HELP! Lack of power and won't free rev past 3,200

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MY1PATH

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I'm running out of ideas here guys. When I got the tuck it wouldn't free rev past 2700 and could barely get on the freeway. Knowing full well this was a Band-Aid I uncapped the limit screw for maximum accelerator and backed it all the way off. This got me about 3200 rpm and turning it by hand, the linkage couldn't even reach the screw anymore.
  • New fuel filter and 4 tanks later still no big improvement. Fuel cleaner/ lubricants where added to each tank.
  • Ruling out the rest of the fuel system I ran the pump directly from a fuel can and was still limited to 3200 rpm in park and neutral.
  • Fresh oil, fresh air filter, all valves adjusted to 0.014" (.35mm)
  • The engine fires up instantly as long as you wait for the glow plug light. It runs smoothly above 900 rpm with a little shake below that speed.
  • Acceleration is smooth but lacking power.
  • Turbo hits 5psi before 1500, 12psi by 1800 and If I stand on the brake pedal I can have 12psi at stall speed. So nothing wrong with boost.
  • I do get puffs of black smoke under heavy skinny pedal they are less now than when I first got the truck.
  • I have not checked if the accelerator linkage is a spline or two off but that was mentioned to me. It doesn't appear to be so but I can try to move it over a spline and see what happens.
  • I have not checked pump timing but I'm told that would not prevent revving unless it was so far off that I would be having other problems too. (starting, stumbling, excessive noise, lots of smoke etc...)
  • Checked banjo filters on pump: no filter on inlet, inlet hole is clean. Filter inside outlet bolt was dirty, cleaning had no effect.
  • Oscilloscope is on the way so I can verify the tach
Before I pull the injectors and pump and send them off for service, is there anything else I should try?
 
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MY1PATH

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No filter there, but inlet is clean.
Forgot to put that on my list above.
I also cleaned the filter found in the return banjo bolt.
Mhmm maybe I'll drag a snake thru the inlet banjo hardline...
 

tweak'e

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check you do not have the return pipe swapped with the inlet pipe.
the filter is on the inlet. inlet should be the larger diameter pipe.
 

Nig

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Kind of has a few traights of what mine was doing, pulling air, running out of tune all the time, wouldnt rev over 3000rpm. i chassed it for yonks same as you, mine has a Delphi filter fitted near the tank, i pulled it off to pull the LR tank out to check the sender unit, over 2 years iv had this ute
i couldnt beleave someone had put the fuel hoses on wrong, i correct them blead the system, problem fixed,
 

MY1PATH

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check you do not have the return pipe swapped with the inlet pipe.
the filter is on the inlet. inlet should be the larger diameter pipe.
Pipes are correct, it would have run fine from the fuel can if that were the problem. I fed the inlet directly from the can, no filter, no restriction unless its in the inlet line that's part of the banjo. Still need to snake that little section of pipe to rule it out.
Kind of has a few traights of what mine was doing, pulling air, running out of tune all the time, wouldnt rev over 3000rpm. i chassed it for yonks same as you, mine has a Delphi filter fitted near the tank, i pulled it off to pull the LR tank out to check the sender unit, over 2 years iv had this ute
i couldnt beleave someone had put the fuel hoses on wrong, i correct them blead the system, problem fixed,
Haha! I read about that last night. Tank is out right now, lines were correct and it sucked the tank right down to the slot on that pickup tube before I drained it. Ran smooth from full all the way to empty. But I will make sure that I put them back right too!
 
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tweak'e

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I also cleaned the filter found in the return banjo bolt.
trouble is there is no filter in the return banjo. filter is always on the inlet side for obvious reasons.

can you throw a pic up of it all ?
 

Cozmic191

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Hi, I was having a loss of power until mine got up to about 3000rpm. Blowing black smoke as well. Mechanic put a blanking plate on egr valve, thought he was saving me money, drilled a hole in it but apparently wasn't big enough hole (since found out it needed a bigger hole) I replaced my egr valve and my problem has now gone. Maybe worth checking the egr valve, could be sticking or need a clean or replacement
 
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MY1PATH

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trouble is there is no filter in the return banjo. filter is always on the inlet side for obvious reasons.

can you throw a pic up of it all ?
There sure is one on my pump.
Pictured is the return banjo bolt from the rear of the pump, the one with with a pinhole in it right?
This one has a bleed plug and looking inside the bleed hole or thru the tip hole there is a small filter inside the bolt. The tip hole has a lip that retains the filter.
I it was gray/black until I flushed it both ways and realized it was white. :ROFLMAO::ROFLMAO::ROFLMAO:

The filter may be catching stuff from the injector return line but I'm guessing that its to assist with bleeding air out of the pump, relying on diesel surface tension to push air out easier than fuel...

1635209382478.png

I don't have a picture of the inlet but with the banjo out and the right light I could see the bottom of the hole and the cross drilled port into the pump. I've seen pictures of the small filter and a spring that goes in there but I don't have that in mine.
 
