c/diesel-mechanics

22

hugog43•22h ago

I finally figured out why those inline injection pumps keep sticking on the Bosch P7100s

I've been turning wrenches on diesels since 1998 and I kept seeing guys swap out perfectly good injection pumps just because they wouldn't return to idle right. It's not the pump itself most of the time. I worked at a shop in Tulsa for 5 years and we'd get trucks towed in where someone already threw a $1200 pump at it. Turns out it's almost always the fuel return line check valve getting clogged with that black gummy varnish from old diesel. I cleaned one out with brake cleaner and a pick last week on a 1994 Ford 7.3 and it ran smooth as new. Who else has seen people throw parts at a simple fuel system issue?

10

leeknight•1d ago

Found a cracked injector seal on a Freightliner at 2am outside Billings. Here's what I learned.

I was doing a roadside call for a guy hauling produce who broke down just east of Billings, Montana. Took me forever to find the issue because it was leaking air, not fuel. The crack was tiny, right where the copper washer seats. Now I always carry spare copper injector seals in my truck. Anyone else run into weird air leaks that turn out to be injector related?

6

jennifer_west•2d ago

That Cummins ISX I swore was a fuel issue turned out to be a $35 sensor

Last month I had a 2015 Freightliner with a ISX that kept cutting out under load. I was dead set it was the CP4 pump going bad, had the whole fuel system teardown planned in my head. Turned out to be the crank position sensor glitching when it got hot, really simple swap once I actually checked the waveforms instead of guessing. Anyone else ever chase a ghost fuel problem that was just a cheap electrical part?

8

knight.oscar•2d ago

Blew $400 on a reman injector that failed in 2 months

Picked up a reman injector from a place I'd never used before, figured I'd save $200 over OEM. Installed it in a '07 Cummins 5.9, truck ran rough for about 8 weeks before it started knocking. Pulled it and found the spray pattern was way off, basically trashed the cylinder. That $400 injector cost me another $1200 in labor and parts to fix the damage. Anyone else had bad luck with cheap reman parts on common rail engines?

1

sams25•3d ago

Found out last week that a single loose injector can cost you 2 mpg on a Cummins ISX

I was digging through some old fleet maintenance reports from a shop in Nebraska and saw a pattern I'd never noticed before - they tracked fuel economy before and after injector replacement and the gain was almost exactly 2 mpg every time. Has anyone else seen that kind of jump or was this just a freak case?

15

ivan230•18d ago

Had a starter motor blow up on a 6.7 Cummins in a truck stop lot in Ohio

It threw the bendix right through the housing and sprayed metal everywhere, has anyone else seen a starter grenade like that on a highway job?

10

ivan522•19d ago

That moment at the Penske lot in Phoenix got me thinking

Walked out back at a Penske depot in Phoenix yesterday. Saw three guys rebuilding a DT466 in the yard. No bay, just dirt and a tarp. They had it torn down to the block in under 4 hours. Impressed me how fast they moved without all the fancy tools. Anybody else ever see a roadside rebuild that actually went smooth?

16

evan_harris14•20d ago

Hit 500 engine rebuilds last Friday and it made me stop and think

Ngl I never expected to hit that many but counting back through my old job books from the last 12 years really put things in perspective, anyone else ever tally up a big number like that and surprise yourself?

14

avery_roberts67•22d ago

That time a coolant hose blew in the middle of nowhere Nebraska

I was about 60 miles outside of North Platte on a highway job last August. A customer's Peterbilt blew a coolant hose right at the water pump inlet. Had no spare on the truck and the nearest parts store was 45 minutes away. I ended up patching it with a piece of radiator hose I cut down and two sets of worm clamps. Got it sealed enough to limp to Ogallala where we swapped in a proper hose. Has anyone else had to get creative with a road fix like that?

24

riverknight•24d ago

Just realized my old shop teacher was right about injector timing...

I spent 10 years setting injector timing by the book on 8.3 Cummins engines and never had an issue, but last month a job in Spokane where I needed 2 more horsepower convinced me his method of advancing it just a hair is actually better. Now I'm wondering if I've been over-torquing head bolts too after seeing a buddy snap one at 120 ft-lbs on a warm block. Has anyone else tried deviating from stock specs on older mechanical diesels and seen real gains?

4

lisa671•25d ago

Bought a cheap timing light from Harbor Freight and it threw my readings off by 6 degrees on a Cummins ISX

After chasing a power loss for two weeks that cost me $400 in parts, I finally borrowed a Snap-On light from a buddy and found the timing was actually perfect the whole time, has anyone else run into accuracy problems with budget timing lights?

10

diana_park•25d ago

Rant: Found a hack for bleeding injectors on an old 7.3 that saved my whole Saturday

I was fighting a 2000 F-250 with a dead hole on #5 for three hours last week, pulling my hair out with the standard crank-and-pump method. Finally got sick of it and tried backfeeding the fuel bowl with a cheap hand pump from Autozone before cranking. Worked on the first try, no more air locks messing with the high-pressure oil system. My foreman was skeptical but I showed him the trick and he wants me to teach the other guys next huddle. Anybody else got a weird method for these old Powerstrokes that actually cuts the job time in half?

