Diesel engine misses at idle

Gazook · Member

Diesel engine misses at idle

Aus-Kiwi · Guru

Do compression test . Get injector serviced ? Or swap injector with another ? If other cylinder does the same ? It's the injector ! If cylinder is the the same its valves or cylinder damage ? If it's latter model ? Check it's getting elect pulse with node light .

blaze · Guru

check valve clearance
cheers
blaze

just see you did it

-- Edited by blaze on Friday 28th of October 2016 12:43:09 PM

Retiredatlast · Veteran Member

Hi

Used to petrol cars myself. In a past life was a petrol mechanic.

My campervan has a diesel 4cyl.

Not knowing enough about them I decided to read up as much as I could as I love research just in case of a breakdown.

I seem to remember how to overcome a one cylinder issue on a diesel that had a "miss" ...as you said on a petrol is is easy.

The way it was overcome on a diesel is to loosen the connection at the injector and bleed it a little with the engine going. This suggests some kind of vapor lock or air trapped. A picture was shown with the mechanic using a "shifter" to loosen the nut. Bit like bleeding your brakes to get the air out of the line. Vapor or air locks on petrol cars does happen.

Its possible the pump may be at fault. I still would add injector cleaner additive to the fuel tank anyway, it may clean more than the injectors.

To my way of thinking it should not be there anyway but if it was possible to suck air into any of the tubes or pump feeding the injectors guess its possible.

I understand these issues arise usually when a diesel runs out of fuel then refueled so air does get into the fuel lines. Most have a hand button type pump on the filter to force it through to get going again. We think that fuel would force all the air out but on petrol cars sometimes it does not.

The downfall is that you have to bleed each connection to the injectors to clear it.

-- Edited by Retiredatlast on Friday 28th of October 2016 08:27:13 PM

blaze · Guru

Isolating a miss to a cycinder is the same as a petrol engine, petrol you take the spark plug lead off, diesel you crack the injector. If there is no noticeable diference in the idling of the engine you have isolated the faulty cycinder. If ther is a difference, like more laboured or dying down, move the the next cycinder. Deisel engines are more prone to a low range miss caused by low compression than petrols and is why I earier suggested to check the vavle clearance. The next test I would do has also been sugusted, a compression check.
cheers
blaze

kezngaz · Senior Member

Im unsure as to weather this engine is common rail or not.
I would strongly suggest you do not crack fuel lines when it is running as the fuel pressure in these engines can be high enough to cause serious injury. Im sure somebody will know the exact pressure.
Hope this helps.
Kezngaz.

rockylizard · Guru

Gday...

Your rang ??

Injector pressures.JPG

Cheers - John

rockylizard · Guru

Gday...

This site might give some information -

http://www.searchautoparts.com/motorage/technicians/drivability/diesel-misfire-diagnosis

This was snipped from that site -

Diesel Misfire 01.JPG

Cheers - John

kezngaz · Senior Member

Cheers John...

T1 Terry · Guru

Gazook wrote:
I recently bought an imported Toyota Camroad motorhome professionally built on a Toyota Dyna truck with a 3L 4cyl motor, only done 90,000 k's.
The engine has a bad habit of missing at idle, just one cylinder. It can happen when hot or cold just that it's not there all the time.
Changed the fuel filter, checked the tappets, changed the injectors. If it was a petrol motor I would just individually isolate the spark plugs to find it.
Is there something I am missing with the distributor or injector pump?
I have taken it to a local mechanic who said he can crack the injectors to determine which cylinder is missing, but, you guessed it, it doesn't miss when I take it to him.
Any ideas, thanks.

My diagnosis would be a broken valve spring, the valve spins and the broken coil winds up to close to where the break is and applies pressure closing the valve, then it spins on past the break and no pressure is applied so the valve drops open.

T1 Terry

Jaahn · Guru

Hi smile

If it is common rail then you cannot crack the individual injector pipes as there are none ! The mechanic did it so it is the old system and it should show up an injection miss. The question is why it is there sometimes and not others.

