2000 GMC Jimmy will not start

in a nut shell it may be a good idea to join a auto club like bcaa or aaa they give you a yearly price at 125.00 a year gives you towing up to so many km then pro rated at low rate for extra kms ;they give you roadside assistanc e from flat tire change to jump start and lock keys in car and a whole lot more perks from travel discounts ,ect to house insurance deals,BASIC TEST KEY IN IGNITION DASH LIGHTS UP ENGINE TURN TO ACCESORYTURN TO START /STAR6TER MOTOR SHOULD WORK , CLICK BAD STARTER OR POOR CONNECTION AT BATTERY OR STARTER WIRE NOTHING THEN IF YOU HAVE BRIGHT HEAD LIGHTS AND ALOUD HORN THEN BATTERY IS GOOD , NOW IF YOU CAN START CAR WITH NEW BATTERY AND TURN ENGINE ON WITH ALL ELECTIRCS ON LETS SAY HEAD LIGHTS AND HEATER FAN THEN OFF AFTER 2O MINUTES AND IT WILL NOT START AGAIN FOR A FEW HOURS LATER MORE THAN LIKELY HAVE ALTERNATOR NOT WORKING

When the car started intermittently, did it run fine once started? There is a possibility since it is a fairly large engine that the battery is not powerful enough anymore to start the engine. If you are using a smaller car to jump-start it, the discharge on that battery could be too little. I can't find any information on the alarm system, but on my car there is a relay that triggers it. Check your fuse box for a relay that you can pull out, as cutting wires is never recommended, especially in these newer cars with their monstrous wiring harnesses. 3 things an engine need to run: spark, compression, fuel. Like stated above, make sure the fuel pump is still working, as there is a chance that is defective, or wasn't installed correctly. Who did the previous repairs on your car? If your mechanic is not trustworthy, they could have easily done something wrong in the installation of the fuel pump. I have a nasty horror story from midas that ended up in replacing the transmission linage cable they broke when installing the muffler, I had to fix the linkage twice once i got it back, once on each end. I took the money to invest in the factory service manual for my car, because the haynes manual did not cover throughly enough. It was 250 dollars, but i got it for 5 dollars on a CD off ebay. I have posted the only manual could find for your car, but it should include wiring diagrams that will help you if it is indeed an electrical problem. Keep us posted. I'm sorry to hear your car troubles with such a new car.
http://www2.partstrain.com/store/?Ntt=Repair%20Manual&N=1623%2010516+4294965606

don't just start to cut wires. slow charge the battery first. check any and all fuses. if you don't have one, you'll need to get a spark tester. you'll need two people for this test... put the spark tester between the number 1 (one) plug and the wire. turn the key so that the motor cranks and observe the spark tester, if there is no spark it is one of two things. the ignition module and/or the computer. hope this helps.

You'll have to check the charging system, fuel system, or perhaps maybe a relay switch that may control the fuel because those including the fuel filter usually go out before a fuel pump is replaced. And also check the alternator and battery. Hope you fix it.