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18 to 12mpg, what kinda maintenance to fix this?

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Sister graduated yesterday and somehow word is out that I know how to play with diesels and a guy hit me up with his 24V saying he wants to give it a tune up. This means set his valves (apparently has never been done, ever, after 160k miles) and check over some other things. I imagine being a 24V I should clean his map sensor and what else is there to check on those things? Now the thing is he went from 18 when new and has dwindled down to 12, I would think if his valves and sensors were off/dirty it would constitute the drop but what other things is there that would cause this? I don't think he has any codes or anything, just never had any maintenance done in it's life out of neglect.

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Codes? Fuel pressure? White smoke in the morning? Check for hot brakes? (Drag) As for the sensor I don't think there whould be that big of drop. As for cleaning sensor only needs to be done if you own a exhaust brake.

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I second the brakes... A couple of years ago, my mpg tanked... had it in to numerous shops (dealer said "no codes" & looked no further). It drove fine even towing except the mileage was off. Cummins has plenty of power. On the second state inspection (a year later) the shop lifted the front to check ball joints... The wheels would barely turn by hand. The discs had rust expanded so the edge dragged the caliper frames!! Who'd a thunk? Wheels did not get hot.

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No codes (reread my post) surely has no fuel pressure gauge or anything. He isn't going to want to spend any money on it so I guess he's SOL on a new lift pump should he need one, which I'm sure he does. I guess everything you do on a 24V costs money so I'll set his valves and check over the rest including brake drag and send him on his way. No way he is gonna spend a dime on it other than the dime he pays me. There's a reason it has went so long unmaintained..:doh: Guess I can clean his injectors :hyper:

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Pull the injectors and recalibrate reset pop pressures and clean them or replace them. In my opinion this should be done every 100k regaurdless for optimum performance/economy along with valve adjustments. If he doaen't want to spend any money on it he will just have to live with the mileage he gets. So its your duty to inform him how much more it will cost him to drive with low mileage than the wee bit he will spend to have the injectors gone through or replaced. If its an auto he could be getting some inefficient performance through it if it hasn't been serviced properly also.Has he added mudflaps bug degflectors running boards since adding to the drag over the years? All things you need to ask since milage has gone down over the years and not all of a sudden.Is the radiator plugged solid with oil from the breather and the fan clutch is staying engaged full tilts due to lack of air flow? Just need to start with the stupid simple basics here if it is the way you say and he checks nothing.

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I planned on telling him he is screwed if he doesn't want to spend any money. I forgot about the breather thing on the 24V's. He told me he hasn't touched it since he bought it so I imagine everything is backed up and clogged and all wore to hell. I've never seen his truck I've just heard rumors about it :stuned: He has been wanting someone to do this for years if that tells you anything. I might not have time to even work on it. It's got 12 too many valves anyways :lol:

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I planned on telling him he is screwed if he doesn't want to spend any money. I forgot about the breather thing on the 24V's. He told me he hasn't touched it since he bought it so I imagine everything is backed up and clogged and all wore to hell. I've never seen his truck I've just heard rumors about it :stuned: He has been wanting someone to do this for years if that tells you anything. I might not have time to even work on it. It's got 12 too many valves anyways :lol:

If the breather spit chunks on the radiator that can put the pressure switch on the ac in shutoff mode.Ask me how i know:lol:mine was so pluged the ac didnt work.
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should also mention low mpg on the 24's can come from several1. toe is off on the front end.2. low tire pressure3. Vp-44 low fuel pressure bad timing = bad mpg4. worn out turbo, waste gate issues or a leak5. sensors are crap, had to clean out my IAT and MAP sensors and i have no Exhaust brake)6. bad fuel pressure.i should say that i have fought an endless battle with my truck over mpg since i passed that car 2 years ago. went from 20mpg consistent to 8mpg this winter. If he fails a snap test then you know it is a boost leak, most likely on the drive side, or the waste gate is open or something along those lines, or it could be a VP-44 on the way out.I know that fixing No.1 and 2 gave me some mpg, the No.1 helped alot with drive load, as my truck runs about 100-`150F cooler now.Im still fighting:banghead: but last tank was 17.5, tank before it was 15.8:ahhh:

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