My glow plugs thoughts, theories, complaints, ideas and beliefs

[Rot Box]

Some of you might remember my glow plug thread awhile back. Long story short I had one of the two yellow 10ga wires melt and loose connection inside the wiring harness plug on my passenger side fender and I found it very hard to trouble shoot with the tools and knowledge I had at the time. It basically melted between the battery and the controller loosing connection with one of the two leads to the controller. Well knowing nothing about this type of circuit it took me a long time to figure out the problem and while checking for voltage with my meter everything seemed to work great (one good wire will still show voltage in the system...) other than I had 12 volts of power from the solenoid but it would not carry over to the GP terminals under load

Anyhow I thought I fixed it as I now have 4ga. cable ran from my battery to the relocated controller/relay (mounted on the passenger side fender) then 4ga. to the leads on the GP's. I thought that by using on one HUGE 4ga. cable to replace all of the two smaller 10ga cables throughout the whole system I would not have any lack of juice and therefor it would work better than it ever has. Well as it turns out (and I found out the hard way) the controller works based off of resistance between the GP's and controller and also water temp so the single big cable really screwed things up for me resistance wise.

At this point... As my 91 is frozen in the back yard I'm wondering

1. Why in the hell did Ford decide to use 2 10ga wires from the battery all the way to the GP's in the first place instead of one BIG ol' cable? Is there honestly a reason for it that I might be overlooking?

2. Why did they use 2 10ga. wires that are typically rated for 30ish amps max each when the system can draw up the 200 amps?!

3. Why did they design the controller to switch off when x amount of resistance is met making my "upgraded" 4ga. cables not work? 4ga. cable = less resistance = shorter glow plug cycle = 5 second cycle not long enough in temps under 40*.

I am now going to keep the 4ga. wire from the battery to the solenoid. However I am going to scrap the 4ga. cable from the solenoid to the GP's and replace it with two 10ga. cable to mimic the stock setup. hopefully the extra length from the GP's to the fender where the controller is mounted (an extra 12" or so) won't mess up the timer too much. I'll keep you guy's posted on how well that turns out....

It just bugs the hell out of me because every 6.2/6.5 and 6.9/7.3 has been a nightmare to start in the winter if everything isn't 100% PERFECT in the GP system... And really I wonder if it can ever be perfect due to the underrated equipment used in the first place. Everyone asks me if I'd swap my IDI one day for a Cummins, and honestly the only reason I would it do such a thing is to pound the last nail in the glow plug coffin because every time winter rolls around (Northern Utah + winter = cold as (%#@^!) I think it would be well worth it!

Right now I'm thinking that the push button is the only way to go. The 10ga. wires are obviously under rated, and i really feel that's the reason we struggle with the entire systems reliability especially the GP's, and there is no way to supply ample power to them with the controller because it can ONLY function based off of the resistance of the two underrated wires... Yep pretty sure the push button it the solution

Sorry for the rant.

 

[papastruck]

I'll join in on this ***** session. Having fried my plugs on Fri. by (I think/hope) holding them on for too long, I can't tell you how much noise there is out there when you try to find legit information on them. If I had a dollar for every vid of people testing glow plugs with test lights... Anyway, the manual is great once you know the limit of how long you can hold yours on for. It should be around 10 seconds max, but I've had to hold mine for 30 (previous set of plugs) to get even a sputter. I think every system is different due to age.

It'd be nice to know what the harness resistance you mention should be, so you could test it, then try to fix it. Also, is it 12 volts to each plug, or does the controller drop the volts to 6? I plan on testing that before I install, but it'd be nice to know what it's supposed to be. The other thing that sux is the service manual punts that to a separate emissions manual, to be purchased separately, so I couldn't get that info.

 

[Fordsandguns]

Why not mount the controller on the pass side valve cover like the factory turbo trucks had them? That way you have the correct harness and resistance to make the controller function right. You can still use the 4 ga. from the solenoid to the controller.

When I got my truck those yellow wires were melted in two also. I used a ground cable from another truck in place of those two yellow 10 gauge wires. Mine is n/a so the controller still sits behind the intake.

 

[ocnorb]

Well, after reading this post today I decided to see how my GP re-wire job worked only to discover that my 6 year old Interstates have gone flat.

 

[Rot Box]

I guess what I'm trying to say to anyone searching around for GP/controller issues or for anyone wanting to move their controller is to learn from my mistakes, and do not try to make sense of what Ford did with this or it will make your head hurt

-For anyone that has a truck that came with a solid state controller: Go ahead and do yourself a favor by replacing the power supply to the controller (replace the two yellow 10ga. wires) with a big ol' 4-2ga. cable just for peace of mind as this will give you issues one day.

-It is a GREAT idea to move the controller/relay altogether if you have a turbocharger that sits directly above it (like most of them do) because it is very difficult to troubleshoot and/or repair the GP circuit in that location.

-Know that if you do move the harness don't replace the two 10 ga. brown wires coming off of the controller with anything but 10 ga and keep them as close to the same length as you can.

Why not mount the controller on the pass side valve cover like the factory turbo trucks had them?

That's a good idea In my case I'd still have to lengthen my leads, just not as far.

