New guy with an issue

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Blackshirt132

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Scott
Truck Year
1986
Truck Model
Sierra 1500
Engine Size
6.2
Greetings, I am new to this site and hoping for a bit of help. I collect antique fire trucks and own a 1986 GMC Sierra, 6.2 L diesel “mini pumper”. For those of you who don’t know a mini pumper is built on a truck chassis and has a fire truck body. They were mainly used for trash fires, auto accidents, car fires, and misc. So my issue is when the truck runs or pumps for any length of time it will not restart. This is when it reaches normal operating temperature at about 180 degrees. So if there is anyone out there that is aware of this issue please let me know. So far I’ve been told: glow plugs, pmd module, injectors, and vapor lock.
Thanks for any help.
 

Charlie

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bucket

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Howdy!

Does it crank over strong but won't run, it does it simply crank over weak and slow?
 

Blackshirt132

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When it’s cold it cranks slow but speeds up and starts. When it’s warm it’s slow it’s slow and doesn’t start at all.
 

Old77

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animal

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Preston

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Welcome to GMSB from Virginia
If it cranks when cold wouldn’t think it’s the glow plugs.is your battery at full charge? Alternator over charging, batteries getting hot, how old is the starter? Could be getting hot when running, as I have been told start with the simple things and go from there also are the battery cables good and clean and tight? Hang in there keep us posted we will figure this out.
 

75Monza

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On my 86 burb, had several issues like that. First, my starter cranking slow when up to running speed would not build enough pressure through the pump to "pop" the injectors. Rebuilding the starter got my cranking speed back up when at operating temp. Still had some trouble with hot starts after that, found that my pump was worn and not building enough pressure because of leaking by the plungers from rotor head being worn. Never really found out what the 6.2 would run like with rebuilt pump and injectors since at that point I yarded it out and bought a 6.5 long block and hooked everything up to that...with a banks stinger system, so much funner, lol.
Also, just curious when it is idling at temp, do you get any blue smoke out the pipes? That could point to worn/dirty injection nozzles.
 

dvdswan

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Welcome to the site.
 

Blackshirt132

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New batteries, new battery terminals, the starter is probably original. I’ll start withe fuel pump and the starter.
Thanks a million
 

1973c10

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Welcome
 

Snoots

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Welcome to GMSB from Georgia!
Nize truck!
 

75Monza

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By fuel pump, I meant the mechanical injection pump that is mounted under front of intake manifold. Pump looks like this
You must be registered for see images attach


located under front of intake manifold. Think the average rebuilt is around $630 or so nowdays, new bosch injectors are around $42 each. The mechanical lift pump is around $54, should be mounted on side of block just like a gas engine. The lift pumps can fail too, best tell is your engine oil level getting higher from diaphragm leaking into the pan. You can check that by just opening the drain line on the fuel filter and cranking engine with pump power wire pulled to see how much fuel you get out...by the way, the filter is another thing that you should change regularly.

You must be registered for see images attach

I used a set of diesel injection pressure gauges to check out my pump pressure when it was hot, pulled the wire off the pump and cranked to see what I had.
Here is a document about the 6.2l that might be helpful.
http://matveynator.ru/f/9efda83135c6d53e16e47aab9a0122c4.pdf
Another item with the fuels nowdays being ultra low sulfur, you absolutely need to use a good fuel additive because these pumps and injectors were designed for the lubrication of moving parts to be from the sulfur that used to be in there. Without the lubrication, the needles and seats in the injectors and the injection pump moving internals wear much faster. I use Stanadyne fuel additive in my old diesels and my 05 Cummins.
Last thing I like to do on all the older diesels is upgrade the filter with spin on filters for better flow and can get better micron filtration than factory filter, here is an example.
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There is no end of ways to play with your truck, lol.
 

donnieray

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Welcome from NC! I'm an old guy with issues.
 

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