I've got a 1990 TT Auto which overheated on the motorway last week. Got it home via the AA, but now as then it will not fire up. All belts are intact and everything is turning nornally but no attempt to fire up. Ignoring cause of overheating (for now), any ideas.:confused:

John your tale starts like almost every overheated zed I see in the workshop, all ok then it overheated and now will not start!

 

It`s a very typical and the outcome can vary but and I hope this is not in your case but often it is bad news.

 

First off lets forget overheat as you say and look at the obvious first:

 

A) Spark and fuel check a plug out on the engine with a coil attached and when turning the engine over does it spark ...yes carry on to B if no go to C

 

 

B) Fuel, does the pump prime when switching the ignition on? if not check immobilsers and or alarms etc check the fuel pump fuse under the black box cover drivers side close to the brake master cylinder. check for fuel delivery, can be messy pulling pipes off and dangerous so use caution the system can be under pressure

If no fuel go to C

 

 

C) Remove the cas unit, with the ignition on and the unit connected turn the shaft, listen for fuel sound in the fuel rail and injectors operating, also have a spark plug connected as before and look for a spark (turn quickly for this) if fuel ok but no spark go to D if neither fuel or spark go to E

 

 

D) with no spark and a cas unit that is operating the fuel pump ok the ptu is the next part to check, there are a few tests in the workshop manual but non better than swapping for a known good one beg or borrow one from someone

 

E) It would appear the cas unit is malfunctioning again try and get hold of a known good one and try.

 

All the above assume no other more serious problem exist and the problem is a control or supply fault only, an ecu check would be a good idea too.

 

 

Now on to the overheating:

 

Check compression figures (an engine with low compression will always be difficult to start especially the colder it is) if low do a wet test by adding a small amount of oil to each cylinder and re-test if the figure rises a bit (most likely) then thats due to a tempory extra seal by the oil down the bores if though it is only marginal and the figure is still low then damage to the valves or valve seats may of occured as they can displace slightly during overheating and compression is lost through them.

 

A final though and always worth a look, check the cam belt timing, the overheat could of been caused by something else and masked a belt timing problem that has now got worse?

 

 

Hope that lot makes sense and good luck.

 

 

Jeff TT