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6.5 reassembled, won't start. Please help! Trying to meet a deadline.

The_Tomato

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Hi all. I have my '94 6.5 td all put back together after doing some bottom end work with the motor still in the truck. It won't start, and i don't know these motors well enough to properly troubleshoot. Installed new timing chain, all gears were aligned mark to mark at the time of their install. The pump gear has the dowel through the slot, not the round hole. The injection pump has no scribed timing mark even though the front cover does. Can someone help me out?
 

The_Tomato

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The truck cranks over great, and has good oil pressure. I'm getting fuel to the t handle valve in the front of the engine bay. I'm getting nothing when i crank though, not even smoke.

Also, the motor ran before i pulled it apart, so i don't think it's a pmd issue or an issue with the injector pump itself.
 

bigblock454

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Did you crack the injector lines slightly open at the injectors to purge out the air? If not crack all 8 open, have a buddy/wife/kid crank it over until fuel starts to pulse out and tighten them back up real quick.
 

The_Tomato

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I tried, but the injector seems to be seized to the line and i don't want to twist it. I've been soaking one in penetrant every so often to see if i can eventually work it free.
 

bigblock454

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If you can get 3-4 cracked open that should be enough to get it running, then once up to a decent RPM it will purge the others. Glow plugs coming on and working? Getting any white smoke while trying to start?
 

The_Tomato

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Glow plugs seem to be cycling based on the dash light, voltage drop, and the audible click from the relay. No smoke of any kind, unfortunately.
 

The_Tomato

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If you can get 3-4 cracked open that should be enough to get it running, then once up to a decent RPM it will purge the others. Glow plugs coming on and working? Getting any white smoke while trying to start?
I got one cracked open and it seems like no fuel is getting to the injectors themselves.
 

The_Tomato

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I loosened it almost all the way up and cranked for a good while and there's nothing. Still getting fuel at the filter and bleeder valve.
 

bigblock454

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Sounds like the IP isn't pumping. So either wiring to either of the IPs fuel solenoids, PMD, ECM etc.
 

Barrman

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It takes about 3 minutes of cranking to go from a dry IP to fuel dribbling at the injectors. Verify you have 12 volts at the solenoid on the top of the IP turning it on. Then verify you have fuel being pumped from the lift pump to the IP. After that it is just a matter of cranking it over to get the fuel flowing. I would suggest no more than 20 seconds on the starter, 2-3 minutes of starter cool down and repeat.
 

campfire

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Did you do any work to the IP and/or injectors? Did you break open any fuel lines? If not, you shouldn't have lost prime and you shouldn't need to bleed the injectors.

If you started with dry lines, yes, it'll take quite a bit of cranking. If you started with wet lines and just lost prime to the IP, it'll take a medium amount of cranking (after fuel flow is restored to the IP).
 

The_Tomato

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Ok, so I checked the codes with a paper clip- 18 and 84. Really not even sure where to go next with this. Safe to say I'm frustrated, as a lifelong gas guy. If i was familiar with this injection system i could probably figure it out, but I'm not.
 

The_Tomato

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Did you do any work to the IP and/or injectors? Did you break open any fuel lines? If not, you shouldn't have lost prime and you shouldn't need to bleed the injectors.

If you started with dry lines, yes, it'll take quite a bit of cranking. If you started with wet lines and just lost prime to the IP, it'll take a medium amount of cranking (after fuel flow is restored to the IP).
Long story short, i dropped the crank to get a machine shop to pull an old, seized and mangled pilot bearing. The truck ran perfectly before i did this, i just didn't have a clutch.
 

campfire

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Ok, so I checked the codes with a paper clip- 18 and 84. Really not even sure where to go next with this. Safe to say I'm frustrated, as a lifelong gas guy. If i was familiar with this injection system i could probably figure it out, but I'm not.

I'm not an expert on DS4 error codes. But I did some preliminary searching for you.

