Checking fuel filter

Helen · Post by **Helen** » Sat Apr 05, 2008 11:03 am

Having a bit of trouble with the 356.

It is losing power during running - intermittently.

I'm thinking fuel flow problem.

So I am checking the fuel pump filter first.

How much fuel should leak out of the cap before it stops? I've had 2 pts so far and no sign of i stopping.

And yes - the fuel cock is off!

Any input welcomed.

Lazza

hot66 · Post by **hot66** » Sat Apr 05, 2008 11:10 am

are you sure the fuel tap is off, not just turned to reserve?

Hendrik Moulds · Post by **Hendrik Moulds** » Sat Apr 05, 2008 11:13 am

I would have thought that it shouldn't be as much as 2 pints.

How intermittent is it and does it go down to 2 cylinders, is it only when idling or when driving? If it does go to 2 cylinders and it's the right hand bank (when you are looking from the back of the car) that is going off then it will almost definitely be a fuel flow problem. Could be the fuel cock as well, I've had to replace a couple in the past!
If not it could be electrical.......

MartinP · Post by **MartinP** » Sat Apr 05, 2008 7:53 pm

Helen - last week I had a similar problem with my 912 engine, except that it was also backfiring a lot. Andy Prill helped me diagnose the problem first by suggesting I let the car cool down, then start up and run for 30 or 40 seconds. Then you peer underneath the car and quickly tap each of the exhaust outlets with a fingertip with a bit of spit on it.

Obviously there are two coming out the front and two out of the back of the engine underside (if you have heat exchangers fitted then the back ones are most accessible by just touching the tube that returns to the exhaust from the back two exits (number 1 and number 3). Each one should be hot enough to make the spit 'sizzle'. If not, then you can slowly identify which cylinder or cylinders have a fuel/spark issue.

On mine, it turned out that number one cylinder wasn't producing any heat and so I had to remove the jets out of that Solex carburettor and blow it all through with an air line which then removed whatever bit of dirt was stopping it from getting the correct air/fuel mixture, but it could have easily have also been that one of the jets was blocked (also easy to remove and just clean up/blow through).

However, if you can identify which cylinder is causing the problem it is also well worth putting a new spark plug in first just in case you have one which has failed.

If Andy Prill is reading this, then hopefully I got it all right and proved that I have a relatively good memory (even if it was only a few days ago!).

Good luck.