Help! L3240 won't start when cold

[bferris01]

Hello all,

So after following post #3 here is what I found.

Under glow plug lead terminal voltage:

I took the wire lead off (only wire- that went to the 1st glow plug and also a bar that connected the other plugs together) and got no reading with the switch off, then turned to ON (glow plug setting) and still got no reading.

Under glow plug Continuity:

I took the red lead from the meter to the top of the glow plug and the black to the chassis and 0.8 resistance.

Under glow rely:

The voltage was the same

I tested the relays (all 3--original OEM, replacement OEM with bigger terminals, and Autozone) and they tested and clicked as they should.


Soooooo.......that would lead me to think power is not getting sent to the main lead wire to the glow plugs themselves? Correct? Meaning- main ignition switch??? How to do I test it? I have checked the back and all connections are tight.

Hope I did you all proud...Thanks again.

 

[The Fred]

Do you Skype?

 

[bferris01]

I can facebook video from my phone or facetime I have iphone?

 

[bferris01]

Also I did poke around the ignition switch and think it is working correct. On the back of it the center spot has 12volt all the time, the spot on the top has none ever ( this is the off position), in the on/glow plug position the terminal on the back has 12 volt as well. So I think that means the switch is working right??

 

[moship]

Did you check the main 50 amp feed to the relay? This is the slow burn fuse and I believe is located near the battery.

 

[bferris01]

Moship - Yes Sir

 

[bferris01]

I checked again and the fuse at my battery is 80Am and good.

At the relay plug I have a red/black wire going into that has 12 volt all the time and a black/red wire leaving the plug and going to the glow plugs.

( When I jump these 2 with a piece of wire and cycle the glow plugs it starts like the day I bought it.


Also I tested the temp sensor:

Unplugged the sensor plug and got good continuity and then with the key in the on position I got 4.8 volts in the plug

Tested the sensor it self and no change on the meter/no continuity.

 

[The Fred]

Your problem is the primary circuit that trips the relay.

Be careful putting voltage where it doesn't belong as the instrument cluster is the controller for the glow plug relay, it grounds the control circuit of the relay allowing it to close.

Take a 12 volt light bulb like a 194 side marker bulb and stick one side in one of the small relay connectors and the other side in the other small relay connector terminal WITH THE RELAY REMOVED. Turn the key on like you are going to let the glow plugs cycle. The bulb should come on just like the glow plug light on the dash.

The workshop manual has all the info you require.

Regards, Fred

 

[arto98607]

Have you measured the resistance in each glow plug?

 

[Fallon]

Have you measured the resistance in each glow plug?

That's not particularly relevant. If he bypasses the relay everything works fine. Therefore the problem isnt with the glowplugs.