Glow plug controller questions

[The FNG]

Hi guys, I know this is a common topic on the board, but I am having issues finding the info through the search.

I have a 94 turbo IDI 7.3l. My WTS light will stay on for the normal amount of time in conditions above 50*f, but on colder days, it will stay on for about 2 seconds. it will cycle on both occasions and both situations will result in a hard start (smoke, coughing/general roughness), although it is less rough when the WTS light is on for the correct time. I can hear the relay work in sync with the WTS light too.

In the past 2 years, I have have replaced the glow plugs (ZD9's-all 8) twice. It seems to fix the problem temporarily, but it eventually becomes hard to start again. This has led me to believe that the issue is deeper than the glow plugs. I was planning on replacing the glow plugs and relay on the controller, but I was recently reading on some sort of solid state retrofit that can be done. I was unable to find info on this.

Any help would be nice. I haven't spent much time under the hood, or checked any of the parts yet for corrosion or melting. What would be the best option for me to do? TIA

 

[RollinitBlack]

I've got 3 of these fords and in my opinion and experience i would buy a complete new controller. I had a friend that bought a truck with a shade-tree manual glow plug controller cheap fix kit. We never could get it to function right. I've had bad controllers and I've also had wait to start lights act goofy. I found that my wait to start light bulb was just loose in its socket...sometimes it'd work other times it would come on and go off abruptly at startup. I'd check the bulb and then buy a real correct controller

 

[Hydro-idi]

There is no need to keep replacing your glow plugs because I do not feel that is the problem. In my opinion, the stock glow plug setup works awesome when it is working properly. I do not see a need to install a manual system but some prefer one system or another. You are having issues with the solenoid mounted on the passenger side fender or the glow plug controller that sits right behind the intake hat.

 

[The FNG]

I don't think it's the solenoid on the fender, I think it's the controller behind the intake hat. I guess my issue is that the controller changes how long the relay is closed based on ambient temperature. The colder it is, the shorter the relay is active. My question is then: Which component is bad, the relay on the controller or the controller itself? If the controller is to blame, I have heard of a "newer and better" solid state version (not sure what I have or if the stock one is solid state). Also, I am assuming that the WTS light is working properly since it goes on/off with the relay every time.

 

[mblaney]

If you are changing the GP relay, check out the part number in my signature. This is a much better relay than the OE or NAPA crap is. the plastic cover will not fit over this relay but it only required minor adjustment to the shunt to get it to fit.

 

[icanfixall]

The 6.9 controller glow plug systems are the ones that don't have the 7.3 style solid state controller. So seeing that you have the 94 model you already have the solid state controller. Its not often they go bad either but things happen. The colder the temp outside is the longer the plugs will stay on. The ebay site named utechcenter has these controllers offered all the time. Just have to surf it. As for the melted plug to the main engine wire harness. That might be an issue and the corrosion in that might be a problem.. Gotta check it..

 

[The FNG]

i read about that plug, i will check that. I suppose that plug can cause these issues? Just weird it would be temp dependent in the reverse way it should be

 

[argve]

You have more than likely a bad glow plug or two.

If your timing is not set correctly it will cause glow plugs to burn out early. If you have a sluggish injector that is either lighting off early or late it will change the timing for THAT ONE cylinder. Which would in turn cause that glow plug to burn out sooner.

What you need to do is one of two things.

One is just throw parts at it until it runs - while this works - it's gets very costly.

Two is to troubleshoot the system. I like this way because it makes more sense and is easier on the wallet.

Ok so how do we troubleshoot the system.

First off grab a meter or test light and test each glow plug when it's UNPLUGGED from the circuit. Now you don't have to remove the glow plug from the engine to do this test having it installed is just fine and it's easier (I'm fat and lazy so if I can get by without doing extra work I will).

1st step make sure engine is cold - meaning it hasn't been running for sometime. This does two things for us - 1 it makes it easier to work on and two as glow plugs heat up their resistance value increases.

