Help required with miss firing engine.

[Steven]

Hello,
I have recently been having trouble with the engine of my 356c.

I was wondering if this sounds familiar to anyone.

- When I first start the car up everything is OK.
- When it is warmed up everything seems OK as well.
- However as soon as I put any load on the engine, i.e. by putting my foot down whilst going up hill, the engine begins to miss fire resulting in the vehicle finally losing power all together.
- It doesn't back fire it just loses power and refuses to fire on all cylinders.
- After the car has been left for a while it seems to improve a little.

What I have done so far to rectify the problem.

- New plugs, leads, points, condenser and rotor arm.
- I have even replaced the fuel pump, which was not the correct one for the car and in bad condition. I have also replaced a dodgy battery.
- There is a very slight bit of green corrosion in the distributor cap, but this doesn't 'seem' to be effecting the car when I check it.

I was just wondering if anyone had encountered a similar problem, before I start checking for sticking valves or replacing distributor caps and coils etc.

Any advice would be appreciated.

Cheers
Steven

[Miggs]

if its misfiring it must be electrical

[FraserMurray]

My 912 did a very similar thing, after replacing the 009 distributor with an 050 it no longer seems to do it. Not sure if that's any help.

F

[Nick Moss]

That could be dirty fuel. The solution is to drain the tank and clean it, blow out the fuel lines and strip and clean the carbs

[Luke]

I know nothing about 356's but my misfire was a combination of coil and points

[Alan @ CanfordClassics]

Hi Steven,

Sorry to read about your problem. With all these motors there are basically 3 things they need air, fuel and a spark. You say the motor idles so it does run, therefore all the items above are working to some degree. The following is a simple diagnostic which may help.

If we jump Air as the car does run, then let’s look at fuel. Remove the line to carb inlet, put the end in a glass container and get a friend to turn the engine over (take the rotor out or something so it does not fire up) this will tell you roughly is fuel is coming from the pump. Then look down the carb throats, and open the throttle (not engine running) use a mirror and light if you need, do you see a squirt of fuel from each one.

If fuel seems to be getting through, then move onto "spark". What is the condition of the rotor and dizzy cap like. These are cheap and worth replacing anyway. Have you checked the timing. Also the 050 bosch dizzy does have a much more suitable advance curve for these and 912 motors. I bought mine from the US I think at 50 or 60 bucks, but that was a few years ago. Once you know the parts are in good condition, with the engine running carefully remove each lead from the dizzy to each plug. Holding it near you should see the spark arcing over the gap, this shows that spark is getting to the plug.. be careful though the coil can give ya a little reminder that you body can also act as an earth. This is only a very simple approach but may help locate the issue.

Good luck

Alan.UK


Other questions which spring to mind
1) what were the plugs like when you removed the old ones
2) did the car run ok before (ie have you made any changes)
3) it you open the throttle under no load (no in gear) does it still miss


Sorry for the essay, but writing this stuff is far more interesting than what I am working on.... "the mechanisms of mobile sediment in shallo...snore"

[912uk]

Just to add to that of Alan the 050 is now out of production by Bosch . But don't panic if you can't find one I have a mate in the states looking in to (well he has already done a few) Converting 009's to the same advance of the 050... whatch this space..

Mark

[FraserMurray]

I think Roger Bray still has 050's in stock but they're not cheap.

F

[Steven]

Just a quick email to thank everyone for there suggestions.

I was planning to give Roger Bray's a call but they don't have any one in the office until Friday. Until then I'll be checking through your ideas.

Cheers
Steven

[louis356]

Yup! sounds like your distributor to me. If it's when you put some load on the engine (going up hill, or just spanking it), then it sounds like the springs in your dizzy are a bit weak.

Does it miss fire when you are standing still and rev the engine or only when its moving?

Dirt would be a bit more hit and miss, and could happen anytime, but when your carbs require more petrol then its more likely to spit some dirt down the needle. (even when the car is standing still.) So if it's when motoring and fairly consistent its probably on the electrical front.

But worth checking carbs for dirt -'cos it's FREE!!

Maestro wannabe

[Bootsy]

Maestro wannabe