1999 24 valve, turn key, hear lift pump, run engine until warm, shut off. return to truck after a few minutes, turn key, no lift pump sound, turn key, will not crank. (yes, starter turns over). Is there a LP relay that might be the culprit. I replaced the lift pump thinking that it was the problem but the brand new lift pump does the same as the old one, i.e. if motor is hot LP will not pump. Wait several hours, turn key to start and the LP agains runs and truck will start. Any ideas??

 

Welcome to DTr!

The not-starting-when-hot problem is commen when the Vp44 is going south, but your LP is not running - that's odd, I don't think I've heard of that?

I don't suppose you have a FP gauge? If not - that is a must-have on these trucks, you can monitor the LP health and perhaps save your VP (the former ~$150, the latter $1.3K)

You might disconnect the LP and thoroughly examine / clean the connections (I assume your system is stock?).....I've not heard of a LP relay giong south, do you have a wiring schematic for the fuel system (I cannot seem to loacte mine)?

 

Clark,

after warm when it won't start, can you just bump the starter and have the lift pump turn on? When doing this the LP should run for 30 seconds.

It sounds like you have an older ECM update, the latest update could solve this.

I just had mine updated, and now instead of when I turn the key on the LP use to come on for 3 seconds, now it just bumps the LP.

 

I will check with dealer about possible ecm update..