can a dc engine run on transformer

You didn't say which GP20 you have, but I'm willing to bet that it was designed to run on AC. So, it should run O.K. with your RW transformer.

Below is a quote from the manual for a GP20

Your GP-20 is designed to operate on 7-18 volts alternating current.

Virtually all Lionel and Lionel-compatible alternating-current

transformers are suitable; we recommend the TrainMaster

Command model railroad control system.

DO NOT POWER YOUR GP-20 WITH DIRECT CURRENT (DC). Damage to

sensitive electronic components may occur.

From what I know of Lionel's engines, all of them will work on AC except for a limit number of DC ones they produced in some cheaper sets ( I may be wrong). Original lionel open frame motors if I remember what my dad said (he was an EE) were so called 'universal motors' that could run on either (with the caveat being that you would need to disable the horn/whistle, they would blow continuously, because those use DC superimposed on the A/C output to work). 

Modern engines other than those using the Pullmor I believe are all DC, what they do is have a bridge rectifier that turns the transformers AC into DC when it gets to the engine, then it works fine.

If you did have a dual engine and ran it on DC, you would need to have a DC supply where you could change the polarity, I believe the E unit wouldn't work. 

In any event, I think that 1991 engine would work just fine, assuming the transformer has enough wattage for it. 

 I have a Williams GP38 with dual motors that can pull just about anything I want so,I was looking for the same results in Lionel.

LOL! I doubt this will happen. Many Lionel's DC motored diesels are lightweight and can barely make a couple of cars. You are better off with the Lionel AC Pulmor motor versions if you want a lionel GP30. You best bet really is the MTH Railking Scale/PRemier GP20 that will outpull ANY lionel GP20 for sure!

I have quite a few DC engines that I run with a Z4000 (AC transformer).  BUT,  I have added a rectifier in line with the output to the track.  So, essentially making DC power. 

Rick

Your engine should run fine with any AC transformer.

The only Lionel engines that will not run with their regular AC transformers are the DC ONLY engines from the mid-70's to the early 1980's.

These engines were made BEFORE the rectifier equipped universal dc can motors were introduced.  There was a GP-20 (TPW) planned with the DC only engine, BUT it was never made that way. 

Ken

So much mis-information, so little time.

- Lotta basics, here:

- the Williams locos have DC motors also, you know.

- essentially all modern O gauge locos - except for specific "Classics" reproductions of one type or another - have DC motors.

- modern Lionel diesels are built exactly the same way, and often by the same hands,

as the other brands, and will also pull the paint off the wall, just like MTH, Williams,

etc.

- there are/were low-end Lionel diesels with a small can motor mounted low in each truck which do not have a load of pulling power, but aren't bad, especially if weighted.

This "cheap" equipment was copied for low-end K-line and continues to this day as

RMT/Aristo products. The gearing is poor, but the traction motor in the truck(s)

is actually far more prototypical than the vertical cans.

- the AC "Pullmor" is the motor that often can't get out of its own way.

- Spinning wheels are not a -power- issue; they are a -weight- (traction/adhesion)

issue.

- AC on the track goes to an electronic reversing unit that, among other things, con-

verts the AC to DC for the can motors.