If anyone can help me i have an 06 f550 6.0 l that will not restart only when hot, have replaced hp oil pump and stc fitting, also stand pipes 2 injectors and dummy plugs in both manifolds, tech line is not much help just putting more parts on, i can here a faint leak only with eot above 180, truck will crank for awhile then start with eot below 180 degrees,, also truck starts and runs great cold no drivability issues felt or seen with ids, ipr reads 25 % cold and up till eot 195 then starts to climb to 30% but if you give throttle and let return to idle ipr returns to 24.79% then 25%, i think its a branch tube but no hard proof, tech line had me replace new hp pump due to low icp when both heads blocked only gets 890-900 psi. any help would be great.

Because you have blocked the heads, and the icp comes up, that will isolate to pump, stc fitting, branch tubes, or stand pipe/d rings. You've replaced pump and fitting, so you're left with branch tubes and stand pipes. Is the 900 cranking? If so, thats not bad pressure. You only need 500 to start. Any fuel pressure issues? Have you tried air pressurizing with the ipr closed?

i had one with a hairline crack in the branch tube. only showed up in hot temps.

I would check your fuel psi. Then if ok try to do an air test when the engine is hot.. I've also have seen some branch tubes that fail when hot. Are there any codes?

i would also check base pressure. put a gauge on the eot sender spot and make sure the base stays in spec.

bowtiehatr said:

i would also check base pressure. put a gauge on the eot sender spot and make sure the base stays in spec.

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bowtiehatr said:

i had one with a hairline crack in the branch tube. only showed up in hot temps.

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bingo.........my thoughts exactly,had a couple like that