My 1991 4x4 regular cab has been pulling a 14,000 lb fifth wheel with no problem. Last week driving from Benson AZ to San Simon AZ, the truck seemed to be heating up more than usual in this weather over this route. <br><br>As it seem to be heating up, the gauge needles began to bounce between readings. I do not know if this is heat related or electrical.<br><br>At idle, the low oil pressure light came on, but I had the correct oil pressure at speed. I use 15W40. should I use a heavier weight oil.<br><br>OR, do I have a more serious problem?<br><br>Thank you for your assistance.<br>Jesse Gray<br>hbarm01@vtc.net

 

I think I'd look for a bad sender, sender connection, or elect plugin somewere in the routing.<br><br>Low oil pressure light can happen if the idle is set too low on an engine, but it shouldn't just pop up for no reason if it was working ok previously. Again, I'd look at all my elect. connections. Go over ALL the plugins/sensors (like on the intake manifold, oil pressure sender/plug etc). Clean them all and use some dielectric grease when you reassemble them.<br>Check the rad after the engine is at operating temp.<br>Shut it down and do your best to feel across and up/down the rad core. Look for some overly hot spots/cool spots.<br>You may be a victum of nothing more than a nackered thermostat, they do go now and then..<br>Are you seeing any more smoke from the exhaust, odd oil pressure readings around town/no load, noticably poor/poorer idle quality, worsening fuel mileage, lower boost numbers etc???<br>This is why using gauges and taking 'baseline readings' is so critical.... later it can help diagnose things...<br><br>I'll keep an eye out on this, in the mean time some others will jump in I'm sure..<br><br>bob.

 

The oil pressure, water temp sender and the thermostat were things that I am going to replace. <br><br>The truck has operated very nicely until the other day. It really was odd. No additional smoke, no oil use, does not use coolant often, and fuel milage is good (20 mpg) and only varies when I am pulling the trailer.<br><br>This is my first Dodge Cummins, so I am not very knowledgable. I just sold my 1986 6.9 L Ford Centurian.<br><br>This Dodge runs circles around my poor Ford.<br><br>Thank you for your assistance.<br><br>Hbarm01@vtc.net

 

Had a smiliar problem with my Dodge when I first got it. Oil pressure would be fine then I would drive for awhile. Oil pressure would drop way low. checked it with a seperate gauge and it was fine. Replaced the sending unit and it has never been low again.<br><br>Carl

 

Thank you for your reply Carl. I am planning to have the coolant and oil presure senders replaced. I flushed the cooling system today and checked the temp with a thermometer and the thermostat started opening at near 160 and was full open about 190.

 

There is a ground wire that, if I remember right, goes from the battery to the body. I just remember having some odd reading and I found a ground wire connected to the body close to the battery that was a little lose. I put a new end on the wire and my readings went back to normal. Might be somthing to look at. I think that our gages are very ground sensitive, if that makes any sense. Hope this helps. Let us know what you come up with. Scott

 

Thanks for the reply ScottB. I will check out that ground wire.