FG649 down on power, slow

[CropDuster]

Im having some problems with my truck really struggling on the slightest of inclines and feeling down on power/slow.
It is a 4D34T 3.9L turbo with the zexel electronic pump.

Boost is peaking at 10psi but it seems very slow to build up and high in the revs before it gets there.
I removed the exhaust to see if it had a restriction but this made no difference
Ive replaced all the fuel filters
I have no boost leaks from anywhere that i can find.

The throttle is slow to react if you push the accel pedal several times in succession ie. the 2nd 3rd 4th etc push of the pedal is just a big flat spot and delay before it revs up again.

Is there only the one throttle sensor on the pedal? or is there another one somewhere else?

The engine check light has not come on at all and I disconnected the diagnostic switch to check for codes but i just get the Orange engine light flashing once every 4-ish seconds continually nfi?

Any suggestions or other things to check would be appreciated.

Thanks
Nathan

 

[kerry]

Dirty air filter?

 

[gait]

the accelerator has two sensors built in, if they read differently the ECU throws a wobbly.

any colour smoke from exhaust?

 

[CropDuster]

Dirty air filter?

I replaced the air filter and even tried with the air box open :Wow1:

the accelerator has two sensors built in, if they read differently the ECU throws a wobbly.

any colour smoke from exhaust?

Two sensors or two readings from the one sensor?
Mine has a 5 wire Denso 198300-8040 tps

Only get a bit of fuel smoke at the top of the revs otherwise it burns clean.

Thanks for your replies

 

[gait]

well that question made me think ......

I have the same 5 wire Denso sensor. Circuit diagram draws it with two internal variable resistors to separate signal inputs at the ECU labeled accelerator sensor 1 and 2. The +5v and Gnd are separate at the ECU but combined to the sensors. There's also a switch in the sensor used for ECU control of exhaust retarder among other things.

Sensor has Gnd, +5v, Accelerator 1, Accelerator 2, Switch
ECU has Accel 1 Gnd, +5v, sensor ... Accel 2 Gnd, +5v, sensor ... accel switch

from memory, that's also consistent with possible ECU error codes I noticed when once engine fault finding.

At least for your problem probably rule out accelerator (at least electrically .... but not mechanically as both sensors are obviously mechanically linked).

Just to confuse, I also have a circuit diagram for an FE that has three wires with two readings from one sensor.

The question had me explore my manual a bit more. The circuit with the 5 wire sensor was in a supplement .... the good news is it looks like it resembles what I have much better than the diagram I had to use when sorting out melted wires. I might get round to making repair more permanent. So thanks for the prompt .....

 

[CropDuster]

Thanks gait, with the sensor unplugged i have the 5v signal at 2 pins which i am assuming are Acc1 & Acc2
I'll have to back probe it next to find out what voltages i have once plugged back in at both zero and wot.

It feels as though its getting no fuel down low which makes it painfully slow to accelerate and with no fault codes showing it doesnt help.

Anyone know what rpm i 'should' be getting full boost?

 

[gait]

somewhere in the manual there may be a test for the accelerator sensor, resistance at the extremes probably

 

[Amesz00]

Anyone know what rpm i 'should' be getting full boost?

Pretty late on the 3.9s, especially if its stock. I think 10 around 2400ish..

 

[CropDuster]

somewhere in the manual there may be a test for the accelerator sensor, resistance at the extremes probably

Yep i found the values on this page http://996.i8.com/Fuso flash code troubleshooting.pdf and im getting pretty much the correct figures so i'll rule that out for the moment.

Pretty late on the 3.9s, especially if its stock. I think 10 around 2400ish..

Thanks, Yep it is stock and that is more or less where im getting 10psi.
Looks like ill just have to keep digging...

 

[kerry]

It might be useful to perform some tests, record the numbers and do some comparisons to others here. List weight of the truck and then 0-20mph 0-30, 0-40, 0-50 and 0-60 times on a flat road or perhaps number of seconds you stay in each gear before reaching 60mp or something like that. I haven't seen those kind of numbers posted here before but they could be useful in diagnosing problems.

 

[CropDuster]

It might be useful to perform some tests, record the numbers and do some comparisons to others here. List weight of the truck and then 0-20mph 0-30, 0-40, 0-50 and 0-60 times on a flat road or perhaps number of seconds you stay in each gear before reaching 60mp or something like that. I haven't seen those kind of numbers posted here before but they could be useful in diagnosing problems.

That could be handy
For me i am just noticing the speed that i usually go up hills where i drive every day are much lower than usual.
One particular hill i used to be able to leave it in 5th and stay at 80-85 km/h but now i cant even get above 80 and thats hitting it at 100 to start with.

 

[CropDuster]

So far i have fixed a few problems but still havent found where all the horsepower has gone.
Hand primer was leaking around the copper washer, when it was replaced they never put a new copper washer on it.
After fixing the hand primer I then found leaking around the bleed screw on the diesel filter. I removed the filter housing and found the thread was stripped and the copper washer was well worn.

With that all fixed it is going slightly better but still not up to speed, not sure what i am going to pull apart next... :Wow1:

 

[PKDreamers]

Hi, have checked the water trap filter?
Have you checked the little gauze filter on the injector pump?
Hows diesel are using?

 

[CropDuster]

Hi, have checked the water trap filter?
Have you checked the little gauze filter on the injector pump?
Hows diesel are using?

Hi Pete,
Yep, no water in filter and its all new.
Yep checked and cleaned the gauze filter was pretty much clean anyway as it had a new pump and injectors fitted 20k km ago.

Not sure how much truck weighs loaded but it would be under 3.5t using 22-25L/100 on BP or Shell Diesel.
It used to use 17L/100 pretty consistently but i wouldnt care if it used 30L/100 if it was a rocket ship

I put a boost controller i had lying around on it and cant get more than 10 psi even with no exhaust, didnt have time to check anything further.

Cheers
Nathan

 

[unkamonkey]

You get that much boost out of yours? I put a test gauge on my old beast and only got around 2.8 LBs of boost. It's OK. I'm used to it's habits. If it is hot out, It is low on power like no boost at all. If I get above 11,000 feet, no boost. I've just put up with it for many years and deal with it. I figure that I'm on a vacation and I don't have to be anywhere too soon...