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1997 K1500 ECSB L56 6.5 TD Auto F44 208k
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Truck is a 97 K1500 L56 6.5 Auto with 208k miles on it. It had sat for 2 years before I picked it up. Previous owner didn't have the starter braced and using a Napa brand starter it broke off the bolts. But before this he spent $3000 with a new fuel pump (I'm guessing lift pump, idk if these have one in the tank), injection pump, and fuel lines. The truck does look taken care of and now that I've fixed the brakes and put on a new vacuum pump it starts and runs pretty well cold but once I get where I'm going and shut it off all bets are off. When it gets up to operating temp it seems like it doesn't want to run. It'll surge and try to stall under anything more than light throttle. Under load it'll start bucking real bad like a dead miss then it'll shut off and it is almost impossible to restart. I haven't tried rebleeding the system since I first got it and it seems to have a random leak coming from up by the tank but it doesn't leak when running or priming just randomly when it sits.
  1. Any help is appreciated, very new to this setup and just want it to run.
 

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Welcome to DieselPlace
Start by performing a lift pump test: Reference Material: Lift Pump/OPS
If it fails the test replace with AC/Delco EP158
Go through all of your grounds: Grounds-Grounds-Grounds The importance of good grounds.....
Install a piece of clear fuel line on the return side of the Injection pump to help look for air in the fuel: installing a clear fuel line

Open your fuel cap. Do you hear a large "Whoosh" sound? If so then you have a fuel restriction and need to modify your fuel cap for better venting
 

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1995 GMC Suburban
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The lift pump (LP) is inside the frame approximately under the driver position.
NOT IN THE TANK.
There are LP and Injector Pump (IP) that deals with the pump..

There is a fuel tank sock in the tank.
It is a special diesel tank sock if it has gasser tank sock then it tends to clogged within a short period of time.
The diesel sock have a valve.

Is there any DTC?
That symptom usually indicate that there is problem with Injector Pump (IP).
May be it is just the PMD which is relatively cheap.
Unfortunately, the only way to test is by putting in a new KNOWN WORKING PMD.
May be it is a bad IP.
 

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1995 GMC Suburban
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17,865 Posts
I forgot, do a LOAD (NOT voltage) test on the batteries one at a time?
Batteries have a heat soak effect also.
 

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I had the same problem with my truck when I bought it from the previous owner. The problem was the crankshaft position sensor (which is relied on by the computer for timing), but I suppose an improperly timed injection pump might cause a similar problem. The computer automatically advances timing until the truck reaches operating temp, which may help the truck run better when cold. Disconnecting the coolant temp sensor when hot or cold may help in simulating if it is a timing related issue.
 
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