Glow plug relay clicks/buzzes loudly

stownsen914 · Oct 21, 2016

I have an 1994 RV with a 6.5 OBD2 diesel. I noticed it being hard to start the other day, and I noticed that the usual noise I heard from the glow plug relay (loud clicking/buzing) wasn't happening. I jumped the relay, and it started right up. I then noticed that a couple fuses were fried, and that replacing them made the glow plug relay started clicking/buzzing again during WTS. Also, when I measure the voltage at the terminal on the relay that gets power while the WTS light is on, I only get 5 volts (the other terminal gets 12 volts all the time). Is my glow plug relay not working properly?

Scott

stownsen914 · Oct 21, 2016

I meant the engine is OBD1. Can't seem to edit my original post ...

OkDually · Oct 21, 2016

Do you have a matched set of equal CCA, batteries?
Load tested those batteries?
Cleaned/checked the battery terminals?

Gone through all of your grounds?

stownsen914 · Oct 22, 2016

Thanks. Well, it fires cranks well and fires right up after I jump the large glow plug terminals. Between that and the batteries looking relatively new, I didn't think to load test them (and yes they are equal size).

The relay shouldn't buzz/click and give only 5 volts on the switched terminal, right? This vehicle is still new-ish to me and I am new to diesels, so I am not sure how it's supposed to behave. It seems to be getting 12 volts supplied to it ...

OkDually · Oct 22, 2016

stownsen914 said:
Thanks. Well, it fires cranks well and fires right up after I jump the large glow plug terminals. Between that and the batteries looking relatively new, I didn't think to load test them (and yes they are equal size).

The relay shouldn't buzz/click and give only 5 volts on the switched terminal, right? This vehicle is still new-ish to me and I am new to diesels, so I am not sure how it's supposed to behave. It seems to be getting 12 volts supplied to it ...

Here is some info on the glow plug relay voltage.
http://www.dieselplace.com/forum/63...iesel-engine/600634-99-chevy-6-5-glow-plugs-no-light-dashboard.html#post5936722

JMJNet · Oct 22, 2016

You HAVE TO load test the batteries one at a time even if they are looking relatively new. Heck, they can be fresh from the store and if you have issues after that, you still have to test it.

Sounds like the GP controller is bad, get an ACDelco brand and not aftermarket brand.

stownsen914 · Nov 1, 2016

So it appears there is some issue with the glow plug controller, but I am not sure if it's the controller itself or in the circuit(s) powering the controller. I am getting full voltage on the hot terminal on the controller at all times, and the WTS light comes on for approx. 6-7 seconds after I turn the key to Run, but I am not getting voltage on the second pole that should get 12V during WTS. I have seen references to yellow and pink wires and that they should get 12V. The wires in my RV's harness are different colors for some reason, so I am not sure which to check. I only get 12V on one of the wires at the plug the connects to the glow plug controller ("D" in the diagram below) when key is on. It sounds like I should get voltage at "C" as well while WTS light is on?

OkDually · Nov 1, 2016

stownsen914 said:
So it appears there is some issue with the glow plug controller, but I am not sure if it's the controller itself or in the circuit(s) powering the controller. I am getting full voltage on the hot terminal on the controller at all times, and the WTS light comes on for approx. 6-7 seconds after I turn the key to Run, but I am not getting voltage on the second pole that should get 12V during WTS. I have seen references to yellow and pink wires and that they should get 12V. The wires in my RV's harness are different colors for some reason, so I am not sure which to check. I only get 12V on one of the wires at the plug the connects to the glow plug controller ("D" in the diagram below) when key is on. It sounds like I should get voltage at "C" as well while WTS light is on?

You should see 12v. in and out of the Controller.

Replace the Controller with an AC/Delco unit..

Crazyxxxinsane · Nov 1, 2016

"C" is just the input sensor that reads that they are getting warm and senses the glow plugs and when to turn them off (the wait to start light). If you have 12V going in at the battery side of the controller, you also need to have the 12V coming out of the other side that leads to the glow plugs themselves. "D" just relays the power from the ignition switch to the controller to turn the controller on to give the full 12v power needed to power the glow plugs. turn the key and check the glow plug terminal and see if it gets 12v. if not, replace the controller.. and as Suggested get ONLY AC Delco electrical parts for these engines.