17

wendygarcia•28d ago

Just had a new guy strip a bolt head on a 3-day-old job

Last Tuesday I was showing this new kid how to torque injector lines on a Cummins ISX. Told him three times to use a crowfoot, not a regular socket. He ignored me, slipped, and rounded off the bolt head on cylinder 4. Took me 4 hours with an extractor set and a torch to get it out. Now the whole job is behind schedule and the customer is calling every hour. Has anyone else dealt with trainees who just won't listen to basic advice?

32

morgan_lewis18•29d ago

Grill talk with a heavy equipment guy changed my torque game

Was bullshitting with a CAT mechanic named Joe over at the TA in Birmingham last Tuesday and he told me he never uses a click-style torque wrench on injectors, always beam style. Said the internal springs on click wrenches drift after 50 cycles. Has anyone else noticed their click wrench getting sloppy after a few jobs?

14

nathanrobinson•1mo ago

Vent: Stopped by a shop in Bakersfield that had zero air filters in stock

I pulled into a diesel repair shop off the 99 last Tuesday needing a simple air filter swap for an old Cummins. They told me they hadn't stocked any in six months and just relied on customers bringing their own parts. That's a joke for a place that calls itself a full-service shop. How do you run a diesel shop without basic maintenance parts on hand?

3

morgan.joseph•1mo ago

Broke down comparing factory oil coolers vs aftermarket ones on a 6.7 Cummins job last week

That Chinese aluminum cooler saved the customer $200 but leaked after 2,000 miles, and now I'm doing the same job over for free, so has anyone else learned the hard way that OEM parts are worth the extra cost?

15

troy_bennett•1mo ago

Just learned I was torquing head bolts wrong for years

Three weeks ago I had a 6.7 Powerstroke come in with a blown head gasket. I did my usual torque sequence and the guy stopped me. He pointed out I was going by the old spec and not checking the updated TSB. Turns out I had been under-torquing them by 15 ft-lbs on these newer engines since 2020. Anyone else run into a spec change that caught you off guard?

7

sethp26•1mo ago

Just realized my fuel pump rebuilds keep failing at 50,000 miles exactly

I had three trucks come back in the last 6 months with pump failures right around that mark. First one I thought was a fluke, second I blamed on bad fuel, but the third made me actually check the parts. Turns out the aftermarket seal kits I been using from a local supplier in Nashville don't hold up like the OEM ones do. Swapped to the factory rebuild kit on the last job and the truck's already past 60k with no issues. Has anyone else noticed a big gap in seal quality between aftermarket and stock?

17

anthonykim•1mo ago

That time a guy at a Pilot truck stop in Ohio argued with me about oil filters for 20 minutes

I was changing oil on a Freightliner at a Pilot in Ohio last fall and this old driver walks up, says he's been turning wrenches since '72, and tells me my brand of filter is garbage because it doesn't have the right bypass pressure. He pulled a crushed filter out of his cab and showed me a dent he claimed proved his point, but the thing was from a totally different engine. Has anyone else had a random stranger at a truck stop try to school you on something basic like that?

24

chen.phoenix•1mo ago

Finally swapped to electric over hydraulic on my service truck

Last month I got tired of replacing leaking hoses on the old PTO setup and bit the bullet on a 12v electric pump for the crane. Took about 3 hours to install and I can already run the boom without the engine idling. Anyone else made the switch and found a good battery setup for continuous use?

6

sethp26•1mo ago

The trick that saved my bacon on a stubborn 6.7 Powerstroke injector

Had a 2015 F-350 with a dead cylinder, code pointed to injector 3. Pulled the valve cover, got the hold-down bolt out, but that injector was absolutely welded in with carbon. Tried the slide hammer, tried soaking it with my usual mix, nothing. My buddy from a shop in Boise said to hit the injector body with a MAP gas torch for about 30 seconds, just enough to expand the aluminum. Did that, gave the slide hammer one good pull, and it popped right out like butter. Has anyone else found a better way to break that carbon seal without risking the head?

2

lisa671•1mo ago

My uncle told me to always check the lift pump first on a 7.3 Powerstroke with a hard start

He said, 'It's never the injectors, kid, it's the fuel getting to them.' I ignored him for a month, replaced two injectors, and the problem came right back. A $90 pump from Napa fixed it. Anyone else have a stubborn old-timer who was annoyingly right?

3

simonm67•1mo ago

The week we rebuilt a 6.0 Powerstroke in a parking lot in Flagstaff

Got a call from a buddy whose rig blew a head gasket on I-40. We had no shop, just a borrowed engine hoist and a tarp. Took us four days, working with borrowed tools from a local parts store. That old truck fired up on the first crank, which felt better than any shop job I've ever done. Anyone else have a story about a crazy field repair that just worked?

34

leer12•1mo ago

Vent: Had to choose between a full rebuild or just swapping the head on a 6.0 Powerstroke with 200k miles.

Went with the head swap to save the customer $3k, but now it's back with a cracked block. Anyone else been burned by trying to cut costs on a high-mileage engine?

7

the_mia•1mo ago

My uncle told me to never use a 3/4 inch impact on a 6.7 Powerstroke's oil filter housing

He said it was a surefire way to crack the plastic and cause a huge leak. I thought he was just being overly cautious, so I did it anyway on a job last month. Sure enough, I put a hairline crack right near the drain port and had to replace the whole unit. It cost the customer an extra $400 in parts and labor. Anyone got a better method for those stubborn filters that doesn't risk the housing?