No Start- The Glow Plugs Strike Back!

[Cowracer]

Into week 2 of the No Start Saga.

My local library has on-line access to All Data Pro with the troubleshooting and wiring diagrams the Dealers use. (For Free, even!) I went through the chart for no-start and this is what I think I found.

I am getting a signal from the ECM to the FSD. The FSD appears to be sending out a signal to the fuel solenoid (I will know more when I hook up a scope to that line). I ohmed out the F-Sol, but I have no idea what a go or bad reading would be. The Shutoff Sol click with power.

I took off the #1 injector line and held my finger over it to see if there was anything coming from the pump. I felt a distinct pulsation, and got a small amount of fuel out of the line.

There seems to be slightly more signs of life during cranking if I unplug the optical sensor, but not enough to actually fire the truck.

At this point, I felt that the pump and all its associated bits and pieces are operational. So I got to thinking about the glow plugs again. I put my handy Fluke meter on the battery terminals and had my son turn on the truck. I only dropped .5 volts while the plugs were on.

I would imagine that they draw a LOT of power (maybe 8-10 amps each?) and I should have seen a bigger voltage drop. (Curious that my dashboard guage shows the voltage dropping down to 9 or so)

So now I am thinking maybe the plugs ARE bad, or bad enough to keep it from starting. I pulled the #1 Glow plug and sure enough it will glow when I hook it up to the battery charger, but it seems to take longer to reach 'red hot' than the plugs relay stays on. Tonight, I will remove all the plugs and Ohm them all out.

Stay tuned!

Tim

New

[tom.mcinerney]

Incandescent bulbs and glowplugs have high initial current draw that moderates only after filament becomes very hot, and resistance rises precipitously. I haven't measured amps to the 6.5L yet, but my VW glows would read-out-of-range to 20 amps at first, then drop to 8-12A after about 3 secs. The 1/4" blade connectors might drop voltage after corroding, a Dremel cleanup may be in order. The glow relay contacts on my VW regularly developed very high resistance, but i think the snap-acting relay on the Chevy (and the controller) are far more advanced/effective.
Mine starting happy at 11*F !!!

[Big Green]

Cowracer,
I can't imagine all 8 would burn out at the same time. If it were me I think I'd check the glow plug relay for output.

Big Green

[JohnC]

Originally posted by Cowracer:
...I took off the #1 injector line and held my finger over it to see if there was anything coming from the pump. I felt a distinct pulsation, and got a small amount of fuel out of the line...Hey, kids, a word of caution: Don't try this at home. Injection pressure is around 2000 psi. while it's unlikely you can get hurt with an open line at cranking speeds, the output of an injector can penetrate the skin. Diesel fuel under the skin is not a good thing...

The safest way is to loosen the line and crank away. If fuel seeps out of the loose joint then all is likely well.

[gmctd]

Disconnect the Optical Sensor allows the engine to start in Limp Mode off the Crank Position Sensor.

Disconnect the Crank Position Sensor allows the engine to start in Limp Mode off the Optical Sensor.

Think it is refered to as Limp Mode with Extended Crank.
Prevents JohnQ from driving off with a broke truck, while allowing functional testing\troubleshooting in a Service Bay.

Proves the operational mode of either sensor - engine will start and run after extended crank time, 15secs or greater, if the connected sensor is functional.

Any injector pipe open would give only small surge of fuel - combined output of four 0.310" plungers at max 0.028" stroke ain't much volume.........

PCM controlled Fuel Solenoid severely reduces even that small volume at crank\idle rpm.

Injectors set max pressure required for injection, which is ~2080psi.

As JohnC states - do be careful!

[ 02-01-2005, 03:25 AM: Message edited by: gmctd ]