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

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Old 07-06-2004, 01:21 PM   #1 (permalink)
Freeze Plug
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I'm looking for some help with my 1991 Chevy K2500 w/ the 6.2 L, vin J with about 130,000 miles on it. If I run the truck and shut it off for about 2 hours on a hot summer day she won't fire up easily or at all. Sometimes it takes 3 - 4 long cranks and in some cases won't start until the engine cools down completely. I can not figure what is going on here. About 1 1/2 years ago I went through the fuel system (i.e. installed rebuilt injector pump, injectors, fuel pump, fuel pump relay, and oil pressure switch). The pump is lined up with the timing mark too. Recently I swapped out the shut down solenoid with a spare one and that did not help. I changed out the original starter, as I read on the forum that as they get older they draw more power thereby starving the shut down solenoid of the 10+ volts to turn it on. This did not help. The batteries were load tested too so the batteries are fine.

I am assuming the rebuilt injector pump was "bumped" up to flow more fuel through and don't know if it would cause it to run too rich (i.e. chokes)? Is that possible?

On cooler days (i.e. under 60 to 70 degrees) the truck starts easily and runs strong.

I appreciate in advance any help, thoughts, or comments.



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Old 07-07-2004, 11:31 AM   #2 (permalink)
Self Ignition
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I have a 82 chevy with the same problem. It has to be a really warm day but mine will do it too sometimes. I'm not really sure what the problem is I was told by one mechanic that glow plugs on these 6.2 s is really important. There is a bi-metalic strip like that on a thermostat in your house. Sometimes it doesn't work right and it won't trigger the glow plugs. I don't know though, anybody with any info would be greatly appreciated.

thanks Justin

2004.5 lly d/a stull stainless running boards, luvern stainless mud flaps, egr mod with plate, 4" mbrp downpipe back with stainless tip, access cover, putco punch stainless grille, edge ez

1982 Chevy Silverado 6.2 diesel (old reliable)
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Old 07-08-2004, 02:07 PM   #3 (permalink)
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usually that is the sign of a tired pump, as they heat soak the clearances inside the pump open up enough to not create enough fuel pressure at cranking speeds.
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Old 07-09-2004, 02:44 PM   #4 (permalink)
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If your truck starts fine when its cold but won't start when its hot it has nothing to do with the glow plugs. Grape is on the right track, its the pump.

Read through the posts under:

6.2L wont start (for some reason this is in the 6.5L list of forums)

oh and something else, lots of times when shops rebuild pumps they don't do the head, this is where the no-start problems are, so just because your pump has been rebuild doesn't mean its not the problem.
95 Chevy Tahoe 6.5L Turbo Diesel 4x4. Straight pipe exhaust, SS Diesel supply air intake. PMD mounted under bumper w/heat sink. Stock everything else. 3.42 gears, 4L80E. Running on WVO with Plantdrive kit. 200k miles.

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Old 07-12-2004, 08:11 PM   #5 (permalink)
Low Boost
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one way to check if its heat soak causing the orifices in the pump head to become oversized is to make sure the engine is already up to operating temperature . turn the engine off and let it set till the the problem occurs, take a pitcher of ice water and slowly pour it over the pump head (where the injector lines connect to the pump) very slowly, mabe two or three to cool off the pump head. then try to crank it. if it starts your pump head is worn out. if not youve got other problems. possibly a glow plug controller, air in the return system ect. try this , if not we'll go else where with it.
DIESEL TECH, 86 chevy 5/4 ton 6.2 (turbo from a continental duce and a half), military trained diesel specialist, 99 tahoe , 73 nova, 67 bronco
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Old 07-13-2004, 02:51 PM   #6 (permalink)
Freeze Plug
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I think grape, jjw565, and fixitman have nailed it down in regards to the pump head being worn even after the rebuild. It makes sense as prior to installing the replacement injection pump I never had a problem with "heat soak", but rather it no longer had the power it use to. I'll try the trick of pouring ice water on the head of the pump to see if it fires when this condition arises. If this test does work the only bright side is I kept my original worn pump and I'll know better what to look for in a rebuilding shop. I'll keep everyone posted and very much appreciate the input.
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Old 07-16-2004, 11:08 PM   #7 (permalink)
Diesel Kingpin
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A gallon of tap water will do it. Just let it sit a coupla minutes before you start it. The head in the pump can seize if you try it to soon. Water on it while running hot will seize it to.
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Old 08-06-2004, 01:49 PM   #8 (permalink)
Block Heater
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I'd like to add that if it still has this problem after you pour water on it that it could be what's called vapor lock , your fuel lines dont have the cover anymore at the tank switch , the fuel lines could be 2 close to the exhaust system , fine when its cold ----forever but shut it off ---vapor lock's -----then cools down and starts again , I have seen the pump gone lots of times but also seen this problem .

hope it help's
ps you can also vapor lock your brake lines as well , but i wouldnt reccomend

Doug Gritner
Doug's Repair
Alexis Creek
British Columbia
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Old 08-13-2004, 12:33 PM   #9 (permalink)
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Send a message via MSN to u2slow

Do the glo plugs cycle on?

My '84 has the same problem. The glo plugs do not come on at all on a hot day if I've been driving it in the last two hours. Makes running errands a hassle.

I take a screwdriver and manually short the GP solenoid for 5 seconds and it starts like a champ.

Time for manual pushbutton on the dash
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Old 08-14-2004, 01:53 AM   #10 (permalink)
Glow Plug
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The glow plugs are not required when your engine is warm. The thermostate controller on the right rear head prevents the glow plug solenoid from being activated. If your engine will not start when it is hot then your injection pump is probably worn out.

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