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Hey everyone I have been the owner of a 6.5 for a couple years now and really wish I would have found this forum when I purchased this vehicle. It has been converted into a short school bus and become my traveling home. I am currently stranded with issues that have me scratching my head and more so aching my wallet.

I've already stupidly replaced my IP. I guess if I admit it publicly I can feel better about eating the experience -.-

The bus died last week as I rounded the corner. Similar to a week before when I was coming through a mountain summit.. Just died and coasted to a stop. Took a few tries to start.. I carried on for another few miles, it did it again. This time no start for about an hour. Then I was on my way; traveled another 75 miles & am now currently stranded. I had originally troubleshooted the IP to be bad as I had someone check with a scan tool and try to manually turn it on; while Service Engine was on- No codes were showing.. Fuel was getting up to IP; although I realized the valve stem in the T-valve had been broken (probably the entire time I've had this vehicle) and leaking slightly. This has been repaired. No fuel getting to injectors.. So I figure the IP is bad.....

So I replace the IP and realize the new unit has the PMD mounted and the old one had it relocated; I read online best to relocate so I plugged the new pump into the old PMD. Still had Service Engine. Then I realized maybe it was the PMD all along; and so I plugged the harness into the new PMD on the new IP... Service Engine light gone...

At this point I believe I should be able to get things running with the service engine gone..I read to purge the lines it needs quite a bit of cranking.. and so I did so for about a dozen times.. of & then I read you are supposed to pull the glow plugs to get a faster crank with no compression and it will bleed the lines faster.

Yesterday I had fuel from the LP - could hear it prime with the key On. Today as I was excited to try to purge the lines and try to pull out the glow plugs when I notice the LP isn't supplying fuel up to the pump anymore..

I also notice I have a battery symbol when turning key on/try to start AS WELL as Check gauges... Also, Ive checked Voltage at the harness the delivers power to all the fuel systems and there seems to be Volts coming from only 2-4 of the 20+ pins.. Feeling stumped.. have replaced Fuel pump relay as well as fuel filter...

Recent changes had me modify an old external (auxiliary) water pump that supplied the old school bus heater in the rear.. I took this wiring and added it to my new water pump for sink inside the coach. & so this new addition has me wondering if I messed up the electrical by switching/ tapping into the bus power- but I believe this is auxiliary and not engine related.. Just giving some background info. I also have dealt with terrible starter heat soak issues -which have me questioning if its been the PMD all along. Also, MAJOR loss of power when going uphill especially in higher elevations. Im talking 20mph maximum.

At this point I really need to determine why the Lift pump is failing. I tried testing the LP hooking it up to 12V power and it kicks on. So I believe theres a loss in deliverance of power to the fuel system and the harness is telling me that with the voltmeter... I'll stop the details now- I hope someone reads this with some insight, thank you if you've gotten this far!
 

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Welcome to DieselPlace

First, start by going through all of your grounds: Grounds-Grounds-Grounds The importance of good grounds.....
Check and post any Codes found here.
Then perform a lift pump test: Reference Material: Lift Pump/OPS
If it fails the test, replace the pump ( AC/Delco EP 158)
PMD w/ resistor installed, needs to be relocated to the inside of the front bumper, mounted on a heat sink, away from any engine heat sources for best PMD health.

Install a piece of clear fuel line on the return side of the Injection Pump to help locate any air in fuel ( as shown here) : Question: - 1999 GMC Bluebird 6.5L TD - PMD &amp...
If you notice any air bubbles within the line then you need to hunt the source of the air intrusion.
 
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Discussion Starter #3
Welcome to DieselPlace

First, start by going through all of your grounds: Grounds-Grounds-Grounds The importance of good grounds.....
Check and post any Codes found here.
Then perform a lift pump test: Reference Material: Lift Pump/OPS
If it fails the test, replace the pump ( AC/Delco EP 158)
PMD w/ resistor installed, needs to be relocated to the inside of the front bumper, mounted on a heat sink, away from any engine heat sources for best PMD health.

Install a piece of clear fuel line on the return side of the Injection Pump to help locate any air in fuel ( as shown here) : Question: - 1999 GMC Bluebird 6.5L TD - PMD &amp...
If you notice any air bubbles within the line then you need to hunt the source of the air intrusion.
Thank you OkDually!
Here’s where I’m at -
Checked all grounds; everything seems to be fine unless I need to trace back every inch of wire. Which I will do- this is a school bus mod so there are a lot of extra wires.

I have no 12v going to LP.
have pulled the LP and attached to 12v- lift pump is fine. Just no power.
also no power to glow plugs. Tracing the main wiring harness now. Any suggestions are appreciated
 

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I’d like to note also, that the other day I had power to glow plugs; had power to lift pump.
Replaced the IP and tried to get the lines bled when I noticed I no longer get wait to start or hear the LP working
 

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Thank you OkDually!
Here’s where I’m at -
Checked all grounds; everything seems to be fine unless I need to trace back every inch of wire. Which I will do- this is a school bus mod so there are a lot of extra wires.

