Hi guys,
We are on a trip. We drove about 400 miles today. About halfway through the trip, I pulled up to a stop light and my check engine light started clanging. I looked at my oil pressure and it was at about 20, at idle. Once the light turned and I took off, it went up to around 55 and stayed there as long as I was motoring down the highway. The same thing happened the next time I went to idle. I assume the check engine light is all about the oil pressure.
So, the questions are, should the oil pressure drop down to 20 at idle? I did some reading on the forum and it seems 55 is about normal at operating speed, which is where I am. I checked the oil level and it is full.
I assume this is a problem? What are the possible fixes?
Thanks
Kevin
BTW, The engine is a Cummins 350.
Thanks
Kevin
I am not familiar with your engine, but my ISM reads about the same at idle and only goes to 35-40 when driving and that is the way it has been since I owned the coach.
My ISC idles at 20 psi hot, 52-55 at 1700 rpm. Doesn't trigger any lights. I would think if low OP was the issue you would get a stop engine light.
I did get a "stop engine" light at one of the stop lights when I had to sit there a couple minutes.
Kevin
That looks like normal oil pressure for an 8.3 engine. It may be a bad sensor. And as
chuck said the M11 when hot only gets up to 40 lbs. When I first got my coach I phoned
Cummins and they said that is normal for the M11
First thing, I would change the OP sender, it's located above the oil filter, has 2 wires going to it.
Do you have a code reader? I'd suggest getting one or borrowing one to see what code was set...it might not be for oil pressure.
After operation on a normal day, 20 psi is good for idle. Different engine but that's what ours idles at. After pumping at a fire, our Detroits would go down to about 5 or 10 psi at the most when the oil was very hot. That was one of the reasons for the fast idle switch. I've seen cars that have flickering warning lights on a warm day when coming to a stop light. When you come off a light, the oil pressure will go up and allow plenty of pressure for the oil squirters to help cool the piston crowns and keep everything at design specs for lubrication and temperatures.
Piece
Check oil level and are you sure you have 15w40 oil,won't cost a dime.
I have the 8.3 Cummins too. Lowest I've seen is 22, usually stays at about 24 at idle when hot. As others have stated, check you level and grade of oil. Seems like you're within range.
It is full of 15w40 oil. Just checked it and the oil was just changed about a thousand miles ago. We drove it around all last summer with the same oil and never has this issue. I feel like the pressure was a little higher last year at 60 instead of 55.
I'm running Shell Rotella T6 15w40, which I have always put in it. I'll try the OP sending unit. See if that fixes it.
Kevin
As others have said, it may be a different code. It doesn't seem like the oil pressure is too low.
My 8.3 hot idles similar to yours.
A new sender will probably fix the alarm but the actual oil pressure will be the same as it was with the old sender.
There is a circuit in the pressure switch separate from the indication that sets the alarm. My oil pressure indication on the gauge is unreliable but the alarm circuit seems to be okay. I use a bluefire and can read the oil pressure threw the ECM and it is fine. This is on a ISM.
Scott
Has anyone considered oil dilution by the fuel? Diesel won't boil away the way gasoline will.
Good point.
Smell it (crankcase oil).
Is volume increasing (higher on the dip stick)? That wouldn't be due to MAGIC-- it would be due to diesel in the oil.
You guys are sharp!
We were on a trip back from Texas. On the way down to Texas, I had an injector go bad. I never thought about it but now that you mention it, I'm guessing you are right and I have fuel in my oil. I guess it's time for another oil change!!
So, since we are talking about it. The engine has 220,000 miles on it. Should I be replacing the other 5 injectors? I'm nervous now about taking it far from home.
Kevin
Kevin,
I wouldn't change them out unless you just like spending $. A new injector can fail right out of the box. Yes have had that happen. Sure you may have another fail the next time out but more than likely you could go another 100K before you have another go bad. Spend your $ on quality fuel filters to keep the system clean. You could also add some of the lubricity products to the fuel.
Mike
Mike
You are spot on for estimating any failure. But the cost to Kevin for "Peace Of Mind" may be wothwhile.
I've thought about starting to dump some Marvel Mystery oil into the tank. What do you guys use for lubricity?
Thanks
Kevin
Some claim these additives are snake oil but I use FPPF Agri Fuel treatment
Mike
I don't think that they are snake oil. These engines were designed for higher sulfur diesel fuel back in the 90's. Now, all you can find is ULSD. Here in Iowa, most of the diesel does have soy diesel in it, which certainly adds lubricity, but I don't believe that is available everywhere. If this stuff were snake oil, I don't believe that MMO would have been around for almost a century. I won't put it in my crankcase. I think the modern oils have everything the engine needs, especially synthetics.
We've had aviation mechanics tell us to put MMO in our airplane fuel to keep the valves from getting caked up with lead deposits from the low lead fuel we have to put through that engine. It works!
Kevin
Kevin,
The "low lead" aircraft fuel has a ton of lead in it. It had even more in the old days. So, a huge lie. Here is a quote: So, this means that even todays 'low lead' aviation fuel contains 21 times the lead content of leaded automobile fuel and 2,120 times the lead content of today's unleaded automobile fuel. Leaded automobile fuel was outlawed in the early 90's due to its adverse health risks. I've been flying since 1967 and have a pretty good handle on what goes into aircraft fuel tanks.
For lubricity, there are a lot of wives' tales out there. Bio-diesel is better for the environment and also provides better lubrication in the diesel fuel system. Lots of other recommendations but check out all the tests on YouTube at: https://www.youtube.com/results?search_query=diesel+lubricity+additive+
How labs test for lubricity: Fuel Property Testing: Lubricity (https://dieselnet.com/tech/fuel_diesel_lubricity.php)
Have a later coach or early? Every time you fuel, there is a possibility that you will pick up some algae. Drive long enough and you will pick up some. So, you need a bug killer as well as a lubricity agent. Bio-diesel only solves part of the problem as the down side is that it absorbs more water (depending on the % of bio) than dino diesel and gets out of spec faster because of that with a little higher possibility of algae growth.
Pierce
We used to own a Piper Pa-22-160 with the Lycoming O-320 B2A engine. My flight examiner, Catherine Hiller, told me to swap out the spark plugs, top for bottom, every oil change or when the mag-drop became interesting.
Don't worry about your injectors wearing out or failing. Do worry about particle contamination, so good oil filters and scrupulous attention to cleanliness when changing them out.
Lynn and I worked for a Tier II auto manufacturer making among other things Bosch injectors. The only was we could meet the fit an finish requirements for the valve body was by inspecting every single bore for fit and finish. The second generation of measuring machine we built hit the sweet spot for speed, accuracy and documentation. Just so long as the operators didn't ship the test samples to the customer.