For a standard 1600: I timed it, did the valves, adjusted the idle but it still die when I slow down to a stop. It will keep running most time if I pump the gas a bit. Is this a carberator thing? Mayby the fuel pump? The plugs did look a bit black, running to rich? I could use a little help figuring this one out. Thanks.
Tim
74 std. bugDear Tim,
Your symptoms are consistant with a failed anti-dieseling solenoid. This shuts off the fuel to the idle circuit when you turn off the igntion, preventing a hot engine from running-on.
The solenoid could simply be unplugged. Check the connectiions.
Or it has stuck in the closed position (carbs need to be cleaned about every 30 months, on average).
Or it has simply failed. It is an 'always ON' solenoid and gets rather warm. Over time, the heat causes the windings to fail and the thing ceases to operate.
See any of the manuals to identify it. It may be replaced with the earlier idle-circuit jet (ie, no solenoid). But you would then have to learn to manipulate the brake & clutch so as to kill the engine when turning off the ignition.
To test it, simply connect it to the battery and ground the case of the solenoid. The plunger should withdraw from the jet with a CLACK!
cip1.com, that VW parts outfit up in Canada, carries replacements. See their on-line catalog. (Not very well organized, however.)
If the solenoid proves good then the problem is probably a blockage in the carbs low-speed circuit, fair evidence it's due for a rebuild. The kit is not expensive and the required skill-level is about on par with a bright nine-year old. You need some carb cleaner, solvent, compressed air (or a can of canned-air), something to protect the work surface (cardboard, newspaper, etc) and a few tools (varies according to the model of carb but basically a screwdriver and two wrenchs)
Instructions are in the kit.
Don't forget to use a new gasket when putting the carb back on, and don't bugger up the throttle wire -- hold the tip with vise-grips or similar when loosening/tightening the screw. The wires going to the electric choke and the solenoid deserve equal attention.
Service your oil-bath air cleaner while you're at it and if you're running an after-market air cleaner, it is probably the cause of your problems, having allowed dust/sand/etc to get into the carb.
There are quite a few other problems that could give the symptoms you've described, from a worn throttle shaft bore to a manifold or even improper timing... probably two dozen branches on the decision tree. But the solenoids are not very reliable (most guys replace them with the early style idle jet) and its failure has a higher probability than the other problems, most of which offer additional symptoms which you've not mentioned.
Good luck with it.
-Bob Hoover
Not a definitive answer but check the boots around the intake manifold. I once had a bug that would die on me everytime I came to a stop. Turns out the boots were loose. Tightening them down fixed it right up.
Mathew
Tim wrote:
Just a heads up; '74 has a 34-PICT carb which uses a different idle cut-off than earlier. If it had failed, you wouldn't be able to just "pump it a bit" to get running again.
You could have a small manifold leak (rubber booties?), worn throttle shaft bushings, idle mixture could be off slightly (smaller screw). A very small manifold leak can upset the mixture at idle (to just one side) enough to cause mis-fire.
If the problem occurs mostly when the engine is hot, the carb could be flooding slightly. This is a real problem in the summer when fuel can boil in the carb. Usually the engine will be hard to start after a hot run too.
Speedy Jim
Bob H. and Speedy J. covered most of it. I found another possibility this afternoon. My engine/carb is new and tight and I've been playing with the dist. curve and carb settings.
I'm running a H30/31 on a 1600DP and today I found that a little tweak of the mixture screws can make a big difference. My timing and jetting is finally perfect and the idle speed was set for 850 - 900 rpm. I thought I had the mixture screw peaked but then I found that the response was less than crisp and when you came down to idle and it would come close to stalling and then catch itself. A 1/4 turn of the idle screw a little richer didn't do much to the idle speed but the throttle response is way more crisp and it settled the idle hunting.
It's simple carb basics but sometimes we overlook it.
RT
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