Keith Browning Posted October 5, 2020 Share Posted October 5, 2020 I have been reading posts about this all around and now I have not one but two in my shop doing this. I don't think it's the same as what we saw some time ago where the TSB had us reprogram the PCM and change the engine oil for cold start strategy concerns. These seem to act up after several hours of hot soak. Turn the key and it cranks for about 5 seconds and sputters a little and then fires up and runs like nothing happened. No codes... passes all testing and inspections. I suspect a fuel concern but our shops fuel line adapter for the pressure tester has gone missing... Quote Link to comment Share on other sites More sharing options...
8WA Sman Posted October 6, 2020 Share Posted October 6, 2020 Does it help if you cycle the key before starting(Extra prime the fuel pump)? I have also seen purge valves stick on a 6.2 SD and not set a code. If I suspect a purge valve sticking I close the vent @ idle and watch the FTP H2O Quote Link to comment Share on other sites More sharing options...
Keith Browning Posted October 6, 2020 Author Share Posted October 6, 2020 It's difficult to tell if cycling the key is the tell tale because you don't know when and if the long crank is going to occur when you go to start... purge valve is also a consideration. Quote Link to comment Share on other sites More sharing options...
forddieseldoctor Posted October 6, 2020 Share Posted October 6, 2020 Fuel pimps bleeding back. I’ve done a couple of them now. All 17 through 19’s. I didn’t have the correct adapter the first time for fuel pressure either, but when I unhooked the line to see what end I needed there was nothing there for pressure. 1 Quote Link to comment Share on other sites More sharing options...
Keith Browning Posted October 6, 2020 Author Share Posted October 6, 2020 Well that is what I have been hearing but I really hate throwing parts without some kind of diagnosis to point me to the pump. BUT TODAY I managed to get a mechanical fuel gauge on BOTH tucks and verified no fuel pressure while cranking for 4 seconds then pressure built up and they started. CALLED the Hot-Line today and went through it and I can't say the engineer was sure there is a check valve or relief in the pump. But we agreed it's pointing to the pump. For the record, I reran the evap test then used DATA LOGGER to open the purge valve fully before cranking and the 6.2L does not flinch at it being open at start up. They did have a slightly high idle though which is expected. Pumps for everybody! Quote Link to comment Share on other sites More sharing options...
forddieseldoctor Posted October 7, 2020 Share Posted October 7, 2020 3 hours ago, Keith Browning said: Well that is what I have been hearing but I really hate throwing parts without some kind of diagnosis to point me to the pump. BUT TODAY I managed to get a mechanical fuel gauge on BOTH tucks and verified no fuel pressure while cranking for 4 seconds then pressure built up and they started. CALLED the Hot-Line today and went through it and I can't say the engineer was sure there is a check valve or relief in the pump. But we agreed it's pointing to the pump. For the record, I reran the evap test then used DATA LOGGER to open the purge valve fully before cranking and the 6.2L does not flinch at it being open at start up. They did have a slightly high idle though which is expected. Pumps for everybody! I totally agree about not throwing parts. I bugged hotline with the first one I had and that was where they pointed me. And when I pulled the line off there was no pressure there. The pressure drops and the fuel vaporizes in the rail causing the long crank. Or so hotline claims. I went after the purge valve first too. I blocked the line off and let it hot soak to verify it. Quote Link to comment Share on other sites More sharing options...
Keith Browning Posted October 7, 2020 Author Share Posted October 7, 2020 I suspect that your description of the fuel line scenario is dead on. The concern is worse during a hot soak or at least it seems that way to me. Quote Link to comment Share on other sites More sharing options...
Keith Browning Posted October 17, 2020 Author Share Posted October 17, 2020 Just to follow up - the low fuel pressure while cranking was corrected with a new fuel pump. Quote Link to comment Share on other sites More sharing options...
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