Electric Gremlin!!??

1990 XJ 4d auto:

A few years ago I notice that the voltmeter gauge and the oil pressure gauge once the engine warmed up weren't accurcate. The Voltmeter would be about 2 volts low and the oil pressure gauge about 10 psi low.

All other gauges were uneffected and accurcate.

On an off-road trip last week while driving on the freeway all of a sudden all gauges except the speedmeter, which is mechanical, went dead. The water temp gauge went off the scale on the hot side, the fuel gauge went off the scale full, the tack just quit, the voltmeter went to "0" and the oil pressure to "0".

Then for brief momment they came alive again.

Once they went dead the second time from that point on all day they were dead.

I completed the trip of about 150 miles and the next morning when I started her up it was as if nothing had happened, all gauges back to normal. (except with the still lower volt and oil gauge as before)

I have to believe that it is somehow related to the heat or resistance of a warmer engine and engine compartmemt. However, before I start down any goose chase I am wondering if anyone out there has suffered a similar condition.

Thanks in advance for any help.

Fred
Explorer 1

Well, as always, clean all the cables, both ends. Renew your grounds, dipstick tube--ICM, ECU, o2 sensors and others. If you still have the POS braided cable from the rear of the head to the firewall replace it with a 4 or 2 ga cable. Clean down to bare metal, treat with anti-corrosive agent, make the connections tight. Good idea to add an extra ground cable from the negative battery terminal to the fenderwell. On your 90 you need to inspect the clutch/brake MC to see if they are leaking fluid down the inside of the firewall, that fluid will get behind the fuse block and corrode things fairly quickly.

Pull the fuse block off the firewall, inspect, clean, repair the contacts.

Somewhere during the above you will probably have corrected the "dead" gauge issue.

You say the oil pressure gauge reads low, that means you put a mechanical pressure gauge on and tested the pressure--correct? If so, you could try a new pressure sending unit.

As for the volt gauge. That is a little problematic as the XJ volt gauge reads at the end of the load and not directly from the battery. Here is a great article on upgrading the XJ wiring: http://www.olypen.com/craigh/charge.htm

Good luck.

Happy ending!

Never over look the obvious! :eyes:

Turns out it was a cracked fuse, not blown but cracked enough to cause all the issues.

That was an easy one, (for once)

Thanks for the other wise good advise,

Fred
Explorer 1

Take Joe's advice and refresh your grounds and cable connections on your Renix Jeep and chock it up to "preventative maintenance." Glad you found the fuse.

I like that electrical upgrade page.

bigalpha said:

I like that electrical upgrade page.

Click to expand...

That is a great article. The only thing I would change is to use the ANL type fuses instead of the bar type.

ANL fuses and holder: http://www.vteworld.com/content/electromech/fuse/html/anl/anlfuse.php

That was a good tip from 5-90.