No check engine light no servies throttle light now water in fuel light nothing no codes the lift pump works the grounds are all good clean and attached well the ffm is clean it's making me mad because I'm a diesel mechanic and checked everything and nothing seems to be wrong lol
The air filter is new and I haven't checked the vacuum system yet and how do u check the lift pump for volume and what is it suppose to be at
I find it incredible that a "diesel mechanic" would ask that. Its obviously clear you half assed checked the lift pump too. You likely found sufficient fuel pressure and ASSUMED that meant sufficient flow too..
THATS THE BULLSHIT IM TALKIN' ABOUT! Look in the mirror.. You been schooled so you knowz everything and try as we might, your not hearing us..
Seriously, wondering if I am wasting my time here.. Do you want to learn this **** or just have someone tell you its the IP and be done with it?
Ive read Heath is capable of accurately diagnosis vehicles and IPs over the phone, although admittently he too must rely on the person on the phone is thorough in all those most "Important Preliminary Checks" that routinely are given a quick look see, maybe a passing sniff test and assumed good... Butt Eye digress..
Did you conduct the air leak test EXACTLY AS INSTRUCTED, Step 1, 2, 3, 4, and so on or did you read "Go to step 6" and assumed you could check both sides at once?
If so, you assumed WRONG just like so many Pro's and DIYrs still do!!
Do you have the proper service manual(s) for this vehicle? PLEASE dont tell us your using Haynes, Chilton and all the other unauthorized service manuals. If so, you MUST forget all that worthless bullshit too. If you arent following the FSM, might as well be wearing a blindfold with one hand tied behind your back.
The return line HALF of the air leak test is intended to check the IP itself for possible INTERNAL air leaks and never intended to check for airleaks upstream.
If jumping to step 6 was an accurate CONCLUSIVE test to check for airleaks of the entire system, it would be step #1 to save techs diagnostic time....
That most poopular short cut only APPLIES to the antiquated DB model pump, the DS model pumps predecessor. Unfortunitely few if any GM techs received the "proper training" and instruction or should I stress the total RE-EDUCATION necessary to properly and competently troubleshooting an EFI 6.5TD in order to arrive at an accurate diagnosis. To this day, many still approach the DS pump diagnostics as if its a DB model.. Censored idiots..
GMCorp spent more time instructing there d-techs how to plug in and read the NEW TECH1 scan tools than they spent actually instructing them on the new REVOLUTIONARY ELECTRONIC FUEL INJECTION SYSTEM. So of course they are extemely proficient at reading DTCs and swapping perfectly good parts. Apparently, the industry is still emphasizing how to use them damned scan tools.
Probably dont want to hear this but you most likely misdiagnosed the APP module too.. Butt Eye digress..
Lets get back to the diesel spa (hint).. If theres enough bubbles entering the IP to be seen exiting the DS model pump, Id be surprised if the engine even tries to start much less runs extremely rough at that..
Expect a rough idle, hard start, smokey cold start, etc etc etc if even the most miniscule amounts of air or fuel vapors enter the IP, although hard start and smokey cold starts (white smoke) is most indicative of air leaking into the fuel system overnight...
Sounds as if you may some creeps hanging out at the hidden air port(s).
When was the last time the fuel tank was dropped and cleaned, fuel sender inspected and tested, fuel strainer replaced? If you cant answer that, its likely long overdue.. Another schelduled maint item that only gets thought of when all else fails. Another thing thats always assumed good, no good mechanic worth his weight in salt ever wants to be seen doin' latrine duty, its beneath them and much like thorough troubleshooting, its not nearly as profittable as swapping out good parts for bad diagnosis..
Following proper procedure, anytime the lift pump is replaced, the tank is supposed to be dropped and serviced while replacing the strainer.
SKIPPING all those most laborious time consuming steps and just R&R the lift pump is HALF ASSING the job, and VOIDS the new lift pumps implied warranty... Unfortunitely, because our lift pump aren't located INSIDE the fuel tank, they all ASSUME they dont need to bother with all that other dumb s'it.. IMHO, its this oversight that spawns PMD Goblins.
Did you test the LPR ciruit for proper voltage? Finding 12volts at the LP i far from conclusive.. Slight voltage fluctuations, faulty grounds, poor connecting "SWITCHES" aka OPS may test good until the circuit is LOAD TESTED. Did they teach you that or do you need a tutorial?
How to Test for Fuel Pump Voltage Drop
Have you removed the FFM, cleaned, inspected and TESTED it for possible air leaks? Do not assume because its not dripping fuel it isnt leaking, specially overnight while parked for extended periods.. Most airleaks dont exhibit wet spots and HELL YES an air leak can exist in the PRESSURIZED side of the fuel supply and NOT LEAK fuel to offer up a clue..
If it were only that easy, I wouldnt need to explain all this s'it to you and the rest of the diesel mechanics who routinely get there ass's handed to 'em, although its usually at the customers expense.
If while doing the test things suddenly improved, you may have inadvertantly tightened a loose hose clamp, and/or resealed a fuel hose, or re-established a ground and/or electrical connections. Thats why you must be painstakingly thorough and FOLLOW PROPER PROCEDRES TO INCLUDE THE INSTRUCTIONS TO THE LETTER. Otherwise, your wasting both yours and my time here..