for a while now my truck has been seeming low on power. wot i max speed is like 80, and it should be able to peg the speedo and then some. not that i need to go fast, but just for example. empty truck up i decent hill ill hit 70 wot.

in the last month it has had new oil, new fuel filter. i unplugged the MAP with no change other than the light coming in. and at idle fuel pressure is hitting about 50psi (from a tire gauge)

What do you all think?
thanks

 

Not with those tires and lift really. Especially if you have 4.10 or lower gears. That engine is out of RPM on mine at 85 with 265 tires and 4.10's. The fuel pressure could be a little higher. 60-65. Your pump is probably weak. You need a real gauge. Then tell us if the needle is bouncing back and forth the full range of the gauge. That's a screwy pump. It shouldn't bounce too much.
Clean fuel filter air filter and adequate fuel and you aren't getting much more from it for speed. These trucks were meant to pull, not race.
Also anything over 3000 RPM for too long and your motor isn't going to last very long. I never run over 70 just for that reason.

 

the tires are 315 70 17 or about 35s with 410 gears, that should kinda put it close to the stock tire size with3.55s. i know it isnt a race truck i was just sayin for an example of how its lacking power, with the lift and tires i used to be able to peg it. im not really pushing 3000 rpms either, mid 2s when she doesn't want to go any more. and it takes a while to get there. also thats assuming the speedo correction, i figured it once, and its less than 10% difference in tire size from stock so the speedo should be the same % off. does the truck have a fuel pressure guage that i can read through a scanner. i have access to one, so i can read the boost and all that when i plug it in

 

What did the fuel filter look like when you replaced it? Was it real nasty? Did you clean the screen in the fuel bowl? Does it free rev in neutral ok? Any smoke or missing when it quits going?

Just some more questions for all to go on.

 

If you put a good gauge on the schrader valve to measure the fuel pressure, what does it mean if the gauge bounces back and forth like 10 psi each way?

How do you guys measure the pressure when the gauge bounces SOOOO much.

 

fuel filter was black. and i got down there and cleaned the screen well. and when i said "quit" it doesnt quit i meant it no longer accelerates

 

My guess is maybe injector orings are bad. Fuel was black in filter and wont rev. See what others say.

King, I've read just to take an average of where its bouncing. Mine wasn't bouncing, just went to 72lbs.

 

How much it's bouncing is a sign that's it's bad. a 40 or 50 psi bounce is bad. 10 psi is fine. New ones do that. I'd say the o rings need some attention too after hearing the filter is black. If it can't build the right amount of hydraulic pressure then it will certainly limit its speed.

 

This is AMAZING! Finally someone with the exact same problem I have! To the "T". Now...when mine is in park...it won't rev past like 22-2300 rpm's with a LOT of smoke. If I hold it in gear while driving, it seems like it runs out of something(fuel?) just over 3000 rpm's. Replaced fuel filter. Cleaned the screen. Did the bb mod on the fpr. Open air filter. Just got a new exhaust(not on yet). Cat might be plugged up... Somebody help us out!

 

I know on a gas motor the cat plugged will cause big power
problem,dont know about a diesel,i took mine off.

 

i have 4 inch straight exhaust, with 3 inch down pipe. so no preplem there. but a sticky closed or partially closed exhaust vavle would to the trick. but mine is all the way open.

 

x2

Have you checked your Fuel Pressure since the FPR shim just to see where you're at? My truck was doing the exact same thing when I bought it (not reving over 2200 in neutral). Replaced the injector O-rings and she's been fine since. NOW I did replace a whole bunch of other stuff at the same time, but that was the one I believe may be most related to your problem. while you're in there replace your GP's if it's been a while, even of there still good. Save yourself some hassle down the road

 

from reading other older threads i thought that might be it, specially with my completly black fuel filter. darn, i just had the valve covers off and did my glowplugs a month ago. the part of the project that took the longest was getting that bolt by the fire wall out. took me like an hour haha

 

I feel your pain that one is the worst.

Don't forget that when you pull the sticks that oil is going to drain down into the cyl's so you can pull it out with a big syringe and a tube, or crank it with the GP's removed and IDM fuse pulled. I went with an 80cc syringe i got from a taxidermy supply place and a length of tube, seemed to work well. Also pulled the oil out of the HPOP first so that wouldn't drain down too

Good Luck

 

il have to make some time to get to that. iv been wanting to at least get diy stage 1s, and if the injectors are coming out......