lly won't cold start

[DIESELMAFIAPER.LB7]

All the glow plugs test good there less then 10k miles old compression is great motor is fresh rebuild only 3k miles.

I am only getting 1.8-1.9 volts to the plugs but have 12v at the controller I believe lly were 4-4.5 volt glow plugs no? The controller is new as well as we had a code for the controller originally and swapped it but it didn't help. If the truck is plugged in or if it's 35* and warmer it will start to.

If you turn the key on the light only stays on long enough to see it. If it's 0 it'll stay on for about 1 sec.... if you cycle the key 4 or 5 times it'll start rough in the cold. This was also a issue before the new motor. All grounds are good I even added a ground right off the controller no change.

So I'm thinking a new controller again or what else would cause it to not get the correct voltage? Harness is fine as well.

 

[millerman04]

Batteries still good I take it?

 

[Chevy1925]

start ohming GP wires and the relay.

 

[DIESELMAFIAPER.LB7]

start ohming GP wires and the relay.

I ohmed the glowplugs in place with wires still on them all were pretty close but i'll ohm the wires separate is there a certain range gm asks for. isnt the relay built into the controller?

the controller voltage when key was on or off the pins all seemed to read 2 volts?? nothing was zero or jumped to 4 volts with key on

Batteries still good I take it?

yes

 

[Chevy1925]

I ohmed the glowplugs in place with wires still on them all were pretty close but i'll ohm the wires separate is there a certain range gm asks for. isnt the relay built into the controller?

the controller voltage when key was on or off the pins all seemed to read 2 volts?? nothing was zero or jumped to 4 volts with key on



yes

im not sure enough on LLY if they went with a different circuitry for the GP controller than a LB7 but all the LB7 is, is a high amp relay. id be more enclined to say the controller is bad if its still showing voltage even after its "off".

are there any codes for it (if they are even availible)

 

[mike diesel]

Lly+ trucks use a 4.7 volt system with fast heat glow plugs and a solid state glow plug controller. There is no relay like an lb7. Even when it is below freezing the glow plug light will only stay on for about 2 seconds. Did the issue start after swapping in new glow plugs or are those the original lly plugs? Lb7 plugs will fit in an lly head but they are not electronically interchangable.

 

[DIESELMAFIAPER.LB7]

No codes and I didn't think there was a relay either mike. But the light literally is on just long enough to see it when it should stay on for 2-3 seconds ecm commands 4-5. In 0 to negative temps it's blinks on for maybe a second and the voltage is low. Also all plugs are brand new the original plugs were in when this started as was the original controller replaced everything and still have the issue. The fuse is obviously good as I get 12v to the controller

so I'm going to try another controller see what that does

 

[Awenta]

Certainly sounds like a controller at this point. Try to get a known good one from someone.

Sent from my SM-N910V using Tapatalk

 

[THEFERMANATOR]

If the glow plugs aren't staying on very long, verify the coolant temp sensor reading is correct. If the CTS reads warmer than it actually is, then it won't command the plugs. Like said above, make sure it has LLY plugs and not LB7's in it. And from what I remember the LLY plugs will only see the 4.7 volts for a split second, then drop back to 1.2-3 volts depending on the temp, battery voltage, and glow plug resistance. So checking voltage at the plugs does you no good.

 

[DIESELMAFIAPER.LB7]

If the glow plugs aren't staying on very long, verify the coolant temp sensor reading is correct. If the CTS reads warmer than it actually is, then it won't command the plugs. Like said above, make sure it has LLY plugs and not LB7's in it. And from what I remember the LLY plugs will only see the 4.7 volts for a split second, then drop back to 1.2-3 volts depending on the temp, battery voltage, and glow plug resistance. So checking voltage at the plugs does you no good.

they are diesel rx plugs maybe they boxed them wrong but they came for a lly that's what I ordered. maybe ill try new gm ones....

also it never hits above 1.7 volts they should stay at 4-4.7 for the 2-3 seconds though

ill check coolant temp tomorrow thanks for the idea:thumb:

 

[THEFERMANATOR]

they are diesel rx plugs maybe they boxed them wrong but they came for a lly that's what I ordered. maybe ill try new gm ones....

also it never hits above 1.7 volts they should stay at 4-4.7 for the 2-3 seconds though

ill check coolant temp tomorrow thanks for the idea:thumb:

I'm pretty sure there's are the ones who sell the same for LB7 and LLY unless they changed recently. Put AC DELCO 63G's back in it and see what happens.

Just looked at there site, and they still list the same plugs for 99-05(DRX00058) which is wrong. 01-04 LB7 is one style, and 04.5-05 LLY is another. The LB7 plugs will bolt right into a LLY, but will do just like your describing because the LLY controller is seeing the wrong resistance.

SOund familiar: http://www.duramaxforum.com/forum/general-discussion/152733-lb7-glow-plugs-lly.html

 

[DIESELMAFIAPER.LB7]

Ya I looked it up yesterday and went wtf really? I called the warehouse and told them to correct the issue. I pulled them all out and put new ac Delco ones in bitch fired right up in the cold again.

Thanks for the help guys:thumb:

 

[mike diesel]

Those dumb asses did the same to me 2 years ago. I had a nice long bitch fest with them and told them they are NOT THE SAME GLOW PLUGS. And they told me I was wrong and that they have engineers who know what they are doing. I told them the engineers are idiots. I made a thread about it on DF.

I knew your issue was glow plug related. Damnit those guys piss me off so bad. ****ing idiots

 

[DIESELMAFIAPER.LB7]

Those dumb asses did the same to me 2 years ago. I had a nice long bitch fest with them and told them they are NOT THE SAME GLOW PLUGS. And they told me I was wrong and that they have engineers who know what they are doing. I told them the engineers are idiots. I made a thread about it on DF.

I knew your issue was glow plug related. Damnit those guys piss me off so bad. ****ing idiots

Ya I am trying to get them to correct there **** up pissed me I chased my tail on this truck smh

 

[THEFERMANATOR]

I'm pretty sure there's are the ones who sell the same for LB7 and LLY unless they changed recently. Put AC DELCO 63G's back in it and see what happens.

Just looked at there site, and they still list the same plugs for 99-05(DRX00058) which is wrong. 01-04 LB7 is one style, and 04.5-05 LLY is another. The LB7 plugs will bolt right into a LLY, but will do just like your describing because the LLY controller is seeing the wrong resistance.

SOund familiar: http://www.duramaxforum.com/forum/general-discussion/152733-lb7-glow-plugs-lly.html

Those dumb asses did the same to me 2 years ago. I had a nice long bitch fest with them and told them they are NOT THE SAME GLOW PLUGS. And they told me I was wrong and that they have engineers who know what they are doing. I told them the engineers are idiots. I made a thread about it on DF.

I knew your issue was glow plug related. Damnit those guys piss me off so bad. ****ing idiots

I knew I had read about this before, thats why I linked to your thread over at DF about it.

 

[mike diesel]

Ah I didn't even see you linked my thread:thumb:

 

[THEFERMANATOR]

Ah I didn't even see you linked my thread:thumb:

You would think after this long they would get it through there heads there LB7 plugs do not work in an LLY.