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6.2L Diesel Engine Discuss the 6.2 GM diesel engine & associated components.

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  • 3 Post By 1967KaiserM715
  • 2 Post By roadhog0
  • 2 Post By Bigboytoys
  • 4 Post By DieselPro
  • 1 Post By jnlperformance
  • 2 Post By legendman

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Old 04-23-2019, 07:40 PM   #1 (permalink)
Junkers
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20 Year 6.2/6.5 Mystery:

Hey, Folks...

I wanted to post a rather lengthy question in hopes of finding an answer. Over 20 years ago, I helped my Dad (a former NASCAR Crew Member on Vel's/Parnelli's NASCAR team) put a 1982 (IIRC) 6.2 Litre Diesel in his 1977 Chevy Pickup. The engine was used and gave good service as a shop truck for his restoration and race car shop.

Years later, he asked me to pull it and rebuild it as it was burning a lot of oil. We bored it for new Mahle pistons, all new bearings, timing chain/gears, oil pump, etc. The cam and lifters looked good, were indexed at removal and reused.

The heads were full of cracks. The local GM dealer (near Fresno, California) sold Pop a pair of new 6.5 Non-Turbo heads for dirt cheap and we put them on.

The 6.5 heads required bending the 6.2 injector lines and the oddball intake, required a special, homemade intake setup.

We put it in and fired it up. It bucked, missed and shook, but didn't smoke either black or white. Interestingly, it ran great before teardown. We replaced the lift pump, ensured there was no bubbles in the fuel supply, and made sure supply pressures were consistent with the service manual.

We sent the injector pump to Advanced Diesel Systems in Fresno and they went through it, but reported finding nothing wrong with it. They even tested it on a 'mule' 6.2 and it ran perfectly.

When we put it back on the 6.2 farm truck, the miss, buck and shake was unchanged. It ran like a gasoline engine that is running out of fuel. Idle was also very rough.

We sent injectors to Fresno and they tested out in spec. ADS also replaced the 'head' in the IP free of charge with no change. We checked everything we could find.

I forget now what the compression was, but it was within spec and at the high end of the spectrum.

Finally, because we needed the truck, I whipped Pop a 307 CID Chevrolet together and we swapped it in, pulling the 6.2 litre out where it remains on a stand to this day - over 20 years later - and with less than 100 miles on it since a complete rebuild.

Recently, Pop and me (he is 82 now) started chatting about the engine and wondered what we did wrong - or what we may have missed - that caused the rough running and power loss.

I thought that maybe the 6.5 heads required different length push rods, but it appears that 6.2 and 6.5 are the same length. The heads were brand new GM, so I did not check the valve steam OAL, and must assume this is OK.

Back in that time, Advanced Diesel Systems in Fresno built a lot of 5.7 and 6.2 Roosa-Master pumps for us and the local Cadillac dealer, and we never had a bad or malfunctioning pump come from them.

This engine predates all the electronic controls, so I have to assume that I missed something very simple.

We are just curious as to what you more experienced 6.2/6.5 folks think about this???

Regards,

- Junkers - Central Valley, California

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Old 04-23-2019, 09:12 PM   #2 (permalink)
1967KaiserM715
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Injection timing off, either accidently swapped/crossed an injector line, or the timing gear was a tooth off. Could be the injection pump timing marks or the mark on timing cover was off/mis-stamped.

Also sounds like 6.5 van heads, as 6.5 truck heads are the same as 6.2 with exception of pre-cup design. Hence the odd intake.

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Old 04-23-2019, 10:17 PM   #3 (permalink)
roadhog0
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Didn't get all the air bled from the injector lines. It takes a minute or so of rough running to get cleared up. Plugged return line so you had high return line pressure?
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Old 04-24-2019, 02:22 AM   #4 (permalink)
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Ya I'll second the crossed injector lines, cause I have done that ....


Air in the lines will also make it run like a hairy dog.


Pull the oil filler neck and turn the engine over with a breaker bar till you can see the pin on the IP input shaft ... is it in a round hole or slotty one? ps it's suppose to be in the slotty one ...



I would double check the line numbering, then crack each injector line loose 1/2 turn, pull all the GP's to make it flip easier, now crank r with power to the IP ... each injector should get a lil wet with fuel, now tighten them, crank again in burbs to not burn out the starter ... till there is a fog of fuel out the GP holes, re install the GP's ... glow .. crank ... and it should fire ... run line my life ... but it should start ...


DON'T USE ETHER ....


If you feel the need use cooking spray, Pam olive flavored is my go to ... nice full olfactory experience IMO ... hose each side of the intake for 4 seconds & not through the filter .... ya some one did that ...



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Old 04-26-2019, 01:27 PM   #5 (permalink)
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Thanks to all....we will be checking timing and line placement...
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Old 04-26-2019, 09:17 PM   #6 (permalink)
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Yea, defiantly check the sparkplug firing order. Timing chain timing always seems to cause problems as well. The GM timing is a bit odd for most.

We like mystery's so bring it on. Set that thing down on the floor and send pics as you go. Guys here can figure it out for you. Even a video would help but hit the basics first.

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Old 04-27-2019, 09:56 AM   #7 (permalink)
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Old 04-27-2019, 10:01 AM   #8 (permalink)
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Ditch the old square cartridge fuel filter housing. Replace with 6.5 filter housing or something equivalent. If you have it. Being a swapout from a gasser? I'm assuming.

The older square cartridge filters are terrible for not delivering enough fuel and leaking like a siv (air intrusion)

Dieselpro is right. A video would speak a thousand words.
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Old 04-28-2019, 01:17 PM   #9 (permalink)
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Once you check out what the others said above you can fire it up on the ground and see how it runs.


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Old 05-01-2019, 10:45 AM   #10 (permalink)
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My guess would be timing. A fresh build and pump has very different timing needs than an old loose pump and engine

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