Cucv won't start

[Richcz28]

So I've had my truck sitting for three weeks now. I know it's bad to let cars sit they like to be driven etc etc. Anyways batteries still crank strong but she won't fire. I really don't know much about diesels so I don't know where to start. I know starting fluid is supposed to be really bad so ... Any suggestions?

Thanks

 

[v30mongo]

6.2 starting

First check the glow plug system. The 6.2 really needs them to start at any temp. below running temp. Next, air in the fuel system. Disconnect the run wire to the injector pump. Then crank the engine with the fuel bleeder open until solid fuel comes out. It is possible you have a blocked fuel filter, but if it ran good last time it is a slim chance. You can change out the filter but remember, you you will be required the bleed the fuel system.

 

[imiceman44]

So I've had my truck sitting for three weeks now. I know it's bad to let cars sit they like to be driven etc etc. Anyways batteries still crank strong but she won't fire. I really don't know much about diesels so I don't know where to start. I know starting fluid is supposed to be really bad so ... Any suggestions?

Thanks

I have had engines like that they run fine when driven all the time, but if they sit for a couple of weeks, they won't start.
Every single one had a cracked hose, or lose fitting in the fuel system.
Trace the fuel system make sure all the hoses are good and all the fittings are tight, then try bleeding the filter, I am assuming you still have the square filter.
If you get any air there, it means you have a leak somewhere.
Once you bleed the air it will start.
I even have this problem now with my Big rig.

 

[colbystephens]

As previously said, glow plug issues and fuel delivery are the issues to look at.

When you crank it are you getting any smoke/mist out of the tail pipes? If so, I'd suppose you have a glow plug problem. No smoke does not indicate that GPs are not the problem, but seeing the puffs will help you know you're getting fuel. The easiest way to check your GPs is to have a test light and put one end of the lead on the spade of the GP and the other end onto the threads of the GP. If the light turns on, you have a good GP. If not, it needs replaced. See, the electricity goes through the spade, into the GP element, and then is grounded via the engine where it threads into the head.

It can be a REAL bear to get the fuel system purged of air. If you're not familiar with that process, read up on it and plan to spend a while getting the system properly bled.

 

[Richcz28]

I'm checking my glow plugs right now. 24 volts is present at the plug, but I put an ammeter between the plug spade and wiring harness plug and I don't see any current flowing. Does that mean the glow plug is bad.

 

[Richcz28]

Out of eight I found only one with 330miliamps of current flowing through it. I think 7 of the eight are burnt out? I'm going to try changing the glow Plugs. From what I've seen online I Beleive them to be ac delco part 13g.

 

[Safari-K5]

I would check the Steelsoldiers website. they make a newer style plug that is self resisting that allows you to run a much better system.

 

[Magnum97]

The way I test glow plugs is with an ohm meter, unplug the glow plug, and then go from the cylinder head to the spade on the back of the glow plug. there should be almost 0 resistance (ohms). anything above 4 Ohms (ish) and I replace them.

 

[colbystephens]

I'm checking my glow plugs right now. 24 volts is present at the plug, but I put an ammeter between the plug spade and wiring harness plug and I don't see any current flowing. Does that mean the glow plug is bad.

I am not sure I understand you correctly w/ regards to how you're checking your plugs, but I think you're not checking them correctly. Take a look at my other post to confirm your method.

But, if they are bad, 7 of 8, then that surely is causing you starting problems. I've started my 6.2 on just 4 or 5 working plugs, but it didn't like it!

 

[Richcz28]

I'm confused reading your method. Would the light not create a closed circuit with one end touching the spade and one end touching the threads which touch the block?

 

[Richcz28]

The Resistance was off the meter on 7 plugs and 95 on one.

 

[colbystephens]

I'm confused reading your method. Would the light not create a closed circuit with one end touching the spade and one end touching the threads which touch the block?

Sorry. I'm not real good with electricity, so I'm even worse when trying to explain it. You probably already know this, but....:

A glow plug works by having the electricity go in through the spade, through the resistor (the part that gets hot) element, and then grounds through the threads/nut into the head of the engine.

So, you just find some way to see if the circuit is broken or not at the element. If you have a self-powered test light that lights up when you close the circuit (i.e. if you even just touch the two leads together), then you can put one lead on the spade and another lead on the nut/threads/head and see if the light turns on. If so, your plug is good. It's just like an electric stove element.

Now, what you describe with the resistance leads me to believe that you do in fact have 7 out of 8 plugs bad.

A bad way to test your plugs (which I have done for lighting a fire while camping after a night of rain) is to pull them out one by one and attach the positive lead of jumper cables to the spade and the negative lead to the nut. If it gets hot, you get to make a fire to cook breakfast, if not... you better hope your truck starts to get you home!

