Yet another cold start problem..

So, the ugly truck is being stubborn starting. 86 6.9. Plugged in, it fires fine. Sitting in cooler weather, prolonged cranking. When she finally catches, lots of white smoke. I recently installed an ATS 085 turbo, new returns and caps, replaced the Autolight glow plugs of death with new Motocraft. IP turned up about 2 flats, very little smoke on acceleration, and she pulls well. Starter is a local rebuild, and spins fast. Batteries are new 880 cca, group 24. A little small, but seems to spin the starter. I replaced the glow plug timer with a Diesel Rx timer, as the old one was physically broken. System cycles for 5 seconds, the does the 1 second click on and off. 10.4 volts at the glow plugs. I installed a clear piece of line into my return system to check for air, and there is none. So, I'm at the sit on my butt and scratch my head point. Pre-turbo, she always fired, even when really cold, single to minus digits, when not plugged in. I pulled a glow plug and static tested it, hooked into my harness. I was a bit underwhelmed by the amount of "glow". So a couple questions...What size wire runs to the glow plug relay from the battery? I'm running a 12 gauge lead at present, glow harness is the original. Could my injectors be leaking down? Starting fine when plugged in leads me to believe not, but I haven't tested them, and they are, elderly. Batteries to small? I think these take the group 65. Resistance in the harness? Any other ideas?

Just throwing it out there, my 94 N/A 7.3 smokes like a demon in the winter on cold start up, takes some time to fire up too. Did you put anti-gel additives in your fuel tank? I am also running a pair of 880CCA batteries.

Fortunately my 86 had the upgraded GPR & I've never had a problem with it. My other 85 & 86 had the older controllers that were problematic to me. I changed those to push button systems which helped greatly. Best improvement was the DB Electric Denso type starter (or whatever brand you want to use) that spins the engine FAST! The original starters just can't meet the RPMs of this type starter. Even in cold weather (10-20 for me), while holding go pedal down halfway, it comes to life quick. All mine smoke white in cold weather until engine warms a bit.

I'm thinking about wiring a push button at this point. Hind sight being what it is, I'm an idiot, as I pulled an updated system out of a junkyard truck this summer, and chucked it in the shed, forgetting about it. Remembered that this morning, but I already purchased and installed the ZD1-a's. Looking at a couple schematics, I realize my primary lead to the relay is way undersized, so that may be a part of it. As for fuel, we are still on the summer mix, they should be switching over to keep the log truck drivers happy here shortly. Still not cold enough to gel the fuel, but it's coming... Back to Napa.

Chris Helton said:

What size wire runs to the glow plug relay from the battery? I'm running a 12 gauge lead at present,

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Holy moly get that changed out!

Factory size is DOUBLE 10ga. I'm running 4ga. There's a LOT of amperage when the plugs are cold, I blew a 150amp fuse on mine. It's possible changing that could solve the whole problem.

How cold is cold? 5sec isn't very long in cold weather, but "cold" is a relative term...

Chris Helton said:

Looking at a couple schematics, I realize my primary lead to the relay is way undersized, so that may be a part of it.

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Sorry just saw this hahaha

I'm thinking that little wire is squealing a bit when I glow my plugs. I'll replace it tomorrow! Cold isn't very cold, yet. 40-50 degrees. Real Cold will be coming soon.

Getting into the single digits where I am and I prime my plugs twice, 8 each. Seems to work OK.

4 gauge cable, still struggling. I think it is time to Ohm out the harness, if that's ok, then I'll rig a button. I'm still kind of baffled why it fired pre-turbo, but is pissy post-turbo.

Agree with chillman, 5 seconds seems short.

If it's still short cycling it's not "sensing" all the glow plugs. Could be one or more bad plugs, could be a harness problem, could even just have slipped off a glow plug.

Chris Helton said:

I'm still kind of baffled why it fired pre-turbo, but is pissy post-turbo.

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Ive noticed this myself as well. I am starting to believe that the turbo is an air choke and it's not getting enough air for the first few compression cycles. I am going to start by cleaning the air filter and see if that does anything.

It isn’t the turbo itself. But it may be something you disturbed or changed while installing the turbo.
How much use since the turbo install? Possible high egts did damage that didn’t really show up until it cooled off?

Not much time since the turbo, 300 miles or so. EGT's have stayed conservative, never above 750-800 degrees. All the glow plugs are brand new out of the package last week. I will put the Fluke meter on each individual connector, and verify a good fit on the spade.

https://classicdieseldesigns.com/co...oducts/glowplug-manual-control-conversion-kit

Install my drop in conversion kit and some fresh glow plugs and the system will be good for the life of the truck.