Normal oil pressure, temp and battery voltage readings?

[ratty]

Hello again. I’m not sure if my gauges are working better with a new ground or if there’s something going on. 

 

When I’m at idle my oil pressure is at 20 and at highway speeds it’s at 60/65. Used to be at 40 at idle and a little higher at highway speeds. 

 

My battery gauge now dips anytime I have blinkers on, ac on headlights etc. from 14 to 10/12. Used to stay at 14. Just replaced the alternator and recharged my battery because it died last week due to the bad alternator. 

 

Temp now rises to 220 and keeps climbing the longer I’m at idle. I shut the truck off once it gets around 240 (maybe a little higher). I have a new radiator and new electric fans. Used to run below 210 and never got above 210 a couple weeks ago with the new radiator and fans. 

 

Thanks for any help. 

 

 

[Eagle]

Factory spec on oil pressure is 13 psi at idle (~ 750 RPM), and 37 to 75 psi above 1600 RPM, at normal operating temperature. All the XJs and MJs I've owned and driven have had warm idle oil presure around 20 to 25 and at 55 to 60 MPH the oil pressure is 50 to 55. The pressures you have now are well within specification, and if you remember them as having been higher I'd say that's VERY unusual.

 

Voltage on mine generally hover around 13.5 -- not that the gauge can be read that accurately, but they're generally "just a tad" below 14. If yours drops to 12 or below when you turn on the lights, I'd say your new alternator is defective.

 

Normal operating temperature on the gauge is always 210 for me, across multiple vehicles.

[ratty]

14 minutes ago, Eagle said:

Factory spec on oil pressure is 13 psi at idle (~ 750 RPM), and 37 to 75 psi above 1600 RPM, at normal operating temperature. All the XJs and MJs I've owned and driven have had warm idle oil presure around 20 to 25 and at 55 to 60 MPH the oil pressure is 50 to 55. The pressures you have now are well within specification, and if you remember them as having been higher I'd say that's VERY unusual.

 

Voltage on mine generally hover around 13.5 -- not that the gauge can be read that accurately, but they're generally "just a tad" below 14. If yours drops to 12 or below when you turn on the lights, I'd say your new alternator is defective.

 

Normal operating temperature on the gauge is always 210 for me, across multiple vehicles.

 

Thanks. I did a multimeter test with the new alternator in. My battery was at 14.something ideling.

 

Good to know about oil pressure. Guess it wasn’t working right before. 

 

Ive read a lot about operating temps. Never went above 210 with the new radiator + fan kit. 

 

Is it normal for voltage to fluxuate so mich while running lights, ac, and other electronics? I noticed while using the blinker, the needle bounces like an 8th of an inch. I got a new powermaster 140amp and my battery is a couple months old. A new north star group 34. 

[Eagle]

30 minutes ago, ratty said:

 

Thanks. I did a multimeter test with the new alternator in. My battery was at 14.something ideling.

 

Good to know about oil pressure. Guess it wasn’t working right before. 

 

Ive read a lot about operating temps. Never went above 210 with the new radiator + fan kit. 

 

Is it normal for voltage to fluxuate so mich while running lights, ac, and other electronics? I noticed while using the blinker, the needle bounces like an 8th of an inch. I got a new powermaster 140amp and my battery is a couple months old. A new north star group 34. 

 

If the engine was idling, then you weren't testing the battery you were testing the alternator at the battery. The battery is 12 volts, not 14. The alternator puts out 13.9 to 14.5 volts when charging the battery.

 

It is not normal for the voltage to dip that much when you turn on headlights or accessories. Do your test with the voltmeter again, and this time have someone turn on the headlights and blower fan while you watch the voltmeter. My guess is that the new alternator isn't putting out the rated amperage. It's producing 14 volts, but not enough amps to keep up with high current draw. (Not that just the headlights would be considered "high" current draw.)

[ratty]

28 minutes ago, Eagle said:

 

If the engine was idling, then you weren't testing the battery you were testing the alternator at the battery. The battery is 12 volts, not 14. The alternator puts out 13.9 to 14.5 volts when charging the battery.

 

It is not normal for the voltage to dip that much when you turn on headlights or accessories. Do your test with the voltmeter again, and this time have someone turn on the headlights and blower fan while you watch the voltmeter. My guess is that the new alternator isn't putting out the rated amperage. It's producing 14 volts, but not enough amps to keep up with high current draw. (Not that just the headlights would be considered "high" current draw.)

