HMMWV Ground Shunt

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Coralsniper

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I tightened up the sparking bolt (negative post) on my shunt and that solved that issue, truck fired up perfectly and I checked and adjusted my voltage it was 29.3 coming out of alternator I set it at 28.4.
I shut the truck off and came back a couple hrs later to drive it to my Dads barn to clean connections but it wouldn't start, cranked over great, wait light acted like normal (8-10 sec wait light) but all she would do is crank, tried it again 40 min later still the same :(

I put it on the 24v charger for the night, I'll ohm test my glow plugs tomorrow, it's done this to me before but always eventually started and that was when it had been running and all warmed up for some reason I dont know.

Could my smart box be the issue?
Maybe it's just dirty contacts, will dirty contacts draw more voltage when warmed up?

I'll attach a pic of my smart box

Sorry for hijacking
 

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papakb

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Corrosion or dirty contacts are resistive and yes, they increase their resistance when they get hot. One cardinal rule with electronics and wiring is that connections need to be clean and tight. It doesn't hurt to coat them with anti-oxidant grease to help exclude moisture from getting to the copper or tinned surfaces where they make the actual contact. Since your wait light is cycling correctly I think it's safe to conclude that the control box is OK but there's no feedback from the glow plugs and they might have gone bad in the testing process. If you have a multimeter you can read the resistance value of the easy ones to get to and see if they show continuity or open. They'll usually read under 8 ohms if they're good.
 

TOBASH

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If your at half tank or less of Diesel then maybe fuel delivery system needs evaluation.

If you pressurize the tank and it starts, then you need to evaluate fuel delivery system.
 
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TOBASH

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I have a full tank and replaced the mechanical fuel pump a few months ago as it had a small leak.
Did you bleed the injectors properly? Just spitballing here. Doesn’t make sense that you crank without starting.
 

Coralsniper

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Sorry I ment to say the low pressure mechanical fuel pump down on the passenger side of the engine. That was a few months ago and its run great since apart from the random difficult hot start.

I charged batteries overnight, cleaned all the contacts I could and checked my glow plugs (they were all in spec).

Went to start it this morning and no start, so I tried something different and let the glow plug light go off, then waited another 20 seconds (leaving the start switch halfway so to keep the plugs heating) and it fired right up, I've always noticed my alternator guage will show the afterglow cycling even without starting the engine and after the wait light goes out, this time I just waited for the cycling to stop (about 15 sec) and then my alternator gauge pegged to the yellow side that's when I tried it and it fired right away.

Now I'm thinking again its something with my start box?
 

Milcommoguy

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Smart boxes are not so smart IMO. Not clear on the sequence of events here. ?? Was truck warmed up before you began the work?? Boxes don't like sparks and the little CPU brain inside can get scrambled or fried. Carefully disconnect negative battery lead and wait a few minutes. Reconnect and see what happens.

Lots of variables going on here. Diesel engines like / need to have some glow action when cold. Doesn't need to be beer ice cold either, and don't try and start with ether. :unsure:

I would lean towards the glow plug test first based on the events. Easiest to do with Volt-Ohm-Meter or VOM on the Ohm scale.

Connect one test lead to terminal PIN and other test lead to threaded area Ground. Glow plug internal resistance should be 1.5-5.0 ohms. If resistance is not 1.5-5.0 ohms, replace glow plug.

The VOM is going to be an important tool in your HMMWV tool bag, wrapped in a rag for protection. Even the freebee VOM from Harbor Tool House will do it. Can't afford free... build a 24 voltage / continuity probe. (next step up from free and for these tests quick and dirty, day or night)

I'll show how in the next episode "CAMO can, YOU can TOO" 📺

Good luck on this fix, let's us know what you fine.

HumV going for a ride this Memorial Day? Run LIGHTS ON and remember those who gave all. 💭🙏

Be nice to your V-O-M & stay tuned, CAMO
 

Coralsniper

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Found the issue with my no start problem, I didn't have any white smoke while turning over, realized I wasn't getting fuel so I started trouble shooting my IP, turns out my fuel shut off solenoid wasn't engaging, it still works just have to turn my fuel cut off switch (anti theft) on and off a few times if I get a no start situation and then it fires right up. Looks like it's time to replace the solenoid as I have 24v at it but it's just randomly not engaging.
 