Forget the valve spring theory there is no room for the valves to stay open in a diesel engine without hitting the piston. If the engine runs ok other wise and smooth it has no mechanical problem. How many Kms have you done in it. Same tank of fuel ?

Put a serious fuel cleaner though it and see what that does, then take it out and get it hot and work it up a few hills and see if that cleans it out a bit. No change then take it to a good diesel shop and have them diagnose it. The pump valves may be gummed up as it has been sitting around in Japan unused for years probably.

Look on the manufacturing plate and see what engine it has. Possibly a B series if it is a 3 ltr 4cyl diesel. Old reliable biggrin biggrin (slow ?)

Jaahn

I

banjo · Senior Member

A friend bought an import Dodge RAM, on his first outing it misfired every now and again on tick over and sometimes under load, he took it to a diesel specialist who diagnosed water in the fuel, They ran a good fuel cleaner through it and it cured the problem.

When these vehicles sit around for a long while with partially full tanks they get condensation build up in the tank, that's why it not good to store a diesel without a full tank of fuel.

Aus-Kiwi · Guru

Yes plus bacteria can bread in fuel too !! New filters blocked with felt looking material .. Pita to diagnose ..Usually after replacing everything else !

beej · Member

Does it have a dual mass flywheel?This story may sound crazy but experance with a transit diesel with a at idle,did all the usual tests with no results.After much shopping around was traced to flywheel failure in advanced position and miss was actually a crank out of balance vibration.New flywheel fixed issue straight away.Interestingly no issue was evident with clutch operation.

Aus-Kiwi · Guru

Yes a slipped harmonic balancer can do the same . Just check if outer ring on balancer is attached properly .

Gazook · Member

Thanks for all your helpful comment's, I've learned a lot.

After reading all and from what I have tried already, I will be draining the fuel tank completely (even after it has had a number of tank refills) give it a good dose of a reliable fuel additive and chase and open any draining taps I can find, in the hope it is an accumulation of gunk from an extended storage time. I'm feeling the only other alternative is the, very expensive, pump distributor overhaul.

I'll let you know how I get on.
Cheers.

Jaahn · Guru

Gazook wrote:
Thanks for all your helpful comment's, I've learned a lot.

After reading all and from what I have tried already, I will be draining the fuel tank completely (even after it has had a number of tank refills) give it a good dose of a reliable fuel additive and chase and open any draining taps I can find, in the hope it is an accumulation of gunk from an extended storage time. I'm feeling the only other alternative is the, very expensive, pump distributor overhaul.

I'll let you know how I get on.
Cheers.

Hi Gadzook smile

That sounds like a plan wink However you have not told us what exact motor it is, so we could make more informed comments.

My comments generally are;

1 after you drain the fuel check it for water by leaving it to settle in an open container. Look at the crap in that water too ! Get it all out to fully dry.

2 Do not rush into a rotary pump rebuild as that is not likely. Every cylinder get its fuel from a single pump piston in a rotary pump so they all should get the same amount.

3 there are two very fine filters hidden in the rotary pump on some models. These can be clogged and can be removed and cleaned or replaced without a rebuild.

I could look for some information on this if you ask.

Jaahn

blaze · Guru

check all your intake hoses for delamination, you will need to remove to check, often delaminate on a bend and may only be a small flap blocking/partially blocking the intake.
cheers
blaze

Aus-Kiwi · Guru

I assume it's intermittent ? Is there much blow by or smoke coming out of oil filler when you take the cap off when idling ? I had similar issue with my GM 6.5 . The electronic fuel injection or should I say electronic injection pumps PMD is rubbish . The place they fitted the driver overheats . The after market cure was to fit a heat sink and PMD out side engine bay, behind number . Another is often the filter INTANK blocks up . Or the lift pump I'd it has one ? Doesn't work properly . I re did all the earths around engine also . Seems they also can suffer from radio interference ? If it's electronic or computer controlled in any way . Btw the 6.5 isn't single rail . Even the stop relay or solinoid can give grieve too. . Just suggesting things to look at . It's aften something over looked ??

Aus-Kiwi · Guru

Behind bumper .. Ahh !! Lol big finger small not so smart phone !!