jetfuel320

I'm trying to figure out if I have a problem. This is the second time for this. About 6 minths ago I had low RPM in gear at Idle. It would drop below 500 and the oil pressure gauge would drop to 0 and all the bells and whistles would go off. If you just give it a little gas all went away. Well it's doing it again. I'm going to adjust the idle up again but why does the idle slowly drop to this point over time and is my oil pressure really dropping to 0. Any help would be appreciated.

Cowhand

I see you have a 98...is it 12 or 24v?

DRM

My 98 12v is doing the *exact* same thing right now. RPM drops to 600-700, oil pressure gauge drops to zero and the dinger goes off. Come back up a few seconds later, or when I rev it up again.

Sending unit is brand new, so it's not the sender.

Rrloren

I had the same problem last year. After a lot of time at the dealer and allowing them to replace the transfer pump I went to a cummins mechanic who replaced the overflow vale for $35 and then I adjusted the idle up to 750 rpm with the a/c on in gear , haven't had a problem since.

marks2500

i had this happen the day before and today, my idle in gear with the ac on is around 600-700 and in park its 850-900. i will be raising the idle today and yes when the dinger went off while backing a trailer, and seeing the needle on 0 sure made me pucker

DRM

Info on replacing the overflow valve?

marks2500

i replaced mine about 1 year ago, and had low idle before, but never had the oil pressure drop to 0 because of low idle.

infidel

Replacing the OF valve is a five minute one wrench job if you don't drop the sealing washers, stuff a rag under the valve to catch a falling washer. Remove the old valve and put new one in it's place. Occasionally the notch in the manifold you see to the left of the OF valve in the picture needs to be filed or ground a little to allow the old valve to be removed. Don't bend the return line to remove the valve, it will make it very difficult to line it up again. New style OF valves don't always have the retainer on top that says not to remove, don't worry it's just a design change.

The object in the lower left corner is the oil fill cap.


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ironmike

This is funny. I just got my 98.and ever once and awhile the oil pressure gauge just drops(bells go off).give it a little gas then its fine.But the idle doesn't change when this happens.huh

Sawyer1

Thanks Infidel you just answered my question that I posted a few minutes ago.