My truck just shut off while trying to get it unstuck after wife drove into sugar sand. Engine turns over, but won't start. Changed glow plugs. Tried changing glow plug relay. Engine won't turn over with new one in ( Tried two. Might be wrong parts. Look identical, except color, bottom plate [new- silver, old- copper], and numbers on back [new- 1305, old- 1306]). Old one in, it turns over. I am new to diesels. This is my only vehicle and need it running soon as possible. What do I check? I have to do this myself because of money constraints.