Troubleshooting a Long Crank When Cold

[mu2bdriver]

When the engine is cold or has not run in several days it takes about 15 seconds to get it fired up. Warm starts are nearly instantaneous.

Components:
N/A engine,
1 year old identical batteries,
Facet electric pump,
6 month old ZD9s,
New Starter,
Timing set to 6 degrees advanced.

When I turn the key to 'on' I get the WTS light which extinguishes after a reasonable time consistent with outside temperature and can hear the electric pump running. I haven't yet looked at the glow plug relay. Is there a test I can do to ensure it's working properly? If the WTS light illuminates and then extinguishes, is that enough to confirm proper GP relay operation?

Thanks in advance.

 

[franklin2]

What is a reasonable time for the light? Expect to crank these engines a little bit anyway. 15 seconds is a little much, but I am wondering how long your light is staying on.

 

[ZWilson07]

Does it take that long on a cold start even if it is warm outside?

Try plugging it in and see if that changes things.

You are going to need to test each glow plug seperately for operation or if some are burnt out.

But of course if it takes that long on a warm day then obviously those aren't the problem.

 

[The Warden]

But of course if it takes that long on a warm day then obviously those aren't the problem.

Not necessarily...I've found that my truck throws a hissey-fit cold-starting even on warm days unless I let the plugs cycle fully.

Even with 6 month old plugs, I would test them...use an ohm-meter; you should have something between 2 and 10 ohms IIRC. 0 ohms is actually bad and indicates a short circuit internal to the plug i.e. current's going through it but, with no resistance, it's just letting the current go directly to ground without heating the plug up.

Also, you might want to check the power cables going from the batteries to the glow plug controller...the factory wiring harness uses two wires, and if a connection goes bad on either of them, you could have only half the current you're supposed to have going to the plugs.

Just some thoughts...good luck!

 

[mu2bdriver]

I'll measure the time the WTS light is on for a full cycle, the outside air temperature, and actual cranking time later today...it won't have been run for 24 hours and should give a reasonable estimate for cold start times. Yesterday, after it went off the cold start advance and I shut it down and restarted, it fired up in less than a second.

 

[mu2bdriver]

I just got around to this...

I measured the resistance on all glow plugs and they were all at 0.5-0.6.

I let the truck sit overnight and the low temps were in the mid 40s. I tried to start it this morning and the WTS light illuminated for 6 seconds and it took 20 seconds of continuous cranking to start. Once it dropped off the high idle solenoid I shut it down and attempted a restart. The WTS light illuminated for a second or two and it started immediately. Could the glow plug controller or solenoid not be providing power to the GPs? Is there a test I can run on the solenoid or controller to isolate that before I tackle the harness? I will take off the air filter and check out the connections and controller itself after lunch.

Thanks in advance.

 

[OLDBULL8]

Also, you might want to check the power cables going from the batteries to the glow plug controller...the factory wiring harness uses two wires, and if a connection goes bad on either of them, you could have only half the current you're supposed to have going to the plugs.

Not so. If one wire is bad, the other wire will try to carry the current and will likely overheat or burn up, since they are protected by fusible links. It's possible that the connector over the rocker cover is corroded badly and will cause the voltage to be low due to resistance, it will show melting if that's the case. Batteries must be up to *****, 12.5 VDC, as the Voltage will drop to 8.5 VDC on a GP cycle. The initial current pull is 196 amps for a second or two if all GP's are working.

Six seconds is a short time at 40*F, should be more like 10 or 12 seconds. Try double cycling the GP's.
I believe you have one or two bad GP's when it cycles that short of time.
Does the GP relay cycle ON/OFF after the WTS goes off, if not, that's an indication of some bad GP's.
Do you know what brand GP's you have?

 

[mu2bdriver]

Not so. If one wire is bad, the other wire will try to carry the current and will likely overheat or burn up, since they are protected by fusible links. It's possible that the connector over the rocker cover is corroded badly and will cause the voltage to be low due to resistance, it will show melting if that's the case. Batteries must be up to *****, 12.5 VDC, as the Voltage will drop to 8.5 VDC on a GP cycle. The initial current pull is 196 amps for a second or two if all GP's are working.

Six seconds is a short time at 40*F, should be more like 10 or 12 seconds. Try double cycling the GP's.
I believe you have one or two bad GP's when it cycles that short of time.
Does the GP relay cycle ON/OFF after the WTS goes off, if not, that's an indication of some bad GP's.
Do you know what brand GP's you have?

They're ZD-9s that I replaced myself in the spring.
I can't hear any solenoid cycling (clicking) when the WTS extinguishes.
Can the WTS light illuminate and extinguish with a bad controller/harness? That is to ask, is the light independent of the power to the plugs?
I'm leaning towards one of those two rather than a bad GP because the resistance is low and fairly even between all of them.
It's as if no power is going to the GPs and is more apparent on a cold start (long cranking) and on a warm start the no power condition is being masked because the engine is warm and it starts up immediately.

Going to go and look at the controller now...

 

[mu2bdriver]

I'm no expert, but this doesn't look right. No burnt wires but plenty if burnt plastic.

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[HS108]

I dont have that cover on mine, but why dont you run a Manual system

I found the article I was talking to you about last night

http://www.oilburners.net/articles/glowplugbypass.htm

 

[OLDBULL8]

I would say you have/had a loose connection from the Z strip to the relay, that's your whole problem. Ya need a new Z strip and relay, or just a whole new controller.

 

[mu2bdriver]

Nos controller is in and it fired right up. The real test will be tomorrow morning after I let it sit overnight. There was melted plastic all over the z strip and the large nuts on the relay.

 

[mu2bdriver]

Success! I let the truck sit for 30+ hours in similar weather conditions and tried it out tonight. WTS light on for ~12 seconds and after extinguishing it fired up immediately. It's very satisfying to troubleshoot and fix this with the upcoming winter!
Thanks again for the help all!

 

[BDCarrillo]

Can you take apart the old driver and see what the problem was? I'd guess carboned up contacts on the primary coil

 

[mu2bdriver]

Sure. I was planning on doing that anyway and putting a new solenoid in it to have a spare available on the shelf. The box and wires were all in good shape. I probably won't get to it until later in the week