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9.5 volts is too low for the PCM to adequately function. Your batteries are weak (even though you have charged them and even IF they show proper static charge). If you believe the batteries to be acceptable, then it is a wiring issue. You ALWAYS need to address low voltage issues before moving on to other things.
 

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Check the battery grounds on the block and frame - both are weak points
A voltage loss test would tell if there is cabling problems
 

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Discussion Starter #23
9.5 volts is too low for the PCM to adequately function. Your batteries are weak (even though you have charged them and even IF they show proper static charge). If you believe the batteries to be acceptable, then it is a wiring issue. You ALWAYS need to address low voltage issues before moving on to other things.
Ok, now...dumb question. Where do I start with trying to diagnose a wiring issue like that? I'm starting to feel a little over my head lol.
I have access to a battery tester, so I'll load test the batteries and double check, but they're less than 6 months old...
 

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Discussion Starter #24
Check the battery grounds on the block and frame - both are weak points
A voltage loss test would tell if there is cabling problems
Thanks for the info, I'll check those points. Any references on the procedure to do a voltage loss test?
 

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Measure on the battery posts(static)
then during cranking -- both sides(the starter is main load on the passenger side) -- electronics are on the driver side
Measure from the positive post to the alternator output during cranking -- both batteries
Measure from the passenger battery negative to the engine block while cranking
Measure from the driver battery to the body while cranking
This tests the voltage drop on each side of the batteries - should be less than one volt
The block connection is a weak point and the frame(under the radiator)
 

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Discussion Starter #26
Measure on the battery posts(static)
then during cranking -- both sides(the starter is main load on the passenger side) -- electronics are on the driver side
Measure from the positive post to the alternator output during cranking -- both batteries
Measure from the passenger battery negative to the engine block while cranking
Measure from the driver battery to the body while cranking
This tests the voltage drop on each side of the batteries - should be less than one volt
The block connection is a weak point and the frame(under the radiator)
Awesome, thank you so much. I'll perform that test my next day off. It should be less than 1 volt drop during any given test?
 

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Just as a point - batteries that are 6 months old really doesn't mean much. There are many examples of even new batteries failing - and who knows how long they were on the shelf. Let us know how the load testing goes.
 

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Discussion Starter #28
Measure on the battery posts(static)
then during cranking -- both sides(the starter is main load on the passenger side) -- electronics are on the driver side
Measure from the positive post to the alternator output during cranking -- both batteries
Measure from the passenger battery negative to the engine block while cranking
Measure from the driver battery to the body while cranking
This tests the voltage drop on each side of the batteries - should be less than one volt
The block connection is a weak point and the frame(under the radiator)
Ok so, I think my batteries are kind of weak, but it doesn't look like anything >1V drop from the cranking voltage.
Static: Passenger- 12.43
Driver- 12.42
While cranking: P- 10.82
D- 11.05
From Alternator P- 10.76
D- 10.81
Passenger to block: 10.65
Driver to Body: 10.94
 

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You didnt exactly follow what I asked, but your numbers still have meaning -- should have read like 0.5 volts -- looking for post to destination voltage loss(read as a positive)
I suppose there are more than one way of looking at a problem ;)

Voltages are not out of line by your numbers -- but concerned where the 9.5 volts came from
usually a problem at the radiator ground location or at the engine block ground - these are overlooked most of the time
the other spot is the body ground for the harness on the drivers fender area - for the computer ground -- yeah I know, why not straight to the battery ...saving copper I suppose
 

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Discussion Starter #30
You didnt exactly follow what I asked, but your numbers still have meaning -- should have read like 0.5 volts -- looking for post to destination voltage loss(read as a positive)
I suppose there are more than one way of looking at a problem ;)

Voltages are not out of line by your numbers -- but concerned where the 9.5 volts came from
usually a problem at the radiator ground location or at the engine block ground - these are overlooked most of the time
the other spot is the body ground for the harness on the drivers fender area - for the computer ground -- yeah I know, why not straight to the battery ...saving copper I suppose
I guess that's what I get for assuming. When I was only getting a fraction of a volt, I assumed I was doing it wrong...I'll do it correctly tomorow lol.
So should I take apart my ground locations, clean them up, and reattach them?
 

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Yeah, I confuse myself sometimes - you looking for less than <0.5 volt
testing the cable and connection under load - so connect to the major parts, like battery post actual and engine block ...you get the idea

If there is no voltage loss, I wouldn't take them apart ...it's your time and wont hurt anything
There is a red grease type spray(cant remember the name off hand) that I get from the truck shop, works well to control corrosion -- spray that on all the connections
 

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Discussion Starter #32
Yeah, I confuse myself sometimes - you looking for less than <0.5 volt
testing the cable and connection under load - so connect to the major parts, like battery post actual and engine block ...you get the idea

If there is no voltage loss, I wouldn't take them apart ...it's your time and wont hurt anything
There is a red grease type spray(cant remember the name off hand) that I get from the truck shop, works well to control corrosion -- spray that on all the connections
Alright, went back and re-did the test correctly this time. I never got more than 0.2 volt...so does this mean I don't have significant voltage drop?
I'll go buy new batteries if I have to. I just want to make this damn thing run lol.
 

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You had >10 volts when cranking, so hold off on the batteries for now -- may need a charger on them tho -- even on a working system, when first turning over the engine, I would not be alarmed if the voltage hit 10 volts -- there is a lot of amp load at the first of the crank

Your at a crank no start or just hard start now?
 

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Discussion Starter #34
You had >10 volts when cranking, so hold off on the batteries for now -- may need a charger on them tho -- even on a working system, when first turning over the engine, I would not be alarmed if the voltage hit 10 volts -- there is a lot of amp load at the first of the crank

Your at a crank no start or just hard start now?
Crank, no start. It tries, acts like it wants to fire but just won't.
 

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With those voltages, I would assume that your glow plugs are all working. Have you tried the block heater to provide even more "help" in starting?
 

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Discussion Starter #36
With those voltages, I would assume that your glow plugs are all working. Have you tried the block heater to provide even more "help" in starting?
I haven't, it's in the 80s during the day here already, so I didnt think to. I'll try it when I get home though.
 

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Discussion Starter #37
With those voltages, I would assume that your glow plugs are all working. Have you tried the block heater to provide even more "help" in starting?
Alright man. I broke down and took it to a shop to get it diagnosed. They're saying that i have blow-by so bad that it won't build enough compression to start.
I never had blow-by before. At all. Is it possible that the rings or pistons cracked suddenly and caused the lack of compression?
 

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I guess it is possible, although it certainly isn't common. I was concerned that it might be a base engine issue. Damage from an overfueling injector is more common.

You need to get a compression test - see which cylinder(s) is the issue.
 
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