Delica Canada | Mitsubishi Van Club

so, I've been having a bump and chug (white smoke) start in the morning for quite a while. I've narrowed it down to air in the fuel system somewhere.
This last weekend, I proved that, but was unable to solve it just yet.

I'f I prime my fuel filter (alot), I can here a slight air leak(constant stream sound, not bubbling sound) from somewhere around the injection pump. I'm fairly certain its air as I cannot find a fuel leak anywhere (IP covered in dust, makes it easy to spot the smallest fuel leak as it would propegate quickly). My question being, what is the most likely cause for an air leak? and what location is that?

I just replaced the IP main shaft fuel seal, no leak there.
Can return lines do this?

Since a month,i have the same problem.I've change all the rubber hose,inlet,outlet,etc..Always the same problem.
I've change fuel filter assembly because there was rust between the fuel filter adapter and the seal of the filter causing bad sealing.
Problem stop for a couple of day but after a long trip (800km),the problem is back.
Always start perfect but after 1 minute there is little misfire with a puff of white,greyish smoke with each misfire for another 1 minute.If i prime the fuel filter before start,no smoke at all.Run like new.
Before,it was doing this only in cold winter day.But since a month,the outdoor temperature change nothing.
I don't know.

Strada 92 wrote:.....Before,it was doing this only in cold winter day.But since a month,the outdoor temperature change nothing.
I don't know.

Sounds to me like something is loose, did you tighten everything to the correct torque? Did you bleed the fuel line after changing the seals (see 13B-3 of Fuel Systems manual). Also on that page is the "Fuel Injection Pump Check" details.

Falco.

Strada 92, I checked the underside of the fuel filter bracket this weekend too. mine looked brand new, just a slight coloration from the rubber seal spinning on/off. put some new fuel lines on too, made no difference.

Falco, I guess I'll have to follow through step by step to see if I come up with something. I know this problem gets worse in the winter, to the point where it can stall the engine.

I'm thinking about getting a fuel pressure gauge, and hooking it into a line. I was thinking between the filter and IP. then I could see if the lines stay pressurized from hand pump (pretty sure they lose pressure), and see what pressure I have while the vehicle is running (4psi +/- 2) from my under standing is where I want to be.

after priming, the line from the tank to the filter should stay full with fuel right? only way for it to drain would be air entering the line.?


any other stories to try and pin point this would be great.

thanks guys.

sound travels. take some water mixed with soap and spray it onto the fuel lines and injection lines. put something like thick cardboard in between the IP and the front of the engine so that when the clutch fan engages, it won't blow air in the area. That will allow you to get a better idea of where the leak is coming from. Just be careful not get the cardboard or whatever you use to get caught in the rotating belts/fan.

if you have not changed out the fuel lines already, old one's get brittle and breakdown from the inside cause air to seep in/out. If you have already changed out your lines, check the metal lines and inlet at the IP and filter housing. look for hairline cracks.

once you track down the air leak and fix it, consider putting an inline pump as close to the tank as possible. 7-8 psi max. this will help winter starting and driving with the winter blend and cold weather.

jfarsang wrote:sound travels. take some water mixed with soap and spray it onto the fuel lines and injection lines. put something like thick cardboard in between the IP and the front of the engine so that when the clutch fan engages, it won't blow air in the area. That will allow you to get a better idea of where the leak is coming from. Just be careful not get the cardboard or whatever you use to get caught in the rotating belts/fan.

if you have not changed out the fuel lines already, old one's get brittle and breakdown from the inside cause air to seep in/out. If you have already changed out your lines, check the metal lines and inlet at the IP and filter housing. look for hairline cracks.

once you track down the air leak and fix it, consider putting an inline pump as close to the tank as possible. 7-8 psi max. this will help winter starting and driving with the winter blend and cold weather.

good ideas...gonna look at some tonight if I have the time.
Can just standard fuel line be used in the engine bay? curious about heat...

Cheers

Leaky injectors will contribute and cause that similar issues as well. We've found some cases where the injector nozzles are not holding pressure and will cause that problem on the high pressure side. When you prime your fuel system using the hand primer on top of the fuel filter housing, it should feel hard as the system gets filled up with fuel....which means the system is good. If it stays soft everytime....there is a leak somewhere on the low pressure side.

Good luck.

CVI wrote:Leaky injectors will contribute and cause that similar issues as well. We've found some cases where the injector nozzles are not holding pressure and will cause that problem on the high pressure side. When you prime your fuel system using the hand primer on top of the fuel filter housing, it should feel hard as the system gets filled up with fuel....which means the system is good. If it stays soft everytime....there is a leak somewhere on the low pressure side.

Good luck.

What if the hand pump gets hard, let it rest for 1 minute or so, then it is soft again but will become hard after a few pumps?


correct me if i'm wrong but would this not lead to a running rich problem upon start-up? if that were the case, it's flooding the engine/cylinder and I would see black smoke.
I'm only getting white/grayish smoke making me think i'm running lean (air in the system).