 

Good idea. It’s strange though because this is a pretty new occurrence. Never had this problem until I deleted my C101. 

[Eagle]

You also installed a new alternator. They are sometimes bad out of the box.

 

[ratty]

40 minutes ago, Eagle said:

You also installed a new alternator. They are sometimes bad out of the box.

 

 

True. It did come with proof of performance. Idle 105, cruise 128, top end 156. 

[Eagle]

And you're now getting 12 volts or less at the battery. Either the alternator is bad, or your battery cables are toast.

[Gene]

9 minutes ago, Eagle said:

And you're now getting 12 volts or less at the battery. Either the alternator is bad, or your battery cables are toast.

 

This thread has been a little confusing. As I read it, the 12 V or less is at the dash gauge, but 14 V was being read at the battery.

Why don't you turn the headlights on or put another load on the electrical system, until the dash gauge reads 12 V. Then use the multi meter at the battery. If the voltage at the battery is about 12 V, then you are very likely dealing with a bad alternator.

However, I suspect that the battery voltage will still be okay, even when the dash gauge is low. This would indicate that the alternator is fine, the problem is with the dash gauge itself, or more likely with wiring or ground somewhere else in the circuit.

If I misunderstood the situation then ignore all of the above.

Gene

[Eagle]

35 minutes ago, Gene said:

 

This thread has been a little confusing. As I read it, the 12 V or less is at the dash gauge, but 14 V was being read at the battery.

Why don't you turn the headlights on or put another load on the electrical system, until the dash gauge reads 12 V. Then use the multi meter at the battery. If the voltage at the battery is about 12 V, then you are very likely dealing with a bad alternator.

However, I suspect that the battery voltage will still be okay, even when the dash gauge is low. This would indicate that the alternator is fine, the problem is with the dash gauge itself, or more likely with wiring or ground somewhere else in the circuit.

If I misunderstood the situation then ignore all of the above.

Gene

 

I believe you are correct.

 

But the dashboard voltmeter still "dips" when he turns on accessories, headlights, or even turn signals. That shouldn't happen. Your suggestion to retest at the battery while having a helper turn lights and accessories on and off is spot on. That's what I suggested in post #4 ... so of course I think it's spot on. 

[Gene]

16 minutes ago, Eagle said:

 

That's what I suggested in post #4 ... so of course I think it's spot on. 

 

 

[ratty]

2 hours ago, Gene said:

 

This thread has been a little confusing. As I read it, the 12 V or less is at the dash gauge, but 14 V was being read at the battery.

Why don't you turn the headlights on or put another load on the electrical system, until the dash gauge reads 12 V. Then use the multi meter at the battery. If the voltage at the battery is about 12 V, then you are very likely dealing with a bad alternator.

However, I suspect that the battery voltage will still be okay, even when the dash gauge is low. This would indicate that the alternator is fine, the problem is with the dash gauge itself, or more likely with wiring or ground somewhere else in the circuit.

If I misunderstood the situation then ignore all of the above.

Gene

 

2 hours ago, Eagle said:

 

I believe you are correct.

 

But the dashboard voltmeter still "dips" when he turns on accessories, headlights, or even turn signals. That shouldn't happen. Your suggestion to retest at the battery while having a helper turn lights and accessories on and off is spot on. That's what I suggested in post #4 ... so of course I think it's spot on. 

 

I'll try this first thing in the morning. I doubt it has anything to do with the alternator and most likely the cables. My negative cable that connects from the battery to block disconnected from the terminal lug last week. I got a replacement but maybe my positive cables are crap too. They are 2awg battery cables that I got online. Could be poorly made. How do I check the cables? 

Thanks for the help. 

[Gene]

Hi ratty,

 

Couple of ways to do this. These techniques will generalize to anywhere in the vehicle.

 

The first way is to realize that, if all the connections and cables and wires are good, voltage anywhere on the hot side of the circuit should be the same. So check the voltage between the positive battery POST and the negative battery post. Then check the voltage between the positive battery TERMINAL and the negative post. If there is any difference, then there is high resistance where the terminal meets the post. Then, follow the smaller wire a short distance over to the relay center. Check the voltage from the end of the cable to the negative battery post. Again, the reading should be exactly the same.

 

You can accomplish the same thing by putting voltmeter leads across the suspected cable. This would be done with the cable connected. Put one lead on the battery positive post, put the other lead at the cable end. If everything is good, you should be reading zero volts. If there is any resistance in the cable, then you'll read some voltage.

