Piston Slap: The Vanagon's a Little Rough Around the Edges?

TTAC’s very own David Holzman writes:

Sajeev,

My friend Polly’s ’83 air cooled, fuel injected, VW Vanagon dies at stoplights, and she has to let it cool down before it will start again. It also runs a bit rough, and it’s normally hard to start.

The engine was rebuilt 5 years ago (in Sturgis, South Dakota, where she’d gone from her home in Bethesda Maryland, for a sheepdog trial, by a VW mechanic whom she rousted out of retirement), and she thinks she’s put less than 20k on the clock since. In efforts to solve the problem, the air flow meter, the wiring, and the spark plugs have been replaced.

Any ideas? Thanks!

Sajeev replies:

In these cases, I go back to a couple of fundamentals of the internal combustion engine: fuel and spark. One of them is misbehaving. I am far from a Vanagon-guru, so let’s discuss the common test points for any EFI system.

Fuel is pretty simple to test: a fuel pressure gauge is mandatory for EFI controlled cars. Depending on the manufacturer, a fuel injected vehicle needs anywhere from 10-40psi of pressure to keep the motor happy in any temperature, any driving condition. If the Vanagon’s fuel system is out of spec, test the pressure regulator (normally that means blocking off the return line, but I can’t comment specifically on this application) and the fuel pump.

But I suspect it’s the other part of the equation: ignition. From start up to full throttle, heat is an ignition system’s deadly enemy. I‘d check the Vanagon’s baseline ignition timing (and whatever timing advance mechanisms exist on the distributor) the resistance of the coil and maybe the ignition module. Shouldn’t be too difficult for a VW whiz, and hopefully the cheapest part is the only problem.

(Send your queries to mehta@ttac.com)