Heavy Equipment Repair Questions? Ask an Expert Now.
Hi, Welcome to Just Answer, I am Clayton. I can help you with this.
How are you
good just trying to figure out this truck
Alright,lets see what we can do
I know you changed the fuel pump, have you acually checked the fuel pressure?
but would it be different un loaded vers being loaded
You said without a load it runs fine, with a loaded is when it does it the most, when the truck is loaded, it demands more fuel
well we changed the fuel pump and computer
You could have plugged fuel filters causing a restriction, pressure relief valve sticking open
I am not saying this is your problem, this is something to check when you have low power
well it is like the computer shuts it down and picks it back up again
If the filter is restricted, then it does not matter if the fuel pump is new, it cant push fuel through a restricted fuel filter, if the relief valve is partially sticking open, then this will lower fuel pressure.
Alright, is your CEL coming on?
but it is only in high rage low range is fine
when the truck is in high range, that puts more load on the engine, and the fuel demand is higher.
no no lights comming on
are you getting any smoke out of the exhaust?
I seriously would put a fuel pressure guage on it while you are driving it and watch the fuel pressure. I have seen the suction line from the tank to the fuel pump collapse and cause a similar problem.
well we stuck a hose in the tank and bypassed the suction line it did the same thing
Ok, good, but we still need to know what the fuel pressure is.
The pressure relief valve can cause low fuel pressure. And or course fuel filters, I would also check your turbo charger
it will take me a while to do it
That is fine, this question will stay open while you check stuff, and if you need to come back and ask more questions, you can at your leisure
Use a 0-100 pressure guage , and plumb it on the fuel temp sensor on the fuel pump
you will have to remove the fuel temp sensor
Check that out, and get back with me.
we bypassed the filter and suction tube and put a pressure guage and at idel is 20 and at really high rev it went to 80 no fluc as long as we held the rev
have you tried to drive it with the guage on it?>
?no got to get a longer hose for guage
let me check the specs on the fuel pressure, There is a mid year change where they changed the fuel pump, nd the engines required great pressures, I think those specs are good
we are looking for a longer hose for the guage so we can drive it
looks like that is enough fuel pressure, It is suppose to be 75, but that is close enough
I would still drive it to make sure it does not drop under a load
be right back
yep i got you
I am back
If all of this is good, then check the turbo, check the wheel play, up and down, then in and out, look for oil residue, and bent or damaged fins on both the exhaust and the intake side.
Let me know what you find, I am giong to step out. Just reply back
when it doged out the pressure went from 79 to 74 so i think we have good pressure. could a sencer cause it to dog out?
the rpms droped too
Ya, 74 is not to much of a drop.
You said you replaced the wastegate sensor?
I have never heard of a wastegate sensor, we might be calling it two different things. where is located so I can get on the same page
it is the turbo sensor we replaced
ohh, on the intake manifold?
There are about two other things tha can cause low power. Check the turbo, and exhaust leaks before the turbo. When is the last time you had the overhead ran?
turbo is putting out good air pressure and i think the computer is derating
milage is 666 thousand
computer could be derating. This is non-EGR?
we switched the computers twice
as soon as you swapped computers, did it run fine, then start to derate?
no right away
does the fan stay on all the time?
I do not think the computer is derating. But cannot be forsure without hookiing it up and seeing if t here are derating faults
does the check engine light work? maybe there are some historic codes that can give us some clues
check engine light does work but does not come on
have you tried to flash out the historic codes?
the only code that comes up is a low voltage but we have had to jump start the truck
have you checked system voltage?
is this at the batteries or the alternator?
all 4 batteries?.
what about the ecm fuse
if the ECM fuse is blown, it would not run
I am wondering if you have a voltage drop in the wiring to the ECM. What does the dash read in voltage?
i'll go look
rough 14.5 volts
was in work performed before this happened?
was any work I mean
no just checked cables to batteries
nothing done with the top-end?
no we haven't this has always been one of our best running trucks
hang on a min, brb again
I found something on the DDEC 5 engines, your fuel pressure is way to high, I am trying to find it on the DDEC 3/4 engines, and high fuel pressure can cause low power
this is a ddec 4 engine we tryed a ddeck 3 engine computer and oil pressure was way high
sorry that was a ddec 5 computer that sent it high not the ddec 3
how did you manage to hook up a ddec 5 computer to a ddec3/4?
it was a egr ddec 4 computer not a five
ok. your fuel pressure should be 84 psi at idle, and rated
i am sorry, at 1800, or 2100
I read that wrong
10 psi drop I don't think would cause your problem, maybe a fuel filter change might get you somewhere
we were at 79/80 psi
well we changed it and now we pypassed the filter
ok.. I dont think the ECM is derating you
It has to be mechanical
have you checked the charge air cooler, or any air system leaks?
