winter starting

[johnsr]

ok to start off the first thing i did was rong but it was all i had the mony for at the time, i had to replace my mill batterys and did not have the extra $500 to get the right ones so i went to wallmart. my truck dosenot have a blockheater in it yet. so the past two mornings i have had to put a space heater under the hood to preheat the engien. works good. my quetsion is the glow plug relay on the firewall, how many times should it cycle when you turn the key on. mine is cycling about once evry 2 seconds for about 30 to 40 seconds. i can hear it klicking when im under the hood.

 

[lindyp38]

i have been cycling at least twice with the really cold temps here in ny

 

[QuickSilver]

I only ever have to cycle mine once, even with it being 15 below here the last couple of weeks. Granted, I keep it plugged in.

 

[mistaken1]

Are you saying it goes on for 2 seconds then off for 2 seconds then on for 2 seconds etc for a total of 30 to 40 seconds?

Does the volt meter drop deep into the yellow then come back to green with the cycles or does it stay in the low green?

When my swellman glow plugs burnt out my relay cycled on and off like I described and the volt meter stayed in the green. I replaced the swellmans with AC60Gs and did a 12V glow plug feed conversion and now the truck starts on one cycle when it is 8 outside without any external heat.

 

[tbearatkin]

mine will click like that. Sometimes after it is warmed up it will do this. Until I can trace the problem (bad heat sensor maybe) I just disconnect one of the small wires on the GP relay. Yes I have to open my hood and put the wire on it before starting it (aren't we all suppose to open the hood and do a prestart check anyway?) Then after my GP cycle and I start the truck I get out and take the wire off the post. No more clicking as I drive down the road. Once warm weather gets here I will trace the problem.

 

[DokWatson]

I'm running walmart batteries too, no problems there. Always make sure all your battery connections are tight! This gets me all the time, stuff loosens and causes all kinds of weird issues.

I had a lot of problems starting, I used to have to cycle the plugs 3-4 times to start. I went through the entire glow plug system, started with doing a manual switch, relay modification, AC 60G glow plugs, and finally bypassing the resistor bank on the firewall. Turns out the previous owner didn't bypass the resistor bank, and my truck has been converted to 12 volts. The plugs were getting 6 volts the entire time. Oh well, at least I knew everything was brand new and would last awhile.

Starts up with hardly any cranking now, immediate fire. Hopefully this gives you some ideas for things to do.

 

[mistaken1]

Once started, depending on the engine temperature, the glow plug controller will cycle the glow plugs on and off.

 

[OL AG '89]

Not wanting to hijack the thread, but you mention the wellman gp's..... are they preferred over the AC's. I thought the AC's had a bad reputation????
I need to replace my gp's but can't find a local source for the wellmans.... Should I buy the AC's instead. Mine is still stock with nothing bypassed or chopped on.

 

[1stSarge]

I think opinions on the site, are pretty much split down the middle, and I’m sure you will get more opinions as to which to use. I think Wellmans are now Diesel Rx...what happened there? Did they get bought out or what?

 

[johnsr]

Are you saying it goes on for 2 seconds then off for 2 seconds then on for 2 seconds etc for a total of 30 to 40 seconds?

Does the volt meter drop deep into the yellow then come back to green with the cycles or does it stay in the low green?

When my swellman glow plugs burnt out my relay cycled on and off like I described and the volt meter stayed in the green. I replaced the swellmans with AC60Gs and did a 12V glow plug feed conversion and now the truck starts on one cycle when it is 8 outside without any external heat.

yes that is exactly what my beast is doing. the volt gage will go about 3/4 of the way yellow and back in the green.

 

[mistaken1]

If the needle is going deep down in the yellow then I would like to think most of the plugs are working.

Did you test you glow plugs with an ohm meter?

If the card is short cycling there may be an issue with the card or one of the sensors.

Do you have copy of the -20 manual? There is a step by step troubleshooting procedure in there that should be followed to determine the problem.

http://www.steelsoldiers.com/cucv/64773-please-confirm-my-glow-plug-relay.html#post768588


As I understand it the wellman 070s are not self limiting. If they have voltage applied for too long they burn out. The AC 60Gs are self limiting and are not supposed to burn out as easily.

