Been having some stumbling under load at higher RPMs. Just installed FP gauge, still some air/bubbles in the gauge line (had to get 1/4" line and a cheap gauge short on funds!) but at idle its only around 5 psi, or less. With the return line pinched off or not at 2-2500 RPM it might get above 10 PSI.

When driving, it starts fine (a bit smokey and rough for a minute or so, then cleans up OK) and runs fine under 15lbs of boost. Above that and 2k rpm, it starts stumbling/smoking grey until I let off the throttle, then its fine for another 15 seconds or so. Gonna go do a drive and see what it does for pressure under load. I'm having trouble searching, anyone have al ink where to get a good OEM replacement lift pump? My local Cummins dealer is very pricey, paid $110 for a crank seal and they want $68 for an overflow valve. Any harm in starving these of fuel? I know when it does it, so I've been driving easy. Thanks for any help.

 

you should have 30psi +- I would start with an overflow valve then pull the pump

 

With 10 PSI and the return line pinched off, my first step would be the lift pump, and then re-test.

 

Went for a drive, normal cruising is around 5-8 psi. Real easy to drop down to 0, stays there for a few seconds then starts stumbling. Good smooth power until then, think I can rule out bad lines for now. On to looking for a pump...

 

Check out My thread,Bogging under load. I had the exact same problem. Turned out to be a clooged pickup in the tank. Genosgarage sells oe cummins lift pumps fo 99$ and they are on the east cost so delivery is only a few days (if you can wait).

 

Thanks for the info, going to order one from geno's this week. I don't mind putting one in for good measure if it does turn out to be something else, will check it all out this week after the snow. Lines don't look too hot either, though it doesn't seem to loose prime like it used to in the cold. Haven't had to do much to it at all in the last year, so I feel like I'm due!

 

Relocate the new LP, to the frame next to the tank. On my 01, I had 3 LPs in 100k mile. The last time, at 120k, I relocated to the frame. At 198k, when I traded in the truck, it still had 15-20 psi.

 

sorry gorms,I posted before I realized you had a 98,Duh..... I'm not sure what the eletric pumps go for,But genos has good prices all around and props for their great customer service.

 

Its a 12V with mechanical lift pump still, bolts to the side of the block. No electric for me if I can help it. We're expecting another foot of snow, so it'll have to wait till the weekend.

Like I asked before, any harm in driving with such low pressure? I've never read anything about it doing harm, just curious though.

 

$25 here> http://www.fostertruck.com/Overflow_valve.htm

 

I drove around for a coulpe hundred miles or so with my problem,Had to go slow,If I really got on it I would stall from running out of fuel faster than I could pull it to the pump. We're lookin at the same snow,I'm in the poconos,I get up that way now and then,We have a facility in Hollis,NH. Good luck

 

Well I noticed something today. On the way to work, I left the house with the fuel light on, 30 mi commute. Did some plowing first, so I had next to nothing when I got to work. On the highway, I could barely do 60 (plow) and even with no load the needle was reluctant to get above 5 psi. Left work, started right up no problem, needle just barely bouncing off 0. Put 10 gal in, instantly shot up to almost 10psi at idle, got up to about 12 at 2k with no load. Drove much better on the highway, could cruise at 60-65 with a bit of pressure. I'd love to fill it up and see how it does but wifey says I can't do that.

So I'm gonna pull the bed this weekend, do new lines if I can get them in time and check the pickup tube/screen. Maybe more pressure on the bottom of the tube with more fuel in it means just a clogged screen. The fuel quality is iffy around here, fuel filters look real bad after 5k sometimes. I remember someone posting good marine diesel hose for like $2/ft, anyone recall where that was? Alot of places are getting $4-8/ft, seems like too much to me. Also, how about a screen that fits in the filler neck? I'm thinking something like a drain screen, finer screen and deeper to fit at least most of a fuel nozzle, even if it does slow fill ups a bit. Just an idea. Thanks again guys.

 

When I was traveling in Mexico and Central America I used a paint strainer bag over the nozzle.
Glad I did considering the crap it filtered out.
Didn't slow fill up one bit.
Kept the bag in a glass jar in the bed.

 

genos (yeah I like them) has line for 2.50 a foot,also I picked up some in-line filters,I think $7 a piece just for a little peace of mind. IMO undoing the straps and dropping the tank is easier than lifting the bed. I had mine out in about 15 Mins.

 

Good tip on that bill, thanks.

Well I changed the filter today which was very dark, expected with 10k on it, but the o-rings were stretched out on the old filter and didn't fit well when I pulled it out. It was a purolator filter, kinda disappointed. Now it pulls over 20lbs at full throttle above 2k, still a bit low at idle, bounces around 14-16 psi. Still only get up to around 20 with no load, all rpm above idle basically. Runs like a truck now! Gonna get an o/f valve and clean the pickup tube screen tomorrow see if what I find. Thanks for all the help.