How do I force Pentax k100d to fire flash in manual mode.?

Question

Using external flash on hot shoe and it doesn't fire consistently.

Answer 1

If you're using an off-brand or old flash this is probably because the trigger voltage is over the 6 volts. Continually using the flash in this condition is potentially harmful to the camera.

Either get a safe sync:

http://search.ebay.com/search/search.dll...

... or get a new flash.

If it's a new flash or you know that the trigger voltage is safe it could simply be the flash recharging between firings. This could take anywhere from milliseconds to seconds depending on the number of batteries the flash uses, type of batteries, and how powerful the previous flash fired was. If flash indicates it's ready and doesn't fire try cleaning the contacts on both the camera and the flash, clean the battery contacts within the flash unit, and change the batteries if possible.