Runs like a junker
 

I have a 1992 C25 6.5 Turbo.
And it runs like junk.

It will fire up. Idle beautifully. But you put it in drive, get on it to go and it will putter along like a stumbling drunk. No power, and going uphill will max out at 15mph and will never go over 2 - 2.5k rpm.

I had a similar problem before and I change the fuel pump relay. and it fixed it.

Now the same problem happens and I change the relay, and it does not fix it.
It smokes like it is flooding, bad. and Well I was wondering if the fuel pump is bad.
It is a in-line rail mounted electric pump.

Any thoughts? Before I throw away more money?

Thanks you,
Mikel

most likely the fuel system is the culprit. check to see if the injectors are at the right pop pressure. also see if you got good fuel pressure to the injection pump from the tank. finally do a 2k rpm test. slowly rev it up in park to 2000. hold it there for a fe seconds than slowly let it down. if it surges or wont do it smoothly pump is probably bad.