I was driving the boss' 98 6.5 the other day. Went to start it when hot, and the glow plug light went off almost immedately. Mine, the WTS light stays on the full time, either cold or hot. No SES light, so, do I have a failing sensor, or does he? Thinkin' it's me.

Mine stays on like that too. The only time I wait for it is when the engine is cold. Very good question though, I'd like to see an answer as well.


My Best,


Justin

I've had 3 of these trucks, 94, 95 and now a 2000. All of them cycled the glow plugs regardless of temperature, time would vary from 1 up to 10 seconds when -40. The light always goes out and then cycles 3 or 4 times in the first minute of warm-up and never stays on. If that helps you any.

I would say the bosses truck is working well and cycled the glows a short duration because it was hot.


If you had started his truck cold it would have seemed more normal.


My '93 never cycels more than two seconds hot but, '94 always cycles at least 3-5 sec. and the '96 as well.

Kevin,


Reading from my 98 manual I'm assuming your 97 glow since it is OBD II most probably controlled by the PCM thru relay; at key on, the the PCM glows for 1-16 seconds as deemed necessary by PCM & ECT sensor value until crank, after start it may continue to cycle glows until sufficient heat is sensed by PCM thru engine coolant sensor.


From text in my 90 manual I'm assuming 6.5 OBDI works simialr to OBDI 6.2's cycle , timing cycle is a bit different there 4-5 sec on then off for 4-5 sec and then back on for 1,5, continuing to cycle for total duration of 20 sec glow on & off. The 98 manual says OBDI was controlld as an analog signal whereas OBDII's are digital and have better glow function as a result.

Further, PCM gets actual glow voltage feedback to turn on WTS indicator driver


Listen when you turn ign on - should hear the Glow Plug Relay click when glo is sufficient, WTS indicator should go out


If you hear click of relay turning off, and indicator remains on, would indicate open link or problem in PCM.


Open link should give DTC.


Edited by: gmctd

That's what kinda threw me here, was if the ECT sensor is off calibration, then it would throw off the glow time. But not only that, if I read this right, it will also throw off the engine timing too? I am I getting that right, or am I mixed up in the head?


Now, one other thing, I have the Kennedy glows in, which, I don't know if that will throw off the glow timing issue either, will it?


Hey QM: what type of software are you running to scan your truck with?

ECT sensor offset low can result in timing advance as if engine were cool.


Be a good idea to have it checked - think QM posted sensor resistance vs temp readings a while back.


Can be tested with a digital voltmeter in ohms range.

My scan program is Ease diagnostic GM OBDI enhanced parameter personal scan tool. Costs $375 for the OBDII kit.


With the scanner on, and a turn of the key you'd see glow plug voltage and glow plug relay voltage.


On mine, They start at 0.1v and jump to ~11.8 and then back to 0.1Edited by: quantum mechanic

So, which of the many sensors in there is the acutal ECT sensor?


Next question: If it is off, does it ususally reflect on the dashboard, or not?


Last question: If the sensor is out of whach, then is it effecting my fuel mileage? Just paid $2.06 gallon . . . at 10-13 mpg, want a little more m's and a lot less g's.


(4.10 rear on a high top van, scratch that, bus)

It's in the coolant crossover, passenger-side, below the heater hose tap on the truck engines.


Can effect fuel mileage, does not effect actual coolant temps or instrument temp gage - that sender is in the driver-side head by the front exhaust port.


Check for Quantum Mech's temperature sender R vs T post - iirc, 220deg = 147 ohms, 190deg = 480 ohms, but don't qote me on that..


Can be easily, accurately tested with $4.95 DVM from Harbor Freight, sometimes on sale for $2.95 - gotta love the orient........

I'll try to see if that ohm function will max out my Fluke 87's capacity for measurement accuracy.http://www.dieselplace.com/forum/smileys/smiley17.gif

They're not called Flukes, for nothing....http://www.dieselplace.com/forum/smileys/smiley2.gif