Rough idle when cold. Possibly diesel bug.

[Ant]

Had a fuel issue for the last few months. Idles a bit rough in the morning and if I dont keep the revs up with the hand throttle or accelertator, it can die and is hard to restart. If the revs start dropping and is about to die I can pump the primer and it runs perfect for half a minute then idle starts dropping off again. If I drive around the block it goes back to normal and will idle fine. No excessive smoke. Cleaned/replaced fuel filters. Blew out the lines. Checked air intake.

Today I checked the fuel tank and foud the fuel to be quite black and all the surfaces are very slimy. Diesel bug I suspect. Pulled all the fuel out (40 litres ) used petrol to clean the tank and fuel lines and blew them out with air gun. And another new fuel filter. Have not een able to put new fuel in yet so not sure if the problem is gone.

Questions! Do I still need to treat the fuel tank for the diesel bug or is it gone now?
Short of pulling injectors and pump is there anything else I should be looking at to solve the problem?

Seems like the pump and injectors are ok because when its been running for 5mins it is fine and when I prime the fuel it improves, so would seem like I am not getting the volume of fuel needed when cold.

[timmay556]

First tell us make/model etc of your car

One thing you can try is when cold is to drive her down hill at say 50kph in 3rd and lift off the accelerator to see if it blows white smoke (engine braking) - if so your injectors could be worn as which is why it runs rough when cold.

[ChurchurDan]

If you fuel has gone dark you probably have a shagged injector pump and it is drawing engine oil in through the seals.
Diesel bug causes a formation of a brown snot like substance in the tank that will also be in you filters. It doesn't discolour the fuel.

[catalystracing]

I put about 50ml of this in every tank full. Been using it for years and have had really good results. It has a biocide in it also to help control any bug. Helps lubricate the injectors which is important for older diesel engines, which Im told relied on sulfur for lubrication of the injectors, which has been removed in modern fuels.

Worth a crack I reckon.

http://www.moreyoil.co.nz/moreys-diesel-smoke-killer/

[Ant]

Cheers for the replies.
Its a y60 safari, td42. Non turbo.

The fuel was definitely more black than brown, with lots of small floating black bits. Might have to get the pump out soon and get it checked. Not going to happen right away as ill need to save big time for that. Bugger

[slidenyo]

perished rubber fuel lines would be my guess,
clog the filters fairly quick and have seen it turn fuel black.
I'd pop the tank lines off and have a scrape with a pick to see if they are shagged.

I had to pull down/clean 6 Johnson outboard carbs about 2 mile offshore due to this and a certain uncles lack of fuel filter

[slide]

If you fuel has gone dark you probably have a shagged injector pump and it is drawing engine oil in through the seals.
Diesel bug causes a formation of a brown snot like substance in the tank that will also be in you filters. It doesn't discolour the fuel.

ChurchurDan's on the mark. It also explains the poor running. Seals sucking in air (make it run poor), and engine oil (discolours fuel).
Time to get the pump off....

[slidenyo]

check simple obvious things first though chap,
it'd be a shame to tear it down and find an internet prognosis was well wide of the mark and left you out of pocket

[Ant]

cheers. have checked most of the basics. gonna take a few months to get done but will update the post when fixed.

[slidenyo]

a good way to detect these issues is to flush the tank,
put fresh diesel in then put a clear fuel filters in line between the tank and lines, the lines and pump and then the pump and return.
then the answer should be staring you in the face ,
ie pump to return goes black (oil),
tank to lines (rubber),
lines to pump rubber.
Could well be a ten minute fix

[timmay556]

like I said, it could just be stuffed injectors. Because the mist/spray pattern will be stuffed due to them being so worn it will idle rough yet once warmed up there is enough heat in the motor to burn the fuel well enough.

I had the same issue when i had a shit tank of diesel go through my GQ patrol.

[darinz]

If it only does it when cold then sounds like glow plugs. Common in GQ's. My one does it and was a faulty relay. Replaced the relay and it then killed a second relay so just live with it. Really bad on a frosty morning but that doesn't happen much up here!

[slidenyo]

Cheers for the replies.
Its a y60 safari, td42. Non turbo.

The fuel was definitely more black than brown, with lots of small floating black bits. Might have to get the pump out soon and get it checked. Not going to happen right away as ill need to save big time for that. Bugger

people seem to have missed this?
if the small floating black bits aren't oil they must be....perished fuel line?

[Ant]

Thanks for picking up on that. not much progress as I am mostly working away from home. Did however get in a trip up to the beach, very soft sand and lots of kms covered. After fully cleaning out the system it felt like a new machine, almost no black smoke even with foot on the floor and 3500 rpm. have not been able to check the tank again after the trip.

I had thought that if it was oil it would mix quite well with diesel and so there would not be floating bits. The fuel filter was full of small floating bits. I still have the diesel in a big container at home so will check the consistency/type of material of the floaties.

I have also done allot of searching about the dreaded "fuel Bug". There are lots of different types, some white, some brown and some black, some that look like tar

Like i said it will be slow progress but im hoping that bits of fuel line are not going to be caught up in my injectors/pump. hope the filter has done its job.

Tanks again for all comments.