Navistar VT365/VT275 and Ford 6.0L Injector

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RyanH
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Posts: 8
Joined: Sun May 02, 2010 12:38 am

Navistar VT365/VT275 and Ford 6.0L Injector

Post by RyanH »

The G2.8 injector in these engines are a Hydraulic Electronic Unit Injector (HEUI) and are susceptible to poor engine oil causing injector damage, resulting in a misfire. The damage is usually scoring of the spool valve that sits between an open and close coil controlled by an Injection Control Module (IDM) or Fuel Injection Control Module (FICM) at 48 volts. This spool valve allows engine oil to enter the injector and apply up to 3900 psi of engine oil to an intensifier piston which drives a fuel plunger that generates injection pressure.

The most common issue with this injector is referred to as stiction. The injector is commanded on but the spool valve either is slow to respond or does not move at all from it's closed position. There are methods with a scan tool to diagnose this issue but I find it interesting to develop new test procedures that may be useful for other applications. Also for the rare International I see in my shop I can test the injectors without a scan tool.

Recently, I have been studying the voltage waveforms of injectors and adding a frequency math channel. The movement of the spool valve (0.017" total travel) interferes with the open coil current flow as it crosses its magnetic field. The IDM/FICM that drives the injector at 48 volts, changes the frequency of the current limiting pulses to compensate for the change in current flow. This results in a frequency waveform that looks like a ski jump. The lower peak appears to show the moment of the spool valve as it reaches the open coil and stops. The two pictures that I have added show the delay from a sticking spool valve vs a good injector. If the spool valve does not move at all, there is no lower peak and just a downward slope.

At this time I am only focusing on the open coil because the close coil is aided by hydraulic pressure to move the spool valve back to the closed position. The delay is generally with the opening of the injector but the close coil can be measured in the same.
Attachments
6.0L Inj Voltage Delay Known Good.jpg
6.0L Inj Voltage Delay Known Bad.jpg
G2.8 injector.jpg

ben.martins
Pico Staff Member
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Joined: Tue May 16, 2017 1:02 pm

Re: Navistar VT365/VT275 and Ford 6.0L Injector

Post by ben.martins »

Hi RyanH,

Thank you for your post and your timing couldn't be better! I'm due to visit a CAT 972 fitted with the HEUI system and have been researching ways to best observe how the system operates. The one I'm going to look at has a very long crank before starting. From the information I've been given so far, fuel appears to be the issue but I think Ill be taken a look at the frequency changes of the driving voltage on the injectors. Out of interest do you know if they have shared supply or are all injectors individually controlled by the ECM?

Hoping to map the interaction of the system from low pressure oil side, high pressure oil side, fuel pressures, injectors and timing to get a more definitive test plan without having to take covers off or getting covered in oil!

I'll post here with what we find and thanks again for the information!

Kind regards

Ben

kicksbutt
OneWave
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Joined: Tue Sep 10, 2013 11:10 am

Re: Navistar VT365/VT275 and Ford 6.0L Injector

Post by kicksbutt »

Ben

Do you have a serial number for the Cat?

ben.martins
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Re: Navistar VT365/VT275 and Ford 6.0L Injector

Post by ben.martins »

No not yet. Hope to get it the first week back but it looks more likely to be when I see the machine!

Once I have had a chance to see the machine and get a better understanding of what's going on, I'll update.

RyanH
Newbie
Posts: 8
Joined: Sun May 02, 2010 12:38 am

Re: Navistar VT365/VT275 and Ford 6.0L Injector

Post by RyanH »

I haven't played around much with the CAT HEUI systems besides one 3126E. On that engine the supply was was a constant voltage. I imagine the low side was in charge of the current limiting but I didn't get the chance to capture it.

The Navistar G2.8 injectors share a supply between four injectors but each injector has two high side and two low side drivers. This isolates them from each other outside of the Fuel Injection Control Module. I am not sure on how CAT may drive their injectors.
Attachments
3126E Inj Current and Voltage.png

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