Any benefit to bypassing the glowplug controller?

78sharpshooter · #1 (**permalink**) 10-30-2009, 10:10 AM

I bypassed the GP controller on my 85 and with 6 seconds of holding the button that thing would start in less than one complete revolution of the crank. On my 93 I have not bypassed the factory GP controller and the other day on a cold morning it took 2-3 revolutions to start. When I go up to the mountains this winter I am a little concerned that it might be painful to start so I was wondering if there would be any benefit to converting this one to a manual GP setup.

PLC7.3 · #2 (**permalink**) 10-30-2009, 03:48 PM

In actual fact changing the Solid State controller to a manual operation is not good. The system works best if left alone. However 8 working Beru Motorcraft ZD9 GPs are a requirement to proper operation when needed.

Rodpod · #3 (**permalink**) 10-30-2009, 05:03 PM

My truck has the GP controller bypassed. I think its ok if you know what your doing.I took my truck to an auto electrician to get some work done and im pretty sure he fried 2 of my glowplugs trying to start it with a flat battery. Also some glowplugs can stay on for longer than others without frying. Mines set to 5 secs just to be on the safe side. And its coming into summer here

archangel · #4 (**permalink**) 10-30-2009, 07:40 PM

Last winter if it was below the mid 20's and the engine was cold, my controller would not cycle.

Now I have no choice as it cycles for less than 1 second if it's less than 90 out!

They seem to have no problem offering the relay, but I can't find the controller for sale anywhere!

JHoffman93 · #5 (**permalink**) 10-30-2009, 08:54 PM

I bypassed my controler with a switch in the cab. I hold the switch until the "wait to start" light goes out and then crank it up. Works great. BTW, if you truck is starting when it is cold after only 2-3 revs you have nothing to complain about.

ford390gashog · #6 (**permalink**) 10-31-2009, 03:28 AM

You can get new controllers and relays for under 80.00 but for the system to work right all glow plugs must work or else the unit will short cycle.

Dave Sponaugle · #7 (**permalink**) 10-31-2009, 01:45 PM

If you bypassed the controller the wait to start light will stay on until you take your finger off the button.

Sounds like you removed the ignition power supply to the relay and replaced it with power from a manual switch.

When talking about glow plugs, the truck year is required.
83 tru 86 old style system
87 thru 94 new style system

Completely different systems.

JHoffman93 · #8 (**permalink**) 10-31-2009, 06:14 PM

Dave, the old truck is getting hard to start again now that it is getting colder. I went out and double checked my wiring for the manual control and I have it wired per your pictures. But I got to thinking, when I first got the truck I was trying to add a better ground to the controller and I put it on the wrong terminal. I added it to the stud on top of that flat metal coil looking thing (don't know what it is). Could I have ruined the controller causing the manual switch to not work right? I am thinking about replacing the controller. All the gp's test good but the truck is only firing on a few cylinders making it relay hard to start when cold and creates quite the smoke screen for a few seconds after it does start.

Dave Sponaugle · #9 (**permalink**) 11-01-2009, 08:39 AM

Battery terminal goes straight to the battery positive terminal, should have battery positive voltage at all times..
Ignition terminal goes straight to the key on terminal, power at that connector only whe the key is in the on (run) position.
The second large terminal on the relay is battery power out, through the bimetal strip to the glow plug terminal and on to the glow plugs.

So a ground on the metal strip would short circuit the relay to ground.

The only ground connection is the black ground wire out of the controller.
When the glow plugs should heat, the white wire from the controller to the relay second small terminal goes to ground, causing the relay to close and send power through the bimetal strip to the glow plugs.

When you install a manual switch on the 87 to 94 new style system, you supply a ground to the white wire terminal through a momentary switch.
When the key is on, power is supplied to the ignition terminal, the ground at the white wire terminal completes the circuit and closes the relay.

If you added a ground to the metal strip, I am going to guess that a fusible link has blown or the relay has burnt up.
Another possible place that power may not be making it to the relay is the engine to chassis connector circled in red in this picture.

The picture is of an 86 wiring harness, on the 87 and newer the glow plug wires would be either yellow or tan, still with both wires in one end of the connector.
Look for signs that the connector has been hot on that end, melted and deformed plastic connectors.

If it has been hot, your only fix is to splice the two large glow plug wires around the connector.

JHoffman93 · #10 (**permalink**) 11-01-2009, 10:26 AM

Thanks Dave, I'll check out the connectors this afternoon but I think I fried the relay when I connected the ground to the bi-metal strip back when I first bought the truck, before I found this great site and the wealth of knowledge all you guys have. Everything is wired properly now but the damage has already been done I'm afraid.

Dave Sponaugle · #11 (**permalink**) 11-01-2009, 11:47 AM

Those relays do wear out over time.
The contacts just stop conducting electricity.

I am manual control on mine, last winter I would have to hit the relay 5 or 8 times before the voltage meter dropped and the glow plugs heated.

New relay, back to one time and it was heating like it should.

You can change just the relay on the new style controller, get the relay for an 86 system, direct bolt on swap wired just like the one on it now.

Don't let them give you a starter relay, looks the same except there is a small S by one small terminal and an I by the other.
They are not wired the same internally.

JHoffman93 · #12 (**permalink**) 11-01-2009, 08:38 PM

Picking up a relay at AutoZone tomorrow for $15. Looks like I'm going to win a bid for a set of gps on ebay for $50 plus $5 for shipping. The PO of the truck gave me a box of parts and I found a complete set of injector caps and orings. I don't see any leaks on the injectors themselves but I have them so I'll probably install them anyway. Still need to figure out how to tighten the #7 line on the IP, it has a small seep.

ghunt · #13 (**permalink**) 11-02-2009, 11:51 AM

I don't know what GP's you're bidding on on ebay, but you don't want to use anything but Motorcrafts. My truck had two Champions in it and they died shortly after I got it, I replaced them with Motorcraft ZD9's.

My GP controller is completely wacked out, it doesn't cycle the plugs right anymore. I had to bypass it with a switch.

f350fan1993 · #14 (**permalink**) 11-02-2009, 11:59 AM

Quote:

Originally Posted by Dave Sponaugle

Those relays do wear out over time.
The contacts just stop conducting electricity.

I am manual control on mine, last winter I would have to hit the relay 5 or 8 times before the voltage meter dropped and the glow plugs heated.

New relay, back to one time and it was heating like it should.

You can change just the relay on the new style controller, get the relay for an 86 system, direct bolt on swap wired just like the one on it now.

Don't let them give you a starter relay, looks the same except there is a small S by one small terminal and an I by the other.
They are not wired the same internally.

Also, the gpr from napa has the same little s and i on it, but it does wire differently than a starter relay. Just make sure that the part # from napa is a GPR-109.

JHoffman93 · #15 (**permalink**) 11-02-2009, 08:39 PM

I lost the bid by a dollar. I thought I had it in the bag and stopped watching it right at the very end because no one had bid on them in 7 days. They were Motorcraft ZD-9's brandnew still in the sealed packages. Thanks for all the feed back on my other post about using plugs from SSDiesel. I think I will be sticking with Motorcraft.