 

[Silver Burner]

As an electrician, I can tell you guys that the 30A rating on #10 wire is what code considers to be the max load that the wire can take constantly forever. The wire can actually handle MUCH more current (and it does obviously) and the amount of time it can handle it is an inverse proportion to the # of amps flowing through it. Basically, the higher the current, the less time it can handle that current before getting too hot. I would say when replacing the wire, go to an electrical parts house and ask for 105 Celcius rated wire as the wire insulation will be able to handle more heat than your typical Hopeless Depot wire.

 

[Rot Box]

^ Good info thanks

 

[icanfixall]

This is why I went to an audio speaker store and bought the wire and terminals from them. The wire is huge and its almost hair like strands of wire in the cable. It carreis morw power to the point...

 

[OLDBULL8]

1. Why in the hell did Ford decide to use 2 10ga wires from the battery all the way to the GP's in the first place instead of one BIG ol' cable? Is there honestly a reason for it that I might be overlooking?

2. Why did they use 2 10ga. wires that are typically rated for 30ish amps max each when the system can draw up the 200 amps?!

#1. Yes, you are overlooking the reason for 2 10ga wires.

Those 2 10ga. wires are FUSIBLE LINK wires. By replaceing them with that #4AWG wire you have effectively bypassed the OEM safety circuit. Fusible Link wire is specially designed, the insulation is flame retardant, the inner wire is NOT just copper as too regular copper conductors, it is designed to "melt" under high current loads after a given time.

#2 The high current (180 amps) flow to the GP circuit is designed to last for only a max of 4 to 5 seconds, then as the GP's heat up the current receeds for the next 10 seconds to about half of that. The foregoing said, that all is considered in a normal 1st cycle with good glow plugs and current transfer relay.

It just bugs the hell out of me because every 6.2/6.5 and 6.9/7.3 has been a nightmare to start in the winter if everything isn't 100% PERFECT in the GP system... And really I wonder if it can ever be perfect due to the underrated equipment used in the first place. Everyone asks me if I'd swap my IDI one day for a Cummins, and honestly the only reason I would it do such a thing is to pound the last nail in the glow plug coffin because every time winter rolls around (Northern Utah + winter = cold as (%#@^!) I think it would be well worth it!

That is why you have a block heater for those low temp areas.

 

[Rot Box]

#1. Yes, you are overlooking the reason for 2 10ga wires.

That is why you have a block heater for those low temp areas.

Thanks for the heads up Any idea where those fuses are located? I'm assuming they are quite large and not in the fuse box considering they can carry 180amps. I would think these would have popped long before the plug/wires melted. Oh well.

I don't always have access to a power source for the block heater

 

[OLDBULL8]

Thanks for the heads up Any idea where those fuses are located? I'm assuming they are quite large and not in the fuse box considering they can carry 180amps. I would think these would have popped long before the plug/wires melted. Oh well.

I don't always have access to a power source for the block heater

There are no fuses. Read it again.

Read this also. http://fusiblelink.net/

 

[sootman73]

Thanks for the heads up Any idea where those fuses are located? I'm assuming they are quite large and not in the fuse box considering they can carry 180amps. I would think these would have popped long before the plug/wires melted. Oh well.

I don't always have access to a power source for the block heater

Here's a little explanation from a supplier website.

The lower the gauge number, the thicker the wire (i.e. 10 ga. is thicker than 16 ga.)
A fusible link is a special section of low tension cable installed by an OEM and designed to open a circuit when subjected to extreme current overload. Its purpose is to minimize wiring system damage when such an overload accidentally occurs in those circuits protected by the fusible link. A short circuit causes the fusible link to act as an element in a “slow-blow” fuse. A fusible link is not intended to be used in place of a fuse but only where a fuse cannot be economically employed. Our fusible line wire meets the requirements of SEJ-156 and the insulation has the characteristics as listed for EAE, SE J-1128Type SXL. The vehicle manufacturer should be consulted about questions on fusible link length and size. General practice has been for a fusible link to be 4 gauges smaller than the circuit wire. Example: if the circuit wire is 12 gauge, use a 16 gauge fusible link. Final determination should be based on O.E.M.application.
Note: Extreme care should be taken to always replace a fusible link with the same gauge and length as installed by the manufacturer.
Gauge: 8

 

[Rot Box]

There are no fuses. Read it again.

Haha ya it just dawned on me what you meant a few seconds ago. My bad thanks again for the help

 

[Agnem]

The entire principle under which the 7.3 controller operates is based on current draw and voltage drop across the controller. Changing the gauge or lenght of any wire or glow plugs will alter the timing and effect the glow time. The proper way to diagnose the glow plug system is to analyze the voltage present at the #2 glow plug (with it attached). On a cold engine, you should have about 6 or 7 volts at that glow plug, and it should slowly climb towards battery voltage as the glow plugs heat up. If the voltage starts out too high, the glow time will be reduced. If the contactor checks out (measure the voltage across the two large terminals - should be nearly zero when energized) then you have bad glow plugs. If you have a voltage across the contactor when energized, then that indicates a faulty contactor.

 

[88beast]

well the 10 gauge is to prevent over resistance and shorted circuts etc. you got to think like an engineer or be inbread and drunk thatll give a similar mind set.
but what i did is push button with a fender mounted solinoid and a large cable 4 gauge iirc. then a custom harness from that starter solinoid to the gps one 14 ga wire per plug. it works great and does fine without issues. but if you keept the same resistance and moved the controler and solinoid itd be a much lesser ordeal as everyone hates crawing over everything to get to it.