Had fuel pump changed on 2001 Jaguar S-type...no problems. Then I changed starter relay coil fuse and now car will not start stating engine fail safe. please help me.

2001 Nissan Pathfinder R50 3.3Liter,3.3 L , NO CRANK! Auto trans or manual trans.? I will guess AUTOmatic trans A/T
all fuses good,. fuse e=40amp and fuse 18,10amps?(MUST)
(batteries can be intermittent)
Is car in USA> it was sold here too but is yours?
does this car have IMMO/ALARM, or remote START kit on it?
when failing does it fails jumper cable jump started off a running 2nd car or truck?
does it fail to crank in NEUTRAL , PRNDL , foot brake shift to N and crank? hummmmmmmm1
1 do held lamps work key one and keyoff.
2: is IMMO lamp glowing wrong/ per users guide.(lost?)
3: alarm active>(failing)
4: remote start kit put in and fails. (I disable all I SEE)
got NVIS (Nissan Vehicle Immobilizer System - Nats)??
NATs tells ECU to not allow engine to run, NO NATS does not stop cranks this car.
the 2 fuses above power the P;/N RELAY (starter relay)
if in P or N the relay closes at key start wire to relay coil action
the 40 amp fuse passes through relay and starter spins and cranks the engine, over.




this is it, if you see wire hacks here, for remote start.
not good that. as you can see IMMO has no bock here.
IMMo cuts spark/fuel

try this link might help you out.
Problem 5 Engine Cranks But won Start
or this one.
Troubleshooting Car That Won Start dummies

Check fuses #1 #2 #9 #10 #11 #12 in the battery junction box under the hood to make sure they are good

Check fuse #8 in the central fuse box inside the car

if starter turns and engine will not ignite remember it is fuel, electrical or mechanical check the fuel pump relay then fuel pumps the relays do fail after 20 years the pumps rarly fail.
Did you change the fuel filter?
if starter does not turrn start checking
Fuses
Relays
Starter
Switch
electrical gremlins are challenging but if you are systematic and have a wiring digrahm you will find the problem

Check the power feed for the pump at the fuel pump relay. Pull the relay out, and with a test light clipped to a ground, probe all the terminals that the relay plugs in to. One terminal should be hot at all times. If no terminal has power, either a fusible link off the battery has failed or a maxi fuse has blown-check a wiring diagram to see how the relay gets power to it.
If the relay has power to it, check the other relay terminals with the engine cranking. When cranking the engine, two terminals should have power-the fuel pump feed, and the signal from computer to activate the relay. If both signals are present, check the pump wire from relay to tank, check the fuel pump ground, and check if the coil side of relay has a good ground-signal from computer goes to coil input side, the coil output terminal should go to ground.
Good luck. Post back with what you find.

check the fuses and relays. fuel pump or ecm fuse may be blown

It could be as simple as a bad fuel pump or clogged fuel filter to something more in depth like a broken timing chain or bad sensors. Check the Fuses first to make sure they are all good then check the relays under the hood. If the fuses are good and the relays then spray some starting fluid into the air intake, If it fires then the problem is a fuel pump or filter if it doesn't you are going to have to test the Crank and cam position sensors to find the bad on and the coil pack.

You are not providing a lot of clues here, but I presume that the reason that you are confident that it is not the starter is because the engine cranks normally when you turn the key, but fails to start, right?
If the engine cranks, and it sound normal while it is cranking, then you lack: - Spark, or - Fuel
A 2000 will occasionally suffer a failure of one or two coils, but almost never loose spark to all cylinders unless you wash the engine and get water in where it should not be. Did you wash the engine with a high pressure sprayer? If not, my money is on fuel.
When you turn the key to the On position, do you hear the fuel pump spin up for a second and then shut off? If not, then either your fuel pump has failed, or it is not getting electricity due to a failed relay or a burned fuse. Look at the fuse diagram in your fuse box, find the fuel pump fuse, and see if it looks OK.
If you hear the initial spin-up but get no subsequent fuel pump operation, it is possible to have problems with the safety circuit in the ignition computer that controls the fuel pump relay, but this is rare. My bet is on the fuse or the fuel pump. Fuel pumps failures on BMWs are not uncommon. My wife lost a fuel pump on her '04 330 with only 80k miles.
If the fuel pump has failed, I suggest that you not replace it yourself. It is not a difficult job, but it can be a dangerous job. Best to leave it to a pro.

RESET THE COMPUTER, IT WORKED ON MY XJ. SAME PROBLEM I HAD.

Hope you got a good deal on that oil change. do you believe in coincidence. I can't imagine how an oil change could do anything to stop the engine from starting. So you have to rule out things like starter and fuel pump. to check the fuel pump go to a parts store and buy a can of starter fluid. Remove the top pf the air cleaner box. Have someone spray starter fluid into the opening going to the engine while you are trying to start the motor. If it fires up the pump is bad if not go on to the starter. For the starter locate the relay under the hood (in a fuse box) labeled for the starter. Remove it. Then run a wire from the positive terminal of the battery (careful not to ground to car) and touch where the relay plugged in. One of the points should kick the starter over. If none of them do i would suspect the starter. if all is ok the next possible suspect is the computer. You will need a dealer for this one but some computers have extended warranties because of problems so ask the dealer about it. I just had one replaced for a customer last summer on a 2001 Chrysler T&C and it was covered under warranty. Whole visit was around $200 If this helps please reply and good luck