How to diagnose bad oil pump?

[Electricat]

Ever since I bought my abused and neglected 114K '95 ATX SHO, it has had oil pressure issues (I have driven it only about 1k). Although it is a little "early", and there is no noticable bottom end knock, I am going to jump on the rod bearing train, and change them out before I drive it more. Hopefully, this will cure the problem....but what if it doesn't?? shrug

I do have an extra (used) oil pump here that I picked up on eBay, but it looks like a major job to change it. And, I know that the SHO oil pump doesn't often fail....but the thought is still in my mind.

Is there some way to check the oil pump while I have the pan off??

I don't want to go through the whole rod bearing thing, to then have to tear it apart again to do the pump...I know it could use a whole front 60k, but time/money/weather aren't cooperating with tearing into that right now. I just want to know if there is a way to check the pump out. Thanks!

<small>[ January 12, 2004, 10:32 PM: Message edited by: Electricat ]</small>

 

[rangerj]

Electricat,

On the right side of the engine block, that is the side back by the firewall, there is the oil "sending unit". An oil pressure gauge is screwed into the place where the sending unit is and the oil pressure is read at various RPM levels.

If the pressures are less than specified the oil pump is usually the culpret.

Given your plans to do the rod bearings, why not test the oil pressure, and therefor the pump, before you open up the bottom end? If the pump is weak you can change it while you are in there.
rangerj

 

[Electricat]

rangerj, I have a mechanical oil pressure gauge hooked in along with the stock pressure sender, using a T fitting, and it shows low readings. I definately have genuine oil pressure problems...

I wish the SHO oil pump was as simple to change as on most cars, if it was I would definatley do it....but it requires disassembling basically the whole front end of the motor.

 

[Rockledge]

Since you are sure about the low oil pressure, then I would go ahead and change out the rod bearings and see what happens. You will be able to examine the bearings and journals for evidence of anything that might be contributing to the condition. The parts are certainly cheap enough.

If you later decide that you need to replace the oil pump, then you can do that while you are also doing a Front 60K, since you will have to remove the timing belt, crank pulley and sprocket to get to the pump, anyway.

This way, if you have to replace the pump, then the only work you will have to actually "repeat" is dropping the pan and removing the oil pump pickup tube. Not a huge undertaking, especially after having just done it recently.

 

[masho95]

Electricat:
rangerj, I have a mechanical oil pressure gauge hooked in along with the stock pressure sender, using a T fitting, and it shows low readings. I definately have genuine oil pressure problems...

So how exactly is the mechanical oil pressure gauge hooked up? Is it hooked up after the stock pressure sender gauge? If so look back at the suggestions of your pressure post. You could still have a bad sending unit.

Like this? OPSU---T----MG
                         |
                       OPL

OPSU=Oil pressure sending unit
MG=Mechanical gauge
OPL=Oil pressure light

<small>[ January 13, 2004, 12:07 PM: Message edited by: masho95 ]</small>

 

[Electricat]

Rockledge, I think you are right aabout the best way to go about trying to solve this problem. Hopefully the rod bearings do the trick...

Masho95, here is how I have the gauge setup, both are getting their own oil supply:

MG---T--OPLS
........B......

MG = Mechanical gauge
OPLS = Stock oil pressure light sending unit
B = Engine block

I did also try it out with the gauge screwed directly into the block, with the same pressure results...

<small>[ January 13, 2004, 10:37 PM: Message edited by: Electricat ]</small>

 

[NotSoSlowSHO]

Id do the front 60k AND the rod bearings now. Simply because you have to pull the oil pan to change the oil pump.

Be sure to order a new pump to block gasket. They like to leak

 

[Best Sho]

Oil Pressure

I have a 93 Sho 124k
What should the oil pressure read?

Thanks

 

[Mike Kopstain]

I wouldn't nessesarily connect low oil pressure readings to a bad oil pump. The oil pump on this motor is very simple with few moving parts. More likely would be the rod bearrings. As they wear, clearance is increased resulting in lower pressure.

Even more likely would be someone looking for the higher oil pressures typically associated with older motors. The SHO's lubrication system is low pressure, high volume, so a 10psi reading at hot idle, which would have most 454 owners in a panic, is perfectly normal on the SHO. Look for that reading to go up 10lbs for every 1000rpm.