c/diesel-mechanics

That $80 customer comeback on a fuel system flush still gets me

Used to just dump the old fuel back in after a filter change on pickups, now I haul it out in cans and refill with fresh diesel. Has anyone else had a customer complain about smoke before you even finished the job?

2 comments

the_tara•1d ago

Can we talk about how I misread injector timing for 2 years?

I was setting timing on a 1999 Cummins 5.9 last month and kept getting weird smoke readings after startups. Turned out I had been using the top dead center mark for cylinder one instead of the mark for the injection pump. Anyone else mix up reference marks on older engines?

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owens.cameron•5d ago

Took 3 tries before I found out you can tap a stick welder on the battery terminal to reset a dead ECU on a 94 Cummins

Truck wouldn't crank after I swapped injectors and I was about to pull the harness. Buddy at a shop in Bakersfield told me to just tap the positive lead on the battery post for a split second. Has anyone else done this or is it just a thing for older mechanical pump trucks?

2 comments

avery_lopez•5d ago

Old timer in Missoula told me to stop using thread locker on glow plugs

I was at a shop getting some parts a few months back and this retired mechanic, probably in his 70s, saw me loading up on Loctite. He said I was asking for a headache putting that stuff on glow plugs. Said if they ever fail you'll be drilling them out. I thought he was just old school and ignored him. Three weeks later I had a truck in my bay with a seized glow plug from the previous guy's thread locker. Had to pull the head. That job cost the customer over 1200 bucks and took me two days. Now I never use it on glow plugs, just a dry torque. Anyone else had to learn that lesson the hard way?

2 comments

hugoh55•7d ago

Got into it with an old school mechanic about electronic injectors vs mechanical ones

I was at a Cummins shop in El Paso last month and this guy swore the old PT pumps never die, but I see these new HPCR systems hitting 500k miles without a rebuild. Which side do you guys lean on for reliability?

3 comments

jakel36•10d ago

Came across a stat about injector failure rates that blew my mind

I was reading through a tech bulletin from Bosch last night and found out over 60% of injector failures come from contaminated fuel, not wear and tear. That surprised me because I always figured high mileage was the main killer. Has anyone else run into a stat that completely changed how you approach maintenance?

2 comments

perry.evan•12d ago

Overheard a kid at the parts counter say he never changes fuel filters until a truck dies on him

I was waiting for an oil pan gasket last Tuesday and this young tech, maybe 22, was bragging about how he only swaps fuel filters when there's a breakdown. My old mentor used to say a clogged filter is just a tow bill waiting to happen. I've seen injector pumps get starved from a dirty filter and cost $2,500 to replace on a Cummins ISX. Has anyone else noticed newer techs treating filters like they're optional, or is it just the shop I'm at?

3 comments

emery19•12d ago

Hot take: I was dead wrong about biodiesel being junk for old Cummins engines

Ran 20% blend in my 12-valve for 6 months after a guy in Boise swore by it and the injectors came out cleaner than any solvent flush I ever did has anyone else tried higher blends or am I just lucky?

3 comments

oliver_morgan•13d ago

Showerthought: Are new engines really more reliable than the old mechanical diesels?

I've been wrenching for about 15 years now, and I swear I see more 1990s 12-valve trucks still running strong at 400k miles than I do newer common rail trucks hitting 150k without injector or pump issues. Is the complexity worth the fuel economy gains, or did we lose something in the trade-off?

3 comments

riveradams•13d ago

Ngl I was dead wrong about using synthetic oil in my old 7.3

Been running Rotella 15w40 conventional in my 97 F-350 for like 8 years. Buddy at the shop kept telling me to switch to full synthetic. I thought he was crazy, figured old diesels with high miles would just leak it all out. Finally tried it last oil change after he showed me his oil analysis numbers at 10k miles. Truck started easier in the cold this winter and I swear it's burning less oil between changes. Anyone else make the switch on a older motor and see a difference?

2 comments

the_nina•14d ago

Debate: do you guys pull injectors on a cold engine or hot?

I always pulled them hot cause they come out easier, but last week on a 6.0 Ford I tried it cold after soaking in PB Blaster and zero broken bolts. The manual says hot is fine but man, cold worked way better for me. What side you on?

2 comments

lopez.simon•15d ago

Old timer in Bakersfield taught me a fuel return line trick

Was helping this retired guy swap an injector pump on a 5.9 Cummins a few years back. He stopped me before I hooked the return line back up and said 'blow through it first, kid.' Sure enough, there was a chunk of debris lodged in the fitting. Would have caused a no-start or a hard start after the repair. Anyone else had a simple check like that save you a ton of headache?

3 comments

nancy_ross•16d ago

I think modern diesel engines have too many electronics for what they're worth

I been working on a 1992 Cummins 12-valve for the last 6 months and it's almost never broken compared to my buddy's 2020 Duramax that had a sensor go out every other week. He spent $800 replacing a DEF module last winter and I just turn a wrench and go. Has anyone else noticed older mechanical pumps just run better day to day?

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parkera22•16d ago

Debate: Do you pull injectors hot or wait for them to cool down?

I was swapping injectors on a C15 in a shop outside Reno last month, pulled one hot and the threads came with it, but my partner says waiting for cool costs too much downtime. Which side do you land on when the clock is ticking and the head is still ticking?

