First ride in truck today- Did not turn out good

[deleted user 89485]

I had to start the truck t move it today and got the “No Charge” light. Looked at my voltmeters and they were at 0. Checked the battery cables and it turns out that the ride loosened them all up. Not only that but the guy I bought it from had installed the cables with split connectors so you can’t tighten them up at all. Great.

 

[glcaines]

I have an M35A3 with the CAT 3116 engine. I routinely have 60 psi pressure when first started cold. It drops to about 40 psi when idling and warm.

 

[319cssb]

I took two photos of the engine just started with cold oil (60psi)

and one with the engine warmed up. (~40psi)

I guess if the oil pressure is above 15psi its ok.
But lets not split hairs here, your engine has issues, big issues. And low oil pressure is part of it

 

[Awesomeness]

People are way too caught up on his mention of the number "40PSI" in the first post, and not using their thinking caps. 40PSI is irrelevent... he had sufficient pressure, then low/no pressure [gauge reading] and a leak. He never even said it was cold at 40PSI, so it could have been at 40PSI after being warmed up. You're letting this cloud your troubleshooting skills.

First, the OP still needs to clean it off and look. Everything else is just theorycrafting.

Next, it seems unrealistic to think the engine actually has no oil pressure. It would die a VERY quick death (minutes, or less) if it had no oil pressure. So let's assume it does have pressure, and some number that is enough to spray oil around. It's also unlikely that he either blew a hole/line/etc. big enough to drop to zero pressure, or that he pumped out enough oil to not be able to pick any up out of the pan (you'd know if you lost several gallons of oil). Oil pumps are intentionally fairly simple and incredibly robust - usually little more than a couple gears in a housing that act as a positive-displacement pump. While they do wear, and can fail, they rarely fail catastrophically without warning or some other obvious cause (e.g. something else breaking that runs metal chunks through the pump, shearing off a drive gear, etc.).

So next thought, is the oil sender on the driver's side of the block? I can't recall. But if that came loose, or broke, that would cause the likely erroneous pressure reading and leak oil. Or are the low pressure reading and the leak happening at the same time just a coincidence?

Also, make sure you've followed the "Low Engine Oil Pressure" troubleshooting flowchart in TM 9-2320-365-34-1. It's going to have you pulling the valve covers, oil pan, etc. to look for actual serious causes of low oil pressure, so it's in your best interest to be very sure it's not something far more benign first (e.g. oil pressure sender).

EDIT: TM 9-2320-365-34-2, page 3-21, steps 45-46 & 49. On the 3116 engine at least, the oil pressure switch and oil pressure transmitter (manual's terminology) are on the driver's side of the engine. I don't know about the C7.

 

[deleted user 89485]

I had a CAT service truck out here yesterday. The first thing he did was connect to the ECU with the CAT ET software. He checked all pressures and they were good. He then did an injector cut out test. When we got to the number 1 cylinder there was no change so something was wrong with cylinder 1. He waited until the truck warmed up because he said the fuel trims change once the engine is at operating temperature. He conducted the cut out test again and it confirmed a problem with #1. He removed the valve cover and found that the intake bridge for number 1 was just laying there and that one of the two pushrods was bent a little. He said this was due to the previous mechanic not making sure the rocker was set properly on the rod. This is what was causing the white mist coming out of the tube. It was unburnt fuel which collected down the driver side of the truck making me think it was oil. He then found that all of the injectors were in the wrong cylinders according to the ECU and that all the fuel trims were wrong. He said this would also cause it to run rough. He said that this usually happens when a mechanic does not understand the motor and just moves injectors around to find which cylinder is having a problem The tech updated the trim files and programmed the ECU with the correct injectors for each cylinder. He ordered the new pushrods and will return next week to install. We are both hopefull that this was the sole cause of my issue. I will update next week. I hope this helps someone with similar issues.

 

[Ohiobenz]

All the exterior visual inspections would not have shown this.... Best phone call made!! Hope this resolves everything.

 

[coachgeo]

glad to hear that it looks like an accurate diagnosis was made. Looking forward the hearing her purr.

 

[glcaines]

Hopefully the service calls aren't costing you too much, but it sounds like it was a good call getting an expert involved.