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Ground Points

Ecarlcl

NAXJA Forum User
Location
Huntington, NY
Where are all the grounding points located on a '90 with the 4.0 that are related to the injection system? I am going to go on a ground cleaning rampage to see if it solves any of my problems....

Thanks
 
The battery to dip stick bracket, the motor to fire wall (near the MAP sensor) and behind the windshield washer bottle. Are the major ones, there are others hidden throughout the vehicle. The one next to the drivers side courtesy light, has caused me problems in the past.
Some of the grounds pass through the C101 connector (don´t remember if the 90 has one or not) and through the C100 connector, engine compartment side of the fuse box. I often test for voltage (lowest scale) from a ground wire to the chassis (using a tool to prick the wire/then reseal with a dab of gasket sealer), on both sides of a connector, whenever I have a questionable ground. There is sometimes standing voltage, like .4 or .8 volts on one side of the connector but not on the other side, a tip off, a ground or connector isn´t making good contact.
The C-100 connector (and the C 101 if present) are packed with some kind of di-electric grease or sealer, I´ve never felt comfortable, with just hooking them back up again and they are a pain (bordering on impossible) to get clean. So I unplug them with reluctance and usually just jump (solder) a wire around the connector.
 
8Mud covered most of the ground points. The fuel injection harness does ground to the stud for the engine oil dip stick. If you have a leaking valve cover you may have oil on that connection.

Another ground location on my 88 XJ and should be the same on your 90 is on the dirver's fender just in front of the washer bottle. Your head lights ground here.

I recommmend you clean the paint off the chassis then apply ox-gard to the connection. It is a conductive grease. dielectric grease is an insulator, and you are trying to improve the connection, dielectric may make it worse.

Here a web site where he answers a lot about improving your electrical system. He also recommends you run a ground from the NEG post to the chassis. In the stock set up the only ground the battery has is the wire to the block and the only ground the chassis has is the strap from the firewall to the head bolt.

http://www.olypen.com/craigh/charge.htm

Ox-gard write up: http://www.olypen.com/craigh/oxgard.htm


I also added a wire from the alternator case to the chassis, try to keep it less than 24 inches long to gain any benefit.
 
I guess somewhere along the way, a previous owner must a put a ground from the battery to the chassis. Using a replacement neg. bat cable, it is about 5" long.
 
Went through my grounds again yesterday. Was loosing a few, volts somewhere. Found a couple of mili ohms of resitance, through the crimped ends of the grounds. Soldered, all of the ground rings to the wires, made a noticeable difference in idle and changed my shift points, enough to notice.
 
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