1986 240 Sounds Like A Diesel!

[Ghettobird]

Hi all,

I recently acquired a 1986 240 with an M46,

My main problem is that when revving up or under load, the old girl sounds like a big diesel truck! with the hood up, its almost a popping, dieselly sound thats really quite loud!

The exhaust was re-done 3 years ago, and i can tell it seriously needs mounts! What on earth could it be???

[Three Fat Tigers]

Odds are it is ignition timing or other fault in the ignition system. Check the ignition timing, and if that is good, then you may have a faulty ignition control unit. If you don't have access to an timing light, you might mark the distributor position, loosen the distributor and try moving it a little in each direction, then rev to see if it improves.

I don't think it could be valve timing but that is also a possibility, you may want to check that as well:

http://www.threefattigers.com/Protocore/Volvo/TimingMarks.htm

Another possibility would be bad gas. You can drain the tank by pulling off the fuel return line from the fuel rail an run a hose from the fuel rail to a gas can, then jumper the #5 & #6 fuses together.

[ProfessorS70]

This sounds like bad case of piston slap to me (from the video)

[rmorse]

First things first... is it diesel or gas? If it's diesel, that might explain why it sounds like a diesel.

[z31jaime]

my old 740 made the same sound and it was just the exhaust manifold gasket.