 

The other way to test is to use ohms function on the multi meter. This must be done with at least one end of the cable disconnected. You would just read ohms from one end of the cable to the other. If it's good, it should be zero, or very very close to zero.

 

Hope this helps!

 

Gene

[ratty]

53 minutes ago, Gene said:

Hi ratty,

 

Couple of ways to do this. These techniques will generalize to anywhere in the vehicle.

 

The first way is to realize that, if all the connections and cables and wires are good, voltage anywhere on the hot side of the circuit should be the same. So check the voltage between the positive battery POST and the negative battery post. Then check the voltage between the positive battery TERMINAL and the negative post. If there is any difference, then there is high resistance where the terminal meets the post. Then, follow the smaller wire a short distance over to the relay center. Check the voltage from the end of the cable to the negative battery post. Again, the reading should be exactly the same.

 

You can accomplish the same thing by putting voltmeter leads across the suspected cable. This would be done with the cable connected. Put one lead on the battery positive post, put the other lead at the cable end. If everything is good, you should be reading zero volts. If there is any resistance in the cable, then you'll read some voltage.

 

The other way to test is to use ohms function on the multi meter. This must be done with at least one end of the cable disconnected. You would just read ohms from one end of the cable to the other. If it's good, it should be zero, or very very close to zero.

 

Hope this helps!

 

Gene

 

Thank you! 

[cruiser54]

Great info here for you ratty. take a look at my Tip 1.

 

The Renix era XJs and MJs were built with an under-engineered grounding system for the engine/transmission electronics. One problem in particular involves the multiple ground connection at the engine dipstick tube stud. A poor ground here can cause a multitude of driveabililty issues, wasted time, failed emission tests, and wasted money replacing components unnecessarily.

All the components listed below ground at the dipstick tube stud:

Distributor Sync Sensor, TCU main ground, TCU “Shift Point Logic”, Ignition Control Module, Fuel Injectors, ECU main ground (which other engine sensors ground through, including the Oxygen sensor, Knock Sensor, Cruise Control and Transmission Sync signal. All extremely important stuff.

The factory was aware of the issues with this ground point and addressed it by suggesting the following:

• Remove the nut holding the wire terminals to the stud. Verify that the stud is indeed tightened securely into the block. If the whole stud turns, you can use a 7/32″ six point socket or wrench to hold it so the nut can be removed. Worst case, cut the wires and remove the stud and nut. Install new terminal eyelets on the wires when going back together.  Scrape any and all paint from the stud’s mounting surface where the wires will attach. Surfaces must be clean, shiny and free of any oil, grease, or paint.
• Inspect the wire terminals. Check to see that none of the terminals are crimped over wire insulation instead of bare wire. Be sure the crimps are tight. It wouldn’t hurt to re-crimp them just as a matter of course. Sand and polish the wire terminals until clean and shiny on both sides. Apply a liberal coating of OxGard, which is available at Lowe’s and other stores. Reinstall all the wires to the stud and tighten the nut down securely.

While you’re in that general area, locate the battery negative cable which is fastened to the engine block just forward of the dipstick stud. Remove the bolt, scrape the block to bare metal, clean and polish the cable terminal, apply OxGard, and reattach securely.

Another area where the grounding system on Renix era Jeeps was lacking is the engine to chassis ground. There is a braided cable from the back of the cylinder head that also attaches to the driver’s side of the firewall. This cable is undersized for its intended use and subject to corrosion and poor connections at each end.

• Remove the cable end from the firewall using a 15mm wrench or socket. Scrape the paint off down to bare metal and clean the wire terminal. Apply OxGard. Reattach securely.
• Remove the other end of the cable from the rear of the head using a 3’4″ socket. Clean all the oil, paint and crud from the stud. Clean the wire terminal of the cable and reattach securely with a liberal coating of OxGard.

2 STRONG suggestions regarding the ground system:

I prefer to add a #4 gauge cable from the firewall to a bolt on the rear of the intake manifold, either to a heat shield bolt or fuel rail bolt. A cable about 18″ long with a 3/8″ lug on each end works great and you can get one at any parts store already made up. NAPA has them as part number 781116.

A further improvement to the grounding system can be made using a #4 cable, about 10″ long with 3/8″ terminals at each end. Attach one end of this cable to the negative battery bolt and the other end under the closest 10mm headed bolt on the radiator support just forward of the battery. NAPA part number 781115.

