Oil Pressure Problems

[jmburton1993]

After driving my bronco roughly 30 miles at 55mph anytime I come to a stop or press in the clutch my oil pressure gauge goes crazy bouncing all over the place until I tap the gas, I generally lose about a quart of oil in this time so maybe its just due to that but was wondering if this could be a sign of worse things to come. Any ideas?

 

[RonD]

The '89 won't have a "real" oil pressure gauge, on the engine is an oil pressure switch, it is either on or off.
The dash board gauge will either show low(switch off) or about 1/2(switch on).

The pressure that turns on the switch is about 5psi.

You could have a failing switch, or your pressure is dropping below 5psi briefly.
If oil pressure gets too low the valve train will make more noise, if you don't hear that then probably a switch issue.

If the gauge needle is jumping above 1/2 way then probably a gauge issue.

Some think they are seeing real oil pressure because needle can go up slightly with RPM, what they are seeing is the voltage increase from the alternator, it is an electric gauge, and FYI, that can be a sign alternator is going out, voltage shouldn't change that much, that's the point of the voltage regulator.

Also check to make sure the ground strap still has a good connection from head to firewall, that's the main ground for the gauges.
If it is missing or loose the throttle cable can be a ground, i.e. tapping throttle steadies the gauge
It's a long shot, lol.

 

[jmburton1993]

I think it may be the Alt. because I can't even roll up both windows at the same time without it putting a large draw on the voltage, the windows will actually stop rolling up at one point

 

[RonD]

Alternator has 3 "fields" that generate AC power, each field has 2 diodes that change the AC power to DC.
The fields or diodes will fail one at a time, so voltage at idle won't be the standard 13.6volts, with one field gone you would probably read about 13.2 or less volts at 700rpm idle.
Headlights dimming at idle is also a sign a field has failed, no it is not normal, lol, Car makers don't spec alternators that can't maintain voltage at idle

You can run on 2 fields for a long time since voltage is "normal" above idle, so battery is being charged and maintained.
When 2 fields fail it is time to shop around or you will be shopping for a battery at the same time

 

[jmburton1993]

Ok thanks I think I may have one failed field. Any ideas on a good place to pick up an alternator relatively inexpensively? Or should I think about upgrading to a higher amp alternator as I'm thinking of putting in some subwoofers.

 

[RonD]

Wrecking yard

Good read here on alternator changes: http://www.therangerstation.com/tech_library/alternator.shtml

You probably have a 60amp alternator now, 80amp was an option

With a higher output alternator you do need to run bigger wire(s) from alternator B+ post to the Fuse or fusible link, and that(fuse) should be upgraded as well for the higher amps.

 

[jmburton1993]

Would the wire upgrade be required with the 80 amp?

 

[RonD]

The '89 BII looks like it has the Power distribution box in the engine compartment, you should see a 60amp fuse in there #3 and then a 50amp fuse, #7, these are both from the B+ post on the alternator.

A fuse's amp rating is based on the power being "drawn" thru it, so you don't need to change anything when installing a bigger amp alternator, because the stock electrics in the vehicle still only use less than 60 amps.
i.e. if you put in a 200amp alternator the truck's stock system still only needs 50amps at most so no more than 50amps would be coming out of the alternator at full load.

When you add something that increases the power draw is when you need to do some wiring upgrades

 

[4x4junkie]

A heavily-drained battery can easily draw max output from the alternator. For this reason I suggest you upgrade the wiring & fuses to match if you upgrade your alternator (FWIW, I put a 95 amp 3G alt in mine and the factory wiring & fuses was adequate for it. Something like a 130A alt would need some upgrades for sure though).

 

[Wasp]

A heavily-drained battery can easily draw max output from the alternator. For this reason I suggest you upgrade the wiring & fuses to match if you upgrade your alternator (FWIW, I put a 95 amp 3G alt in mine and the factory wiring & fuses was adequate for it. Something like a 130A alt would need some upgrades for sure though).

What type of upgrades are we talking about? Improved ground, lager diameter wires if so to where?

J

 

[RonD]

What type of upgrades are we talking about? Improved ground, lager diameter wires if so to where?

J

Larger wire and fuse(s) for the alternator's B+ connection.

The battery's large ground cable connected to the block will already be large enough for higher output alternator(up to 250amps), but some also add a ground strap to alternator's case and run it to the battery's ground on the block so the metal to metal bracket grounds are not the only connection.

 

[4x4junkie]

^^

That.

On mine it had the two wires (#8 AWG each I think) w/two fuses setup, which I thought were both 60 amp fuses (for 120A), but I'd have to go look at it again to be sure.
If you went to a 130A alt, I'd replace the two-wire setup with a single #4 or so wire & 150A fuse.

 

[jmburton1993]

Would a bad alternator keep it from starting. Today it wouldn't crank on me it'll turn over just not crank. Changed the cap and rotor, ignition coil, and fuel filter and can hear the pump cutting on but still no starting.

 

[RonD]

Would a bad alternator keep it from starting. Today it wouldn't crank on me it'll turn over just not crank. Changed the cap and rotor, ignition coil, and fuel filter and can hear the pump cutting on but still no starting.

If I understand correctly then no, that wouldn't be an alternator issue.
Starter motor is turning engine but it doesn't start up?

If battery has enough of a charge to make engine spin then it would have enough power to supply fuel and spark.

You could try putting some gas or starting fluid in the intake, if engine fires then fuel is the issue, if it doesn't the spark is the issue.

Good worksheet here for TFI ignition: http://www.therangerstation.com/tech_library/TFI_Diagnostic.shtml