Cold Starts

[BlueRoadster]

Ok, I got my 1985 Hmmwv this weekend and as the previous owner had said it does not like to start cold. When the temps outside are cold you need ether to start it (first start only, it starts fine the rest of the day even if the truck temp is cold). He said when it is warm outside it starts fine. He has replaced the glow plugs and the light cycles but I dont see a drop in voltage as has been stated will occur. The volts are in the yellow when I look at it (of course I looked after the wait light was on so I wouldnt have notices a drop then, but when the light went off there was no change in voltage).

Hopefully I haven't confused anyone and someone will be able help tell me to fix my problem.

Thanks in advance,
Grant

 

[hummer4x4guy]

Your regulator could be set too low. There is an Allen head cap plug on top of the alt. Take that off and a regular sized Phillips screw driver will fit into the hold and connect to the adjustment "knob". Test your voltage coming off the alt and if it's too low turn that sucker one way or the other and with luck you can get it set to the proper voltage.

 

[Dock Rocker]

I wouldn't trust anyone. It's way to easy to swap glow plugs. I would check behind him for sure. Also test the voltage at the glow plug as the truck is cycling.

 

[BlueRoadster]

Hummer 4x4 guy, I am testing the regulator to see if it is putting out 24volts?
Dock Rocker, Would the voltage be 24? Or is it derated at the plugs?
Also I failed to mention when I am trying to start in the morning it does have white smoke coming from the exhaust as I turn it over.

Thanks guys,
Grant

 

[hummer4x4guy]

There is that cover on the alt under it all your wires connect to the alt there. You can test the hot wire (forget which one) and the ground and you need to be at 28v for a 24 volt system.

 

[papakb]

There are 4 wires that run to the 60 amp alternators in a HMMWV. One heavy ground wire that attaches to the bolt outside the small cover, one heavy 8 gauge wire that connects to a stud under the cover, this is the output where you would measure the output voltage while adjusting the regulator. There is a third small wire that attaches to a small #10 stud under the cover. This is the ac output that goes to the PCB that tells the truck it's running, and a second small wire with a Packard connector on the end that connects to the wiring harness. This wire is the exciter wire that is hot when the run switch is turned on. When adjusting the regulator output you would measure between the 2 heavy gauge wires while adjusting the regulator. Turning the adjustment clockwise LOWERS the voltage and turning it counter clockwise INCREASES it. You want to adjust this for 28 volts with the engine running. Doing this should put the voltmeter needle right on the small line in the green area of the gauge. This is where the needle should be with the truck running and the alternator is outputting. Remember that lead acid batteries are rated for 12.6 volts with the engine off so with 2 in series you are only going to have 25.2 volts which will put the voltmeter needle at leftmost edge of the green zone or the righthand edge of the yellow zone.

When you turn the truck run switch on and the glow plugs are drawing current to heat up the voltmeter needle will drop even further to the left. When the wait light goes out the needle should move back the the right. If this isn't happening you need to check you glow plugs and if they test good then it's time for a new PCB. Search the forum to make sure you get the correct combination of Protective Control Box (PCB) and glow plug controller/temp sense unit, GPC or TSU. There are about 6 different models out there today and they need to be matched correctly to work.

Kurt
KG6KMJ

 

[hummer4x4guy]

Oh don't forget a grounding kit from kascar if you don't have one on the truck.

 

[papakb]

Those grounding kits are so easy and cheap to make why would anyone who can work on these trucks buy one? My 2 cents worth.

Kurt

 

[darkturbo]

Those grounding kits are so easy and cheap to make why would anyone who can work on these trucks buy one? My 2 cents worth.

Kurt

Hi Kurt.. I guess some people just dont have the time and/or tools to make them. But yes, you are correct, 1hrs job with common tools. PM me if anyone need help with the ground harness..

 

[hummer4x4guy]

Time.. I lack the time. But when ya only need one and its lasted this long it hasn't broke the bank for me.