Now if using a meter place one lead on the bullet end of the connector and the other lead on a solid clean ground, this can either be the nut portion of the glow plug, a clean piece of metal on the engine or the neg terminal of either battery. A good glow plug will measure when COLD 1-2 ohms, a red hot can't touch it will measure around 30 ohms or higher. (this I know from bench testing one years ago - yes I was bored at work).

Test each and everyone of the glow plugs. Replace the ones that are bad.

Now if using a test light....

Place the clip of the test light on the positive post of battery and place the tip of the probe on the bullet end of the connector. If the light comes on then the glow plug is good. if not then that glow plug is bad - replace it.

Now that we have determined which ones are good and which ones are bad you can either replace all (very expensive) or just replace the ones that are bad - I always go with just the ones that are bad - one bad glow plug does not make it harder on the rest it actually makes no difference to the others at all what the other one is doing.

Now look at all connections on the glow plug controller. Make sure they are clean and tight. The reason for this is because the glow plug controller determines how long to keep the glow plugs ON for via measuring the voltage drop across the glow plug circuit vs the voltage drop across the big zig zag piece of metal on the controller. If the connections at any point here is corroded or bad then the time that the glow plugs are ON will suffer. Also make sure that the ground that the glow plug controller uses is good as well. Typically it grounds to one of the mounting bolts for controller.

Look at the harness that supplies power to this circuit as well because bad connection here will effect how long the glow plugs are ON because remember it measures voltage drop across the glow plugs to determine if it's 70 degrees outside or 30 degrees.

One of the fastest ways the system tells you there is a problem is because the WTS on time gets shorter than it should be. Causing a hard start condition. One bad glow plug typically you can limp it through but two bad (has been my experience) requries a lot of faith and recyclinging the key to restart the firing of the glow plugs a couple of times to get her to fire up coughing and belching in 50 degree temps in the morning.

if you have any more questions don't hesitate to ask. Lots of folks on here have knowledge and will pass it along.

 

[icanfixall]

When the temps drop an electrical problem will seems worsr because the cold seperates the possible bad connections. Ever see whats used to find a bad connection to a circut board. CO2 or freon because its so cold it opens up the bad circut connections and then they are easier to locate... Nothing worse than an intermitent open circut. Good luck finding the problems but I feel the posting here will get to the problem.

 

[franklin2]

Aren't you glad you asked this question and started this thread? Now you have a clear picture of what's bad and what you need to do to fix it . An intermittent problem like this is going to be hard for anyone to fix, even if they were there looking at the truck.

 

[The FNG]

Yes, awesome replies

 

['94IDITurbo7.3]

i like the manual control b/c when the engine was just shut off you don't have to worry about the glows glowing.

Mine will glow for the same amount of time whether the outside temp is 2*F or it is 80*F, or if the truck has been sitting for 2 weeks for was shut off and restarted with in seconds of shut down. i have been told that operation is perfectly normal. personally i think that if that is the way this system is designed then it is a POS.

since i joined i have yet to get a definitive answer as to how the solid state(7.3L) system works. One thing i do find "odd" is that my coolant temp sensor for the factory gauge never get's higher than the n on normal, meaning that sensor is always reading cold. my friends truck, who's glow plug system works like i feel the system should work(doesn't glow when the engine is warm), the temp gauge works fine. i think it is wiring diagram time.

 

[RollinitBlack]

Im almost positive that it is very important for all the glow plugs to be working correctly. if you have a bad glow plug or 2 it messes up the amount of time that the controller heats them up. I know this from personal experience

 

[The FNG]

I was just thinking about the timing thing. I never had this issues with the glow plugs until I had my IP replaced. How would I check my timing? I am assuming you cant use an inductive timing light like you would on a car.

 

[argve]

There used to be one that you could - I know I had one - This device hooked to the number one injector line and would create a pulse so that the timing light could light off then you would flash it at the crank and if you had a degree tab on the crank you could read (grease and such cleaned off it) you could set the timing. Now most use a deal where it uses a pickup on the crank and displays the timing on the screen of the device then you can set the timing. I think Gary (Icanfixall) has a few - he's a horder of that stuff so he might be able to direct you more in the use of one of those. I have only seen that type in action at the IDI Weekends when Mel does his timing clinic on the trucks.