For those of us with Comanches, it’s very important to remove the driver’s side tail lamp assembly to access the ground for the fuel pump. Remove the screw holding the black ground wire. Scrape the paint from the body and corrosion from the wire terminal.  Add a 10 gauge wire, with an eyelet on each end, from that grounding point to a bolt on the frame. Better yet, on both Cherokees and Comanches, complete Tip 29 for the best fuel pump grounding. Be sure to scrape all mounting points to bare metal and apply OxGard also.

If you want to upgrade your ground and battery cables with custom made parts, contact Neal at www.meanlemons.com 

Revised 02/04/2017

 

[ratty]

On 8/19/2018 at 8:21 PM, cruiser54 said:

Great info here for you ratty. take a look at my Tip 1.

 

The Renix era XJs and MJs were built with an under-engineered grounding system for the engine/transmission electronics. One problem in particular involves the multiple ground connection at the engine dipstick tube stud. A poor ground here can cause a multitude of driveabililty issues, wasted time, failed emission tests, and wasted money replacing components unnecessarily.

All the components listed below ground at the dipstick tube stud:

Distributor Sync Sensor, TCU main ground, TCU “Shift Point Logic”, Ignition Control Module, Fuel Injectors, ECU main ground (which other engine sensors ground through, including the Oxygen sensor, Knock Sensor, Cruise Control and Transmission Sync signal. All extremely important stuff.

The factory was aware of the issues with this ground point and addressed it by suggesting the following:

• Remove the nut holding the wire terminals to the stud. Verify that the stud is indeed tightened securely into the block. If the whole stud turns, you can use a 7/32″ six point socket or wrench to hold it so the nut can be removed. Worst case, cut the wires and remove the stud and nut. Install new terminal eyelets on the wires when going back together.  Scrape any and all paint from the stud’s mounting surface where the wires will attach. Surfaces must be clean, shiny and free of any oil, grease, or paint.
• Inspect the wire terminals. Check to see that none of the terminals are crimped over wire insulation instead of bare wire. Be sure the crimps are tight. It wouldn’t hurt to re-crimp them just as a matter of course. Sand and polish the wire terminals until clean and shiny on both sides. Apply a liberal coating of OxGard, which is available at Lowe’s and other stores. Reinstall all the wires to the stud and tighten the nut down securely.

While you’re in that general area, locate the battery negative cable which is fastened to the engine block just forward of the dipstick stud. Remove the bolt, scrape the block to bare metal, clean and polish the cable terminal, apply OxGard, and reattach securely.

Another area where the grounding system on Renix era Jeeps was lacking is the engine to chassis ground. There is a braided cable from the back of the cylinder head that also attaches to the driver’s side of the firewall. This cable is undersized for its intended use and subject to corrosion and poor connections at each end.

• Remove the cable end from the firewall using a 15mm wrench or socket. Scrape the paint off down to bare metal and clean the wire terminal. Apply OxGard. Reattach securely.
• Remove the other end of the cable from the rear of the head using a 3’4″ socket. Clean all the oil, paint and crud from the stud. Clean the wire terminal of the cable and reattach securely with a liberal coating of OxGard.

2 STRONG suggestions regarding the ground system:

I prefer to add a #4 gauge cable from the firewall to a bolt on the rear of the intake manifold, either to a heat shield bolt or fuel rail bolt. A cable about 18″ long with a 3/8″ lug on each end works great and you can get one at any parts store already made up. NAPA has them as part number 781116.

A further improvement to the grounding system can be made using a #4 cable, about 10″ long with 3/8″ terminals at each end. Attach one end of this cable to the negative battery bolt and the other end under the closest 10mm headed bolt on the radiator support just forward of the battery. NAPA part number 781115.

For those of us with Comanches, it’s very important to remove the driver’s side tail lamp assembly to access the ground for the fuel pump. Remove the screw holding the black ground wire. Scrape the paint from the body and corrosion from the wire terminal.  Add a 10 gauge wire, with an eyelet on each end, from that grounding point to a bolt on the frame. Better yet, on both Cherokees and Comanches, complete Tip 29 for the best fuel pump grounding. Be sure to scrape all mounting points to bare metal and apply OxGard also.

If you want to upgrade your ground and battery cables with custom made parts, contact Neal at www.meanlemons.com 

Revised 02/04/2017

 

 

Thanks. I have gotten a 2 gauge cable set and added a ground to the tail light (due to looking at your website). I’ve replaced the negative wire a couple of times, but haven’t sanded away any paint. Hopefully it’s as simple as that.. I can’t figure it out. 

 

Theres not s specific combo to reattach it all (nut-grounds-dipstick/nut-dipstick-grounds) is there? Sorry if that’s a dumb question. 