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MY1PATH

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Hi, I was having a loss of power until mine got up to about 3000rpm. Blowing black smoke as well. Mechanic put a blanking plate on egr valve, thought he was saving me money, drilled a hole in it but apparently wasn't big enough hole (since found out it needed a bigger hole) I replaced my egr valve and my problem has now gone. Maybe worth checking the egr valve, could be sticking or need a clean or replacement
I can see that, Diesel EGR uses a throttle body to suck the exhaust gas in. If you block off the EGR but leave the throttle body alone you choke the engine even more.

This truck is not equipped with EGR. And the manifolds are the non-egr castings so nobody (inspectors) can ever tell me it was removed either. :)
 

MY1PATH

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i couldnt beleave someone had put the fuel hoses on wrong,
I'm going to put red shrink on the new return hoses, I will also put some red paint on the return fitting and return line coming from the frame. Dummy proof it for future me.
 

tweak'e

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There sure is one on my pump.
Pictured is the return banjo bolt from the rear of the pump, the one with with a pinhole in it right?
This one has a bleed plug and looking inside the bleed hole or thru the tip hole there is a small filter inside the bolt. The tip hole has a lip that retains the filter.
I it was gray/black until I flushed it both ways and realized it was white. :ROFLMAO::ROFLMAO::ROFLMAO:

The filter may be catching stuff from the injector return line but I'm guessing that its to assist with bleeding air out of the pump, relying on diesel surface tension to push air out easier than fuel...


I don't have a picture of the inlet but with the banjo out and the right light I could see the bottom of the hole and the cross drilled port into the pump. I've seen pictures of the small filter and a spring that goes in there but I don't have that in mine.
nice to see a pic of it.
yes the return is at the back with the bleed screw in it.

i never heard of them with a filter on the return. its kinda pointless as damage has been done by then.
mind you other manufactures don't have any filters in the banjo's. i suspect they have it to stop any bits of hose getting into the pump.
but on a return any crap will go into the tank and get sucked up and into the main filter.
who knows, manufactures do weird things at times.
 

MY1PATH

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Next time I have it off I'll get some different angle pictures so it can be seen inside the bolt.
Once I am done playing with the fuel tank I'm going with these next steps:
  1. check the linkage angle, is it a spline off?
  2. pull the top half of the pump off. If I don't seen anything obvious then I'll likely pull the whole pump for service.
 

tweak'e

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take some pics of the injection pump and part numbers if you can see any.
some one may have fitted a random pump to get it going.

the other thing is up the fuel screw 1/4 turn and see if it improves. just be careful as with no egt gauge fitted its hard to say what the fueling is.
 

MY1PATH

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I did up the fuel screw but it did not solve the problem, might have made it run out of fuel sooner because its using more... but I can't be certain.
Pictured are the pump numbers front and back. I think they are correct, front number matches up with a Nissan part number in a parts catalog.

1635397857188.png


pump 104640-7850.jpg Pump_16700-58g02.jpg
 

MY1PATH

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Finished my Fuel tank service and color coded my return line. (it's smaller too)
Truck had been parked for 2 weeks and I'm glad to be driving it again.
I'm going to commute with it for the week and then dig into my next troubleshooting steps...

Once I am done playing with the fuel tank I'm going with these next steps:
  1. check the linkage angle, is it a spline off?
  2. pull the top half of the pump off. If I don't seen anything obvious then I'll likely pull the whole pump for service.


red return.jpg Tank_Fuel_return.jpg tank_primed.png tank_painted.jpg Before after.jpg
 

tweak'e

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o well, thats not a service its a full blown restoration. nice one.
 

MY1PATH

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yeah, your right and for the time put in I wish I had started by just painting a new tank :banghead: But I saved $300 (for now)
 

MY1PATH

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Cold mornings before the turbo heats up, it feels great but overall still lacking in power.
Revving... It was actually my tach. I checked it against a laser tachometer, the needle was in the wrong place and the potentiometer on the back of the tach needed turning. I made an access hole so I could do it in real time... I feel pretty silly now.
Slow to get to highway speeds, lots of throttle to stay there... well, I think climbing out of your torque band and not having another gear can do that. I guess its time to ditch the 26.5" tires for something 31" or 32" tall... www.grimmjeeper.com/gears.html says that will give me a ~400 rpm drop in my highway cruising speeds.

Tach Calibration_drilled.jpg Tach Calibration_hole punch.jpg Tach Calibration_POT.jpg

 

MY1PATH

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Also, my new pump is here, I'm excited but I still have to wait for the tools. Here are the highlights from the builder.
  • 11mm QD32 head
  • stock off boost fuel (for low smoke)
  • +10-15% Full boost fuel
  • 2 deg more advance in the top end
  • It will run 18-20 psi intercooled as-is, just reduce diaphragm shims if going higher.
 
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