intermittant low power

[btoscano]

I have an intermittant low power problem. Seems to happen when its hot outside. I've had the truck for 2 weeks so I don't know how long its been an issue. Sometimes its very energetic and sometimes its lethargic. One day I strugged on the 101 in NoCal, 2 days later I drove I-17 from Phoenix to Flagstaff (steep grade, 100-120F) and had no problems! No smoke, just feels like its not getting enough fuel.



Fuel filter was suspect at first and replaced with no change. Lift pump changed with new Cummins dealer part. Fuel shutoff solenoid replaced after it failed to draw current.



Dealer suggested pickup screen in tank might be clogged. Maybe this is related to my fuel level sender unit being totally inaccurate (but low fuel light is accurate)? Or could it be air in the lines/loose connection?



Should I start by dropping the tank and checking for trash in the tank or a blocked screen? Or should I start by rigging up some test gear?



Currently no guages are installed in the truck but I plan to get on that soon.



Thanks,

Brian

 

[btoscano]

Starting is never a problem. Low power means it has trouble on the hills. If accelerating on a freeway entrance ramp uphill it can get to 60 or so, otherwise it struggles to maintain 72. When its working good it will climb to 88 and get to 80 with authority.



Brian

 

[dodgenstein]

Sounds like you have done all the usual easy to get to items. It could very well be a clogged intake screen in the fuel tank. It probably isn't related to the inoperative fuel gauge though, mine works (doesn't work?) just like yours. I believe the pivot on the float arm gets worn and causes this. For what it's worth, it's fairly simple to replace the fuel assembly, after draining the fuel, or my choice, removing the bed.

 

[btoscano]

My truck has a topper so its probably more involved to remove the bed that someone without? I have not removed a bed before. How does one do it? I have a tractor with a front end loader, does that make it easier to lift the bed off the frame?



I looked at the fuel line assembly and the left hose came right off! As if it was not secured well. I pushed it back one a time or too and now I can't simply pull it off. Is that a supply or return line? Maybe it was letting in air? The right line is tight and I did not try to remove it.

 

[dodgenstein]

I haven't traced the lines to know which goes where, so I can't help on that. On bed removal, there are only six 3/8" bolts that hold the bed on. Two up front, and four by the back bumper. They go up vertically from the bottom. Two are outside the frame up front, and the four at the back are inside the frame. The taillight harnesses unplug at the back of the frame, and then you remove the filler neck. If you are careful, you can remove the screws around the filler cap and thread the neck down as you lift the bed and not have to remove the hoses from the tank end.

 

[btoscano]

The low power is still intermittant. Most often happens in middle of the day, with the A/C but its also happened once in the evening (after it started doing it in the daytime). I'm not even pulling a trailer!



Today I pulled the bed to inspect the fuel tank. The tank is CLEAN. The fuel screens were darkened from use, but not clogged with goop. I wiped a white shop towel all around the tank and it came out diesel fuel colored. No grime.



The filler neck grommet was cracked in 2 places on the outside, but inside sealed well and the filler neck sealed well against the grommet in the tank.



I ordered a new level sending/pickup unit (since the level doesn't work) and a new grommet from the dealer. I'm going to install tomorrow.



There were 8 bolts and 2 wire connectors holding the bed down. My Kubota front end loader made the job of lifting the bed fun. We just chained it to the FEL bucket.



I'm figuring this is NOT the problem though.



I've already changed the lift pump, fuel filter, air filter, checked the quick disconnects for good fitment, put wrenches on the metal lines to check for tightness, made sure all the clamps for the intercooler boots were tight, ...



Anybody have other suggestions? Is my injection pump the only thing left that could be doing this intermittantly?



When it works, the truck works great! I can do 92 MPH up one of the steepest interstate grades for miles (at night, no A/C). During the day 88 MPH is not that hard to reach. But when its not working good... it struggles to get up to speed and can loose speed on grades around 72 MPH.



Thanks,

Brian

 

[btoscano]

I'm not sure if its related or not, but fuel economy is not real good compared to what some report. I'm getting 15. 5-17. 5 on the freeway at 72-80 MPH actual, 77-85 indicated. No visisble smoking.



Brian

 

[WJune]

My mothers mint 95 CTD got 25 mpg from Wis to Phoenix, then dropped to 18 mpg along with the same complaints you discribe. A (trusted) dealer mechanic put it on (the machine) an told her it needs a pump rebuild at $1000. I said "hold on, lets try the easy stuff first", which it sounds like you have already done. She started by getting a bottle of PS (power service) additive at Checker auto. One treatment brought it back to life ! I wouldn't beleive it, were it not my own mother. She has put a 1000 or so miles on it since. Hope you are as lucky.

 

[btoscano]

I have run about a gallon of power service through it so far. No improvement!



-brian