steeler Posted October 30, 2021 Share Posted October 30, 2021 On 10/28/2021 at 3:09 PM, Hulio said: How do you tell which cups or injectors are bad? Once you pull the old ones out are they damaged by the removal process? Might seem Petty but at several hundred a piece why do all six when one has gone bad in less than 100k? Is it usually the injectors or just the cups? Can you replace one without the other? Am I mistaken or is it simply extreme pressure that holds them in until the injector is installed and torqued? No way to really tell which one /ones are bad without removing and inspecting them. Usually when I find 1 leaking, there are a couple more that are either leaking or about to. Imo no point in doing 1 (assuming you are lucky enough that the first one you pull is the culprit) because the others will be leaking soon. The injectors /cups once installed, mate to each other, so you can't just replace 1 without the other. They say you can reinstall an old injector into the same cup after removal, but I don't think I've ever encountered a situation where I did that. When they come out, it's because I know they are leaking so it's all going to be replaced. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/56944-injector-cup-failures/page/2/#findComment-482093 Share on other sites More sharing options...
Hulio Posted May 3, 2022 Share Posted May 3, 2022 When they come out because you know they are leaking how do you know they are leaking? Air bubbles in the tank is how I've seen it diagnosed and I've seen that be wrong. Bubbles can come from any leak in the fuel system Quote Link to comment https://www.bigmacktrucks.com/topic/56944-injector-cup-failures/page/2/#findComment-496595 Share on other sites More sharing options...
Onyx610 Posted May 4, 2022 Share Posted May 4, 2022 Sometimes they leak inside the cup too. Not always the outside. There is a video I posted before with a guy giving a good explanation. Let me find it. Quote Link to comment https://www.bigmacktrucks.com/topic/56944-injector-cup-failures/page/2/#findComment-496697 Share on other sites More sharing options...
Onyx610 Posted May 4, 2022 Share Posted May 4, 2022 Quote Link to comment https://www.bigmacktrucks.com/topic/56944-injector-cup-failures/page/2/#findComment-496698 Share on other sites More sharing options...
Joey Mack Posted May 4, 2022 Share Posted May 4, 2022 To check for air in the fuel on an MP, there is 2 ways. Commonly, you hook a long clear line with a banjo fitting on one end that fits correctly to the banjo bolt on the fuel return, located at the front of the head behind the lifting eye. Then you run it back into the filler neck of the tank and submerge it into the fuel, run the engine and look for bubbles/suds.. and there it is.... another setup has you hook to the fuel filter pad, on the left side of the engine, unfortunately, I forgot which port you hook too. once again, a clear hose with the correct banjo fitting on one end. jojo Quote Link to comment https://www.bigmacktrucks.com/topic/56944-injector-cup-failures/page/2/#findComment-496699 Share on other sites More sharing options...
Vmac3 Posted May 4, 2022 Share Posted May 4, 2022 22 hours ago, Hulio said: When they come out because you know they are leaking how do you know they are leaking? Air bubbles in the tank is how I've seen it diagnosed and I've seen that be wrong. Bubbles can come from any leak in the fuel system Any part of the suction side of the fuel system will draw air in. Seen fuel water separators cause this a few times and corroded block off plates where the primary fuel filter would sit. V 1 1 Quote Link to comment https://www.bigmacktrucks.com/topic/56944-injector-cup-failures/page/2/#findComment-496707 Share on other sites More sharing options...
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