I think whenWhen "had" is used for past perfect tense (i.e., "had jumped", "had looked", or even "had had") it's pronounced with either a short "e" sound or maybe a schwa sound rather than a short "a" sound.
Something similar applies as well for perfect and future perfect tenses with the word "have". For example, "will have been": "have" is not pronounced with a short "a", but rather a short "e" or schwa.