Starting issue only when warm

pianobus · 07-11-2017, 01:58 PM

Hello,
I have a '92 International idi 7.3 diesel/Thomas shorty which has the following issue: While it has cold-started reliably for me since i got it a couple months ago, it seems to dislike starting warm. I'll crank for 5-6 seconds, wait, crank, wait, hook up a second battery, and eventually it will start, but not before it's run down my batteries a bit and started to make me nervous. New parts in the system: Battery, alternator, glow-plug relay, glow plugs (some maybe but not all, i'm not sure, but a shop checked them out) and also both fuel-filters.
Any ideas?
Also, not that i'm going to make a habit of this, but is there anything wrong with roll-starting this vehicle? i've done this for years with other manuals with no obvious ill effect, but i've heard some opinions that this is bad.
Gratefully,
Aaron

brokedown · 07-11-2017, 04:08 PM

Does it always hard start when warm? What does it do if you drive it for a little while (15 mites or more), turn it off, and then start it right back up?

If it starts right up under those circumstances, but doesn't start right back up if you let it sit for 20 minutes and it doesn't want to start again, its probably related to the temperature sensor used for the automated glow plug system.

cadillackid · 07-11-2017, 04:22 PM

most diesels will start wothout glowplugs when they are hot.. it could have the same issue my DT-360 has which is when its hot, the fuel pump likes to lose prime..

im not familiar wit ha 7.3 IDI, (so I may be totally wrong).

but does it have a manual primer pump on the fuel pump? if so.. then try pumping that before you try and hot start it..

on my DT-360 it will start and run for like 5 seconds then die if the pump has lost prime..
-Christopher

brokedown · 07-11-2017, 04:43 PM

The problem i'm familiar with is the difference between "hot" and "warm". My GM 6.2 was really bad about it, and my friend's 7.3 IDI has the same issue. Both got the button as a fix. When a motor needs a little glow but isn't getting it, it can leave you stranded with a dead battery.

cadillackid · 07-11-2017, 07:59 PM

Quote:

Originally Posted by brokedown

The problem i'm familiar with is the difference between "hot" and "warm". My GM 6.2 was really bad about it, and my friend's 7.3 IDI has the same issue. Both got the button as a fix. When a motor needs a little glow but isn't getting it, it can leave you stranded with a dead battery.

this is for sure... and im still trying to figure out to this day how the DT360 / DT-466 start without glow plugs or grid heaters at all (well until the DT-466E.. it has a heater in some of them)..

it was 03f outside one night and I didnt have my DT-360 plugged in. and it still kicked over. it doesnt have glowplugs..
-Christopher

cowlitzcoach · 07-12-2017, 02:53 AM

Quote:

Originally Posted by cadillackid

this is for sure... and im still trying to figure out to this day how the DT360 / DT-466 start without glow plugs or grid heaters at all (well until the DT-466E.. it has a heater in some of them)..

it was 03f outside one night and I didnt have my DT-360 plugged in. and it still kicked over. it doesnt have glowplugs..
-Christopher

It is all in the design of the combustion chamber.

I had a Mercedes-Benz 300D for several years. With the glow plugs cycled it would start every time before the engine made a full revolution. When warmed up the glow plugs wouldn't even turn on. On the other hand, if it was stone cold and the glow plugs didn't turn on you could crank the engine until it killed either the starter or the battery and it would never once even burp like it was going to start.

Booyah45828 · 07-12-2017, 10:30 AM

That's why they're called IDI engines. They have a pre chamber with the glowplug located inside and the injector sprays fuel kind of like a stream directly onto the plug, starting combustion in the prechamber, for it to travel into the cylinder and push the piston down.

With a direct injection engine, there is no prechamber. The injector sprays in a fan pattern into the crown on top of the piston. It's a lot finer of a spray and therefore ingnites easier when cold.

IIRC, the reasoning behind IDI an DI engines is because before the broad usage of turbochargers, when naturally aspirated engines were common, the powerband of an IDI engine was wider then that of a DI engine. I also think I remember something about cleaner emissions and more power but could be wrong. Now every diesel has a turbo and the DI design is better functioning.

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