94 GMC gradualy looses power untill it won't pull itself

The title says it all. 1994 GMC Sierra 2WD, 5 ltr, automatic, 206k miles. Within 50 miles the engine would loose a little power and the check engine light would come on. As I would continue driving the truck would loose more and more power until finally it would not pull itself more than 10 mph. Shorting A and B on the diagnostic plug in shows one flash, pause then two quick flashes of the “check engine” light. Fuel pump? Electronic Ignition Module? Other?

Last service? re: tune up?

What was done? Change plugs/coil/wires?

Original fuel tank and pump/fuel filter?

Next time that happens loosen the gas cap…

The flashes with repeat 3 times then go to the next code. The 1-2 code is the ready code, meaning the computer is in diagnostic mode. If the Check Engine light comes on, there is another code in there. Leave it blinking, and read the next code.

Thanks guys,
I changed the plugs and wires about 30K ago. Original fuel pump and tank.
This came on too quickly to be a single burned plug or wire, the loss of power was not accompanied by mis-firing, just loss of power.
I have the original gas cap. This is a sealed system that builds up pressure inside the tank.
I let the check engine light flash the same 1-2 sequence for 4-5 times before I shut off the ignition key. How long should I wait to see another code? I will be more patient this time.
If the fuel pump is bad what pressure should it run good or bad?
That do you think of a bad electronic ignition module? Do you guys only think it may be fuel or fuel pump related?
Thank you again.

You may have gradually fouling plugs, next time remove one and check for fouling.

Is it burning oil?. if so, You may have some worn or broken rings.
Check your air filter for wetting to the point i will not allow any air through.
And check your exahust (CAT converter) for plugging with soot. This burn off and builds up again especially as you drive it. Check the back pressure on the exhaust.

OK, flashing check engine light; after the 1-2 flash, it flashes four times, pauses and repeats four flashes.

The loss of power came on very quickly, within 50 miles. Isn’t that too quick for a plugged converter? Also too quick for broken rings?

All this is good and thank you for your help.

Faulty engine coil(s)

14 year old fuel pump? If it were me, I’d change it along with the filter and test the fuel tank for water.

You may have a faulty EGR system (valve?)

Are you using the correct octane rated fuel?

Low cylinder compression or perhaps an air leak at the intake manifold or plenum.

Code 44 indicates a lean exhaust. Combined with loss of power, my guess is that fuel pressure is dropping off for some reason. A weak fuel pump is a possibility.

At a friend’s suggestion I checked the plugs. They are mostly white with the remnants of black from normal running. Does this suggest running lean as the fuel pump fails?
I plan to try to get a fuel pressure gauge from Autozone and check the fuel pressure for min. 60 pounds.

Well guys I replaced the fuel pump and the truck started just fine. 2carpros.com suggested some ground wires and O-2 sensors I should check, but the fuel pump seems to be the trick.
Thanks mucho,

Fuel FILTER!!!