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Tractor Talk Discussion Forum

'95 GMC 6.5TD engine

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JCSinGA

09-06-2006 14:23:21




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Is anyone here knowledgable on these engines? I've not found many people with much of anything good to say about them.
I'm going to have to rebuild this engine and my electronic injection pump is bad as well.
What kind of wasp nest will I get into if I installed a manual injection pump. I know I'll need a cable and brackets.
Can the injectors be used with either pump? Going to have some electrical plugs that wont be plugged I assume will throw a "check engine light" is there a way around this?
It's a 5 speed truck so I wont have any shifting problems, one good thing I guess LOL.

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jdemaris

09-07-2006 06:09:52




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 Re: '95 GMC 6.5TD engine in reply to JCSinGA, 09-06-2006 14:23:21  
Detroit Diesel designed the 6.2-6.5 engine series for General Motors - from the ground up, and I suspect - at least at the outset - fuel economy was the goal - and not durable and heavy-duty pulling power. 6.2s and 6.5s use the same cranks, heads, basic blocks, etc. But, for the most part, the 6.2 blocks were better than the 6.5s. There were minor updates as power was increased - with the cooling systems, rear main seal, etc. When GM starting using electronic controls ca. 1994, fuel mileage went down - not up, and reliabilty went WAY down. The electronically controlled system on the 6.5 went through three major changes - the last (third) was pretty reliable. Most of the new system parts are retrofitted to the older 6.5s. The 1993 turbo-charged 6.5 diesel with mechanical injection and thick-casting block is probably the best of the series ever built - in regard to reliability and fuel mileage. General Motors Corp. claimed that it was too difficult to meet the newer emmissions standards for diesels with the 6.5 - and that is why they changed over to the Japanese Isuzu Powermax engine. G.M. owns most of Isuzu anyway - so I guess, why not? Most people I know that have diesel Chevys with the Isuzu V-8 are disappointed with the fuel mileage.
The military 6.5s ALL retain mechanical injection. In regard to a changeover- from electronic to mechanical - there is small book published with the info needed. After 1993 or 94 (depending on the casting #), the 6.5 block got cheapened and lightened. Subsequently, there are cracking issues. The 6.5s being built now (mostly for the military and marine use) are thick castings again, just at all the 6.2s and first year 6.5s were. One of my 6.2s recently blew up with over 500,000 miles on it. So, I can look at it two ways. 500,000 miles with NO teardown is pretty good. But, what upsets me is - it blew with absolutely NO warning. Engine started and ran great. Good oil pressure, never ran hot, etc. I was going down the highway at 70 MPH - and the engine set-up. In fact, it happened so fast, the fan belts flew off the engine. I pulled the engine out and took it apart. The crankshaft broke into three pieces and tore the main-bearing webs clear out of the block with the bolts still intact. The rod and main bearing journals, and bearings, all look pretty much like new with very little wear evident. So - it appears the weak link is the crank and this engine could of easily went more miles if not for that. I have read that 6.2s and 6.5s break cranks when the harmonic balancers get worn. I checked my balancer on my blown engine and it looks fine.

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billpa

09-07-2006 08:10:02




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 Re: '95 GMC 6.5TD engine in reply to jdemaris, 09-07-2006 06:09:52  

JDemaris
I think you will find out on the 6.2 engines the main bearing webs break out of the block first there fore the crank has no support and breaks. my 6.2 webs broke out of the block,came apart at 134000 at 20 mph
Billpa



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Bob

09-07-2006 08:44:25




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 Re: '95 GMC 6.5TD engine in reply to billpa, 09-07-2006 08:10:02  
EXACTLY.

They suffer from main bearing web cracking, and when the main castings eventually separate from the block, the crankshaft is no longer fully supported, and breaks. Sometimes, there is an odd vibration, ot noise for a while, before the crank "lets go". I have three blocks I should take in for scrap that broke up that way. They even have the NAVISTAR Diamond symbol cast into the center valley area of the blocks!

I have a "beater" 1985 Suburban, and when I dropped the pan to put in a rear main see last winter, I noticed some pretty good cracks forming in the bearing webs. Since there's no fix, I put the seal in and have been driving it, 10,000 more miles, so far, and it hasn't let go, yet! Who knows, it may happen in the next 100 miles, or after another 20,000 miles.

As for what block was best, most 6.2 "afficionadoes" say the 1982 blocks were the best, because they had a high nickel content in the cast iron that was then taken out by the corporate "bean counters".

If you get a NEW 6.5 now, they are being cast by NAVISTAR, and machined by GEP (General Engine Products), and are again supposed to have added nickel in the iron, for wear toughness in the bores, and resistance to cracking.

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jdemaris

09-07-2006 12:10:57




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 Re: '95 GMC 6.5TD engine in reply to Bob, 09-07-2006 08:44:25  
The high-nickel blocks show up now and then. Yes, the first 1982s had it. So did many later military-spec. engines. At one time, the blocks were color-coded and stamped to indicate high-nickel content. GM also did it with various high-performance gas engines. I've got a high-nickel block 327 from the late 60s and also had a Z-28 302 that had it. But, besides the alloy used, the casting thickness was reduced in 94. In regard to the block main-bearing webs breaking first and thus causing the crank to break? Could be - in some cases. But, I also know of few 6.2s and 6.5s that broke cranks and still ran - with all main-bearing supports still intact. One 6.2 I looked at broke behind the rear-main - so the flywheel was no longer attached. The guy that started and owns the 6.2-6.5 diesel Website says he believes such failures are due to worn harmonic balancers. I personally, don't believe it. I suspect the cranks are cast (not forged) and simply not durable enough to last forever - and sometimes much less. With bigger diesels, especially in road-tractors and farm tractors, we had many high-hour cranks welded and reground and I never saw one fail (break to pieces) like my 6.2 did. I did have an IH B-275 ag. diesel tractor that had all its main bearing webs crack.

