solid state controller

[dmaxjoe]

My 84 has been switched to the solid state controller 5 yrs. ago. Lately the wait to start light has only been staying on about 8 seconds then starts clicking. I tested glow plugs yesterday and changed 1 bad one. I went to start the truck and the light stayed on for 25 seconds and I shut the key off thinking the controller was stuck. I started the truck a few minutes later and light went off after 28 seconds . I have started it a couple of times since then and the light stays on for about 25-28 seconds every time. What the heck is going on? I don't want to burn out all the plugs. This seems like way too long of glow time.

 

[OLDBULL8]

Thats normal. Been kinda cold in Michigan hasn't it, here in Ohio too.If you have MC/Beru plugs don't worry about it. There is a thermister embedded in the controller that determines how long it stays on, also the resistance of the GP's. Now you can tell if you have any bad ones. If you noticed, it 's on/off for up to 2 minutes.

 

[dmaxjoe]

It seems to be working. I was just concerned about that long of a time. It has never gone that long before and my 91 goes about 18 seconds max in these cold temps.

 

[OLDBULL8]

Not all thermisters and GP resistance is exactly alike.

 

[dmaxjoe]

"Thermister" ? Is that the wavy metal thing on the controller?

 

[Black dawg]

My ford manual says "zero to 15 seconds depending on engine temperature". Ive never seen more than 15 seconds ever.

 

[dmaxjoe]

I'm doing alot of searching and reading here. I am trying to understand the way this controller works. I am wondering if I have a low voltage problem. Would that cause a longer glow time?

 

[Shadetreemechanic]

I'm doing alot of searching and reading here. I am trying to understand the way this controller works. I am wondering if I have a low voltage problem. Would that cause a longer glow time?

It could. glow plug on time is a function of resistance in the plug itself. The hotter it gets the higher the resistance. Low voltage would lengthen the time to heat and give you a longer glow time.

 

[icanfixall]

Check the main engine wireing harness plug for corrosion or being melted from that.... The plug cam be found between the passenger fender and the head. Its about 2 inches long and 1 inch wide. The 2 yellow wires feed power to the controller. The resistance thru that plug is high. Those pin connecters are just too tiny to carry enough ampage if they get corroded. Mine melted so I btpassed it with 6 gauge speaker wire... Now I have full volts and amps directly from the solenoid-battery....

 

[MR.T]

"Thermister" ? Is that the wavy metal thing on the controller?

I believe the wavy metal item in the controller is actually a current shunt, basicially a low ohm resistor that produces a voltage drop proportional to current -- the controller measures the voltage drop and infers the current.

How the controller works isn't documented anywhere I've seen. Here's a post I made with some glow controller data. As Black Dawg mentioned the manual says 15 sec max, I don't think I've seen more either. If there is a max time limit, it's done in the controller.

Edit: What is the WTS time with a warm engine?

 

[dmaxjoe]

I just returned from a 5 mile trip to the store and warm starts are 18-20 seconds. I have maybe 7-8 starts since yesterday and all is good. I will check the plug and all the wires tomorow when I have more time.

 

[Black dawg]

Id check the voltage and if its not really low Id unplug something before you fry those plugs.

 

[LCAM-01XA]

How the controller works isn't documented anywhere I've seen. Here's a post I made with some glow controller data. As Black Dawg mentioned the manual says 15 sec max, I don't think I've seen more either. If there is a max time limit, it's done in the controller.

Your block was at almost 40F tho, there is a big difference between that and an engine block that's been sitting in the teens overnight. I'm actually currently experiencing the same "issue" as dmaxjoe, few days back my truck promptly filled its yearly quota of two fried glowplugs, so I replaced them with two good ones I had from last year and now I have very long glow times too - yesterday I fired her up at 22 seconds (light was not off yet either), today I waited till 24 seconds and again fired up before light went off. All my plugs measure at 0.3-04 ohms as installed in the engine (readings taken between the plugs positive terminals and a good clean spot on the fuel filter head), I checked the controller's own ground today and this is good as well. I have 4-awg sereo amp cable powering the GPR in addition to the two factory 10-awg wires, so voltage and current delivery at the GPR is not a concern in my case. I have installed full sets of new ZD9 plugs in this truck twice already (meaning I now got lots of spares), and never have I ever seen glow times as short as 15 seconds when the ambient temperatures are down in the low 20s - usually around 20 seconds on a overnight-cold engine.

 

[franklin2]

Everyone loves these old trucks because they have no electronics to fail, well almost. To go completely electronics free(except the alternator regulator I suppose), just install a manual button for the glowplug controller, and YOU decide how long the glowplugs will stay on.

 

[MR.T]

It sure makes it hard to diagnose the glow controller with the lack of documentation on how it's supposed to work. And, who's got the time to reverse engineer stuff.

I had regular glow plug failures a few years ago, similar to LCAM-01XA. I was too busy at the time to get scientific, and just replaced the controller -- no plug failures since.

As a point of reference, all the original plugs lasted well over 10 years in mine before having the first of the recurring failures. Anyway, a bit of spare time lately, and an excuse to play with some new tools. Waiting for some cold weather to see what the glow amps and time is like under those conditions.

DMAXJoe, 18-20 seconds for a warm start (re-staring withing a couple minutes of shutdown?)... Heck, I think you should replace the controller just so you can tell us if there is any difference. Inquiring minds want to know.

LCAM, how long does the WTS stay on for a re-start on yours? What ambient temp? Black Dawg, what's your hot start glow time and ambient temp? Do you have to replace plugs each year?