WTS light - no start - glow plug issue - help plz

[bluefishbeagle]

My truck is a 1993 7.3 IDI Turbo Stright Shift

Truck has been cranking hard for some time but would crank. Sometimes the GP relay would cycle sometimes not. Starting cold was easier than hot most of the time but not always. I did however always get the WTS light although it would stay on different lengths of time.

Fixes so far.

1. Batteries new less than one year ago, check good
2. New glow plug relay
3. Checked all glow plugs one was bad replaced with new.
4. Starter seems to be original truck has 125,000 miles so it is getting old.

What it's not doing now, (problem has got worst since I've been working on it, hmmm connection maybe :-)
1. No Start (normal methods).

What it is doing:

1. Turn key on and glow plug relay will not click, WTS light comes on for 1/4 second and goes out. Remember the GP relay is new.
2. Truck volt meter comfirms that the GP's are NOT drawing power.

At the GP relay:

With Key ON: (No click at the GP relay)

1. 12 volts present on the Main plus wire (large black one) and the terminal with the white wire and the other small terminal (it has three wires one is red) no voltage on the other large terminal with the crooked resister band (my guess is that this one feeds the GP's).

With Key OFF:

1. 12 volts on the main plus wire, no voltage any where else.

Here's how I can get it to start:

Turn key off:
1. On the GP relay jump the terminal with the white wire to the Main plus terminal (GP relay clicks closed) and wait for 8 - 10 seconds, immediately turn key to on and to start. Truck starts normally.

Any help, wiring diagrams, past experiences etc would be very appreciated.

Thanks

[danngreen]

Starting cold was easier than hot most of the time but not always...... problem has got worst since I've been working on it

considering that, I would think about replacing that starter before the GP/relay/wiring. starter will wear out if you've been cranking it while working on it. maybe im biased but I thought i had a GP problem or air in the lines and it was the starter the whole time.

This is a wiring diagram I have:


Sounds like you're bypassing the controller circuitry and kicking the GP's on directly to get it to start. I would still pull the starter and take it into a shop to check it over. Can you estimate the RPM's when you're cranking it? If the starter is marginal then the GP jumper trick could make the engine turn over just a little bit easier, causing it to start.

In general, when testing the GP controller, use a test light instead of using a meter on the bendy-metal terminal which goes to the actual GP's. The reason is that there should be a pulse wave (on-off-on-off) at that terminal but a digital meter won't respond quickly enough to a pulse wave and will show a low voltage instead. The test light should flash on and off and you should be hearing the GP relay click on and off.

If it's not clicking and the relay is new, then check the wiring. Since you're getting 12V on the mains terminal and 12V on the ignition terminal, check the resistance between the ground wire and the battery ground post. should be an ohm or hopefully less. that's weird you get 12V at the white wire terminal but jumping it to 12V will make the relay click. Does the relay click once when you have someone turn the key?

[cdnsarguy]

Don posted this info years ago.......

If you have 2 or more bad GPs, the controller may not cycle at all.

Two problems that occur with the solid state ( 1987 to 1994 IDI engines ) GP systems. If a GP burns out ( circuit resistance goes up ), the controller cycles the GPs at a faster rate which doesn't let them get to max operating temp. If 2 or more GPs fail, the controller may not cycle the GPs at all ( very rapid or no clicking heard ). When you check the GPs, use an ohmmeter. A high resistance ( not necessarily burned out ) GP can cause circuit resistance to go up and the controller will then cycle the GPs too fast. You probably will not find this problem with a test light. Resistance spec for GPs = .5 to 1 ohm cold. Second problem. A poor controller ground ( black wire attached to valve cover stud ) will cause the controller to leave the GPs on longer, often damaging or failing them. If you are having mulitple GP failures, I would check closely the controller ground. Now the confusing part. Bad ground --> longer GP on time ( slower cycling ). Burned out GPs --> faster cycling If you have both situations, it may appear that the controller is cycling the GPs at the proper rate. Bad ground slows it up while the burned GPs speed it up ---> normal cycling. The system acts/sounds like it's working normally, but you have a hard starting concern.
By........DieselDon

Glow plug torque is 12 ft lbs, I always use antisieze on the threads.

One point what brand of GPs did you install...... if they were not Motorcraft-Beru ZD9 chances are they are already burned out.......

[bluefishbeagle]

Even though the GP controller was new (installed only about 5 days) I suspected it might have went bad because when put on initicially it did click when the key was turned on. I took it back to the ford dealer and they replaced it. Now the relay clicks when the key is turned on. I don't know why it failed so soon, hopefully it's not going to happen again.

Is it normal for the GP relay to cycle after the initial warm up? Mine used to but does not do that now or at least not all the time.

The starter at times spins the engine very fast but sometimes it turns it so slow that you'd think the battery was almost dead. This happens when the glow plugs are pulling power at the same time the engine is cranking. I'm getting another starter and will report back on the results.

[cdnsarguy]

I would suspect the fender mounted starter relay may be part of the problem... if it is OEM replace it..... could be a cheap fix for the starter problem.

[Snotzalot]

Guys,

Looking at the above wiring diagram, it appears the cold advance solenoid and the low idle solenoid are supplied current off of the same sender, the engine temp switch, correct?

As I have previously mentioned I'm having loping issues at cold start (only) and I suspect my cold advance isn't working. How does the cold advance function? Is it an internal IP function or is it an external (solenoid) function? I'm working on a van so I can't just open the hood to visualize/inspect things.

Any other things that would affect the cold advance????????

[bluefishbeagle]

While I did have a problem with the GP relay/controller it may have been induced by me while trying to get the engine started by jumping the relay (hey I was 160 miles from home and it was 101 degrees outside). That said I replaced the starter and WOW what a difference!!! My truck now starts like NEW!!!

Thanks to all for the help. This forum is a great place!!!!!!!!!!!

[danngreen]

right on!!