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RJ-AZ

09-06-2006 20:41:15




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 Re: '95 GMC 6.5TD engine in reply to JCSinGA, 09-06-2006 14:23:21  
I have been driving and working on a 95" HD3500 with the 6.5 for the last 11 years. It"s a fairly hoest engine if treated right, coolin system upkeep is a must. I have 182K on the truck, first engine went 120K before holing #8 piston. Scond engine was a $5K crate motor and is doing OK. Still underpowered in the application.

Biggest problem on the pump is the driver board. this was addressed a day or two ago.

If you are determined to change everything back to early 6.2/6.5 mechanical pump you will almost have to reinvent the wheel. Everything from glow plug contoller, injector lines, turbo, foot throttle will need to be changed out.

If you are getting a hiccup going down the road or it dies out and won"t restart untill it cools down it may be the fuel driver board located on the LH side of the injection pump. Do a google search or go to one of the diesel boards for more help.

Can"t wait for my new 06" F550 PSD 6spd truck gets in :>)

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Bob

09-06-2006 17:33:44




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 Re: '95 GMC 6.5TD engine in reply to JCSinGA, 09-06-2006 14:23:21  
You need to get the system "scanned", and see what's wrong with your electronic injection system.

After a few years of updates, they got them really good, for the most part.

The electronic pump will generally help the engine start better and run cleaner and better than the mech. pump, with SLIGHTLY better mileage.

If you insist on going mechanical, you can use the same injectors, but be sure to get the mech. IP for a turboed 6.5. You will pay a premium price for that pump, over a NA 6.5 or a set-up 6.2 pump, but it has a different head and rotor for the higher fuel flow, and higher "pop pressure" injectors used with the turbo 6.5.

One thing you may not have thought of... the ECM used with the electronic IP also controls the glow plugs, and, if that 'puter is unhappy with what you've done by putting on a mech pump (as it SHOULD be), you MAY have the install the glow plug controller for an older engine. (The controllers LOOK the same, but aren't. The controller used with the electronic IP uses a 3 wires of it's 5-pin connector, and the "standalone" controller used with the older engines uses 4 pins of the same 5-pin connector.)

Post back, if you need more help!

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Bob

09-06-2006 17:33:48




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 Re: '95 GMC 6.5TD engine in reply to JCSinGA, 09-06-2006 14:23:21  
You need to get the system "scanned", and see what's wrong with your electronic injection system.

After a few years of updates, they got them really good, for the most part.

The electronic pump will generally help the engine start better and run cleaner and better than the mech. pump, with SLIGHTLY better mileage.

If you insist on going mechanical, you can use the same injectors, but be sure to get the mech. IP for a turboed 6.5. You will pay a premium price for that pump, over a NA 6.5 or a set-up 6.2 pump, but it has a different head and rotor for the higher fuel flow, and higher "pop pressure" injectors used with the turbo 6.5.

One thing you may not have thought of... the ECM used with the electronic IP also controls the glow plugs, and, if that 'puter is unhappy with what you've done by putting on a mech pump (as it SHOULD be), you MAY have the install the glow plug controller for an older engine. (The controllers LOOK the same, but aren't. The controller used with the electronic IP uses a 3 wires of it's 5-pin connector, and the "standalone" controller used with the older engines uses 4 pins of the same 5-pin connector.)

Post back, if you need more help!

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Bob

09-06-2006 17:33:38




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 Re: '95 GMC 6.5TD engine in reply to JCSinGA, 09-06-2006 14:23:21  
You need to get the system "scanned", and see what's wrong with your electronic injection system.

After a few years of updates, they got them really good, for the most part.

The electronic pump will generally help the engine start better and run cleaner and better than the mech. pump, with SLIGHTLY better mileage.

If you insist on going mechanical, you can use the same injectors, but be sure to get the mech. IP for a turboed 6.5. You will pay a premium price for that pump, over a NA 6.5 or a set-up 6.2 pump, but it has a different head and rotor for the higher fuel flow, and higher "pop pressure" injectors used with the turbo 6.5.

One thing you may not have thought of... the ECM used with the electronic IP also controls the glow plugs, and, if that 'puter is unhappy with what you've done by putting on a mech pump (as it SHOULD be), you MAY have the install the glow plug controller for an older engine. (The controllers LOOK the same, but aren't. The controller used with the electronic IP uses a 3 wires of it's 5-pin connector, and the "standalone" controller used with the older engines uses 4 pins of the same 5-pin connector.)

Post back, if you need more help!

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Joe-Bob/IN

09-06-2006 16:23:36




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 Re: '95 GMC 6.5TD engine in reply to JCSinGA, 09-06-2006 14:23:21  
Try these sites, extremely helpful people there plus a lot of archived info on changing to the manual pump. Usually though there is just a sensor out on the pump which can be replaced to save a bundle! We have two 6.5L's and although they aren't the greatest engine they are pretty good on fuel and have better pulling power than most gassers. Mine has 171K and dads has 151K without any engine trouble yet. Knock on wood.

www.thedieselpage.com - has a membership to post

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