Chevy/GMC 6.2L and 6.5L Discussion of Chevy and GMC Trucks with 6.2L and 6.5L Diesel Engines

6.5 will idle fine, but shuts down after driving 15 to 20 minutes, but restarts

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  #21  
Old 12-21-2013, 06:39 AM
sureshot's Avatar
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Default ops mod

if u look up "ops relay mod" you will see that 1 of the 3 wires coming out of your ops go's to power your lift pump. find out which color it is and do a power test (close to ops) if u have power run a new power lead right to your lp. ive done the mod but cant remember the color code. hope this helps. ps the truck has to crank over i believe to send power.

---AutoMerged DoublePost---

grey wire should be live when turning or running. it can run right to your red lp wire under your drivers side frame.
 

Last edited by sureshot; 12-21-2013 at 06:39 AM. Reason: Automerged Doublepost
  #22  
Old 12-21-2013, 04:59 PM
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With a 94 you won't hear the LP run when you turn the key to run,the LP relay is only active during cranking and once running the OPS takes over control of powering the LP.

The condition you have is normal without the extra wire hooked up-check to see if the LP is working when the engine is running by putting your hand on it with the truck safely parked.(or jumer the orange and grey wires at the OPS harness connector)
If you can feel it working then open the water in fuel drain Tee-valve with the engine also running to con firm that it is pumping.
If the engine continues to run all is well,might want to put a catch can under the general area of the drain hose to catch fuel.

if the engine stalls out then the LP is shot since they can run but not pump any fuel.

if after feeling the LP with the engine running and it doesn't act like it's doing anything you need to verify that power is getting to it via the OPS circuit.
using a test light check for power at the LP harness with the engine running or by jumping the orange and grey wires at the OPS harness.
If no power is getting to the LP run a new wire from the OPS harness grey wire to the LP harness,cut close enough to each harness end to still make a good connection.
 

Last edited by racer55; 12-21-2013 at 05:08 PM.
  #23  
Old 03-01-2022, 08:21 PM
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Originally Posted by SheDiesel
Hey everyone, I have a 1994 6.5 chevy 1500, automatic, This truck has sat up for approx. 1.5 years, and now trying to get it to run again. Job I know, let me give you a little history on this, the guy I got it from was a second owner, he said he purchased the truck and installed a new pmd, let it idle until it ran out of fuel, and just never did anything else with it as he didn't know how to bleed the lines, and he had another truck, well a few months ago I end up with truck (he owed me money)thinking, a set of new batteries, added fuel, and new fuel filters, a touch of eather, and varoom, well only if I really had good luck, but here goes, new batteries, and a touch of eather, and we cranked up just fine, yippee, took it for some short trips, around property, and all seems well, decided to take it to town, on open road, and once around 60 or so, it sputters, and dies, figured trash in line from sitting up, cranks right back up and again, we try to go about our way, and a few minutes later sputters and dies, well this time looking around we find bad fuel leak, seemed to be from back of motor, so towed it home and look for issue, cannot really pinpoint leak, so we get new filter, and re do it, no go, then researching, find out there is a valley where the fuel is more than likely gathering to pour out, so off comes the intake, don't see any visible leaks, but change orings in filter canaster, and all rubber fuel lines, and intake back on, upon bleeding the air from the system, and checking, luckily no more leaks, system dry, start up with a touch of eather, and sputters a bit and dies, again sputters and dies, (expected) then she cranks with no missing, sputtering nothing, sounding like she should, let it sit in yard and idle, for a while, a pop or two initially, then smooths right out, temps look good, fuel pressure looks good, all systems go, down the road, plenty of power, but some light issues, and back, no misses skips, and no leaks, thankfully, well after idling for 5 mins or so, back down the road, not to get 2 miles from home and she shuts down, no sputtering, no spitting, just like the key was shut off, any ideas anyone, and the starter needs to be retightened, so I just came in tonight,

Please help, need a way to go, as my f150 died,


hey! I know this is an old thread. I’m having same issue! Wondering if this would cause the dash to read low oil pressure as well!
 
  #24  
Old 03-01-2022, 08:24 PM
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Originally Posted by RivervalleyJohn
I had almost the same problem on my - 95 gmc and it was the lp that failed,well not the lp but the oilpressure switch that makes the lp work when the engine is running.If your truck is build the same way as mine you can check the lp by get shifter in Drive and try to crank it,in crank position you hear the lp ticking to give fuel in starting moment and then when it has started the oilpressure switch is supposed to give power to the lp.

would this cause the oil pressure on the dash to drop low and show the “check gauges” light?
 
  #25  
Old 02-26-2023, 04:45 PM
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My fix when this happened was to loosen ,clean, and tighten All GROUNDS, add a new ground from BTY#1 to the block, and a ground wire to the big pump from the battery.,
Days of hair pulling was fixed for free, .
 
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Quick Reply: 6.5 will idle fine, but shuts down after driving 15 to 20 minutes, but restarts



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