Hard to start when hot?

Does it have a stock size oilpump? Check valve clearance.

J.

I have an external oil filter with the in and out through the oil pump and the valve clearances were set by the garage when they did a partial rebuild earlier this year. The problem was there before this work as well as now.

Thanks

Will

I offer 2 possibilities:

1) Failure of Ignition switch contact after long running time. Easy test: Watch the OIL/GEN lights whilst cranking. Both should be ON, though the OIL light might go out after some interval of cranking.

But if *both* go out during cranking, then the switch is failing. Note that the Starter section of the switch may continue to operate normally.

2) More likely, I think: Engine bay heat after a long motorway drive "soaks" into the fuel pump and the carb bowl, raising the petrol temps. When it reaches a critical point (well below the boiling point of water), the fuel will begin to boil. In the pump, this will raise pressure in the outlet pipe to very high levels in a short time. The pressure may get high enough to overpower the float needle valve, flooding the carb.

Fuel in the bowl will also boil. Yes! You can actually hear it do so. And, if you look down the throat, you can see great white clouds of vapour. There may also be a stream of fuel siphoning out the brass vent tube. And the accel jet nozzle may begin dribbling raw fuel.

All this raw fuel dumped into the manifold will make the engine very hard to start.

Later engines (about 1971) had a fuel pump with a pressure relief built in as VW began to recognize the problem. But the carb situation remains to this day a baffling problem. I think it is more severe today due to reformulation of the fuels, but I can't prove that.

There is no one easy fix. You can install an insulating spacer under the carb. Or block off the manifold heat. Add washers to the float needle valve to lower the float level. Prop open the deck lid slightly to increase cooling. No guarantees that any/all of these will solve the problem.

Speedy Jim

Edit: There could be other ignition-related failures, such as the Coil failing as it gets very hot. Ditto for the condensor.

To test for this kind of thing would require checking spark at the HT lead during the time that the engine refuses to fire.

Jim

If the engine overheats, it will become harder to start. Yours does seem to be running on the hot side, but oil temperature is not the only thing to look at. You can super-cool the oil and make the gauge happy, but the heads may still be cooking.

Time to look at all the cooling system components, including engine tin and engine bay seals, thermostat, flaps, fan blades, belt tightness...

Don't lower the float level. It makes the engine run leaner, throughout the range and may cause further overheating and even engine damage. If the float needle valve leaks and causes flooding, it will continue doing so no matter where your float level is set at.

Since it starts right away after a longer wait, your carb bowl most likely never got empty due to boiling and evaporation. Fuel would have to mysteriously re-appear within an hour, without running the fuel pump, for that to be possible :)

So maybe it flooded. You'd need to investigate this while it's hot and not starting well. Check the valve lash too. If you have stock aluminum pushrods, they make the valve clearances get SMALLER as the engine warms up. If the valves were adjusted too tight when cold, they may never close fully when hot.

Do you hold the gas pedal to the floor when trying to start that hot engine? I vote that it is flooded after it sits for a few minutes!

I have a 69 Ghia (1600 twin port) which starts perfectly when cold even when it hasn't been started for a few weeks. However it doesn't start very well when I the engine is hot. If I am on a long motorway drive and stop for 10-20 minutes the engine needs to turn over a lot on the starter motor before it will start. If I stop and start straight away it will start without any problem. If I stop for an hour it starts again without any problem.

This has been a problem since I bought the car 3 years a go. Since then I have had a partial engine rebuild, new fuel filter, new fuel pump and rebuilt the carb.

The VW garage that rebuilt the engine checked the timing and carb adjustment. They suggested that the problem may be the petrol evaporating in the fuel pump but couldn't explain why the evaporation may be happening or how it happened. The insulation block is in place under the fuel pump. The oil temperature gauge is reading 220°F (105°C) when doing about 60mph for an hour or two on the motorway on a hot (by British standards) day. My VW garage checked the engine over and suggest that the sensor may not be accurate as there is no reason for it to be that hot.

Any thoughts would be very appreciated.

Thanks

Will

Same in my Type 3. Eventually worked out when engine cold floor the accelerator to set chokes and it starts dead easy but when at working temps I dont touch the accelerator. I put it down to just an endearing idiosynchracy!. John

Hi, thanks for all your responses - I'll check through everything suggested.

I have tried different ways to re start from hot as when I first got the car and found the problem - I thought I may be flooding it by too much accelerator. Now I turn it over quite a bit before putting my foot down. Although as suggested above It does feels to me like trying to start a flooded engine. And this sound like it could be caused by too much heat. I will re check all the cooling system and get a carb spacer.

Thanks for you help.

Will

doesn't sound like you are overheating(at least not excessively), and a bit of carb flooding is "normal" with these engines... do as VW suggested in the manual when starting a warm engine, hold the accellerator pedal to the floor(no pumping) then turn the key..

A long time ago during Summer, our old car stalled at an intersection. A country boy stopped and helped us. He said it had a vapour lock. He walked across the street and bought a cold bottle of pop from a Coke machine. Then he slowly poured the cold soda pop onto the intake manifold right below the carburetor. The old car started.

Any cold liquid would work.

If no cool liquid is readily available and you are alone out in the boonies, you could open the deck lid and take a whiz on the fuel pump to cool it off.

Note : this is also a good last resort remedy for a heat injury.

I have a 1973 VW Beetle with a stock T-1 1600cc DP engine.

I tried the following tips.

Check fuel pump pressure.

For my model, it should be between 3 and 5 p.s.I.

I used the small hole gaskets on the heat riser.

They are kind of hard to find. I got mine from

This is supposed to help keep the heat riser on the intake manifold from getting too hot.

I wrapped the fuel hoses coming out from the fuel pump with aluminum foil to help dissipate the heat from the fuel.

Then I covered the foil wrapped hoses with wire loom to help hold it in place.

But yesterday, I got the engine up to operating temperature and then shut it off.

After a few minutes I tried to start it.

It was hard to start.

I put the gas pedal to the floor and held it there while cranking the engine.

It started but I had to use the gas pedal as a foot exerciser to get the engine running smooth.

This link might help:

start very well when I the engine is hot. If I am on a long motorway

I remember back when I first bought my '70 bug I had a problem with vapor lock in the fuel line. The metal part of the line inside the engine compartment rested on the manifold. I used a bit of wire to suspend it from the fan shroud and never had that problem again.

More than likely it is simply purculation of the fuel. The engine temps transfer to the carb when it sits for a few minutes. There is no air flowing through the carb to cool it. So the fuel boils and floods the jets and thus cylinders. You can usuually add another gasket (as thick as possible) under the carb and this will help. Also when restarting hot keep the throttle open fully for a second or two, this will help clear the wet fuel out.