Milcommoguy

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So now there's a fuel cut-off solenoid. That's a good idea for the thief thing. Get two blocks and found on the side of the road...dead. Almost like the netrual safety start switch.

Not stock. You didn't clue US in on that little "tid bit" Keep in mind... you now have something in line that adds another box in the logical steps to get it to run. (not saying it was or wasn't)

Is this an auto shop test or WHAT ! LOL aua OK .... ok haven't had my Humv "O''s" yet. (looking for another MWO tag at the bottom of the box)

Those rigs sitting around, funky fuel or just bad a luck IP pump fuel cut off parts can get sticky / stuck. Not much action to shut the IP fuel supply down inside. Could pop the top (may need security bit) and peek, poke and clean-up being careful on reassembly (a little tricky so go easy. See the TM)

Most important. another on the road. U got it, CAMO
 

osteo16

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So now there's a fuel cut-off solenoid. That's a good idea for the thief thing. Get two blocks and found on the side of the road...dead. Almost like the netrual safety start switch.

Not stock. You didn't clue US in on that little "tid bit" Keep in mind... you now have something in line that adds another box in the logical steps to get it to run. (not saying it was or wasn't)

Is this an auto shop test or WHAT ! LOL aua OK .... ok haven't had my Humv "O''s" yet. (looking for another MWO tag at the bottom of the box)

Those rigs sitting around, funky fuel or just bad a luck IP pump fuel cut off parts can get sticky / stuck. Not much action to shut the IP fuel supply down inside. Could pop the top (may need security bit) and peek, poke and clean-up being careful on reassembly (a little tricky so go easy. See the TM)

Most important. another on the road. U got it, CAMO
Lol... I’ve been tinkering around for an anti theft switch Idea... Thanks....

I’m gonna run a keyed line off the neutral start switch.. brilliant.. key must be on for Neutral switch to make circuit.. key out, circuit broken.. this way I have a relatively low voltage keyed switch that won’t burn down my rig.. and if it fails I just crawl underneath and hook my switch back up factory
 

TOBASH

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Black dog customs has the fuel cut off switch for sale on their website, its plug and play.
They are charging $80 for 2 wires terminated in Packard connectors and a $.50 toggle switch. I can (and did) build that for 3 dollars.

I can't believe what passes for reasonable price when people buy HMMWV parts.

IMHO
 

osteo16

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They are charging $80 for 2 wires terminated in Packard connectors and a $.50 toggle switch. I can (and did) build that for 3 dollars.

I can't believe what passes for reasonable price when people buy HMMWV parts.

IMHO
i was just gonna spend $0 and use some wire I had laying around... just my 2cents - 2cents
 

Milcommoguy

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hmmmm.... looked at it, and im confused.. no way are two wires gonna cut off fuel to my m998 6.5 that i cant do for $5.00 ...but for $15 bucks I mighta bit on that
That wire and switch product goes in line with the injector pump solenoid. Hide the switch so the buggie man can't find it. With switch open NO FUEL, no start, no brainer.

Sure it works... But at that price, wire must be $ 8.75 a foot and a buck for the switsh. I get the labor and parts thing. Something anyone could build in a hour and have lots of money left over for a big BIG pizza party.

Build yourself and save for a party, CAMO
 

Retiredwarhorses

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Lol... I’ve been tinkering around for an anti theft switch Idea... Thanks....

I’m gonna run a keyed line off the neutral start switch.. brilliant.. key must be on for Neutral switch to make circuit.. key out, circuit broken.. this way I have a relatively low voltage keyed switch that won’t burn down my rig.. and if it fails I just crawl underneath and hook my switch back up factory
This is actually a better solution than the fuel cutoff, the fuel cutoff will still allow someone to crank the truck, the NSS will not spin the starter.
 

papakb

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With a hidden switch you could also break the posative line to the ignition switch. That way the dash all looks original with the normal 3 position start switch. When you think about it and if you know what your doing there are 100 ways to disable the truck.
 
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