I have no 12v going to LP.
have pulled the LP and attached to 12v- lift pump is fine. Just no power.
also no power to glow plugs. Tracing the main wiring harness now. Any suggestions are appreciated
When checking grounds, remove each one, inspect/clean all contact points and reinstall.
If any are in questionable shape replace them.
One bad ground can cause a lot of issues in a 6.5L

Check all of your fuses for Lift Pump power and glow plug power loss. Check all battery conections and battery grounds.
 

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Is there another fuse panel I should be aware of? Have checked the one near parking brake as well as under the hood driver side.. fuel pump relay has been replaced. Really need to remove and check all grounds...

With the OPS plugged in, I have “Check Gauges” with it removed the light goes away.. could this mean my OPS is bad and not signaling to fuel system?

glow plugs also no voltage..

Thanks for your patience and help! Truly appreciated- I am stuck stuck for the past week lol
 

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Is there another fuse panel I should be aware of? Have checked the one near parking brake as well as under the hood driver side.. fuel pump relay has been replaced. Really need to remove and check all grounds...

With the OPS plugged in, I have “Check Gauges” with it removed the light goes away.. could this mean my OPS is bad and not signaling to fuel system?

glow plugs also no voltage..

Thanks for your patience and help! Truly appreciated- I am stuck stuck for the past week lol
Fuse panels are next to parking brake and in the engine compartment.
OPS is in the power supply link. If it is bad you will have problems. If you replace the OPS only use AC Delco brand : D1815A (Van) application I believe for your bus..

Make sure you are getting 12v. to the glow plug controller and with the assistance of someone turning the IGN key, make sure you have 12v. leaving the glow plug controller going to the plugs.
Here is a thread with some info on the no glow plug controller light: My glow plugs won't cycle
 

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not sure of your year but the lift pump on 94 has a fuse on the firewall that is fed from the ops. It is in a holder next to the 12v buss bar.
 

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Discussion Starter #10
Fuse panels are next to parking brake and in the engine compartment.
OPS is in the power supply link. If it is bad you will have problems. If you replace the OPS only use AC Delco brand : D1815A (Van) application I believe for your bus..

Make sure you are getting 12v. to the glow plug controller and with the assistance of someone turning the IGN key, make sure you have 12v. leaving the glow plug controller going to the plugs.
Here is a thread with some info on the no glow plug controller light: My glow plugs won't cycle
Well the old man helping me brought a new OPS to try and it didn’t work. Is not the ACDelco brand tho... Standard brand.. STD... is it essential to have AcDelco? Should I remove it ?

I have 11V going to glow plugs relay.. no volts going to glow plugs
 

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Do you have a center mount turbo?
 

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Does the OPS conn. that plugs into the OPS have 1 TAN wire or 3 wires?
 

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Well the old man helping me brought a new OPS to try and it didn’t work. Is not the ACDelco brand tho... Standard brand.. STD... is it essential to have AcDelco? Should I remove it ?

I have 11V going to glow plugs relay.. no volts going to glow plugs
When it comes to any electrical part in a 6.5L you need AC/Delco brand parts or you'll get some electrical gremlins.
Replace the glow plug relay with AC/Delco
 
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Your 2000 does not have an OPS switch, just an oil pressure sensor.
GM finally got rid of the OPS on the vans.
The PCM (computer) controls the LP thru the LP relay.
When you turn the key on and wait do you hear or feel the GPR activate?
 

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Discussion Starter #17
Your 2000 does not have an OPS switch, just an oil pressure sensor.
GM finally got rid of the OPS on the vans.
The PCM (computer) controls the LP thru the LP relay.
When you turn the key on and wait do you hear or feel the GPR activate?
So is it pertinent to switch the oil pressure sensor to an AcDelco?

The LP relay = the fuel relay correct? This has been replaced too. The other day I could hear the pump kick on and the glow plug really click.. now- nothing.
 

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When it comes to any electrical part in a 6.5L you need AC/Delco brand parts or you'll get some electrical gremlins.
Replace the glow plug relay with AC/Delco
So even if it’s just the Oil Pressure Sensor, I should replace the brand new one with ACDelco?

& glow plug relay? Did you mean to say OPS or are you responding to my no volts at glow plugs?
thank you
 

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Your OPS is just the oil pressure sensor and is only for the oil pressure gauge.
It will not cause LP problems. OEM A/C Delco is always the best choice.
Check your fuses, especially the ECM-B and ECM-I, they are in the under hood fuse/relay box.
 
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