1989 dodge ram van b-150 3.9L

floods out won't start changed fuel reg. didn't help
mpg went from 15 to 4 what do I do next?

Do you have blue or orange spark at the spark plugs?

Do you have blue or orange spark at the spark plugs?
blue

Since you didn't mention that the engine is skipping, you probably have a leaking fuel injector. Using a mirror, open the throttle all the way, and look down into the throat of the throttle body and see if you can see fuel dripping from one or both of the injectors. Check this immediately after turning the engine off, this is when the fuel pressure at the injectors would be the greatest.

no fuel leaking

Any trouble codes from the computer?

nothing flashing don't know how to check

Cycle the ignition key On-Off-On-Off-On within 5 seconds.

Count the number of times the CEL (check engine light) on the instrument panel flashes on and off. The number of flashes represents the trouble code.

There is a slight pause between the flashes representing the first and second digits of the code. Longer pauses separate individual two digit trouble codes.

Examples of a flashed DTC is as follows:
Lamp flashes 4 times, pauses, and then flashes 6 more times. This indicates a DTC code number 46. Lamp flashes 5 times, pauses, and flashes 5 more times. This indicates a DTC code number 55. A DTC 55 will always be the last code to be displayed. This indicates the end of all stored codes.

It might flash each code 3 times, I don't remember if that was the case in 89.