Cat 950gii shut off when hot

[Shivan Dookeran]

ok guys im back out to work after the entire country was shut down due to covid since april.. now we have a cat 950gii serial num AXX00529 that starts fine when cold but after getting up to temp about half an hr it shuts of and refuses to start . Changed all the filters and fluids incl fuel and oil .
The injector actuation pressures is reading double that of the desired pressures
only thing i am seeing weird when it shuts of is the fuel pressure goes to 0 but as i release the key it jumps up to 297 , i am not sure if the sensor is malfunctioning .

any and all help will be surely appreciated

 

[BigWrench55]

The injector actuation pressures is reading double that of the desired pressures

I think that you answered your own question.
If injector actuation is double. Then you got a leak. When the oil is cold it's thick enough to get it to start. But I bet that your actuation is still higher than normal. If possible remove the valve cover when this happens and have someone crank the engine. You will likely see oil pumping up around the injectors.

 

[Shivan Dookeran]

thanks for the reply ,guess i will have to open it up and check . if the seals were leaking wouldnt it be the other way around , desired would be double than actual ?

and what about the fuel pressure going to 0 ? will that affect anything ?
tomorrow ill try starting when cold and taking down all the measurements and then bring it up to temp and possibly try replicating the problem and post the pressures.

 

[BigWrench55]

You are right. I mis read the question.
That's a head scratcher for sure. I haven't worked on a cat and heui system in some time. I forgot more than I know about them. Hopefully nige will come along and point you in the right direction. Any fuel in the coolant or exhaust gases?

 

[Nige]

When you replaced the fuel filters were they completely full of fuel, or only part full.?

I’d put a pressure gauge on the fuel supply side and run the machine. Watch to see if the pressure does anything strange just before the engine dies. If it remains stable then I would have thought you need to be looking at the HEUI side of the system.

You have access to ET. What Part Number of flash file does the engine ECM have installed right now.?

 

[Shivan Dookeran]

question, when i run the injection actuation pressure test first click its at 870 then going up to the higher values the pressure is 2305 which is less than the desired pressure of 2611. does this mean the injector seals are bad?

 

[Nige]

question, when i run the injection actuation pressure test first click its at 870 then going up to the higher values the pressure is 2305 which is less than the desired pressure of 2611. does this mean the injector seals are bad?

Let me see if I have this right.....
In your scenario.
Desired Pressure 2611
Actual Pressure 2305

Actual Pressure as stated by you is LESS than Desired Pressure. In this case the electronic system will not come out to play and there will be no smoke from the chimney.

The problem could be any (or any combination) of the 3 possibilities listed below.
Injectors leaking internally.
Injection Actuation Pressure Control Valve (IAPCV) on the fritz.
HEUI Pump f**cked.

One thing it will NOT be is leaking injector seals.

 

[Shivan Dookeran]

no smoke from the chimney? means it wont start?


and yes when i run the injection pressure test i am getting that error

 

[Nige]

no smoke from the chimney? means it wont start?

Yes indeedy. With an electronic engine like this one until the Actual Pressure reaches the Desired Pressure you will see a status flag somewhere on the ET screen that says “Injection Disabled”. When the AP goes above the DP the flag will disappear and the ECM will activate the injectors. Try it with the engine cold and you should see the sequence work.

 

[Shivan Dookeran]

what if the actual pressure is waaay above the desired pressure?

 

[Nige]

what if the actual pressure is waaay above the desired pressure?

That question is only valid if the pressures are shown on ET while the engine is cranking over on the starter, NOT when it's stopped.
Only when the engine starts to turn over will the ECM start to calculate the DP.