Cold Start?

[Mattiee7]

After 4 weeks my 3.0CSA took about 30 secounds of cranking, is this usual ?

I have put a new fuel pump on last year so not that.

Its also had a weber conversion and once stared was fine...

Regards
Matt

 

[Ohmess]

Well, all the fuel will drain or evaporate out of the float bowls in the carbs over that period of time.

 

[Stevehose]

My friend's does the same thing, you can install a check valve in the fuel line by the carbs to keep fuel from draining back so far.

 

[jmackro]

you can install a check valve in the fuel line by the carbs to keep fuel from draining back so far.

Yes, though the fuel will still evaporate.

After 4 weeks my 3.0CSA took about 30 secounds of cranking, is this usual ?

Yes, it is normal for a car with a mechanical fuel pump. If the fuel in the carbs has drained or evaporated, then the fuel pump has to fill the float chambers before the car can fire. And with a mechanical pump, the only way to accomplish that is to rotate the whole frigg'n engine.

One benefit of electric fuel pumps is that they begin working as soon as you turn the key to "ON". If the car hasn't been started in 4 weeks, just let the pump hum for ~10 seconds and then actuate the starter.

 

[bluecoupe30!]

like Steve says, check valve is the answer. lived this same thing, spent a lot of time thinking I had a defective fuel pump, or air leaks at fuel hose connections. But it's true, fuel flows all the way back to tank, and after sitting, it takes a lot of cranking to call that fuel back, and if your battery is not fully charged, it may not crank well enough to do the job. Simple check valve solved everything. Same configuration, CSA + Webers. Mike

 

[jmackro]

But there are two check valves in the mechanical fuel pump. Why would adding a third check valve solve the problem?

 

[bluecoupe30!]

whatever the theoretical reason for the check valve(s) inside the mechanical fuel pump may be, they do not help if car is not started for a week or so. tried all that. installing one in-line before the carbs keeps some fuel just before fuel pump and simply solves hard starting problem. immediately eliminated problem for me. just sayin'

 

[sfdon]

For many years BMW sold their own checkvalve to fix this problem on late 70's / early 80's FI cars that already had them built into the pump and weren't working properly.
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