I have a 1994 Nissan pickup 2400 2.4L manual trans I can push start but wont start by key replaced starter and starter relay get clicking sound out of starter relay but will not turn over

Manual Transmission, or Auto? If Manual, when it doesn't start, does it click once when you turn the key, but nothing else happens? If so, replace the Clutch Relay - under the hood on the passenger side fender. I've done this a few times on my Nissan. Cheap part ($30), but incredibly irritating when it starts acting up. If you hear repeated clicking, it's either the starter or solenoid, so a starter replacement would be in order.

Clean the battery post's and terminals and hot wires to starter and the ends of the ground wires. Try to jump start it if it starts it may be your battery or your starter is going bad.

Do you have power at the starter when the key is in the start position ?
Have you checked the clutch safety switch ?

It could be that relay, or a dead spot on the starter.
Can you jumper the starter and make it crank ?

if your battery good relay and starter good would check all connections

if the starter is clicking, the problem is most likely the starter. try tapping on the starter with a hammer while someone is making it click click click with the key. it it starts working, it probably wont last very long. you might as well replace it, or carry a hammer and someone to click the key.
MAKE SURE THEY DONT RUN YOU OVER IF IT STARTS. you know.. make sure it is in neutral, brakes on , tires blocked, etc.
If there is an oil leak, and the starter is very greasy, that is probably why it quit working. so make sure you address the leak, or it will quit again.

Sounds like you starter sylanoid is bad. try replacing it i think on that model you have to replace entire starter . I would have it tested to see if it is bad

check for power to the starter at the starter's connectors while you have someone turn the key. If there is power, change the starter. If not check your ignition switch, (manual trans)clutch pedal switch, and starter fuses/relays. Hopefully this helps

Sounds like a bad starter or starter solenoid.

its mounted on the right fender well