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Car Wont Start

S

satancom

New member
Morning All,

Car is a 2.5 Lux on a 1984 plate. This morning it refused to fire.. Its in a garage at the moment so I havene't seen it. Anyhow I was welding on it last night so its probably related.

We were welding the passenger side sill, my mate was welding under it, and I was up a ladder watching for fire inside the cab and splashing a little water if it got hot hot (carpets are out). Anyhow there was no welding near the wiring loom and all wiring was kept up and out of the way, so I don't think any wires have been melted through.

Also before we started we put a proper surge protector on the battery and it lit up to confirm it was connected properly. So again it shouldn't be that..

BUT thats all we did last night and it refused to start this morning so its probably something we did :(.. Turning over but not firing.. My plan is to check for power at the fuel pump and then pull a plug to check for a spark..

Anything else it could be, anything common?
 
a build in immobilizer maybe ??? - if i forget to start the car after disarming - after about 10 seconds my car will only turnover and not start - till i press my immobilisers button ..........- could be a bit far fetched - but i got caught out like that before lol
 
Thats something I forgot to mention... It did have an alarma and seperate imobiliser fitted.. However the wiring had been truley butchered and they had been reduced to just flashin LED's that did nothing. My first task was to remove all the aftermarket alarm and imobiliser gubbins and wiring.

SO it should not be an imobiliser. I do have a fuel cut off swicth.. although that shouldn't have been flicked and the garage did switch it back and for after not starting to double check. Please not the garage are not spending any time resolving this as it my mates place and they are kindly letting me use their lift.. they have paying customers cars to work on :)

It could be something simple. Or it could be very nasty.. Are the ECU's likely to get damaged easily, and are they cheap second hand?
 
Hi Satancom,
if the serge protector was fitted it would be unlikely that you fried the ECU, not impossible though. there are a few easy things too check first. spark and fuel. both quite easy. pull a spark plug and earth it with a grounding wire to the body of the plug. if you dont have access to a noid light you can use a test light between the terminals in any of the injector plugs. you will have constant power with ignition on. the ECU supplies the earth to trigger the injector. they are the first things to check and we go from there.
Sean Buchanan
 
Excelent.. Gives me a nice check list.. So if theres no power at injector with ignition on my ECU may be fried.. or a wiring problem, or an ignitiopn problem, or a fuse problem :D

Busy tonight then!
 
the ECU gets its impulse from the speed and reference sensors. it may be a good idea if you have no injector pulse to check the 2 connections at the rear of the engine where the speed and reference sensors connect to the engine wiring harness. these connectors get brittle over age and fall apart.
If you have no spark work your way backwards, sparkplugs, high tension leads, rotor and cap(rotor is a known failure point when old) coil lead then the coil.
Sean Buchanan
 
Note the fuel pump relay means that if you don't have a spark, you won't have fuel, so alway check and ensure you have a spark before looking for fuel.
 
Well it took about 2 mins to fix. Whilst placing the surge protector on or removing it from the battery one of the live cables came away from the ring terminal.

A new ring terminal and she burst into life on the first turn. Back to welding again tonight. Thanks again for your help :)
 
could i carry this thread on!! i have the same problem! but not fixed. i tried a new coil, and that did not work. is it worth replacing the DME relay? i will check the senor wires as i did not know that. maybe worth ordering a new set of HT leads aswell.
Oh im new by the way! just bought the porsche for track days.

Al
 
Its always the DME!

Not always maybe but it is a regular problem - lots of the guys carry a spare in the glove box.

Well worth checking.

Mike
 
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