Diesel diagnosis

[David Ward Biofuels Forum Newbie Find all posts View Profile Close David Ward]

I have a 1990 Mazda 626 and have put in a naturally asperated engine of the same year. 2.0l. 4 things worst first.
1. embarrassing lots of grey smoke. Clean paper held over exhaust for about a minute reveals droplets of moisture only no black carbon. moisture dries to nothing. Engine is warm (fan comes on).
2. Hard to start when cold. I get it going with aerostart. restarts OK when warm
3. when returning to idle after reving, stalls but will restart.
4 idle screw wound right in to achieve idle.
injectors have been swapped with old motor (3 out 0f 4) injectors changed if carbon pattern around nozzle was irregular. Best pattern was small circle of carbonaround nozzle diameter about 3mm
Any advice out there? I'm happy to get someone to look at it but I don't know who to go to and who to trust in SA.

[Tony From West Oz Vice Chairperson of WARFA Find all posts View Profile Close Tony From West Oz]

Re: Diesel diagnosis

I had a Mazda Capella of that year which I ran for a long time on cooking oil.
Does yours have the Pressure Wave Supercharger? No, now I see you have stated "Naturally Aspirated"

Is the cloth on the exhaust when engine and exhaust are hot? Otherwise, condensation from a cold exhaust could be the cause of the droplets.
What fuel are you using? This engine will not start well on >25% veggie oil, even when in good condition.
Have you done a compression test? This will tell you about the condition of the rings and valve seats. If low compression, have someone do a "Leak Down Test" to identify if rings, inlet or exhaust valves are the cause. Valves are relatively cheap to re-seat.
Are there any fuel leaks from the engine? Fuel leaking out can indicate where air can leak in. Put clear hose on return line from IP, so you can see air in the return line.


Note: a compression tester for petrol engine will be damaged if used on diesel engine.

Regards,
Tony

[smithw Senior Member Find all posts View Profile Close smithw]

Re: Diesel diagnosis

Even before the compression test I would have a look at the cam belt and make sure the timing is right, they can come lose and jump a tooth partially if the engine has been rotated backwards which can happen on installation or removal of the engine. as Tony says air leaks on the fuel lines, Fuel filter, air filter, rags stuffed inside the manifold, or the exhaust Some Mazda engines break the cam bearings but you would probably hear that. Make sure the marks on the injector pump are lined up too. Are there bubbles in the coolant when the engine is running?, which could indicate a head, head gasket or liner come lose. Lots of things to check.
good luck with it.

[joe Moderator Find all posts View Profile Close joe]

Re: Diesel diagnosis

check the glow plug relay is sending 12volts for at least 5 seconds, check eack glow plug glows. Also check the filters aren't blocked as well as sucking air. There may be a gauze filter in the IP itself on the intake pipe.

[David Ward Biofuels Forum Newbie Find all posts View Profile Close David Ward]

Re: Diesel diagnosis

I had a Mazda Capella of that year which I ran for a long time on cooking oil.
Does yours have the Pressure Wave Supercharger? No, now I see you have stated "Naturally Aspirated"

Is the cloth on the exhaust when engine and exhaust are hot? Otherwise, condensation from a cold exhaust could be the cause of the droplets.
What fuel are you using? This engine will not start well on >25% veggie oil, even when in good condition.
Have you done a compression test? This will tell you about the condition of the rings and valve seats. If low compression, have someone do a "Leak Down Test" to identify if rings, inlet or exhaust valves are the cause. Valves are relatively cheap to re-seat.
Are there any fuel leaks from the engine? Fuel leaking out can indicate where air can leak in. Put clear hose on return line from IP, so you can see air in the return line.


Note: a compression tester for petrol engine will be damaged if used on diesel engine.

Regards,
Tony

Engine was at running temp (fan cut in). New timing belt I must recheck. Fuel is straight diesel at the moment. (Leave this with me for a couple of weeks. This was a pressure wave car but the current engine is from a grey import with 180,000 on the clock.

Thanks all
Dave