glow plug/votage gauge question

[max1008]

Ive searched 179 posts so sorry if I couldnt find it.

Truck usually starts fine. All stock system except for doghead relay.

Typically when the truck fires I hear the relay click a few times and every time it clicks the voltage will drop momentarily and then go back with another click of the relay. When it clicks on, my alt2 belt squeaks a little bit due to over-tightening.

Tonight I had a hard time starting it, with a shot of uhh something, it fired right up, belt squelled for awhile and then went away. I took a ride around the block. I turned off the truck, wait light turned off and it started up. relay clicked but voltage did not drop.

any idea why voltage wouldnt be dropping when the gp relay kicks on? I should replace my glow plugs but i want to make sure its not something else before i replace them.

 

[tstone]

I would bet that the contacts are worn - wearing out. I had the identical issue on one of my 1009's. I put a pilot light on the same terminal so I could tell if the solenoid contacts were working when it was activated (or you could test it with a test lamp or an ohm meter). I found that the contacts were bad; I picked up a standard replacement at Tractor Supply cheaper than the auto parts store.

Good luck.

 

[Keith_J]

There is also field voltage. To make current, it takes voltage through the slip rings into the field and this voltage comes from the batteries.

When started with glow plugs running, voltage depression can create a condition where the alternators are quite limited. Alternators are less RPM dependent than old school generators but they still have reduced output at low speed. IIRC, the 100 amp 27SI Delco alternators can only put out 100 amperes at engine speeds above 2000 RPM. This is why you can have an alternator dash light when first starting.

The alternators are only trying to keep battery voltage above 14.2 volts, usually around 14.5.

 

[max1008]

Ok that makes sense. If the contacts are worn on the relay the glow plugs will not get power.
That will be my first test.

 

[doghead]

I suggest you follow the step by step troubleshooting procedure in the -20 TM. It is thorough and easy to follow.

 

[max1008]

Just printed it out doghead! Figured it would ask before tearing through everything.

 

[max1008]

I tested the relay per the TM and I am not getting voltage from ground to the orange wire until the ignition is on. That would mean that the relay is still good.

But if the contacts are worn it will appear good but not making a good connection?

 

[doghead]

Did you test your Glow Plugs yet?

If you have voltage out of the GP relay, for now you have no reason to believe it is bad(yet). If all of your GPs are good, then we should test your GP relay further. This can be done by simply using your digital multi meter set on DC volts, then put each probe on each of the large terminals on the GP relay. With the key on, you should real 0(zero) volts. If your reading voltage across the relay with it on and the GP load applied, the relay is bad(contacts).

 

[max1008]

I was reading .99 ohms from my first glow plug. I will test the rest of them tonight.

If I do a resistor bypass can I still use the 070 glowplugs?

 

[doghead]

Yes, but I really recommend using AC Delco AC60 glow plugs. You'll need to replace your old terminals also.

And, I really recommend you do resupply the GP relay with 12v.