I just had the injector nozzles replaced. so as long as the shop didn't screw me, this should not be the problem.


Edit, found this on another diesel forum **White smoke is atomized but unburned fuel. It's the result of failure to ignite.

Black smoke is fuel which has ignited but only partially burned.
When there's too little air for complete combustion, the hydrogen fraction of the fuel burns first, leaving excess carbon. The excess carbon is the black smoke.**

strada-caster wrote:
What if the hand pump gets hard, let it rest for 1 minute or so, then it is soft again but will become hard after a few pumps?

Exactly the same problem with my truck.And if you open the bleeding screw,there is always a bit of air that escape.
And i cannot find any external leak.

thank you all for your help,really nice.

Strada 92 wrote:

strada-caster wrote:
What if the hand pump gets hard, let it rest for 1 minute or so, then it is soft again but will become hard after a few pumps?

Exactly the same problem with my truck.And if you open the bleeding screw,there is always a bit of air that escape.
And i cannot find any external leak.

thank you all for your help,really nice.

I second that thanks...

I picked up some clear tubing from the plumbing section in canadian tire last night, 1/4 and 5/16. hopefully this will help me identify the culprit section.
FYI, this tubing is in no way fuel rated. It won't be on the truck for long, just testing purposes.

Strada 92 wrote:Since a month,i have the same problem.I've change all the rubber hose,inlet,outlet,etc..Always the same problem.
I've change fuel filter assembly because there was rust between the fuel filter adapter and the seal of the filter causing bad sealing.
Problem stop for a couple of day but after a long trip (800km),the problem is back.
Always start perfect but after 1 minute there is little misfire with a puff of white,greyish smoke with each misfire for another 1 minute.If i prime the fuel filter before start,no smoke at all.Run like new.
Before,it was doing this only in cold winter day.But since a month,the outdoor temperature change nothing.
I don't know.

I recall from one of your other posts somewhere, your glowplugs cycle after start up(mine do not). Could you see if you misfires are timed to the glowplug cycling? or
you say it only puffs about one minute after start up..maybe thats when the glow plugs stop cycling and one cylinder isn't quite where it wants to be....

Yes the glow plugs cycle after start,i can see it on my voltmeter and i can hear the click soon after start-up.And misfire are mainly after the glow plugs cycling.
When the misfire were when the temperature was cold,one cylinder isn't quite where it wants to be....maybe.But in summer?I don't think so.

Since couple of day,the misfire are almost disappeared.It's really weird.Maybe because they start to change the kind of fuel for colder weather?

I saw a post from FalcoColumbarius about injectors on a Pajero.He thinks that ULSD fuel can be the cause of problem.
Maybe it's the cause of our problem.ULSD fuel is not really good for our old trucks.Lack of lubricity for IP,injectors,etc...

Strada 92 wrote:Yes the glow plugs cycle after start,i can see it on my voltmeter and i can hear the click soon after start-up.And misfire are mainly after the glow plugs cycling.
When the misfire were when the temperature was cold,one cylinder isn't quite where it wants to be....maybe.But in summer?I don't think so.

Since couple of day,the misfire are almost disappeared.It's really weird.Maybe because they start to change the kind of fuel for colder weather?

I saw a post from FalcoColumbarius about injectors on a Pajero.He thinks that ULSD fuel can be the cause of problem.
Maybe it's the cause of our problem.ULSD fuel is not really good for our old trucks.Lack of lubricity for IP,injectors,etc...

Strada92,

Try this and tell me what happens.

When you start your truck next time, if it is still coughing, hit the gas enough so that the turbo kicks in. I find that when the turbo gets moving, the engine seems to fire correctly, and continues firing correctly after I let off the gas. I'm gonna try this a few more mornings to see if this trend continues.
Yes, you will find the engine coughing a little harder(more rapidly) until you get the RPM's up to about 2000rpm so the turbo kicks in.

I've read that turbo diesel engines don't start as nicely as non-turbo engines. maybe the oil being cold enough, not allowing the turbo to spin might be chocking the engine somehow.
just a thought.

strada-caster wrote:so, I've been having a bump and chug (white smoke) start in the morning for quite a while. I've narrowed it down to air in the fuel system somewhere.
This last weekend, I proved that, but was unable to solve it just yet.

I'f I prime my fuel filter (alot), I can here a slight air leak(constant stream sound, not bubbling sound) from somewhere around the injection pump. I'm fairly certain its air as I cannot find a fuel leak anywhere (IP covered in dust, makes it easy to spot the smallest fuel leak as it would propegate quickly). My question being, what is the most likely cause for an air leak? and what location is that?

I just replaced the IP main shaft fuel seal, no leak there.
Can return lines do this?

May be the hand pump causes the problem?