The wellman 070s have the correct (.187) spade for the stock connectors whereas the 60Gs have a .250 spade. You can grind the .250 spade down to fit the .187 connectors or replace the stock connectors. Rather than grind the 60G spades I replaced the stock connectors because some were damaged and some were a loose fit.

 

[johnsr]

i have a copy of the -20 and -20p, just need to get them printed and bound in to some kind of book. have not tested the glow plugs yet. and volt gague is going almost to the red.

 

[mistaken1]

Follow the troubleshooting procedure, in my case the plugs were open and the meter did not move out of the green but you may have a short in something (meter to the red) that is causing the controller to short cycle.

As others have pointed out clean and tighten all electrical connections including the batteries.

 

[johnsr]

i should be mad right now but im not. i just tested my glow plugs and the #'s 1,2,7 and 8 are still good. just the 4 in the middle of the motor are bad. i also tested the volts coming in to and out offf the relay 25v in. 15 at the glow plugs. if i am right the big resistor on the firewall is bad, should be 12v in. am i right or rong?

 

[mistaken1]

The big resistor will only drop voltage when current flows through it. There is procedure to test it in the -20 TM.

You may already know this but what the engineers did was create a series/parallel circuit using a big resistor (located on the firewall behind the air cleaner) in series with the glow plugs which are in parallel.

Ideally this series parallel circuit is a balanced voltage divider, the resistance of the firewall resistor is the same as the resistance of all the glow plugs combined. Since the resistances are equal whatever voltage is applied to the circuit will be divided evenly between the resistor on the firewall and the glow plug group.

When everything is working correctly the glow plug relay closes allowing current to flow to the glow plugs. The two devices in series (the resistor and the all of the glow plugs as a single electrical unit) divide the voltage, 12V drops across the resistor (it gets hot) and 12V drops across the glow plugs.

If one of the glow plugs fails then the resistance of the glow plug group which was equal to to the resistance of the firewall resistor now increases. That means that the voltage is no longer divided evenly. Now the glow plug group sees a higher voltage. The glow plug controller if it is working correctly senses this higher voltage and shortens the glow plug cycle to compensate. The remaining good glow plugs continue to see this higher voltage which can cause another glow plug to fail.

The second failed glow plug increases the resistance in the glow plug group meaning the remaining good glow plugs see an even higher voltage. This higher voltage leads to more glow plug failures which in turn leads to higher voltages until all the glow plugs are burned out.

I measured new wellmans at 1.2 to 1.5 ohms each. Using 1.5 ohms and calculating a parallel circuit I get 0.1875 ohms. So assuming the firewall resistor is equal and has a 0.1875 ohm rating and using 26.4 volts get 70.4 amps. 70.4A times 0.1875R equals 13.2V. Nice even theoretical voltage division.

Using the same 1.5 ohms per plug if one glow plug is open the glow plug group resistance increases to 0.21429 ohms, with two open glow plugs the glow plug group resistance increases to 0.25 ohms, with three open glow plugs the glow plug group resistance increases to 0.3 ohms and with four open glow plugs the glow plug group resistance increases to 0.375 ohms.

Using the same 26.4 volts divided by the new 0.5625 (0.1785+0.375) series/parallel resistance I get 46.93 amps. Rounding to 47 amps times 0.875 ohms gives me 8.81 volts dropped across the firewall resistor and 47 amps times 0.375 ohms gives me 17.58 volts dropped across the glow plugs.

In reality the battery voltage drops when under a load, resistances vary based on the item measured and the connections to items.

If you were measuring 15V with four good glow plugs and four open glow plugs that seems about right. If you are measuring 15V will all good glow plugs then the circuit is not well balanced and there may be a firewall resistor issue. You could bypass the resistor and feed the glow plugs with a straight 12V and not worry about over voltage to the plugs.

Ask doghead for details on a simple 12V glow plug feed conversion.