 

[DokWatson]

I'm checking my glow plugs right now. 24 volts is present at the plug, but I put an ammeter between the plug spade and wiring harness plug and I don't see any current flowing. Does that mean the glow plug is bad.

STOP. The plugs are NOT supposed to have 24v supplied to them. The resistor bank on the firewall must be toast. They are all fried because they are supposed to receive 12v. You need to get rid of the resistor and supply power to the plugs from the two prong junction block near the master cylinder, and replace all your glow plugs.

 

[Richcz28]

Re colbystephens: I see what your saying now. I Thought you wanted me to use the light with the plugs in the engine but I should be removing them for your method to work. Thanks for all the help. I'm not great with electricity either so it's all a learning experience.

Re dokwatson: Its not supposed to be 24v even on a Cucv?

 

[DokWatson]

Re colbystephens: I see what your saying now. I Thought you wanted me to use the light with the plugs in the engine but I should be removing them for your method to work. Thanks for all the help. I'm not great with electricity either so it's all a learning experience.

Re dokwatson: Its not supposed to be 24v even on a Cucv?

No, the only thing that you need to worry about that receives all 24 volts is the starter. Everything else runs off 12v.

 

[colbystephens]

Re colbystephens: I see what your saying now. I Thought you wanted me to use the light with the plugs in the engine but I should be removing them for your method to work. Thanks for all the help. I'm not great with electricity either so it's all a learning experience.

Re dokwatson: Its not supposed to be 24v even on a Cucv?

Well, you don't have to remove them for my method. You can leave them in the head, just make sure you're touching the leads to the right places. But, sounds like you have a bigger issue to address first!

 

[Richcz28]

STOP. The plugs are NOT supposed to have 24v supplied to them. The resistor bank on the firewall must be toast. They are all fried because they are supposed to receive 12v. You need to get rid of the resistor and supply power to the plugs from the two prong junction block near the master cylinder, and replace all your glow plugs.

Do you by chance know part numbers or specific names for the resistor and power supply. I am having trouble locating replacements.

 

[Fordum]

STOP. The plugs are NOT supposed to have 24v supplied to them. The resistor bank on the firewall must be toast. They are all fried because they are supposed to receive 12v. You need to get rid of the resistor and supply power to the plugs from the two prong junction block near the master cylinder, and replace all your glow plugs.

Dok, his voltage could still be right. A resistor pack only drops voltage when in series with a certain load.
If the plug was open, then a meter would see 24 volts because the meter would not supply a load to the system.
But when the plug was inline, the voltage to it would be 12.

One the other hand, something sounds suspicious. He said that one plug read 95 ohms, and he measured 330ma.

12 volts into 95 ohms would be about 126ma, but 24 into 95 would give 253ma, which is in the ballpark of what he was reading.

So it could go either way. Its just that most of the time a resistor opens instead of shorts.

 

[DokWatson]

Dok, his voltage could still be right. A resistor pack only drops voltage when in series with a certain load.
If the plug was open, then a meter would see 24 volts because the meter would not supply a load to the system.
But when the plug was inline, the voltage to it would be 12.

One the other hand, something sounds suspicious. He said that one plug read 95 ohms, and he measured 330ma.

12 volts into 95 ohms would be about 126ma, but 24 into 95 would give 253ma, which is in the ballpark of what he was reading.

So it could go either way. Its just that most of the time a resistor opens instead of shorts.

I see what you are saying... if his glow plugs are all toast there's barely any load to drop the voltage across the resistor. One glow plug fails, they all go because the voltage increases and fries them. Fairly sure this is what happened to the OP.

Do you by chance know part numbers or specific names for the resistor and power supply. I am having trouble locating replacements.

Ditch the resistor, you don't need it. Get new glow plugs and wire them to the junction block on the firewall. Follow the fat red/blue wire on top of that solenoid. This is how I wired my CUCV (Also upgraded to a beefy solenoid)

If you decide not to go this route and you replace the glow plugs and find the resistor is still not working right, I've got a CUCV resistor bank sitting here for you.

 

[AJMBLAZER]

Colby, the CUCV's ignition system is a bit different than the civilians. Sounds like you are trying to diagnose a civilian setup and he's reporting a military setup problem. I know I couldn't diagnose my CUCV's GP's the same as a civilian truck's.

The CUCV Technical Manual is available for free download over on www.SteelSoldiers.com . Get that first thing. The tech content on the forum can be meh sometimes though. They're usually pretty good on the CUCV specific stuff though.

I ran Wellman 070 plugs in my CUCV.

From what I remember CUCV's drop the 24v to 12v at the GP's where civilian trucks drop the 12v to 6v. I may be confused about that...?