 

Edit: Just messed with the configuration. Doesn't matter. 

[Ωhm]

Check ground G102 located under the dash. This ground is used by both the voltmeter and oil pressure gauge. Yes its tied to G103 (dipstick) through Spice G, but still needs to be checked for proper grounding.

[ratty]

Ok

[ratty]

1 hour ago, Ωhm said:

Check ground G102 located under the dash. This ground is used by both the voltmeter and oil pressure gauge. Yes its tied to G103 (dipstick) through Spice G, but still needs to be checked for proper grounding.

 

Is that the ground by the hood release cable? I did add another 10awg wire from that ground to another point. 

[Ωhm]

Not sure how close it is to the hood release cable, but it pigtails out of the harness with the wiper switch connector and the headlamp delay module (if equipped) connector.

[ratty]

Also just noticed my music sort of skips when I turn the blinkers on.

[cruiser54]

19 hours ago, Ωhm said:

Not sure how close it is to the hood release cable, but it pigtails out of the harness with the wiper switch connector and the headlamp delay module (if equipped) connector.

 

 

The ground point for the complete instrument cluster on your XJ or MJ is located up under the driver’s side dash. If you lay on your back and look up under there with a flashlight, without wearing a hat, you will see a black wire attached to a shiny piece of metal almost directly above the hood release knob. The screw will have either a ¼” or 5/16″ head on it.

This ground point is responsible for handling the ground circuit for the following items: Dome lamps, seat belt and key warnings, transmission power/comfort switch, wiper switch, headlamp switch and delay module, fog lamp switch, cargo lamp switch, all instrument panel grounds and illumination, power windows and door locks, cruise control dump valve, and a few more things.

The problem is that where the ground point is located does not share good contact with the chassis where the ground should be. The solution is simple:

• Make up a jumper wire with #10 gauge wire about 10″ long. On one end, crimp on a ¼” round wire terminal. On the other end, crimp on a 3/8″ round wire terminal.
•  
• Remove the screw from the existing ground wire and attach the small terminal of your jumper so that the original wire and your new jumper share the same attaching point, one over the other.
•  
• Look above the driver’s side plastic kick panel just forward of the top of the hood release knob. You will see an 8mm stud there. Attach the large terminal end there with a washer and nut over it tightened securely. Use a coating of OxGard at all ground contact surfaces when attaching the screw and nut.

**Special note for Comanche owners: Make your jumper wire 12″ long and attach it on the driver’s side kick panel close to the fusebox on the 8mm stud.**

 

 

[HOrnbrod]

1 hour ago, cruiser54 said:

If you lay on your back and look up under there with a flashlight, without wearing a hat,

 

^^ Very important info.  

[Ωhm]

Even with your cap on, G102 (CAB & IP ground) finds G103 (Engine Compartment ground) through Splice G and then through C100_G4 to G103. Beefing up G102 is a good thing, but G102 still needs to find G103.

[ratty]

2 hours ago, cruiser54 said:

 

 

The ground point for the complete instrument cluster on your XJ or MJ is located up under the driver’s side dash. If you lay on your back and look up under there with a flashlight, without wearing a hat, you will see a black wire attached to a shiny piece of metal almost directly above the hood release knob. The screw will have either a ¼” or 5/16″ head on it.

This ground point is responsible for handling the ground circuit for the following items: Dome lamps, seat belt and key warnings, transmission power/comfort switch, wiper switch, headlamp switch and delay module, fog lamp switch, cargo lamp switch, all instrument panel grounds and illumination, power windows and door locks, cruise control dump valve, and a few more things.

The problem is that where the ground point is located does not share good contact with the chassis where the ground should be. The solution is simple:

• Make up a jumper wire with #10 gauge wire about 10″ long. On one end, crimp on a ¼” round wire terminal. On the other end, crimp on a 3/8″ round wire terminal.
•  
• Remove the screw from the existing ground wire and attach the small terminal of your jumper so that the original wire and your new jumper share the same attaching point, one over the other.
•  
• Look above the driver’s side plastic kick panel just forward of the top of the hood release knob. You will see an 8mm stud there. Attach the large terminal end there with a washer and nut over it tightened securely. Use a coating of OxGard at all ground contact surfaces when attaching the screw and nut.

**Special note for Comanche owners: Make your jumper wire 12″ long and attach it on the driver’s side kick panel close to the fusebox on the 8mm stud.**

 

 

 

Perfect. I did this last week. Thanks!