Oil Pump replacement

Son just bought a 2003 Dodge 1500 Pickup (4.7l engine)
It has chronic low oil pressure when idling -we're thijnking "new oil
pump"
But there are two issues that concern me about that:
1) Why would a 4 year old vehicle need a new oil pump already?
2) Is there any way to replace thispump without pulling the engine?
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Frank Rowe wrote:

how low is "low?"
nate
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Frank Rowe wrote:

How low AND have you actually tested it with a real gauge?

Poorly maintained engine is the most likely reason. If the engine wasn't taken care of what about the rest of the vehicle.

Pull the engine mounts, then jack the engine up enough to pull the pan.
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Steve W.

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As has been said, first test the pressure with a pressure guage at the oil sending unit. The in dash guages are usually not very accurate.
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On Thu, 06 Sep 2007 19:15:23 -0400, Frank Rowe

In the great majority of cases the oil pump is not to blame. The problem is more likely to be worn rod/main bearings -- perhaps accompanied by crankshaft, rod end or main saddle wear, depending on how far the problem has progressed.

Was it ever allowed to run low on oil? 3 minutes at highway speed with no oil pressure, perhaps due to failure to check the dipstick, will cause more damage to the bottom end of a motor than 200k miles with clean oil at the proper level.
Don www.donsautomotive.com

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_I_ haven't driven the truck, but my son says the gauge on the dash reads mid-range when running at speed, but drops to near zero at idle - and he gets a rattle from the engine at the same time. So I believe it truly is low on pressure. As to the cause - we're hoping it's the pump. We're replacing it this weekend, and if the problem persists, we'll look at new bearings, etc next.
I don't know about the other questions, such as whether it's been run low on oil, or otherwise abused. He just bought it, and I don't know the history.
Now for the fun part: we started on it tonight; turns out dropping the oil pan is easy - there's enough clearance between it and the cross-beam that it comes right off (after removing a support bracket & a crossmember of dubious function). Here's the fun part - on this particular engine, the oil pump is actually wrapped around the crankshaft at teh front of the engine. So we have to strip the whole front of the engine and _remove_the_timing_set_.Since this is an overhead cam V-8, that entails pulling both valve covers and removal of THREE chains and sprockets to match.
I'd like to have a word with the bozos that designed this one....
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Before you go to all that work to remove a pump that might be good, drop a few bearing caps and inspect the bearings.
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Frank Rowe wrote:

Its NOT the pump in all probability.... as you've probably already discovered since it is now Monday morning :-/
That design is very common now because it eliminates any gear-drive for the oil pump, and actually makes the oil pump considerably more reliable overall. My wife has 250,000 miles on an engine with a direct-drive oil pump just like you describe (also a Chrysler, just though a belt-timed v6 instead of a v8). Never a lick of trouble with low oil pressure at all.
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Frank Rowe wrote:

Its most likely the oil pressure SENDING unit giving a false low reading. Before you tear into a 4-year old engine, put a trusted MECHANICAL gauge on it and verify that it really has low pressure.
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