Xj12 No Start [Was: weak spark]

Xj12 1984 weak blue spark
New battery new plugs new coil
Still weak wont fireup
Any suggestions please

Blue is strong! Define weak. Timing checked? Leads go to the correct cylinders? Do you have fuel?

1 Like

Steve,

I agree with David, blue spark is strong yellow spark is week.
What is your fuel pressure at the fuel rail? Are the fuel injectors clicking when the engine is cranked (listen with a mechanics stethoscope while someone else cranks the engine)?

The usual suspects for these XJ12 “cranks but doesn’t start” problems are clogged fuel filters, bad fuel pump, debris in fuel tanks, and lost signal (broken wire) from ignition amplifier to the EFI ECU to fire the fuel injectors.

Did this car sit for a while undriven or did this problem just show up in a car that was driven regularly and previously working fine?

More history on the car may be helpful.

Paul

**
I agree with the others, Steve - this doesn’t seem to be a non-start caused by weak sparking…

Retry sparking by using a spare spark plug gapped to 3 times the normal. Verify that the fuel pump is running while cranking…

One of the many, many causes of a non-start - so you likely need more tests…

Frank
xj6 85 Sov Europe (UK/NZ)
**