Rough, Smokey Starts

Does your Mitsubishi L300 make a strange noise? Need wheel alignment specs?
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Crankshaft Culture
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Rough, Smokey Starts

Postby Crankshaft Culture » Fri Nov 03, 2017 11:36 am

1989 4D56-powered Delica.

Now that it's gotten to be about 45 F/ 7 C in the mornings, our Delica starts rough and smokey. Once warmed up, it's fine and runs like a champ. However, we have a camping trip coming up where it can be 18 F / -8 C in the mornings and I don't want to get stuck out there.

• I already replaced the glow plugs with genuine Mitsubishi units. That doesn't seem to help.
• Glow plug relays click twice. Starter cranks strong and engine fires quickly.
• However, when it does fire the idle is very rough and there is a lot of smoke.

If the relays are clicking, is it fair to assume that doesn't necessarily mean they're sending juice to the plugs?

What's the first course of action; testing the relays' current?

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Rough, Smokey Starts

Postby Growlerbearnz » Fri Nov 03, 2017 1:32 pm

I'm guessing the smoke is white and smells a bit like fresh diesel? You've got the right idea- a lack of heat in the engine is causing poor combustion.

I would test the voltage between the glow plug rail and cylinder head. You should see 9V or higher while the relay is on (before starting and for about 30 seconds after starting). Just to be sure I would also pull each glow plug and power it with jumper cables for about 5 seconds, and make sure each one actually glows.

It might just be that your engine is a little tired and has lost some compression. If you're being super thorough a compression test would be the next step. A new engine should make 440psi, the lower limit is 320psi, with no more than 45psi difference between any two cylinders.

Other things to check are worn injectors and injection timing.

In the meantime, when cranking, you should hold the accelerator about halfway down. Once the engine starts, keep the revs at about 1200rpm until the smoke clears, then drop it to about 1000rpm until the temperature gauge starts to move (use the idle speed control knob on the dashboard). That should make your startups easier.
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Rough, Smokey Starts

Postby Mr.SA » Fri Nov 03, 2017 1:46 pm

Growlerbearnz wrote:I'm guessing the smoke is white and smells a bit like fresh diesel? You've got the right idea- a lack of heat in the engine is causing poor combustion.

I would test the voltage between the glow plug rail and cylinder head. You should see 9V or higher while the relay is on (before starting and for about 30 seconds after starting). Just to be sure I would also pull each glow plug and power it with jumper cables for about 5 seconds, and make sure each one actually glows.

It might just be that your engine is a little tired and has lost some compression. If you're being super thorough a compression test would be the next step. A new engine should make 440psi, the lower limit is 320psi, with no more than 45psi difference between any two cylinders.

Other things to check are worn injectors and injection timing.

In the meantime, when cranking, you should hold the accelerator about halfway down. Once the engine starts, keep the revs at about 1200rpm until the smoke clears, then drop it to about 1000rpm until the temperature gauge starts to move (use the idle speed control knob). That should make your startups easier.


Interesting point with the compression, I had compression numbers below the lower limit, cant remember off the top of my head but maybe around 220? and Ive gotten mine started after sitting overnight in -25 to 30F temps, a couple nights in a row. and many more below 0. If its above about 20F mine starts no problem with only a little white smoke. Makes me think either the compression test was faulty in some way or compression isnt a huge deal for cold starts.

Anyway, what i found super helpful is using an additive meant to help starting in cold temps. when i know its going to be super cold ill add a lot. that at least makes getting it started easy, doesnt help a ton with the white smoke.

What I usually do if its really cold out is start it, try and let it idle a little bit if it will, but pretty quickly feather the throttle some to get the engine to stop sputtering, then idle it just a little over idle for a couple minutes, then drop the revs down to normal idle. like you said.

mine has that idle/throttle adjust knob that you can pull and tighten to set the throttle at a constant RPM, might be a manual only thing, but its really handy for starting in the cold.

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Rough, Smokey Starts

Postby Growlerbearnz » Fri Nov 03, 2017 2:04 pm

Mr.SA wrote:Interesting point with the compression, I had compression numbers below the lower limit, cant remember off the top of my head but maybe around 220?


My numbers are from Mitsubishi's workshop manual, so they're probably quite conservative. I imagine an engine making less than 320psi would work ok, but not as well as Mitsubishi thought it should.
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Rough, Smokey Starts

Postby Crankshaft Culture » Fri Nov 03, 2017 2:49 pm


What I usually do if its really cold out is start it, try and let it idle a little bit if it will, but pretty quickly feather the throttle some to get the engine to stop sputtering, then idle it just a little over idle for a couple minutes, then drop the revs down to normal idle. like you said.

mine has that idle/throttle adjust knob that you can pull and tighten to set the throttle at a constant RPM, might be a manual only thing, but its really handy for starting in the cold.


I have the adjust knob, too. However, I think my lock is broken on it, as it does not lock. I can only actuate the throttle, not keep it in one spot.

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Rough, Smokey Starts

Postby Furi » Fri Nov 03, 2017 3:33 pm

Growlerbearnz wrote:
In the meantime, when cranking, you should hold the accelerator about halfway down. Once the engine starts, keep the revs at about 1200rpm until the smoke clears, then drop it to about 1000rpm until the temperature gauge starts to move (use the idle speed control knob on the dashboard). That should make your startups easier.