From https://www.troublecodes.net/gm/94-95_65/
18
Pump Cam Reference Pulse Error
84
Accelerator Pedal Position (APP) Circuit Fault


The PCM is comparing the input from both the crank position sensor and the optical sensor inside the IP. This code doesn't tell us which input is wrong, just that the two don't agree. Is it possible that the pump isn't meshed properly with the timing gears? Or that the crank position sensor isn't installed/functioning properly?


Or... from https://www.dieselbombers.com/chevy-gmc-6-2l-6-5l/92920-1995-chevy-2500-6-5l.html

Also try to remove your optical sensor connector and reinstall it. Corrosion often sneaks it's way in to the connectors and remove/install gets you good contact again. The optic sensor can be part of the "reference error" as the PCM compares the Optical sensor pulse to the crank sensor pulse. If the PCM "sees" something it isn't expecting you get a reference error. It knows something is wrong, just not what.

Air in the lines can also cause a code 18. The optical sensor can't "see" through aerated fuel well, it needs straight fuel. This could be something as simple (and hard to find) as a rust pinhole in a line somewhere.

Low fuel pressure/flow can also cause this. You've replaced the filter and lift pump, but did you check the output? Have you checked the "sock" on the pickup tube in the tank?

Along the same lines with the optical sensor, what fuel are you running? IE: straight diesel, dyed fuel, WVO, WMO, etc. Once again, if the fuel isn't relatively clean and clear, the sensor can have trouble "seeing" through it.

Just for some background, the optical sensor is in the IP. It's the "black thing" on top LH side of the IP with the electrical plug in it. It "looks" through the fuel and there is a disc that spins with the IP rotation in front of the sensor. The disc has slots cut in it and these slots are what the optical sensor "sees" as it looks through the fuel. The PCM uses this input to tailor timing of the injection event. The disc is spinning pretty fast and the slots are a very precise measurement, that's why anything that "impairs" the optical sensor (IE: dye, air bubbles, etc) is a problem.



May as well check the simple stuff, too. Pull the return line off the IP and verify that fuel is flowing out of it when the key is on. This proves that fuel is flowing to the IP. If so, you just need to get it out to the injectors.

Were any fuel lines disconnected during this process, that would have introduced air bubbles? If so it could be as simple as bleeding these bubbles out.
 

The_Tomato

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I'm not an expert on DS4 error codes. But I did some preliminary searching for you.

From https://www.troublecodes.net/gm/94-95_65/
18
Pump Cam Reference Pulse Error

84
Accelerator Pedal Position (APP) Circuit Fault



The PCM is comparing the input from both the crank position sensor and the optical sensor inside the IP. This code doesn't tell us which input is wrong, just that the two don't agree. Is it possible that the pump isn't meshed properly with the timing gears? Or that the crank position sensor isn't installed/functioning properly?


Or... from https://www.dieselbombers.com/chevy-gmc-6-2l-6-5l/92920-1995-chevy-2500-6-5l.html





May as well check the simple stuff, too. Pull the return line off the IP and verify that fuel is flowing out of it when the key is on. This proves that fuel is flowing to the IP. If so, you just need to get it out to the injectors.

Were any fuel lines disconnected during this process, that would have introduced air bubbles? If so it could be as simple as bleeding these bubbles out.
It's entirely possible i missed something with the gear installation. I hate having to pull apart the front cover again, but it's probably the next step to try. The crank position sensor is brand new, so i don't think it's faulty, but it's always possible. Everything is Chinesium nowadays.

No, no fuel lines were disconnected. That's what's confusing me. I'll keep yall updated with what i find tomorrow.
 

campfire

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It's entirely possible i missed something with the gear installation. I hate having to pull apart the front cover again, but it's probably the next step to try. The crank position sensor is brand new, so i don't think it's faulty, but it's always possible. Everything is Chinesium nowadays.

No, no fuel lines were disconnected. That's what's confusing me. I'll keep yall updated with what i find tomorrow.

What did you find?
 

2INSANE

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Following. I am anxious to get an update.
 
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