Truck Hard to start when cold

ISPKI

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Hey guys,

Ive been diagnosing this issue with my 94 f250 7.3 N/A. It is a pain in the a$$ to start after having sat for a little while, usually several days to a week at least. Truck has 158K on it.

The issue is: The truck sputters and coughs while trying to start, feels like partial combustion, billows grey smoke (unburned fuel?) usually for a solid 20 or so seconds. Sometimes longer, other times it actually starts easily.

I have installed new fuel filter, electronic fuel facet lift pump, replaced all my return line caps, O rings, lines, clamps etc. I just installed a new GP harness from Classic Diesel (looks awesome btw) since my old harness was falling apart. Killed the batteries yesterday trying to start it after the harness install so I am guessing that wasnt the main issue. However, I juiced it back up today and it started after ~4-5 seconds of cranking.

I believe my injectors and pump are original. Replacing the pump isnt a realistic expense right now due to the virus outbreak and what not.
 

ISPKI

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Little side note,

Once the truck starts, it runs great, smooth (ish), plenty of power and will restart all day long just fine.
 

Cubey

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Sounds like some bad glow plugs and maybe also malfunctioning cold idle advance.
 

Randy Bush

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Have you confirmed that your batteries are good , sounds like that may not be up to par. A slow cranking engine will not start, or start very hard.
 

IDIBRONCO

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Air ingress in the fuel system? Sometimes its a really slow leak...
I will second this one. I'm not saying that this is guaranteed to be your issue, but the whole "hard to start after sitting for a while, but will start all day long, easily" situation makes me think it's a fuel drain back issue.
 

ISPKI

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The batteries are definitely solid, about 5months old, 900cca, just tested on a load stand at a local shop a few weeks ago. It cranks hard and fast.

Glow plugs have less than 8k miles on them.

Fuel drain back is interesting. I know it's not draining back through the electric lift pump, that has a 1way check valve right at the fuel filter and the lines are clear so I can see there is no air there. Plus, the shrader valve spits clean consistent fuel with no air. Is it possible that it is draining out through the return line back into the tank? If it was draining out of the return rail, that could cause air entrapment in the return system right? What prevents it draining out normally?
 

IDIBRONCO

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What prevents it draining out normally?
I'm pretty sure that it's vacuum from a sealed system. It could be something as simple as the fuel heater on top of your fuel filter seeping. If it seeps fuel while the engine's running, it will seep air when the engine's not running.
 

ISPKI

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I'm pretty sure that it's vacuum from a sealed system. It could be something as simple as the fuel heater on top of your fuel filter seeping. If it seeps fuel while the engine's running, it will seep air when the engine's not running.

Nah ive checked around at everything for leaks and im not seeing any leaks or even wetness. So, would it be possible for fuel to drain back if the fuel tank wasnt vacuum sealed? I am asking because I had my fuel gel up in the tank this winter and I ended up dropping it and plumbing new filler neck, vent line, etc. Wondering if theres a leak somewhere in that area.

Would a low pressure check valve be feasible or do you think that would screw up the fuel system? I can get check valves that open with 1 or 2 psi.
 

ISPKI

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Sounds like some bad glow plugs and maybe also malfunctioning cold idle advance.
How can I check the cold idle advance?

So I looked into the cold idle system. I know that the fast idle switch/sensor is working as it idles high for a minute or two after starting and then kicks down.

However, the afterglow feature of the glow plugs sounds interesting but I am not sure that would cause my truck to be hard to start on a warm day like today (~70 degrees, much hotter in the sun with the hood open).

My truck is wired for manual GP so the afterglow feature doesnt work. Would it hurt anything to heat up the GPs while cranking to imitate the afterglow feature that the controller once provided?
 
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IDIBRONCO

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Would it hurt anything to heat up the GPs while cranking to imitate the afterglow feature that the controller once provided?
I don't do that while I'm using the starter, but if it's cold, I'll do it a few times after the engine's running. It does seem to make it quit smoking (from cold cylinders) a little sooner.
 

Greenie

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I went through the same issue and replaced the batteries, injectors, injection pump and return lines. It still started hard. Finally I replaced the original starter which sounded OK but was not turning the engine over fast enough for it to start. Bought the starter on Ebay - think it was a DB. Inexpensive and easy fix. Since the starter is very inexpensive it might not hurt to buy two just in case the quality doesn't last as long as the original starter did.
 

ISPKI

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Hmmm, my starter is an old unit, sometimes doesn't even respond when I turn the key, all I get is the clinic of the starter relay. Maybe it's time to replace that. What is a good cranking rpm? I will have to check again but I *think* I'm around 200ish
 

Dane Rickford

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I have a starter I bench tested and seems to work good if you’re interested in it. Someone on Craigslist was going to buy it so I boxed it up for shipping, but then the CL person never gave me the shipping address and I didn’t hear from them again. The starter is yours for $50+ whatever shipping if you want it
 

ISPKI

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I have a starter I bench tested and seems to work good if you’re interested in it. Someone on Craigslist was going to buy it so I boxed it up for shipping, but then the CL person never gave me the shipping address and I didn’t hear from them again. The starter is yours for $50+ whatever shipping if you want it

Wellllll **** Dane. My local parts store has a DB electrical high torque starter on order for me, should be here in a few days.
 

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