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ksmech11 · 06-18-2018, **(Subject: Oil in fuel )**

Got a 2011 prostar with a cummins 871. Just had in frame done 10k miles ago. Oil pressure was bouncing around from 11 psi to 20 psi at idle. Then at running be at like 30-35 psi and drop below 20 psi. driver shut down during unload. On way back oil psi stayed at 30-35 psi. I did a full service on it. Found what i believe to engine oil in fuel filter. Took sample and it is very dark. Some guys say this is normal. Im not sure if there is a coralation between the psi readings and the oil in the fuel. The tanks are clean. No algae. Any thoughts?

Rawze · 06-18-2018, **(Subject: Oil in fuel )**

just keep in mind that ...

ISX is notorious for making ashpaltene in fuel system as a normal process. Biodiesel blends accelerate this. Some mechanics use it as an excuse to blame it as being soot, algae, or oil contamination in the fuel by mistake. It is quite normal for a fuel filter to turn dark/black when it is doing its job properly and nothing is wrong. Places like speedco will put in a 50-mocron filter in your oil water separator/Davco, but in all seriousness, they need a 10 micron filter in them to keep normal fuel deposits at bay.

Chamberpains · 06-18-2018, **(Subject: Oil in fuel )**

Sounds like the black Gunk is asphaltene which is perfectly normal in a Cummins ISX.

Have you confirmed the oil pressure with a mechanical gauge? Could possibly just be something as simple as an oil pressure sensor.

ksmech11 · 06-18-2018, **(Subject: Oil in fuel )**

I wasnt aware of the asphaltene. I changed the oil pressure sensor. After another unit got back here with the Davco filter set up, the fuel looks the same. Thanks alot guys!

ksmech11 · 06-19-2018, **(Subject: Oil in fuel )**

Update, Ran unit through a few heat cycles. Needed the truck so i sent the driver out. At about 9:30 lastnight, Driver called. Truck RPMs went out of control, red shut down light came on, engine started knocking. Driver shut it down. After 15 min driver started truck and all was well. Brought out another unit to swap. Drove it back to shop, 70 miles. Didnt skip a beat. Im assuming there is a ECM issue. Maybe water intrusion. We have gotten about 6 inches of rain in the last 2 days. Gonna tear into it this morning.

Rawze · 06-19-2018, **(Subject: Oil in fuel )**

(06-19-2018 )ksmech11 Wrote: Update, Ran unit through a few heat cycles. Needed the truck so i sent the driver out. At about 9:30 lastnight, Driver called. Truck RPMs went out of control, red shut down light came on, engine started knocking. Driver shut it down. After 15 min driver started truck and all was well. Brought out another unit to swap. Drove it back to shop, 70 miles. Didnt skip a beat. Im assuming there is a ECM issue. Maybe water intrusion. We have gotten about 6 inches of rain in the last 2 days. Gonna tear into it this morning.

could be ECM. Coul also be other issue causing high voltage when raining like a failing alternator. I have seen plenty of alternators make high voltage when they get soaked.

871's in particular will rev out of control if there is a bad, internally leaking fueling actuator as well. just keep that in mind.

Chamberpains · 06-19-2018, **(Subject: Oil in fuel )**

What code came with the shut down light?