Nissan Navara 2.5 Denso

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Nissan Navara 2.5 Denso

Postby STC » Tue Jul 04, 2017 3:49 pm

This has an intermittent fault for Low Fuel Rail Pressure although I have not been able to replicate the fault.

I have done some basic checks, replaced the fuel filter. It has had a few new FRP Sensors.

I am able to command the specified Fuel Pressure with my scan tool up to 1800 bar.

However at an idle speed of 750rpm the FRP will only reach 860 bar.
@ 1000 rpm - `1060 bar
@1552 rpm - 1460 bar
@2025 rpm - 1800 bar

I'm thinking I should get 1800 bar at idle but then the software is only opening the IMV (SCV) from 53 to 60% Duty Cycle.

If I open it 100% I do get 1600 + bar and up to 2200 bar with increased RPM.

It builds pressure and starts within one second.

Any Ideas ?
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Re: Nissan Navara 2.5 Denso

Postby steevegt » Tue Jul 04, 2017 4:32 pm

Hi,

This system is a one point control, only having the SCV as a way to control fuel pressure?

Is the rail pressure stable at Idle? If it is not, it may point to a bad SCV, as I have found some (Denso ones) to fail often.

The pressure not reaching 1800 bar at idle, I guess someone with the same system can try it and see how much it will be.
What command did you use in the software? The one named "Leak Test" or something like that? If I'm not mistaken, I have tried that before in a Denso system, and I think that it will get the 1800 bar, but it also reved the engine a little bit.

Maybe trying a dummy SCV and see how much pressure the pump will get cranking vs how much the SCV controlled to 100% gets. You could also compare the slope of the pressure waveform of both. If there is a significant difference, I guess you can call it a bad SCV!?

Did you measure the low pressure circuit (intake pressure to the pump)?
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Re: Nissan Navara 2.5 Denso

Postby Dcunning35 » Tue Jul 04, 2017 8:32 pm

If this is denzo , on transit if the system has seen repeated high pressure ,blow off valve triggered it sets an algorithm off which limits scv duty. On transit a reset of the pressure relief restores this and most commonly its a sticking scv that causes the high pressure a current measurement will help you see if it sticks but if you play with throttle at idle you can set off a surdge and see frp and scv oscilating in rhythm.
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Re: Nissan Navara 2.5 Denso

Postby victor2k » Tue Jul 04, 2017 8:47 pm

STC wrote:This has an intermittent fault for Low Fuel Rail Pressure although I have not been able to replicate the fault.

I have done some basic checks, replaced the fuel filter. It has had a few new FRP Sensors.

I am able to command the specified Fuel Pressure with my scan tool up to 1800 bar.

However at an idle speed of 750rpm the FRP will only reach 860 bar.
@ 1000 rpm - `1060 bar
@1552 rpm - 1460 bar
@2025 rpm - 1800 bar

I'm thinking I should get 1800 bar at idle but then the software is only opening the IMV (SCV) from 53 to 60% Duty Cycle.

If I open it 100% I do get 1600 + bar and up to 2200 bar with increased RPM.

It builds pressure and starts within one second.

Any Ideas ?

Your system work at a very high pressure...860 Bar at idle is more than double as the normal!
Please check the quality of your diesel...this abnormal values make me to think you have a gasoline/diesel mix.
For a low fuel rail pressure I will search the back leak of injectors,the fuel pump and the limiter of rail pressure(on a high mileage cars this can leak...)
Last edited by victor2k on Tue Jul 04, 2017 9:08 pm, edited 1 time in total.
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Re: Nissan Navara 2.5 Denso

Postby STC » Tue Jul 04, 2017 8:54 pm

This system is a one point control, only having the SCV as a way to control fuel pressure?

Hi Steeve
Yes this is single point control and the Rail Pressure is very stable. As I said I cannot replicate the fault, neither can the garage but the customer takes it for half a day and brings it back with the light on. Apparently it is at light load driving slowly.

Bosch KTS calls it a High Pressure Fuel Pressure Test but does not raise RPM above idle whereas most others do. That is why I am not ready to throw a pump on it.

I didn't try dummy SCV because I can achieve 1800 bar at idle with the SCV fully open - and it gets there quick. Neither did I paralyse start to see what it can achieve cranking, under normal conditions and with SCV wide open. Will do next time.
The low pressure side is good at around 500mB (absolute) and steady.

The problem is I cannot get it to fail, equally I can hold it at 1800bar and it will remain steady for 30 minutes.

(It has done just 51,000 miles (80,000 km))

I was hoping for a silver bullet here with the fault not present.
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Re: Nissan Navara 2.5 Denso

Postby STC » Tue Jul 04, 2017 8:58 pm

Victor

Your system work at a very high pressure...860 Bar at idle is more than double as the normal!


You misread my post. At normal Idle I have about 280 - 300 Bar.

I have 860 Bar only when running the High Pressure Test with the Bosch KTS.
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Re: Nissan Navara 2.5 Denso

Postby victor2k » Tue Jul 04, 2017 9:17 pm

STC wrote:Victor

Your system work at a very high pressure...860 Bar at idle is more than double as the normal!


You misread my post. At normal Idle I have about 280 - 300 Bar.

I have 860 Bar only when running the High Pressure Test with the Bosch KTS.

Sorry for the mistake...anyway try to use other tool(launch or Nissan Consult) to diag the car .
Bosch KTS isn't a good friend of japanese cars and sometime the values readed in data list have no sense :D
Last edited by victor2k on Wed Jul 05, 2017 7:34 am, edited 1 time in total.
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Re: Nissan Navara 2.5 Denso

Postby victor2k » Tue Jul 04, 2017 9:31 pm

"Bosch KTS calls it a High Pressure Fuel Pressure Test but does not raise RPM above idle whereas most others do. That is why I am not ready to throw a pump on it".[/quote]
Some systems need to increase the speed of engine at 3000 rpm to perform the leak test,also you need to touch some engine temperature...this will be find in the manual repair.
Regards.
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Re: Nissan Navara 2.5 Denso

Postby STC » Tue Jul 04, 2017 9:36 pm

Danny

I looked at the High Pressure Blow Off as it is known weak spot on the Denso Systems of that era, quite easy to spot as the FP will drop of instantly. Not so with this car, also I have taken it up to 2200 bar momentarily and it held.

On transit a reset of the pressure relief restores this

Not sure what you mean ?
I have re adapted the Pressure Regulator with the scan tool. Playing with the throttle, which I have done several times does not induce the failure.
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Re: Nissan Navara 2.5 Denso

Postby Dcunning35 » Tue Jul 04, 2017 10:20 pm

The blow off or sudden drop off triggers an algorithm in the pcm software but this is on transit with the denzo s t system so I dont want to muddy the waters.
On transit if the algorithm is set it limits the frp and is rest via ids service functions reset fuel pressure regulation and ofset . The pilot fuel and hp.pump learning also needs to be done .
This may not be the case with the nissan , if you can open the scv and create max pressure the operation of the scv is a good place to start .
Good luck
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