973Man]

Well if you below the 10 PSI of fuel pressure strange thing might happen as far as power and acceleration.

Keep it in the green for best performance.

[burb31]

yeah....looked at work.....I guess I need an adaptor for cummins insight.The plugs at work wont fit my truck.....I checked out the instructions online for the raptor 100....looks pretty easy....worst part looks like trying to get the line on the fuel tank....I'll probly order it some time this week.

[Mopar1973Man]

If you sit up under the truck you can see the top of the tank fairly good but getting the line released can be a royal PITA... You migh have to loosen the lock ring and lift the sender slightly to release the fuel line...

[burb31]

I just jacked up the truck and checked the ratio.....4:10 ratio....I guess I really cant ever get good mpg out of this thing....its a good thing I only drive 5 miles to work!....Its got 315 tires on it and the shaft turned just over 4 x's after one tire rev.

[Mopar1973Man]

So that explains why some drop the 315 tires on trying to get the gear ratio back down to 3.55 gear by changing tires... But looking at thes pics will enlighten you a bit. Just the ~20 pound reduction gain me roughly 2-3 MPG... Rotational mass and rolling resistance plays a big roll in MPG game. Big O AT 235/85 R16 Cooper STT 265/75 R16 Comparing the Cooper STT 265/75 R16 to the Big O AT 235/85 R16

[burb31]

You dont have 4:10 ratio do you?...I got a 315x75x16...the door says I should have 245x75x16....I'm sure I would be better off mileage wise to put this back closer to stock even with the 4:10. You think it would have that much of an impact with that rear end?

I'm anxious to see the mileage difference when I swap lift pumps...I'm betting my lift pump not working wasn't helping the mpg much.

--- Update to the previous post...

I wouldn't have thought those would be a 20lb difference

[Mopar1973Man]

People wonder why the ricers get 30-40 MPG... They got tiny tires and the weight of the tirees are no more than maybe 30 pounds, have little to no rolling resistance, rotational mass is by half. Then even with my 7,900 pound truck on the scale I still touched a high mark of 25.3 MPG... My typical is 21-22 MPG. So if you going to aim for the actual MPG mark and not going to be towing it would be better to change the gears out for 3.55 gears. But if you towing heavy I would leave it alone.