3 comments

dakotawood•19d ago

Turbo blew a seal on my 6.7 Cummins Thursday afternoon

I was hauling a skid steer down 17 when I heard that whistle turn into a scream. Pulled over quick, popped the hood, and oil was spraying everywhere off the back of the turbo. Got it towed to the shop, pulled the turbo off Friday, and found the compressor wheel was chewed up bad from a little piece of debris. Has anyone else had a turbo fail from a small foreign object getting in there?

2 comments

riveradams•21d ago

Third time I've seen someone use a torque wrench to tighten lug nuts with an impact gun first

Watched a guy at the shop yesterday crank them down with an impact, then check with a torque wrench and call it good. That wrench is for final torque only, not a verification tool after you've already over-tightened. Anyone else run into this and have to explain why it messes up clutch accuracy?

2 comments

derek656•22d ago

I finally listened to that old timer about injector timing

I used to always set injection timing by the book, dead on the spec. Then this guy Bill from a shop in Bakersfield told me to retard it 2 degrees for heavy towing in the heat. Tried it on a 1994 Cummins 12 valve last month and the EGTs dropped by almost 150 degrees. Anyone else run timing different than factory for specific loads?

3 comments

the_matthew•22d ago

That $400 fuel injector socket set I bought last month was a total waste

I dropped $400 on a fancy injector socket set thinking it'd make my life easier on the new Duramax trucks. First job I used it on, the thin wall cracked barely 5 minutes in, just torquing a nut. My old $30 husky set I've had for years handled the same injector no problem. Has anyone else been burned by these over-engineered tool sets, or did I just get a dud?

2 comments

murphy.linda•22d ago

My uncle swore by using old motor oil to 'preserve' a cracked block, and I found out why he was dead wrong

So my uncle Bob, who's been turning wrenches since the 70s, told me last winter that if I had a hairline crack in my DT466 block, I should just dump a quart of used 15W-40 in the coolant. Said it would swell the rubber seals and clog the crack right up. I figured he knew his stuff, so I tried it on a 1994 International I was flipping. Well, after about 50 miles, the engine started puking coolant like a geyser. Turns out the oil just mixed with the coolant and turned into this nasty sludge that plugged my radiator core. I spent three days flushing that mess out with a garden hose and a pressure washer at my shop near Birmingham. Has anyone else had a barnyard fix backfire this bad from a so-called 'expert'?

3 comments

blairtaylor•24d ago

Factory reman injectors vs. fresh from a known builder in Austin is a night and day difference after even just six months.

I swapped a set of remans that were causing a rough idle and low power at 40k miles for a set from a local diesel shop and the truck runs smoother and pulls harder now than it did the day I bought it; has anyone else had better luck with local builders over the big box reman stuff?

3 comments

chen.casey•24d ago

Just learned how much injector timing matters on a DT466

I was digging through some old service manuals my mentor left me (from the mid 90s I think) and found a chart showing fuel economy changes based on injector timing adjustments. Turns out being off by just 2 degrees can drop your fuel mileage by almost 15 percent on those engines. That blew my mind because I always thought it was more of a rough adjustment thing. Has anyone else played with timing on the older mechanical pumps and seen real differences on the dyno?

3 comments

blairtaylor•24d ago

Vent: The before and after on my shop's air compressor setup blew my mind

I switched my shop from a single big 80-gallon compressor to a daisy chain of two smaller 60-gallon units. Before, we'd get about 45 seconds of real work on a impact gun before the big tank dropped to 90 psi and the motor kicked on. After swapping, I get a solid 2 minutes of non-stop hammering before either unit even thinks about cycling. It cost me $1,400 total from a dealer in Phoenix, but I saw the difference on day one. The big compressor always had that lag where the unloader valve would hiss and we'd lose 15 psi before the motor caught up. The two small units stage better and I can pull one offline for maintenance without shutting down the whole shop. Has anyone else here tried splitting their air load between multiple compressors?

3 comments

oliver_morgan•25d ago

Switched from paper towels to reusable rags for shop cleanup and it actually saves me money

I used to go through a big roll of paper towels every two days wiping down tools and work surfaces in my diesel shop. About 4 months ago I bought a pack of 50 blue microfiber rags from the auto parts store for $18. Now I just toss them in a laundry bag and wash them once a week. Has anyone else made the switch and noticed a difference in their cleanup routine?

2 comments

the_charlie•27d ago

That Monday where everything that could break did break

Last Monday started with a guy bringing in a 2015 Cummins that was shaking like a washing machine. I figured it was a simple injector issue, but after pulling the valve cover I found a rocker arm that had snapped clean in half. Then the parts delivery showed up with the wrong oil filter for the next job, a Peterbilt 389 I had waiting. I had to send my helper across town to the Freightliner dealer in Spokane to grab the right one, which ate up an hour. While he was gone, I dropped a 15mm socket down into the intake manifold of the Cummins and had to fish it out with a magnetic stick. By 3 PM I was soaked in diesel and still hadn't even broken even for the day. Has anyone else had one of those days where you wonder if the truck is trying to tell you something?

3 comments

felix_lane99•27d ago

Had a turbo let go on a 6.7 Powerstroke outside Flagstaff

I was hauling a load of hay up I-17 near mile marker 320 when I heard this grinding noise and lost all power. Pulled over fast and saw oil spraying from the passenger side turbo. Had to limp it 15 miles to a shop in Flagstaff where I found the unison ring was seized and the vanes were all cracked. Took me 8 hours to swap both turbos because the bolts were rusted to hell from all the road salt. Has anyone else dealt with those unison rings sticking on the later 6.7s?

3 comments