Relay, Controller 6.9 Questions - Diesel Forum

Randy26933 · 11-22-2009, 09:56 AM

I have an intermittent problem with what I believe is the GP relay. A week ago I tried to start my 86 F250 w/ 6.9 and the glow plug light did not come on. I cranked and cranked and eventually it took off and blew enough smoke to kill every mosquito in a five mile range.

I started it a day after that and the GP light came on and it started right up.

Yesterday the GP light would only come on for a second,but after enough cranking the engine eventually started up.

Today I snuck up on it when it was cold and put a test light on the "out" side of the relay to see if it was putting out current to the GPs. Of course it started right up after staying lit for ten seconds. (GP light and test light)

My question is this, Is the relay (on the wheel well) controlled by the controller (on the intake) ? Could a bad controller tell the relay to shut off? I replaced the relay and GPs last year and have not had a problem until now.

I suppose the relay could be bad, but since I put the test light on it I can not get it to not work.

Any suggestions would be greatly appreciated, thanks.

Scoobywagon · 11-22-2009, 10:32 AM

Yes, its likely the controller. I'm headed into work a little later and I can look up the wiring diagram for it. That'll let you test properly.

Scoobywagon · 11-22-2009, 12:39 PM

Ok. Just looked this bad boy up.

It would be best to do this with a digital multi-meter, but if all you have is a test light, we can still figure it out. First, ground your test light at one of the batteries and probe the forward terminal for power. If there's power there, then wiggle the wire that connects back to the battery and make sure that the power doesn't go away. Next, jumper from the positive terminal to the trigger terminal and check for power on the output side. IF you have power, then cycle the relay a few times to make sure that it operates consistently. If it does, then you have a bad controller.

chuckster57 · 11-22-2009, 01:04 PM

Quote:

My question is this, Is the relay (on the wheel well) controlled by the controller (on the intake) ? Could a bad controller tell the relay to shut off? I replaced the relay and GPs last year and have not had a problem until now.

The relay on the fender well is for the starter, and it is controlled by the ignition switch. Doesn't have anything to do with the GP relay.

IIRC the "controller" is in the back side of the P/S head, and the relay is the part your describing on the intake.

Evel486 · 11-22-2009, 01:36 PM

Starter relay is horizontal mount on inner fender. Not sure about 86 but 83 the gp relay is vertical mount on pass side wheel well.
Wait to start light is connected glowplug circuit- no wts light, no gp power. Scoobywagon is steering you right.

Randy26933 · 11-22-2009, 08:26 PM

If there's power there, then wiggle the wire that connects back to the battery and make sure that the power doesn't go away. Next, jumper from the positive terminal to the trigger terminal and check for power on the output side.

Scoobywagon,
Which one is the "trigger" terminal? There are four terminals, two big, two small. One big for power in, one big for power out and two small ones that for all I know run the defroster.

I did run the test light to the output side of the relay and each time the GP light came on the dash, the test light lit.

And, am I referring to the components by the right names? Relay on the wheel well and controller on the intake? Evel 486 described the relay (if thats what it is) I have, on the pass. side wheel well.

Scoobywagon · 11-23-2009, 12:40 PM

Yes, you're using the correct names. I don't have the diagram in front of me, but the trigger terminal should be the small one with the red wire. At least it is on my truck. You need to disconnect the relay from the controller to do this test properly. What we're doing is testing to make sure the relay is operating properly. That means that so long as there is power in, you get power out when you trigger the relay. It sounds like that's what's happening here, so I suspect your controller is going kaputsky.

Joe Mc · 11-23-2009, 01:39 PM

On my 86 the light purple wire activates the gp relay. On a cold engine you should get a steady 12 volts on the purple wire every time you turn the key on, if the controller on the back of the intake is working right.

Randy26933 · 11-23-2009, 04:51 PM

I got a steady light on the trigger wire (yeah, purple) when the key is turned to the "on" position.

But am I not understanding something?

I pulled the plug off the contoller and did the test as Scoobywagon laid it out to me and got a light each time. Which I took to mean ; relay ok, controller kaputsky.

If I understood what Joe Mc says I'll get a light if the controller is working RIGHT.

NAPA is happy to sell me a controller for a paltry $154.00.

Besides being happy to learn about this system and new terminology, (kaputsky) let me give a big hand to the Ford engineers who can find the most horrendously obscure hard to reach places to put vital parts on a vehicle roughly the size of an aircraft carrier.

chuckster57 · 11-23-2009, 05:23 PM

Quote:

Originally Posted by Randy26933

Besides being happy to learn about this system and new terminology, (kaputsky) let me give a big hand to the Ford engineers who can find the most horrendously obscure hard to reach places to put vital parts on a vehicle roughly the size of an aircraft carrier.

beats the daylights out of trying to squeeze your paws in the engine bay of a transverse mounted foreign engine

for a simple belt change

Scoobywagon · 11-24-2009, 02:00 AM

Quote:

Originally Posted by Randy26933

I got a steady light on the trigger wire (yeah, purple) when the key is turned to the "on" position.

But am I not understanding something?

I pulled the plug off the contoller and did the test as Scoobywagon laid it out to me and got a light each time. Which I took to mean ; relay ok, controller kaputsky.

If I understood what Joe Mc says I'll get a light if the controller is working RIGHT.

All we've really done so far is to verify that your relay is working properly. UNfortunately, the problem you're actually after is intermittent and not currently in a failure mode. The upshot is that relays don't HAVE intermittent failure modes. They are very simple devices and so they either work or they don't. Since we've verified that your relay is working properly and that you don't have a loose power connection between it and the battery, the only component left in the system is the controller. The only OTHER possibility is that one (or more) of the wires in the harness to/from the controller has a break in it. Its not particularly common, but it does happen. Unfortunately, there's not a particularly good way of testing that without a known-good controller.

mikeceli · 11-24-2009, 09:05 AM

Lurking. My 86 F250 has similer problem.

Randy26933 · 11-24-2009, 03:33 PM

Made NAPA happy and got the controller. All systems seem normal. Got it good and warm to make sure there were no leaks, now I'll wait several hours for it to cool off and try it again.

I would like to thank you all for the tips and tricks. Scoobywagon, if you are ever in this neck of the woods there will be a frosty Canadian Cola waiting for you.

Scoobywagon · 11-25-2009, 01:09 AM

Quote:

Originally Posted by Randy26933

Scoobywagon, if you are ever in this neck of the woods there will be a frosty Canadian Cola waiting for you.

You're quite welcome. I'm a big fan of a good, frosty barley-pop. I'm on the other side of the country. I'm down for a meet and greet any time, though.

WhiteGardens · 11-25-2009, 01:12 PM

Quote:

Originally Posted by mikeceli

Lurking. My 86 F250 has similer problem.

Is it the Solid State controller like the 87 and up, or the old style controller from 86 down.