Hard starting when hot 68 VW


#1

This is a 68 VW dune buggy. Starts fine when cold. When the engine warms up it just does not turn over, or barely. When it cools down it starts up. New starter, battery is strong but doesn’t seem to have the power needed. Help! Thanks Bruce


#2

So the problem is that during attempts at hot starting the starter isn’t turning the engine over fast enough or at all?


#3

Bad coil or dirty electrical connections?


#4

Heat increases resistance in starter windings as well as battery cables.

I understand that the starter actuates reliably, but cranks sluggishly or not at all, right?
The new starter behaves exactly the same way the old starter behaved? If so, then we can probably rule that out and focus on the cables to ground and to the battery.

I don’t recall where the starter is located on a bug engine. Can you get to it so you can measure the voltage at the starter terminals when you crank it?

If you have good connection in all cables and grounds, the next suspect would be something tightening up in the engine when it is hot. One way to test that theory is to measure current draw of the starter using an ammeter (amp meter?) when the engine is hot and cold. If it draws more amps trying to crank a hot engine, then you probably have internal engine problems that are not going to be easy to find.


#5

Sounds like its getting ready to sieze on the main bearings. Since its so easy to pull the engine,do it and see if crankshaft end play is correct. Is it a mechanically modified engine? You can use a 6V starter with a 6V flywheel and a 12V battery that really turns them over


#6

Probably a bad starter and worn armature support bushing. This is pretty common on the air-cooled VW engines.
You can test the starter current draw with an inductive ammeter and it should draw, after the initial surge, about 125 amps or so.

If you replace the starter there is one thing you MUST do and that is replace the armature bushing that is located inside the transaxle case. The armature on an air-cooled is not supported by a boss on the starter motor but by the transaxle case itself.

With the starter removed you can look up inside the hole and see the bushing. The way you have to remove this bushing is by screwing a thread tap into it all of the way. As the tap bottoms it will push the bushing out.
Another caution. You CANNOT simply install the new bushing as it is. These bushings are made of Oillite, a porous bronze type material.
You must place one open end of the bushing on a fingertip to seal the end off first. Now fill the bushing with heavy motor oil all the way to the top. Now take another finger tip and seal the remaining end of the bushing off. Press the fingertip very firmly onto the oil and hold it for a minute. After a bit you will start to see oil oozing out of the pores in the bushing and it’s now ready to install. Failure to lube the bushing like this will lead to a short bushing life and premature starter failure.

Hope some of that helps anyway.


#7

Not fast enough and at times barely at all. Thanks