 

[johnsr]

ok. i was planing on replacing allmy glow plugs at once and rechecking my voltage when done. i find it to be funny that the 4 middle glow plugs whent as a group. i would have thought it would be more random. as for a quick fix i have a pair of civy 6.2l j code heads gathering dust, if they have 4 good glow plugs can i swap out the good used ones for the bad one untill i can get the money for new ones? or am i just wasting my time?

 

[mistaken1]

Eight functioning glow plugs are better than four.

Also since the remaining four are seeing a higher voltage they will fail that much sooner.

The stock cucv glow plug terminals are .187". The wellman 070 have the same .187 spade size.

The AC 60G have a .250 spade size meaning they have to be ground down to fit the stock .187 terminals.

Another option is to replace the stock terminals with .250 terminals available in auto stores, hardware stores and even wally world.

 

[1stSarge]

The big resistor will only drop voltage when current flows through it. There is procedure to test it in the -20 TM.

You may already know this but what the engineers did was create a series/parallel circuit using a big resistor (located on the firewall behind the air cleaner) in series with the glow plugs which are in parallel.

Ideally this series parallel circuit is a balanced voltage divider, the resistance of the firewall resistor is the same as the resistance of all the glow plugs combined. Since the resistances are equal whatever voltage is applied to the circuit will be divided evenly between the resistor on the firewall and the glow plug group.

When everything is working correctly the glow plug relay closes allowing current to flow to the glow plugs. The two devices in series (the resistor and the all of the glow plugs as a single electrical unit) divide the voltage, 12V drops across the resistor (it gets hot) and 12V drops across the glow plugs.

If one of the glow plugs fails then the resistance of the glow plug group which was equal to to the resistance of the firewall resistor now increases. That means that the voltage is no longer divided evenly. Now the glow plug group sees a higher voltage. The glow plug controller if it is working correctly senses this higher voltage and shortens the glow plug cycle to compensate. The remaining good glow plugs continue to see this higher voltage which can cause another glow plug to fail.

The second failed glow plug increases the resistance in the glow plug group meaning the remaining good glow plugs see an even higher voltage. This higher voltage leads to more glow plug failures which in turn leads to higher voltages until all the glow plugs are burned out.

I measured new wellmans at 1.2 to 1.5 ohms each. Using 1.5 ohms and calculating a parallel circuit I get 0.1875 ohms. So assuming the firewall resistor is equal and has a 0.1875 ohm rating and using 26.4 volts get 70.4 amps. 70.4A times 0.1875R equals 13.2V. Nice even theoretical voltage division.

Using the same 1.5 ohms per plug if one glow plug is open the glow plug group resistance increases to 0.21429 ohms, with two open glow plugs the glow plug group resistance increases to 0.25 ohms, with three open glow plugs the glow plug group resistance increases to 0.3 ohms and with four open glow plugs the glow plug group resistance increases to 0.375 ohms.

Using the same 26.4 volts divided by the new 0.5625 (0.1785+0.375) series/parallel resistance I get 46.93 amps. Rounding to 47 amps times 0.875 ohms gives me 8.81 volts dropped across the firewall resistor and 47 amps times 0.375 ohms gives me 17.58 volts dropped across the glow plugs.

In reality the battery voltage drops when under a load, resistances vary based on the item measured and the connections to items.

If you were measuring 15V with four good glow plugs and four open glow plugs that seems about right. If you are measuring 15V will all good glow plugs then the circuit is not well balanced and there may be a firewall resistor issue. You could bypass the resistor and feed the glow plugs with a straight 12V and not worry about over voltage to the plugs.

Ask doghead for details on a simple 12V glow plug feed conversion.

Great post mistaken!!

I did all this math a long time ago, trying to figure out why the voltage would destroy the other plugs if one failed, the only flaw with the system though, is that this is only true if a plug fails “open” or at least a high resistance. Then the controller will protect the circuits. But if one fails shorted. Then none of this applies.

 

[mistaken1]

Great post mistaken!!

Thank you.

I did all this math a long time ago, trying to figure out why the voltage would destroy the other plugs if one failed, the only flaw with the system though, is that this is only true if a plug fails “open” or at least a high resistance. Then the controller will protect the circuits. But if one fails shorted. Then none of this applies.

LOL that's true. I have not thought that one through but it seem to me large current flows would damage things.