Alright heres alil background on the fueling setup for my buds rig. 04 LB7 with EFI Live with a very healthy tune, modified CP3 with a dual feed line kit, Fass 95, with stock injectors. Alright so when he pulls his truck EFI data log says he has around 23k psi, great. But when he's about midway through his run the rail psi drops off to about 16k. The truck doesn't sound like its missing or popping from lack of fuel during the run, but the data logger shows this huge drop. Any ideas?

 

Well first gotta ask the obvious how recent has the fuel filter been changed?

Mine does the same thing sometimes would hold just fine others drop off like crazy like it was a relief valve
https://www.dieselbombers.com/durama...ve-timing.html
if you scroll down to post 14 that is where the discussion starts.

But if its a constant thing every time he pulls i would say he's running to much pulse width for what his fuel system can handle. What is his max PW

 

With the dual feed line he has no more fprv, so my guess it would be injectors or some issue tuning. There's a little trick he can do tell him in efi live to go to table b1010 and the very last two cells hell him to set them to zero, it should command the pump to flow more.

Tell him to check his balance rates. To test the return rates he can do a general test with out pulling the valve covers, it don't tell you exactly how many injectors have bad bodies but itl give him an idea. Has his oil pressure dropped recently? Tell him to check his oil the injectors can cause some funny problems.

How much pressure does he get to the cp3?

 

You should tell him to post up a llog of the run too

 

His max pulse width is set to 3250 and I'll see if I can get a copy from him.

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He's workin on gettin a copy and is that too much PW?

 

if it can keep pressure, that a kind of pw some people run for a 500hp tune with stock turbo and stock inectors