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keyed ignition wont' start HMMWV

C

cucvegas

Member
59
12
8
Location
NW Arkansas
I have tried three different keyed ignitions on the HMMWV, and none of them have worked correctly.

The first one I got from Federal military parts. I used a multi-meter and made sure the wires from the vehicle were labeled correctly (Battery, Ground, and Ignition).

I wired them to the new keyed ignition, and when you turn the key to "on", the wait light comes on and cycles the glow plugs as expected. However, when you turn the key to start the vehicle, all the gauges lose power.

I talked to Steve at Federal Military parts, and he had no idea why it wouldn't work, so he sent me a new switch in case that was the problem. It was not. The new switch did the exact same thing.

I then bought a 3rd identical ignition switch from the_amazon for $10 and made the wires with male bullet connectors. This did the same thing as the other two.

Any suggestions?

The switch has power (24V) between battery and ground when in "off" position. In "on" position it has 24V between ground and ignition. When turn the key to "start" in the spring-loaded position, it goes to 0V between ground and ignition. The "accessory" terminal on the switch is not used.

When I plug the original ignition switch back in, it all works fine.

Thank you!
 
Suprman

Suprman

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You need to have 24v at the run position when cranking or the fuel solenoid will not be powered. And the engine will not start. A lot of the cheap start switches don’t leave power to run when cranking.
 
suzukovich

suzukovich

Active member
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Gibsonton Fl
Sounds like the keyed ignition not making contact internally. Try spraying with electronic parts cleaner into where you insert the key..

Sent from my SM-J727U using Tapatalk
 
AAVP7

AAVP7

Well-known member
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Dortmund, Germany
The wire names on these switches are misleading. They don´t have a "ground" wire, going to actual vehicle ground. One lead comes from the battery 24 V +; and the other two are outputs to either the "run" circuit, or the starter (via the control box).

The symptoms you have sound pretty much like you grounded the switch somehow. We recently had a member overhere with the same problems.
 
suzukovich

suzukovich

Active member
389
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Gibsonton Fl
Still need to check grounds, I also have a battery cut of switch between the ignition and the battery. So it was easy to trouble shoot. I had a bad neg battery post. When I replaced the batteries for the most part problem went away. Still need to install the ground upgrade. When you put the key in run position it turns on the power. Turn it to start, truck starts up. In his case it sounds like the power is disconnecting when he turns the key. I went through three switches until one worked right. They are all made in china. Also check to insure wires connecting to the switch are tight. Easy to check. The contact points are on the back of the switch. Insure the wire contacts are separated.

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Suprman

Suprman

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Stratford/Connecticut
You can cheat and put a big diode between the crank and run leads. So when you are cranking you have voltage at the run position but not vice versa. Just make sure you put the diode the right way.
 
C

cucvegas

Member
59
12
8
Location
NW Arkansas
Final update: I found a switch that works.

I got a $12.99 generic “[FONT=&quot]Universal 3 Wire Engine Starter Switch for Car, Motorcycle, Tractor, Forklift, Truck, Scooter, Trailer,” from the_amazon, and it works great. The switch itself is very light weight and feels cheap, but I like the key better because it has a much wider area to turn and doesn’t feel like a file cabinet key like the ones that came with the Dorman brand switches.

I used 14 gage wire with bullet connectors to mate with the military plugs, so for less than $20 I’m pretty happy with it.

Thank you to everyone that commented.
[/FONT]
 
C

cucvegas

Member
59
12
8
Location
NW Arkansas
Final update: I found a switch that works.

I got a $12.99 generic “[FONT=&quot]Universal 3 Wire Engine Starter Switch for Car, Motorcycle, Tractor, Forklift, Truck, Scooter, Trailer,...l[/FONT][FONT=&quot]

from [/FONT][FONT=&quot]the_amaz[/FONT][FONT=&quot]on, and it works great. The switch itself is very light weight and feels cheap, but I like the key better because it has a much wider area to turn and doesn’t feel like a file cabinet key like the ones that came with the Dorman brand switches.

I used 14 gage wire with bullet connectors to mate with the military plugs, so for less than $20 I’m pretty happy with it.

Thank you to everyone that commented.[/FONT]
 
suzukovich

suzukovich

Active member
389
141
43
Location
Gibsonton Fl
cucvegas said:
Final update: I found a switch that works.

I got a $12.99 generic “[FONT=&quot]Universal 3 Wire Engine Starter Switch for Car, Motorcycle, Tractor, Forklift, Truck, Scooter, Trailer,...l[/FONT][FONT=&quot]

from [/FONT][FONT=&quot]the_amaz[/FONT][FONT=&quot]on, and it works great. The switch itself is very light weight and feels cheap, but I like the key better because it has a much wider area to turn and doesn’t feel like a file cabinet key like the ones that came with the Dorman brand switches.

I used 14 gage wire with bullet connectors to mate with the military plugs, so for less than $20 I’m pretty happy with it.

Thank you to everyone that commented.[/FONT]
Click to expand...
Glad it worked out. My be post a pic of the ignition switch

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K

karlsmith

Member
40
1
6
Location
Sevierville, TN
Same issue here. Freightliner, standard chinese one you find for $50 on all the humvee sites, and the original switch that worked, but now doesn't. The only thing I did was disconnect the battery, installed and followed the wiring diagram. I installed the Kascar wiring harness months ago, but I did recheck the ground by the washer reservoir. Glow plug light comes on strong for the standard time, however nothing on all three switches when I move it to crank. A couple of questions:

- If I try to shuffle the wiring around just to see if I did it wrong, do I chance blowing my starter box?
- What other grounds could be involved besides the ones that are secured with the Kascar grounding harness?

The day before I tried this mod, my buddy said that my driver's side headlight (LED) was significantly dimmer than the passenger's.

Thanks for any input or ideas!
 
suzukovich

suzukovich

Active member
389
141
43
Location
Gibsonton Fl
Get another one, my first one didn't last a month. . Also remove the Battery cables before you install the switch

Sent from my SM-J727U using Tapatalk
 
Last edited:
K

karlsmith

Member
40
1
6
Location
Sevierville, TN
One other thing, all my gauges are working, glow plug light, all work. Tried new batteries as well and it won't even crank with the original one that worked the whole time. And yes, I have disconnected the battery when changing ignition switches. Any suggestions?
 
Dock Rocker

Dock Rocker

Active member
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Location
Jackson ms
karlsmith said:
One other thing, all my gauges are working, glow plug light, all work. Tried new batteries as well and it won't even crank with the original one that worked the whole time. And yes, I have disconnected the battery when changing ignition switches. Any suggestions?
Click to expand...
Are you 100% you have the wires to the original ignition in the correct order?


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