Manual glow plug wiring

[antennaclimber]

The glow plug card works on a 12 volt system because the glow plug system is a 12 volt system.

In the stock CUCV config, the only part of the GP system that is 24 volt, is between the bus bar and the resistor. Once the relay is closed, the resistors and the glow plugs in combination with each other drop the voltage to 12 volts to each glow plug. You will have 24 volts to the top of the GP relay when the relay is open.

The best way to check glow plugs is to pull the wire off of each one and then test the resistance between the tab and ground. Typically they are between .8 to 1.2 ohms.

I would not change the fuel filter until the GP system issue is repaired. By doing this you may add another issue to the no start problem. Fix one issue at a time.

 

[joshua bebbino]

Glow plugs are getting 12v and just changed the glow plugs , still no start, checked the batteries both have 12.8v , also checked the volts going to the starter, that was 12v , is that correct? Fuel filter wasn't clogged

 

[MarcusOReallyus]

Not sure what is going on with that resistor pack deal... I would remove that the truck is 12 volts not 24

Let's get an understanding of where we really are before ripping things out.

You can not go back to stock because the truck is not stock

Why not? Many butchered trucks have been put back to stock with help from this forum. It's usually the simplest way to solve a mess made by someone who did not understand the 24/12v system. People who don't know how much they don't know can be very creative in how they screw things up. Trying to reverse engineer an idiot's mess is a great way to invest a lot of time for little or no return. It's much simpler just to put things back to stock, and then troubleshoot. Usually we find that a big mess was created by someone trying to solve a simple problem.

my understanding ... is that the GP card will NOT work with a 12v system.

That's not correct. It depends HOW it was converted.

It's important to check the voltage at the top of the relay while the relay is engaged (on) and when it is not. Both values matter. Joshua, can you report on that?

 

[Matt5]

I know where we are, the resistor will do nothing at all but cause an issue... it's a 12v system, if the resistor is removed and something stops working, great, know why? CAUSE IT WAS GETTING LESS THAN 12 VOLTS... I have said not to touch and to ignore other things... (no cranks, gp wires) but REMOVE the resistor because it can do NO GOOD being hooked up. I never said burn it or throw it out or blow it up... I just said I would remove it.

How about you full quote me btw please? I said I COULD BE WRONG (but you left that part out)... in reference to wiring the GP card back to stock... I am aware I have very little idea on how the system works outside of stock because all my trucks are kept stock. Whatever enough on that...


FOR THE OP.

I just want to recap to make sure I got where we are right.

Truck is 12 volts
Truck has a push button glow plug system (you are glowing for 10-15 seconds)
Glow plugs get 12 volts (checked at a GP terminal)
Glow plugs have been replaced
Truck cranks and produces white smoke
Engine runs good once it is started.


If doable could you take a short vid of the cranking? I wonder if starter is maybe still 24 volts seeing as the resistor bank was left hooked up... slow cranking would cause issues with a hard start but you would always crank just as slow because... you have charged batteries just 1/2 the voltage the starter wants.

A few pics might be good too just of the engine to see how many alternators you have how the batteries are hooked up etc.

If not doable, does the motor spin over fast?

Could also be injectors... but that's a $$$ thing to check.

 

[Tinstar]

A dying starter will cause the cranking issue.
Cranks, but not fast enough.

Mine was dying a slow death and made me think battery’s, etc when she wouldn’t fire.

Replaced starter and engine cranked faster than ever

Just a thought..........

 

[joshua bebbino]

I will upload pictures shortly, I just checked the voltage at the top of the gprelay and without the key in it was getting 12v and with the glow plugs switch engaged also 12v.

 

[MarcusOReallyus]

I will upload pictures shortly, I just checked the voltage at the top of the gprelay and without the key in it was getting 12v and with the glow plugs switch engaged also 12v.

Okay, good. You are checking with a voltmeter, is that correct?

When you checked for 12v at the GPs, were you testing with a meter? Or test light?

Earlier, you said the top red wire went to the resistor, "I guess". Have you confirmed where it goes? You also said it goes to the "bus bar". Which bus bar? Have you measured the voltage at that bus bar? If so, what did you measure?

Did you check the resistance of the GPs, using the method described by antennablimber in post 21? Or did you just replace them?

 

[MarcusOReallyus]

How about you full quote me btw please? I said I COULD BE WRONG (but you left that part out)

Of course I left it out. It wasn't relevant. I was quoting the parts to which I was responding. Quoting entire posts is a stupid waste of screen space and is bad forum practice. It wastes everybody's time, and it's especially inconsiderate of people who are reading on a small screen like a phone. If I were carefully cutting out parts of your post to make it look like you said something you didn't, you'd have a valid complaint.


Putting together everything he's said (even though some of it is contradictory), it does sound like the truck was converted to 12v, with the resistor bypassed. If that's the case, the resistor isn't relevant at all. Most people don't bother pulling them out once they are bypassed.

 

[joshua bebbino]

yes voltage was taken with a multi meter, there's 3 red wires connected to the top of the relay, the top most one goes to the gp switch, then next one below goes behind the air filter to a rectangle looking thing(I guess this is the resistor, then the final red wire goes to the top bus bar behind the battery. I have not measure the voltage at the bus bar.

 

[joshua bebbino]

 

[joshua bebbino]

Also, I just changed the glow plugs but voltage was checked with a multimeter as well as a test light

 

[MarcusOReallyus]

Okay, good stuff.

Now we need that measurement of the bus bar. If the bus bar is 12v, and the connection goes through the resistor, there's your problem. The GPs aren't getting enough voltage to get hot. That resistor is intended to drop 24v to 12v to feed the GPs. If it's being fed 12v, your GPs are getting 6v. Matt alluded to this earlier. My only problem with his suggestion to remove is that we really didn't have enough info at that point. I was suspecting the same thing, but a few more measurements were needed.

Let's do this: Measure the voltage at the bus bar, THEN, measure the voltage at the top of the relay while the relay is turned on. If it's 12v both places, the resistor has been bypassed, and the P.O. just didn't bother to take it out. IF that's the case, it's irrelevant. You can leave it in or pull it out - it's not making any difference.

Since you have measured 12v at the GPs, I think you are going to find the resistor has already been bypassed and you can fuggedabodit. It's not your problem. Time to look somewhere else, like perhaps compression or fuel timing.

 

[Milspec2]

The relay on the firewall usually has 3 connections on the bottom heavy post that should be Orange, heavy are Glow plug feeds, light is sense back to card. Top heavy should have a heavy red wire that goes to either the resistor bank or directly to the battery, preferably 12 gauge or heavier. If mounted correctly the bottom sense post is where 12 volts is applied to close the relay, top is ground return through the glow plug control card. Originals had rubber isolated relays, needing the ground through the card to operate the relay, bad ground to card, power IC fries on card.

 

[Milspec2]

Hard wired is power wire from fuse panel to one post of single pole/single throw switch or much better high amp momentary (located at any auto store), wire from other post on switch to bottom sense post on relay. push switch, relay closes until switch is turned off or released. If the relay is still an isolated ground, run wire from upper sense to good ground or battery -

 

[Milspec2]

Also in reading this, white smoke is an indication of low fuel pressure as well. Hard starting can be the Injector pressure regulator being plugged open causing low pressure to the injectors. Easy enough, use 9/16 and pliers to pull it out, blow it out with break cleaner, put it back in. Takes less than 5 minutes total and tells you if Glow plug system is working, but your fuel system isn't