Jeep won't start

[kmerian]

I have a problem that is frustrating me. My 89 jeep cherokee 4.0 won't start. I do hear a click and a hum(which I assume is the solenoid) in "P" and "N" and nothing in any other gear, also my reverse lights do come on in "R" so I don't think it is the NSS, I noticed some corrosion on the batt terminals (especially on the neg terminal) so I cleaned them and it did not help, any ideas?

[JDPascal]

Did you remove the cables from the battery posts when you cleaned them?

Take the negative cable off first - then the positive.

use sand paper on the posts and scrape the inside of the clamp hole with a small knife if you don't have the right battery tool.

if the cables are really bad, cut the top off a pop bottle and mix water and baking soda in it. Let the cable ends soak in there over nite. Dry them and clean the contact surfaces so they are shiney before you put them back on (pos first then neg)

While we're at it- how old is the battery? Good time to charge and check it at a shop somewhere.

JD

[kmerian]

I did clean both terminals with a brass brush, both the connector and the terminal in just the order you mentioned. Battery is only about a year old I had to replace it the same time I did the alternator, I am going to have the battery tested tomorrow. Because I noticed tonight that the interior lights dim slightly when I try to crank it and the seat belt buzzer changes tone also. Gonna feel like a dummy if it is just the battery is bad.

[kmerian]

Had the battery tested, it was almost completely dead, replaced it and put the new one in and same thing. Still just a click and a hum from under the hood, except I noticed a slight hum that also appears to be coming from the rear (fuel pump?) :

Batt cables mabye?

[JDPascal]

Sometimes there is internal corosion in the cable ends...

Tightening the cable clamps on a new battery should get you more than a click when you try to start it.

Check the connections at the other ends of the cables too. (starter and engine block)

Can't recall the starter circuit layout but is there a starter relay somewhere??

JD

[Saudade]

Yep. Happened to my '88. Had badly corroded battery cables.

Does the "hum" from under the hood occur when you turm the key to run or start? Does it go away?

You could also have a bad bendix on your starter. If the hum only occurs in Start position, it could be your started turning.

[kmerian]

The hum only occurs if I hold it in the start position, am going to check the battery cables next

[kmerian]

It's the starter. A mechanic friend of mine came over and tested the cables and the wiring to the relay. all ok. He then took out a hammer and tapped on the starter and it fired right up. Sometimes we forget the simple stuff.