1981 SC will not start

[Jacob Odgaard]

Good morning,

I am hoping that someone can help me with my starting problems.
Previously my 1981 3.0 SC has had no problems starting, but this morning it wouldn't.

It sounded like it was going to start, but then there was a loud bang and after that no sign of it wanting to start.

Some more information:
The starter is turning
The car is parked in a garage
Temperature was a couple of degrees above freezing
The car was used 5 days ago in dry weather

I will appreciate any information that will lead me in the right direction.


Regards

Jacob

[Laneco]

Blown air box?

angela

[Paulporsche]

Jacob,

Welcome.

The best thing to do first is to search here for threads on starting problems. It is very common for CIS cars to do what you described when the weather turns cold. Poster Souk has a thread on seasonal adjustment.

Quite often it is a too lean mixture. This may be caused by an improperly set mixture, or an out of spec Warm Up Regulator (WUR). It can also be caused by a blown airbox as Angela said, or vacuum leaks.

On CIS cars you should always make sure that all ignition components are good before looking into the fuel injection.

Many of us have the Bentley manual for these cars. It is for US cars, but I think would still be very helpful for you. There is also a fuel gauge available from JC Whitney that can measure WUR function.

Good luck and post a pic of your car when you can.

[psalt]

Hello Jacob,

The loud bang is a bad omen, but don't assume the worst, start with the basics. Is there fuel in the tank ? Do not trust the gauge if it is below 1/4. Check for spark using a spark plug while an assistant cranks the starter. Next check the fuel pump by removing the air filter and lifting the air flow sensor with the key "ON". You should hear the fuel pump running. If everything checks out, I would remove the spark plugs, see if they are wet and clean and gap them. You should avoid touching the throttle while starting the engine. It should fire and immediately run at a elevated idle speed. You don't say how long you cranked the engine, but it is very easy to flood the engine, despite the time switch on the CSV.

[jmohn]

Originally Posted by Laneco

Blown air box?

angela

Given he heard a "loud bang", that would be my first guess.

j mohn
'78 SC

[holtjv]

If the loud bang was just a backfire and not a blown airbox, his pop off flapper may be stuck open. Pull off the air filter, richen the mixture, bob's your uncle...

[Paulporsche]

Also check the rubber plenum on top of themixture control unit. A backfire like that can blow it off its mount. Make sure the steel band around it is tight.

Do you have an airbox popoff valve? Is it epoxied in and opening/closing freely?

[don gilbert]

yes, for sure check the pop valve, somtimes it looks ok but is just barley attached, (huge vac leak)i havent had a lot of luck with epoxy, i now have been grinding the fins all the way down to where it sit flush and use black urathane to hold it in. havent had one come loose yet. messing with my mix alot ive had some huge backfires and havent blown a box yet,

[Jacob Odgaard]

Thank you all for the good inputs,

I have now returned after work and it did not take long to see that the air box is blown. All the small screws holding the parts together have been ripped out and one of the straps for the cover has been torn off. Furthermore I can see there is a crack in the lower part.

When i pressed the parts together, I could start the engine immediately.

The entire box will definately have to be replaced, but I will see if I can make a temporary repair by gluing the parts together - something to do in the weekend.

I see that our host is offering air boxes, so I will just have to determine whether I have a 38 mm intake or a 44 mm intake. That will be the long term solution.

I will also try to incorporate a pop off valve, as I guess this could happen again tomorrow.


Thank you all


Jacob