2500Ram

I just filled up with diesel and only got 11.74mpg. Now I pulled our camper to our favorite campground last weekend and I normally get just over 14mpg towing our 6-7000lb TT to the same place. I have been noticing more black smoke lately but not much. A fuel gauge is going in next weekend, were camping again, same place, this weekend but just curions on the over 2 mpg loss all the sudden.

Thanks.
Bill

Lil Dog

Hook up that gauge for fuel pressure pronto... I suspect your LP has left his world for a higher place...

2500Ram

Plz don't tell me that. I should have known it was coming though.

Any positive ideas like a dirty IAT sensor, please please please

2500Ram

How can I test the fuel pressure without a gauge ASAP. Shrader (sp) valve will a digital tire gauge work in a pinch, is it even close to the same size? Sorry I'm a noob

Lil Dog

Ya know I wish I knew for sure.. Sorry, I hope someone on the 24V train can help with this..

You may try posting this again over in the 24V forum or PM the moderator to move it over for better exposure. Or try a search in the 24V area...

2500Ram

Thanks Lil Dog.

Bill.

edwinsmith

Excuse my ignorance, but why would low LP pressure cause fuel mileage to go down?

Edwin

Lil Dog

Well strictly on a pressure front... If the lift pump pressure is lower, then the injector pump has to spend more time to reach injector pop-off pressure. With this delay you get firstly late timing and secondly you need to add more fuel in the process due to the change in timing to achieve the same power output. The VP 44 does electronically control timing, but if your pressures are low, it doesn't know that and will still try to achieve the same injection event timing. So it will signal the pump to begin the injection to cylinder 1 at the proper time, just the delay in pressure delivery, delays the actual injector timing..

2500Ram

Well for what it's worth, we went camping with our 6-7000 TT in the mtns and no problems what so ever with power. Like I said before fuel pressure gauge is going in this weekend with an oil change, fuel filter and for good measure cleaning the IAT sensor.

Just for the record what are the signs of a LP going out besides the dead pedal. Will you hear the turbo spool or with the lack of fuel not so much. I know pressure is you best bet but...

Bill.

iker42

Where did you fill up?

2500Ram

Same place as always, King Soopers. Never had a problem before....

iker42

hmm....i was gonna say, places like Flying J have bad reps with fuel miliage

Clunk

I use a fuel pressure test gauge from most chain type auto parts stores then modified it to run the gauge inside the truck. It'll also check the fuel pressure on my '97 & '92 Olds Bravadas (w/correct gauge) and the R12 freon pressure on my '86 Cutlass & '92 Bravada. If you happen to have an R12 install kit w/guage, it'll work on the Schrader Valve on your VP for checking your lift pump pressure.

2500Ram

TTT

Just for the record what are the signs of a LP going out besides the dead pedal. Will you hear the turbo spool or with the lack of fuel not so much. I know pressure is you best bet but...