Modded GPR System - Diesel Forum

beda2007 · 01-31-2007, 03:38 AM

I have replaced many GPR's in my truck and at a cost of 42$ to 75$ decided to do something different and hopefully more reliable. In these trucks the GPR is supplied 12volts to one small terminal and the computer controls the ground to the other to turn the plugs on and off (common for commercial aircraft with heavy loads as well). I used a 1977 Ford F-250 starter relay to turn the plugs on and off. The problem was that the starter relay uses the mount for the ground. I also used a common fog lamp relay from the lighting isle at the local parts store to control the larger starter relay. The reason for the older starter relay was the high amp draw of the older starters. To accomplish the task I used the pigtail from the old GPR relay and cut the ring terminals off the small wires and installed a 1/4" female spade terminal on each wire and hooked them up the the fog lamp relay control coil terminal (polarity does not matter). Then take a 5/16" ring terminal a 6" piece of 16ga wire and another 1/4" female spade terminal and made a jumper from the batt side of the Starter relay with larger cable from the old GPR to one of the load terminals on the fog lamp relay. Next make another jumper out of yet another 1/4" female spade terminal a 6" piece of 16ga wire and a number 10 ring terminal that will go from the other load terminal on the fog lamp relay to the "S" terminal on the starter relay. The other large wires on the GPR go to the remaining large terminal to the plugs themselves. The "I" terminal on the starter relay is unused unless you want to install a light to know when the plugs are on. The mounting is up to you. You can elongate the holes in the starter relay a little and it will mount where the old GPR mounted. The materials needed include 1ea Fog lamp relay, 1ea 1977 Ford Starter relay, 4ea 1/4" female spade crimp ternimals, 1ea 5/16" ring termial, one number 10 or 3/16" ring termial, and 2ft 16ga wire. The total cost is about 15.00 dollars and a little time. I have a drawing of the wiring but cannot figure out how to put it on here.

STurbo90 · 01-31-2007, 04:00 AM

Not to sound dumb, but what is the current draw of the GP's when active? I've looked at the UVCH and the wires seem to be only 16ga? Maybe 20 amp draw X 8?? [img]/ubbthreads/images/graemlins/shrug.gif[/img]

Why not just use a larger SPST relay instead of the starter relay? That would eliminate the need for the extra SPDT relay?

I have used the PAC 200A's before and they seem to be pretty durable.

I've never had a problem with my gp system before, so I've never really checked it out.

beda2007 · 01-31-2007, 04:08 AM

The current draw was not the biggest concern. The durability was as well as the cost. The starter relay is the only thing that will have to be replaced from now on at a cost of $10.00.

STurbo90 · 01-31-2007, 04:29 AM

[ QUOTE ]
The current draw was not the biggest concern. The durability was as well as the cost. The starter relay is the only thing that will have to be replaced from now on at a cost of $10.00.

[/ QUOTE ]

Not specifically referring to the GPR system, but that seems backwards to me, the durability is directly related to the current.

In any electrical circuit, "Current draw" should be the biggest concern.

If your using a relay/switch that's "switching capability" is the same/or lower then the required current draw, then the relay/switch will fail often, requiring the relay to be changed more frequently.

beda2007 · 01-31-2007, 05:16 AM

The starter relay is rated for higher amps than the glow plugs use. You are correct though. The post above mine was saying the relay was oversized and why not use a smaller one.

Garbage_Mechanic · 01-31-2007, 01:56 PM

ST90, that Pac 200 relay looks like the other famous Stancor relay. Maybe there are two chices now?

STurbo90 · 01-31-2007, 02:28 PM

[ QUOTE ]
ST90, that Pac 200 relay looks like the other famous Stancor relay. Maybe there are two chices now?

[/ QUOTE ]

No, I don't think so, I think PAC rebadges everything they sell unless its an interface? [img]/ubbthreads/images/graemlins/shrug.gif[/img]

I have not paid attention to any GPR threads, because I have never had a problem with mine. So maybe guys are already using the Stancor relay? [img]/ubbthreads/images/graemlins/shrug.gif[/img] and I just never noticed.

[ QUOTE ]
The starter relay is rated for higher amps than the glow plugs use

[/ QUOTE ]

That is all I was asking, in the first post?

What is the current draw of the GP's when active? Telling me the starter relay is more then enough doesn't tell me what the draw is??

Garbage_Mechanic · 01-31-2007, 02:33 PM

I'm not sure but that relay you linked to looks like the Stancor bullitproof relay that is talked about often. I've not had problems either, but I may install one as a PM. I think if the relay points get weak, the voltage drops in circuit. Lower voltage = higher amps, higher amps = burnt UVC harness. My theory anyway.

Brian Cloke · 01-31-2007, 03:26 PM

On my truck I see on my digital amp meter a draw of 180 amps which
decays as they warm up.
Cheers .
Brian. [img]/ubbthreads/images/graemlins/warmsmile.gif[/img]

STurbo90 · 01-31-2007, 03:40 PM

[ QUOTE ]
that relay you linked to looks like the Stancor bullitproof relay that is talked about often.

[/ QUOTE ]

I believe it, that was the reason for:

[ QUOTE ]
I think PAC rebadges everything they sell unless its an interface

[/ QUOTE ]

**bugman** · 01-31-2007, 04:55 PM

I think that we figured one day that the glowplugs will draw anywhere from 175-195 amps depending of their condition on start up. The Stancor 586-902 is rated at a continuious 200 amps with a surge up to around 500 amps. Now with the glowpugs staying on for up to 2 minutes with a possible draw anywhere from 150-195 amps I like the Stancor. I have been running mine for over 3 years with no problems and I know that there are others that have ran them longer. The nice thing about it is that it will bolt right in with no other modifications, no spliceing wires, no extra relays and not having to worry about replacing it when it burns out as a starter relay would. At least in my case. As for those that like to control the relay themselfs all you need to do is put a switch in line with one of the control wires. But I myself believe that with them staying on for a little after each start helps on the carbon burn off that a lot are fighting when they have a stuck one when they go to replace the plugs.

Jim