My 88" 2500 Chevy 3/4 ton will only run for about 30 minutes then cuts off, if I let it sit it will start right up and then do the same thing. is it the fuel pump relay or the pump its self

Overheating fuel pump or ignition module?

serial number/keygen for registry reviver

Have you checked base fuel pressure with a gauge yet ?
Sounds like the pump is weak.

You would need to figure out if it is fuel or ignition related to proceed.
Someone would check for fuel pressure and spark when it stops running.
Could be the fuel pump relay, the ignition module, a crank sensor, or other things.

If you're not losing any brake fluid then it sounds to me as though the master cylinder is bleeding fluid between to two chambers allowing fluid to pass from one to the other which would decrease the pressure on one of the lines leading to the proportioning valve, thus setting off the 'brake' light.

Orrrrr,

IF it does NOT have the hydroboost system the following steps MAY help diagnose if it's a booster problem.

(Copied and pasted from a youtube comment)

Test 1) 1. Start the car 2. Let it idle for 2 minutes 3. After 2 minutes turn off the car 4. Pump the brake pedal 3 times 5. The pedal should rise every time if it does then the Booster and Check valve are OK 6. If the pedal doesn't then the is an issue with the either one, run tests 1 and 2.

Test 2) 1. Start the car 2. Let it idle for 2 Minutes 3. After 2 minutes push down the brake pedal and HOLD it 4. While holding the pedal down turn off the car 5. The pedal should NOT rise for at least 30 seconds 6. If it doesn't rise then the Check Valve is good 7. If the pedal rises before 30 seconds then the Check Valve is faulty.

Test 3) 1. Shut off the Engine 2. Pump the brake pedal 4 times 3. On the 4th one keep it pushed down and start the car while holding the pedal down 4. The pedal should sink down. 5. If it sinks, the booster is Fine.

Myself, I'm leaning towards the master cylinder having an internal 'leak' or bypass problem.

Hope this helps.

It sounds like you need a tune-up & you need your timing set.And also you can adjust your idle on your carburetor so it wont die..

check your fuel filter under the left side of the vehicle on the frame. if this proves to good, your next step might be checking your catalytic convertor. have you checked all of your vacuum lines? one thing you can do is have your friend inside to start the vehicle and while it is idling and the air cleaner is off, look inside at the fuel injector and you throttle it and see if the injector is spraying fuel.

ICM idle control module, loc throttle body, it may be dirty, remove clean or replace, its easy..

you will need to do a security relearn.
1.turn key to on position and leave on
2.after 10 minutes the light will flash and go out turn the key on to off 3x then leave on again.
3. do this 3 times for 30 minutes then after 30 minutes your 3rd time and after turning the key 3 times the 4th time start the car. it should start right up.

Any chance you've got 'Titanium' spark plugs. We had this same issue, and found it was caused by a mechanic replacing our plugs with the titanium ones. If they were hot, they didn't ignite properly during startup. If you let the car cool, it would start right up (~2 hours). Changing the plugs for good quality old-style plugs and the problem hasn't occurred since.