Need help troubleshooting a '98 Chevy 6.5L Diesel

[T-Bone]

Need some good information to help a friend of mine with his 6.5L diesel problems. The thing has quit him 2-3 times in the last week. He got a guy to scan for codes and he's got a code that says something like "lift pump secondary voltage".

Thanks in advance.

 

[knightkrawler00]

Is it a P0231 Fuel Pump Feedback Voltage Low? Aftermarket scanners don't always have the same descriptions as factory scanners. If that is the code, then the ECM is not seeing the voltage it wants at the lift pump. When the ECM turns on the fuel pump relay, power is sent to the fuel pump on circuit 120, the gray wire at the pump. Circuit 120 then returns to the ECM at pin D5 in connector 1. The ECM should see B+ on the wire whenever the fuel pump is commanded on. I would first go to the fuel pump relay. The truck is stalling and setting the code, so most likely that part of the system is working correctly and power is getting lost somewhere. Now comes the fun part of trying to find where power is going away. Could be as simple as replacing the relay. But, you may also have a wire that is intermittently going open or shorting to ground.

The ECM sends a relay signal to the relay at pin B3 on circuit 465, a dark green wire with a white tracer.

Ground is supplied at pin A1 it's circuit 451 and it's a black wire with a white tracer.

Fuel pump power comes from the ECM B fuse and enters the relay at Pin B1 circuit 440, orange wire.

Power from the relay to the fuel pump leaves the relay at pin A3, that's the circuit 120, gray wire, that the ECM is monitoring for voltage.

Good Luck

 

[flatlander72]

6.5

Good chance the injection pump driver is going out. They can run fine and then die out of the blue, shut off the ignition and try to restart and sometimes refire and other times not. How many miles on the truck? Chevy extended the warranty to 12 years/ 120,000 miles because of all the probs with the drivers/injection system.

 

[hilinerider]

get the kit to move the pdm module off the pump and either onto the top of the intake or to the fender, get a pdm with the heat sinc, cheap short term fix is to take off the pdm and get it out of the valley, leave plastic cover off top of engine to let heat out

 

[triple]

I relocated my pump driver with a heat sink, added the wiring harness extension and still had issues. Usually a bad pump driver means a bad pump. Email or PM me the vin and I'll tell you if the pump was ever changed.

 

[skidooer1]

I installed a huckstorf diesel pmd relocation kit, lift pump, and oil pressure switch on my buddies 6.5 after he was having issues with it randomly dieing and so far a year later it has had no issues. always replace the oil pressure switch since that is what triggers the lift pump to run.some trucks you will find that the optical sensor in the injection pump is fried and in that case replacing the ip is the only fix. but in any case the pmd and injection pump are sold seperatly so you can always start with the cheaper fix and go from there. btw always replace the pmd, don't just do the relocation.I think we had about $350 dollars into his when we were all said and done. matt

 

[skidooer1]

http://www.hdiesel.com/product.asp?id=42

heres a link

 

[T-Bone]

Thanks everyone. Every he and I have talked to thinks it the pmd. I think he's gonna try the relocation kit.