Oil sender on Cummins ISC

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Tom

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During our last trip I noticed that the oil pressure gauge on the coach was pegged hard over, although Silverleaf was reading a valid oil pressure from the diagnostic connector. See this discussion. Yesterday I finally got around to trying a replacement gauge; It wasn't an identical one, but I figured worst case it might need a sender with a different resistance and would read something when hooked to the original sender. I also picked up the correct sender for the new gauge.

On removing the old gauge, it was physically stuck at something over 100 psi (full scale is 120 psi), although I'd confirmed before removing it that it's pegged against the stop with the engine running. After hooking up the new gauge with the original OEM sender, the new gauge didn't read anything.

I was about to replace the sender when I realized that the OEM one has two wires on posts, whereas the new one (and the others I'd seen at a couple of auto parts stores) had only one. I can't read the schematics in my owners manual because they've been shrunk too much, but I'm guessing that maybe one wire goes to the ECM and the other goes to the gauge on the dash. Does this sound right? If so, does anyone know if I could just switch the wires at the sender, or would the ECM shut the engine down because it would now be reading "incorrect" oil pressure?

Looks like I might just need to buy a new gauge and a new sender from a Cummins dealer or Monaco (?), although I'm having a tough time believing they both went out at the same time.

TIA.
 

rsalhus

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Tom

I would like to see some pictures of that oil sensor/sender/gauge replacement.? ?:)

I'm getting a permanent fix for the temporary fix (what a joke) in my oil pressure sensor on Thursday.? There was a recall on oil pressure sensors that included ISL engines, but I'm not sure if it included your year's engine.? Did you read my post "Cummins 'Temporary Fix'" that I posted a few days ago under Tech Talk?
 

Tom

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rsalhus said:
Did you read my post "Cummins 'Temporary Fix'" that I posted a few days ago under Tech Talk?

Hi Rolf, thanks for the heads up. I had read the other discussion, but somehow didn't make the connection with my problem. It sounds like one half of my sensor is bad and I need to call Cummins.

Attached is a photo of the el cheapo oil gauge and single post sensor that I bought in an attempt to troubleshoot. Out here in farming country I don't have a lot of choice of places to buy parts off the shelf unless I need parts for a CAT engine in a farm tractor.
 

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rsalhus

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The Cummins recall for the permanent fix ran from Jan 2004 until the end of Dec 2005 and is now expired.  Call Cummins Customer Assistance Center at 1-800-DIESELS and find out if your coach has had the permanent fix installed (have your engine serial number available).
 

Tom

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Here's the scoop on my oil sending unit.

I called Cummins and they stated that there was no recall on the sending units on my ISC engine vintage, although the Tech Support guy told me about the temporary and permanent fixes for the engines that were covered in the recall. I also learned that the sending unit installed by Cummins only feeds the ECM and that any dash gauge is fed by a separate sending unit installed by the coach manufacturer.

I then called Monaco and their Tech Support felt the sending unit was at fault and confirmed that they install a separate oil sending unit for the dash gauge. They also told me it would be covered under warranty and they're sending a new one out to me (they have them in stock).

Great support from Monaco yet again.
 

rsalhus

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Tom

Yeah, that's kind of the story I got too.  The OEM (coach manufacturer) installs its own sending unit which feeds their own oil pressure gauge.  Cummins acts like they know nothing about the OEM sending units or the oil gauge, so when they make a change to the oil pressure sensor it's up to the owner to contact the OEM to see whether the sending unit is compatible or not with the new sensor.  It's not Cummins' problem.  I won't know whether my sending unit will work with my oil gauge until after they install the new sensor.  It might work or it might not, but Cummins isn't going to do anything extra to make it work.  And in my case, even if it does work, it will still only send an artificial value (something like 48 PSI) to the oil gauge when there is oil pressure.  Nothing like doing what's best for the customer, right?  Not!!!

Are you going to install the sending unit yourself?  Do you know where it is located?
 

Tom

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rsalhus said:
Are you going to install the sending unit yourself? Do you know where it is located?

That's the plan. Should take only a couple of minutes if it's as easy to get at as the Cummins one (they're on opposite sides of the block).
 

Jeff

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Freightliner does it a bit differently. They have a computer that talks to the engine and Allison units and uses their data to provide dash displays.
 

Tom

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Jeff, I'm not sure why Monaco does it this way (didn't think to ask the Tech guys on the phone). The ECM already has this data and outputs it via the diagnostic connector, which is how I'm able to read it using Silverleaf VMSpc on my laptop.
 

rtaylor

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If its the 2 post sending unit you get from Monaco it should be located behind the alt. Make sure you keep the wires away from the manifold I get alot that have burned up by the manifold.
 

Tom

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Thanks for the heads up. But, what I asked Monaco to ship me is the single post sensor on the opposite side of the block. While I was under the coach I made a mental note that the Cummins 2-post sensor wires are a bit close to the exhaust manifold.
 

rsalhus

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I got the permanent fix installed today for my oil pressure sensor problem. ?It was kind of funny watching the Cummins NPower guy search for my diagnostic plug to hook his computer to. ?I guess Rexhall didn't put one in for the mechanics to get at easily. ?He updated and calibrated my ECM for the new sensor and printed off a sheet of interesting statistics about my ISB engine. ?Like, the maximum speed attained during the last 17K miles was 96 MPH! ?Wow! ?The previous owner must have been a wildman! ?And another statistic said that 24% of the last 17K miles was spent idling. ?Makes me wonder how accurate those numbers really are. ?:p
 

Tom

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96mph, that's some fast coach you have there Rolf. Glad you got the permanent fix installed.
 
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