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P1688

Elknih
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Elknih

Elknih

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Well after installing my gauges and DDRP I finally got the P1688 "dead" code. My gauge still wasnt showing as much pressure as I thought it should have (12-15 idle...I could pull it below 5 with throttle). I'm pulling pressure thru top filter housing from outlet banjo thru a snubber. I assumed I should swap the filter anyhow. Regardless after I got up to temp, the truck stalled. When hot and bumping the starter the lift pump didnt seem to be running. Had no pressure and no start. I pulled code to get the P1688. Can the VP code cause the lift pump to not run (when hot)? After a few hours, I started truck and drove it to the house. Same pressures 12-15 at idle.I'm assuming just get a new VP? Any thoughts on vendor?

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cajflynn

cajflynn

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The truck pulses power to the lift pump on startup. If you want to see startup pressure you need to remove the fuel system relay and then turn the starter over. The truck won't start but you will be able to see the pressure. As for the 1688, it probably means the pump is bad. Buy one from someone who has a warranty you trust.

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