'89 Waggy Oil Pressure?

Area for General FSJ related chat.
Post Reply

Topic author
MReno
Posts: 158
Joined: Sun Mar 03, 2019 6:39 pm

'89 Waggy Oil Pressure?

Post by MReno »

All, I fully serviced my oil system by draining, removing, and cleaning the oil pan, rebuilding oil pump (and added a mid plate), replaced the oil switch and oil pressure sender, replaced oil filter and installed fresh oil.

When the engine is running the oil pressure gauge reads @75psi if I recall, and when applying some gas, the gauge increases to about 90 psi. Does this seem correct? I thought I read 40psi is appropriate for idle, and 60psi when accelerating? Any thoughts on this?
1989 Jeep Grand Wagoneer
Newbee to owing an old classic that needs some work, but she runs!
User avatar

tgreese
Posts: 7118
Joined: Fri Jun 08, 2012 6:31 am
Location: Medford MA USA

Re: '89 Waggy Oil Pressure?

Post by tgreese »

Seems a bit high. 10 psi for every 1000 RPM is the usual rule-of-thumb. Even 40 down the highway would not be bad. If this is with cold oil, pressure will drop as you go to full operating temperature.

I would check the readings with a separate mechanical gauge. You can get a decent gauge and tubing at Summit Racing for about $20 https://www.summitracing.com/parts/sum-g2934/overview/ Keep the plastic tubing away from the exhaust manifold! If the mechanical gauge reads considerably lower, I would next test the in-dash gauge with resistors as described in the TSM. If that reads as expected, your new sender has the wrong range for the gauge.
Tim Reese
Maine beekeeper's truck: '77 J10 LWB, 258/T15/D20/3.54 bone stock, low options (delete radio), PS/PDB, hubcaps.
Browless and proud: '82 J20 360/T18/NP208/3.73, Destination A/Ts, 7600 GVWR
Copper Polly: '75 CJ-6, 304/T15, PS, BFG KM2s, soft top
GTI without the badges: '95 VW Golf Sport 2000cc 2D
Dual Everything: '15 Chryco Jeep Cherokee KL Trailhawk, ECO Green
Blockchain the vote.

Topic author
MReno
Posts: 158
Joined: Sun Mar 03, 2019 6:39 pm

Re: '89 Waggy Oil Pressure?

Post by MReno »

In checking the pressure again last night, upon start up it was 55psi, when I accelerated a bit it went up to about 65psi, and I see no leaks, so I believe I am good to go.
1989 Jeep Grand Wagoneer
Newbee to owing an old classic that needs some work, but she runs!

candymancan
Posts: 3652
Joined: Tue Mar 22, 2016 11:32 pm

Re: '89 Waggy Oil Pressure?

Post by candymancan »

Seems really high, mine has been reporting this higher latetly too, i suspect the switch is bad, or i have some electrical interferance or hell the gauge is bad or maybe it really is reading that high.. I need to check with a mechanical gauge

When it was working normally though my idle in gear (650 rpm) HOT like really hot driving for 30 minutes or more oil pressure was 20psi, IDLE HOT in park (900-1000rpm) is 35-40psi. When driving at any RPM any speed my oil pressure is 55-60.

I believe this is the normal oil pressure for AMC 360's i spoke to a older dude who worked at AMC dealerships and he told me 20psi idle in gear was factory oil pressure for the 360's, you should check the oil pressure when the engine is really hot.. not when its cold or luke warm. Drive it around for 30 minutes then note the oil pressure at idle in gear, idle in park, and when driving
1998 Jeep Grand Cherokee 5.9L Limited 219k
1998 Jeep Grand Cherokee 4.0 I6 laredo 430k
1990 Jeep Grand Wagoneer 155k
1976 Jeep J10.. 85k(repaired)

Topic author
MReno
Posts: 158
Joined: Sun Mar 03, 2019 6:39 pm

Re: '89 Waggy Oil Pressure?

Post by MReno »

Thanks Candymancan. I'll recheck oil psi once I her tagged and street legal.
1989 Jeep Grand Wagoneer
Newbee to owing an old classic that needs some work, but she runs!
Post Reply