My 1989 isuzu trooper will not start it is not battery or alternator i replaced the fuel pump and it started 3 times then after sitting for a few minutes it wouldnt start anymore any ideas?

A few things to check:

1. Did you repressurize the system after replacing the fuel pump? THIS IS THE MOST COMMON ISSUE. You must cycle your ignition switch from OFF to ON several times before first start after depressurizing the system;
2. Has the vehicle been bumped hard, violently jarred, or in an accident? RESET THE INERTIAL SAFETY SWITCH;
3. Are you getting correct fuel pressure? If not, replace the fuel pressure regulator.

Slacken injector pipes and check your getting fuel.The fuel tank is a fault with the trooper, The feed pipes are at the top of the fuel tank, and corrode causing the main feed pipe to draw in air.You have to remove bottom pan under tank and then the three bolts each side of the tank to drop down,taking care not to pull on the outher pipes.im quite sure that's your problem.Any ait that can get sucked into the fuel line.That engine will not start.

electrical fault all day

It actually could be a number of things. I need to ask you more questions to narrow my prognosis down. You mentioned the weather being cold, lately. How cold? Freezing?When was your last tune up and do you eventually get the car started after trying for a while? If you do how does it run?

The alternator keeps the battery charged up. Most likely it's still good it just sounds like you need to replace the belt. Hope this helps.

there is a sending unit for the guage.but if it has been running a few minutes and gets hot you may need to check the thermostat or water pump.check the water pump by taking the radiator cap off.then start the vehicle,look into the radiator and see if any coolant is flowing or circulating.do the cheapest fix first

change the charge light relay (the blue one) located offside front wing fuse box, get off ebay or from millners.co.uk

Oil level!!!

Have a 2.6 with the same issues. only mine will almost always start after disconnecting the fuel line and reconnecting it. I have replaced the fuel pump, inline filter and pressure regulator. My car dog friends are telling me it's the injectors.

have someone kick at the gas tank while you are turning key if it starts it is fuel pump