Diesel 240: Odd noise

Well, I've had no luck figuring this problem out. Maybe someone here
can help.

'82 240 Diesel. Ever since I got the car, there has been this noise
that sounds like pre-ignition would in a gas car and it happens at the
same times it would in a gas car-accelerating, on hills, etc. I
checked the exhaust and valves and all that. Here's where it gets
weird:
The problem is bad with #2 diesel.
The problem is nonexistent on bio-diesel.
The problem is worse on vegetable oil.
At first I thought it was the extra lubricity of the bio-fuels, but it
gets bad on the vegetable oil (yep, have the kit).
Any ideas what this might be? Someone suggested the vacuum pump, but I
have trouble believing a pump noise would be effected by the fuel.
Thanks!

 

The way you describe it the sound it apparently increases with speed
so it sounds engine related. Do you have an exhaust leak somewhere?
If not then it sounds more serious. If the car was converted to run
on fuels other than diesel is it possible that the installer screwed
something up? Maybe the timing?

 

Since it changes with the type of fuel and the degree of load on the
engine, I'd almost have to guess that it is related to combustion chamber
deposits and heat. My guess is that the Bio-diesel runs a bunch cooler,
hence the noise disappearing, while the SVO runs the hottest. Have you
pulled your injectors to see if there are any built-up deposits on them?

I agree with you regarding the vacuum pump.

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I agree with you regarding the vacuum pump.

The vacuum pump can make a lot of noise! Mine does sometimes. Sounds like
knocking on metal. I don't know what to do about it, and it disappears just
like that after a few moments.

 

At first I thought it was the extra lubricity of the bio-fuels, but it

Where can I read more about this bio-fuel-kit?
Do you have a link for me?

 

Yeah, but does the sound change depending on the type of fuel that you're
running?

 

Here's a couple...

http://www.fryoil.org/

http://www.biodiesel.org/

http://www.biodieselnow.com/