turbo air system
and you physically inspected the turbo
make sure the waste gate is not sticking open, or stuck open
yep turbo is good and waste gate is working
I have told you to check everything that could possibly be checked, and you have. Your truck has 666,000 miles on it, it is way over due for an overhead adjustment
I would adjust the overhead and see if that brings your power up
im going to go check the waste gate again
how much air pressure does it take to hold or close the waste gate
Pressure opens the wastegate, probably 25-30
unless something is wrong with the waste gate it is operating with a air compresser hose blown into the waste gate
how much pressure are you putting to it, your air compressor could be 60+ lbs
but if it isn't opening it should be blowing black smoke or blue smoke right?
if it is opening to soon, it will not make enough boost, and the manifold sensor won't see the boost, so might not enrich the fuel.
210.29-217.19 kPa (30.5–31.5 psi)?
1.016 mm (0.040 in.)?
Yours is a 14.0l, or 12.7?
it is the same regardless, when you apply 30.5 to the wastegate, it should move .040 of an inch
thats if its a garret turbo, if it is a borg warner turbo. Here are the specs on it
BorgWagner Turbo Systems®?
234.22-234.63 kPa (33.97–34.03 psi)?
1.45-2.26 mm (0.057–0.089 in.)?
We have a digital presure guage and regulator just for this reason
You might try wiring the wastegate shut and see what happens, it will build power,until you build to much then it will derate you
Do that at your discretion
but it would still should derate you for the moment
If you do this, it could overspin your turbo. I would not advise it
we are going to try wiring it open and see what happens
if you wire it open, it will do the opposite
you wil lose power
the wastegate is designed to prevent the turbo from overboosting
if the waste gate opens, the exhaust will bypass the turbine wheel and exit the exhaust and not spool the turbo as fast
its a safety feature for the engine and the turbo basically. If it comes open to early, it might be the problem. The springs do get weak in the actuators
well it only de rates for a moment and picks back up and does it again
after you wired the waste gate shut
no its been doing it all a long
make sure the fins of the turbo are not hiting the side of the cold side..
check movement up and down as well
on the shaft
we wired the waste gate open and other than a little lack of power the truck ran good it did not derate us at all it ran 75mph at 1700 rpms before we we could not get it past 1600 rpms at 55 mph. turbo pressure before it derated us at 25 psi and after wiring waste gate open turbo pressure was at 17 psi does all this sound correct?
It is very possible the wastegate spring is weak, or the wastegate is not adjusted correctly. Sounds like you might have fixed the problem.
I would like to know if you are getting derated, the only way to tell is have somebody hook up to it and look at torque percentages. If it is derated, it will tell you
Are you still with us?
we put another waste gate controler on it and we are back to square one
you put another wastegate on it?
the round thing with the arm on it that has a hose going to it to open the waste gate
would it hurt to run with the waste gate open
closed you mean?
if we wire it open
because when we did the truck would run fine
if you wired it OPEN, then it would have a hard time building boost, which would cut your power
but with the waste gate closed it would only go 50 55 mph at 1500 rpms
with waste gate open we could run 75mph at 1700 rpms
so when wired it open, you were able to get 25 psi?
That was before we wired it open that is when the truck started to mess up. after wiring it open we were at 18 psi truck ran good
I wonder if the boost sensor is making the ECM think it is making more boost than it actually is
That is what we are think too
we took one off our junk trucks and it does the same thing
The wastegate is held CLOSED by an internal spring, should OPEN at around 30-35 psi
yea the truck messes up befor the waste gate can open
Depends on the turbocharger...do you know what kind of turbo you have
you can see boost pressure?
we hooked a guage to the manifold and drove it
he's going to see what kind of charger it is
I am scratching my head, I gave you all the possibilities
can you tell by the vin number
ya..if it has not been changed
let me go looko
we haven't changed it
I am having difficulty with the website. You can look on the turbo, it will say Garret, if its a Garrett, it will have a tag with Borg Warner on it
it has a detroit symbol on the turbo
They both will...
does it say garrett on the cold side(intake side)
I am all out of ideas. Do you want another expert to help you out?
The garret should open around 30-31 psi, and move .040 of an inch at this pressure
Does the waste gate have two nipples on it?
no just one
if it is not building enough boost to open the wastegate at 31 psi, then it could be derating. It takes combustion to make boost
well Clayton Thank you for all your help in Pointing us in the right direction. we figured we just wire it open so the truck can run.