If holding accelerator half way down; would there be a concern of flooding the engine?

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Rough, Smokey Starts

Postby Growlerbearnz » Fri Nov 03, 2017 4:06 pm

Furi wrote:If holding accelerator half way down; would there be a concern of flooding the engine?


No, that's practically impossible on a diesel. There are no spark plugs to wet, and the injection pump's fuel delivery is limited by engine speed. Holding the pedal halfway down only helps the injection pump respond quicker when the first cylinder catches.
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Rough, Smokey Starts

Postby Furi » Fri Nov 03, 2017 4:18 pm

Growlerbearnz wrote:
Furi wrote:If holding accelerator half way down; would there be a concern of flooding the engine?


No, that's practically impossible on a diesel. There are no spark plugs to wet, and the injection pump's fuel delivery is limited by engine speed. Holding the pedal halfway down only helps the injection pump respond quicker when the first cylinder catches.


Good stuff. Surely will help during cold starts. Seems for newbies just starting our van's in cold weather has a learning curve :) Would it be best to just continue cranking until the cylinders catch? Or crank for a few seconds and then retry?

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Rough, Smokey Starts

Postby Mr.SA » Fri Nov 03, 2017 10:45 pm

Crankshaft Culture wrote:

What I usually do if its really cold out is start it, try and let it idle a little bit if it will, but pretty quickly feather the throttle some to get the engine to stop sputtering, then idle it just a little over idle for a couple minutes, then drop the revs down to normal idle. like you said.

mine has that idle/throttle adjust knob that you can pull and tighten to set the throttle at a constant RPM, might be a manual only thing, but its really handy for starting in the cold.


I have the adjust knob, too. However, I think my lock is broken on it, as it does not lock. I can only actuate the throttle, not keep it in one spot.


mine you twist either way to tighten or loosen. so i pull it out a bit, turn it right to tighten and it stays

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Rough, Smokey Starts

Postby Trinker » Sat Nov 04, 2017 9:29 am

Mine has a block heater, if you live somewhere cold I highly recommend it, saves the wear and tear of cold engine starts and reduces the amount of time sitting in your driveway idling. Also no white smoke! I have the same issue when I can't plug in, even with new ngk glow plugs, functioning relays, and a re-furbished glow controller (ecu). My next step is going to be pulling the injectors and getting them tested/serviced. I'll let everyone know how that improves both cold start and general performance!
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Rough, Smokey Starts

Postby Growlerbearnz » Sat Nov 04, 2017 1:21 pm

Crankshaft Culture wrote:I have the adjust knob, too. However, I think my lock is broken on it, as it does not lock. I can only actuate the throttle, not keep it in one spot.


On the body of the knob mechanism, behind the dashboard panel, there's a metal band that acts as a spring to clamp the shaft. The metal band gets weak and old- if you find a regular spring of the correct size and wind it around the metal band it'll help it clamp more firmly.

Here's one I prepared earlier:
idleControl.JPG
idleControl.JPG (294.29 KiB) Viewed 223 times


Furi wrote:Would it be best to just continue cranking until the cylinders catch? Or crank for a few seconds and then retry?


I reckon if it hasn't started after 8 seconds of cranking, turn it off and back on again to let the glow plugs heat up again. In extreme cold weather I've seen people cycle the glow plugs twice before cranking. (That one time I was in Fairbanks at Christmas. I live on a temperate pacific island- what was I thinking!?!)
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Rough, Smokey Starts

Postby Crankshaft Culture » Sat Nov 04, 2017 4:28 pm

Fixed the throttle adjuster. Turns out the collar that helps lock the throttle was loose. Super easy.

Now, I checked the buss bar for voltage as I heated the glow plugs and the bar read 9V. So they should be warming (they're brand spankin' new; the van behaved the same way with the previous plugs).

Cycling the plugs 2-3 times does seem to start it better but it still smokes and sputter even at 48° F /9° C.

What about the temperature sensor? Our gauge does work, although it never gets above 1/4 of the way warm at absolute max, even after a 310 mile/500 km trip.

Again, once it's been started it starts fine. It's just that initial Smokey start.

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Rough, Smokey Starts

Postby Growlerbearnz » Sat Nov 04, 2017 9:21 pm

The temperature gauge sounds about right, but it won't hurt to change the sensor out just in case. It's cheap enough. (As you've no doubt read by now, the temperature gauge sensor also drives the glow controller.)
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Rough, Smokey Starts

Postby sk66 » Sun Nov 05, 2017 7:50 am

Maybe the 6v glow relay/resistor isn't doing its part?
The fact you hear it click twice should mean the 12V quick glow is working correctly (IME, the glow plugs should be on for ~6sec).

My next guess would be the injectors could stand cleaning... I've had pretty good results using the fuel additive type cleaner.
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Rough, Smokey Starts

Postby feetforbrains » Mon Nov 06, 2017 7:55 am

Trinker wrote:Mine has a block heater, if you live somewhere cold I highly recommend it, saves the wear and tear of cold engine starts and reduces the amount of time sitting in your driveway idling. Also no white smoke! I have the same issue when I can't plug in, even with new ngk glow plugs, functioning relays, and a re-furbished glow controller (ecu). My next step is going to be pulling the injectors and getting them tested/serviced. I'll let everyone know how that improves both cold start and general performance!
What kind of heater are you using? I really need to install a plug in, but I'm having some option paralysis.

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