Glagulator · Nov 1, 2016

Your glow plug relay is probably more like this.

http://www.dieselplace.com/forum/attachment.php?attachmentid=500185&stc=1&d=1477987042

stownsen914 · Nov 3, 2016

Glagulator said:
Your glow plug relay is probably more like this.

I'm glad you posted this diagram. Actually my glow plug controller seems to match the wiring diagram that I posted, and not the one you posted. I hadn't realized there were different versions of the controller. Looks like 212-366 has the three pins for the plug, while 212-367 has four pins. Mine has four. I almost bought the wrong one ...

Before I purchase it, I have seen some references in other posts on the forum to checking the coolant sensor input, or to test unplugging the sensor to see if it makes a difference in the controller's behavior. I found what I believe to be the coolant sensor on the left front side of the engine below the valve cover. I believe that's cyl. #1 from some searches I did. (It's actually on the right rear on my RV since the engine is turned around compared to a pickup). For what it's worth, I unplugged the sensor and did not notice any change in the behavior I mentioned earlier in the thread.

Time to get the new controller.

Glagulator · Nov 3, 2016

So you have a mechanical injection pump?

JMJNet · Nov 3, 2016

Yes, there are more than 1 types.

When installing the controller, make sure you are not tightening those big lugs too tight. I have heard some people are overly excited when tightening those and it ruins the controller.

stownsen914 · Nov 3, 2016

Glagulator said:
So you have a mechanical injection pump?

Yes, apparently I do. I discovered that in an earlier thread when I was trying to find my PMD ... only to find I don't have one.

JMJNet said:
Yes, there are more than 1 types.

When installing the controller, make sure you are not tightening those big lugs too tight. I have heard some people are overly excited when tightening those and it ruins the controller.

Thanks. I guess those big lugs are for contact area, not to be torqued like you normally would on a bolt that size.

Glagulator · Nov 3, 2016

You should reflect that in your signature. You will get more accurate information and help.
94's have electronic IP's but some RV's and most vans still had the mech. pumps.
The GPR you have is self regulated and used with mech. IP's, while the 3 pin is controlled by the PCM on electronic IP engines.
And yes, the plastic will crack if over-tightened, I highly recommend a genuine AC Delco unit.

stownsen914 · Jan 8, 2017

I put in the new Delco glow plug controller. In starting it a few times in the past couple months (it's an RV so has limited use in the winter), starting does seem better, but still not right. The WTS light sometimes comes on for a few seconds, sometimes flickers, and sometimes comes on just for an instant. I can start the engine by jumping the two large terminals on the glow plug controller. Could the flickering WTS light be caused by a bad temp sensor or a bad ground? Or bad glow plugs? Would disconnecting the temp sensor be a valid test to see if I get more "normal" behavior from the WTS light?

Thanks as always for your input.

Scott

OkDually · Jan 8, 2017

stownsen914 said:
I put in the new Delco glow plug controller. In starting it a few times in the past couple months (it's an RV so has limited use in the winter), starting does seem better, but still not right. The WTS light sometimes comes on for a few seconds, sometimes flickers, and sometimes comes on just for an instant. I can start the engine by jumping the two large terminals on the glow plug controller. Could the flickering WTS light be caused by a bad temp sensor or a bad ground? Or bad glow plugs? Would disconnecting the temp sensor be a valid test to see if I get more "normal" behavior from the WTS light?

Thanks as always for your input.

Scott

On electronic Injection, Unplugging the temp sensor will fool the PCM into thinking it's -40* and thus will command a longer glow time..
It should be the same or similar for your mechanical Injection.

If you do unplug the temp sensor for starting be sure to plug it back in after the engine is running.

JMJNet · Jan 8, 2017

How is the conditions of the Glow Plugs?
You may want to check the GPs cables also?

Glagulator · Jan 8, 2017

The mechanical glow plug controller is completely self contained and regulated. I would be looking at the grounds and the 12v. feed wire to the GPR, should have a fusible link. Could also be a problem with the 12v. ignition signal. If you have the "glow plug inhibit switch" you should deactivate it, that's what GM did.

stownsen914 · Jan 9, 2017

Thanks. Did a bit of searching. Looks like the glow plug inhibit switch may be in different places for different years? Would it be on passenger side (in a pickup) to the rear of the exhaust manifold?

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