Hmmwv fuel solenoid

Hi all,

looks like Iv got my first hmmwv which I’m very happy about but won’t start at the moment. got a suspected faulty fuel solenoid as will crank but not get signs of anything from exhaust.

so my questions are......

is it idiot proof to replace the solenoid and once and once I have old one out to test it can I just run a positive lead from the battery’s?

many thanks

Need to check about 20 other items before condemning the solenoid for no start condition.

NDT said:

Need to check about 20 other items before condemning the solenoid for no start condition.

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Thanks for the reply, can I ask what you would check for then before condemning the solenoid?

papakb said:

Before you kill yourself checking those 20 other things do this, the #54 wire on the top of the injector pump energizes with the ignition switch and actuates the fuel solenoid. Unplug it and make sure it is seeing 24 volts when the ignition is turned to RUN. If it's there, reconnect it and listen for the solenoid to click when the switch moves to run. No click, no fuel. Changing it is a simple, straightforward job replacing the top cover on the IP, just a couple of screws.

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Thanks for the heads up, appreciate it. I’ll check that power feed as soon as I can. At least solenoid is straight forward to replace if need be. I’ll just buy a new solenoid and not the whole top cover.

Glow plug impedance, glow plug controller operation, fuel to mechanical pump, fuel filter condition, fuel to injection pump, no bubbles in fuel at injection pump, fuel to injectors, THEN check solenoid.

DON'T do electrical work without DISCONNECTING the batteries...

Also you might want to empty the fuel tank and replace with new fuel and you want to bleed the system to ensure no air AND ensure fuel is being delivered. Fill the tank 2/3 or so in case you have a bad fuel pump.

DO NOT use starter fluid. It will ruin the engine.

Warm engine with sunlight and that might bypass bad glow plugs.

Make sure air filter is not clogged.

Then you can worry about all the other bits and pieces IMHO.

Good luck...

T

Ok so a update......pulled the solenoid and that’s fine, fuel pump chucks out lovely. So I moved on to glow plugs, when I first turn the wait switch it goes from negative to 24volts for give or takes 10secs then turns of etc. So when I then pull a glow plug out and turn the switch they are not heating up. Is this pointing towards the control box or bad earths?I did then test the glow plugs independently and they heat up lovely.

its me said:

Ok so a update......pulled the solenoid and that’s fine, fuel pump chucks out lovely. So I moved on to glow plugs, when I first turn the wait switch it goes from negative to 24volts for give or takes 10secs then turns of etc. So when I then pull a glow plug out and turn the switch they are not heating up. Is this pointing towards the control box or bad earths?I did then test the glow plugs independently and they heat up lovely.

Click to expand...

So is "everywhere" a new state ? site rules require a location.

Are you grounding the glow plugs when testing? The block is 5he ground when they are in the motor. If its not grounded when testing, no glow.

Thanks all for contributing, I'm following along and learning.

gimpyrobb said:

Are you grounding the glow plugs when testing? The block is 5he ground when they are in the motor. If its not grounded when testing, no glow.

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What's best procedure for grounding the glow plugs when testing?

When I test my glow plugs, I put them on a battery charger. I hold the body with the ground and touch the lead with the positive. The GP needs to get red hot on the tip, not the body. If the tip doesn't light up its bad.

Great, testing mine tomorrow.

Note... While using an old school battery charger to "light up" a glow plug is a sort of simple test (12 or 24 volt doesn't matter may just take longer to glow red to white hot) SOME fancy battery chargers will not output voltage to energize a glow plug. They are looking for a voltage to begin the charge cycle.

And if it does draw current, It will get HOT AS HECK, asbestos finger tips required, CAMO

I posted a glow plug melt down here on SS, but can't find it.

Ok very good point, I guess I can run a earth wire wrapped around the glow plug to block to double check.

Sure... It's a valid test without a multimeter. Something Macgyver would pull out of his hat and it works. That's one reason why I always carry a couple of GOOD clip leads in my tool kit. (previous post) "What's in your tool bag"

Guess it would be nice to see them light up when out. Macgyver would just leave them in the block. (it's a 30 minute show) Connect clip lead to known 24 volts source ie:battery, Pull all the glow plug leads, and touch and look for a spark when making the connection to the tip of each plug. (scratching like motion) No spark and looking carefully, bad plug. Do again to each remanding plug.

Time for a commercial break, CAMO

I have had the plugs out and tested direct from battery’s, but what I think is a possible problem is the feed to the glow plugs when in place. Hence me thinking control box or bad earths.
any suggestions in testing plugs when in place.

The plugs themselves are pretty simple. Basically a very low resistance (1.5 to 6 ohms depending on variables) nichrome wire heating element. In this example figure a 24 volt system and a 3 Ohm glow plug. Apply the Ohms law Voltage (V) = Current (I) * Resistance (R). and that this one plug draws 8 Amps. So, one could figure if all plugs are a working 8 Amp each times 8 plugs equals 64 Amps. (average this simple case)

Do it again with say 1.8 Ohms per plug and we get 13 Amps each plug. Add it up, now 13 Amp times 8 plugs for a whopping 104 Amps. Both these examples are real world conditions for glow plug current draw and both trucks glow plugs are converting electrons to heat. The later example is getting there a lot quicker.

Time is the next variable. Think of it like a toaster. Like yours light brown, leave it in a short time. Burnt on the edges, a bit longer.

My quick test is easy, but requires an clamp on Amp probe. I can take a reading of all of them by clamping on to the common feed out of the control box and flip to run, reading total current (like above big Amps), or individually (better check, each Amps) to each one and add up the currents for a total. Any with no current = bad plug/s. Takes more time to add it up (toes and fingers) and cycling to RUN. Total time to test all 8 less than 2 minutes. Note. control box need to be working and not timed out. That would be a bigger problem.

OR


Multimeter test just as easy. Pull one plug lead and determine if 24 Volts is present at the lead (poke positive probe up into cup contact and other to ground) Have help select to RUN while the waiting to start light is on during an attempted cold start. (quick sample 3 seconds. You have voltage or not, done) No voltage, bad box likey. Got voltage... pull all plug leads and measure each plug resistance to read in the ballpark 1.2 to 6 Ohms. Much more that 10 Ohms, replace.

The resistances of each plug won't be all the same, but should be balanced around an average.

I read here many times "truck tries to starts, smokes, ran good last week, and / or won't run now" Sure there a many like variables, but for starters (pun) knowing and understanding this basic electricity of glow plugs will eliminate the guessing / trouble shooting. Got to start some where and this is the least dirty and smelly.

Be sure hood prop is locked in place, CAMO