How to sort out a poor running Type 1 motor (part 1 – valve clearances and electrical / ignition system)

Our air-cooled VWs have always enjoyed a healthy reputation for bulletproof reliability and will often keep going, despite mechanical problems that would see most cars on a one-way street to their local garage. That’s why it’s easy to simply ignore rough running issues or put off opening the engine lid on a car that’s a pig to drive. Disgraceful as it sounds, that’s just what happens sometimes.

Of course, even the best maintained and serviced cars can have their issues, with cutting out, flat spots, loss of power and backfiring all traits most of us are all too aware of. But why put up with this when there’s simple steps you can take to get your pride and joy running sweetly again?

Here’s part 1 of our guide to point you in the right direction when it comes to sussing out what’s wrong, and how to put things right again.

Don’t miss part 2, which covers fuel system issues and carburettor tuning!

01 Valve clearances

One thing that tends to get overlooked until the engine is hot and stranded at the side of the road, running like the timing is out or backfiring, is valve clearances. Strictly speaking, these should be checked every 3000 miles and the cork gaskets replaced. Clearances should always be checked and adjusted when the engine is cold. To check, pry off the spring clip and remove the rocker cover. Expect to catch some oil with a rag. Now, remove the distributor cap and turn the engine until it is at top dead centre (TDC) on number one cylinder. You will see the notch in the rotor arm line up with the notch in the distributor body. You will also see the notch in the lower pulley line up with the join in the engine case. With this done, slide under the car on the right side (RHD driver’s side, LHD passenger side) and get in position at the cylinder furthest forward.  This is number one cylinder. Slot in the feeler gauges with a thickness of 0.15mm or 0.06in between the rocker and valve stem. If they are loose or tight, then you will need to adjust, by loosening the 13mm nut and using a flat screwdriver to wind the valve adjuster in or out. Moving to No.2 cylinder, turn the engine backwards 180 degrees (you will need to make a mark at the bottom centre of the lower pulley, so you can locate this easily). Continue in this way for the other two cylinders.

02 Check coil

A weak spark can cause all kinds of poor running issues, so it’s best to check the coil first. If you leave your ignition on for long periods, then the coil can burn out. When checking the coil, make sure it is cold, have a fire extinguisher handy and ensure there is no fuel around in the engine bay before proceeding. Also be aware of the extreme high voltage produced by the coil and be sure to use insulated grips and rubber gloves. Ensure 12V is going to the coil; the terminal marked 15 is the positive side of the coil and the terminal marked 1 is the negative side. Turn your ignition on (do not start engine) and put a test light on the coil – one side to positive, the other to negative. The light should illuminate. If you have an ohmmeter/multimeter, you can do further checks. Firstly, remove all the wires from the coil, then attach the red and black terminals of the meter to the positive/negative on the coil. The reading should be 3-4.5 Ohms. If the coil is bad, it will show a higher reading. Next, put one of the multimeter terminals into the centre of the coil and one onto either onto either one of the terminals. You should get a reading of 9,500-10,000 Ohms, maybe lower. A reading of 11,000 Ohms or more, or a reading of zero, indicates a bad coil.

03 Dodgy dizzy

Most air cooled VWs came with a vacuum advance distributor. The vacuum advances the timing slightly just off idle, so makes for a smoother pull away. However, many owners fit a Bosch 009 or similar, with a mechanical advance. These run okay on stock engines, but are really meant for use with dual carb setups. The problem is they are slower to respond to load changes, which produces a flat spot upon acceleration. If you have a stock carb and engine, then a vacuum advance distributor is best. The vacuum can on a vacuum distributor takes the vacuum from the inlet manifold via a steel tube, with a rubber hose on each end. Ensure the hose is not perished, or brittle, as this will cause a leak. To check the vacuum can is working, remove the distributor cap, rotor arm and dust shield, if fitted. Now remove the vacuum hose from the carb end and suck on it; you should see the plate that the points attach to in the distributor move, then return once you stop sucking. If this doesn’t happen, it is likely that the diaphragm is ruptured. You can replace the vacuum can, without replacing the whole distributor.

04  Absolutely pointless

If the points and condenser haven’t been replaced for a while, it’s probably a good idea to change them. There are several different types of model and year specific points and condensers, so check first before purchasing parts. Check the shape and location of the condenser bung that inserts into the distributor body if unsure. Many people replace the points and condenser setup with an electronic ignition module, thinking it will be maintenance-free and solve all ignition woes. I used to be one of these people, until I had a couple of units fail. By all means use an electronic ignition module, but carry old school points and condenser too to get you out of a fix, should it fail. While you are inside the distributor, check the ground wire to the base plate is intact and in good condition.

05 Perfect timing

A poorly timed engine can cause a lot of problems, which can lead to the early demise of an engine. The trouble is, most consider ignition timing a dark art and some VW mechanics don’t even take the time to identify the correct timing setup for the distributor in front of them; there is a vast array of different distributors, each with their own unique timing setting. John Muir’s book How to keep your Volkswagen Alive comes up trumps here, giving a rundown of all models and their timing settings. A timing light is an essential tool for setting things up; sure, you can set up static timing to TDC, but why wouldn’t you invest in a timing light and setup the timing correctly, when it’s so crucial to your engine’s health?

06 We have ignition

If you haven’t serviced your car recently, then the ignition system is a good place to start. Try to specify quality German items, as some aftermarket parts literally aren’t fit for purpose and may do more harm than good. Start with the rotor arm, and look to see it is all in one piece and the contacts are clean. Also, check the spring inside (if it has one) is intact. Now look inside the distributor cap; the carbon contact is on a spring and this should be functioning correctly, otherwise it won’t make contact with the rotor arm. HT leads can degrade inside and break down; this often happens with one lead, so the problem can be diagnosed by swapping leads around. Spark plug colour can tell you a lot about your engine; a light brown indicates a plug that is in a good running engine. Heavily fouled pugs indicate a problem in the fuel/ignition system.

And there’s more…  Don’t miss part 2, which covers fuel system issues and carburettor tuning!

Words & photos: Mark Walker & Ian Cushway

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