Can fuel pump cause engine not to rev above 1000 RPM ona gas engine?

Yes and No how that for an answer? On a fuel injected engine the motor will not run if theys not enough pressure so you will not be able to get 1000 rpms. On a motor that uses a carb that could occour but most likely theys a fuel filter that is plugged up. So check fuel rail pressure on injected motors most pressures are around 35-45 psig and if you do not know what you are doing do not proceed because you spill gas anywhere on the motor and its hot or a spark occours the the big problems happen like fire and no eye brows, loss of hair on head or arms or worse. Thats my opinion.