Gen 3 Suzuki Jimny 1.3 (M13A) – Cranks slowly, no spark

Hello,I’m looking for help troubleshooting a Suzuki Jimny 1.3 petrol, manual, 4WD that cranks but will not start.
I’ve been working through this quite methodically over a longer period and am now running out of ideas on what the next logical step should be.

Vehicle details

• Model: Suzuki Jimny
• Model year: 2004 (first registered 2004-08-23)
• Engine: 1.3 M13A DOHC 16V VVT
• Power: 60 kW / 82 hp
• Fuel: Petrol
• Transmission: Manual
• Drivetrain: 4WD
• VIN: JSAFJB43V00186004

Symptoms

• Starter motor cranks the engine, but:
  • cranking speed is unusually slow
  • engine does not fire at all
• No improvement when jump-starting from another running vehicle
• Brand new, fully charged battery fitted → no change

What has been checked / replaced
✅ New battery
✅ Starter motor cranks every time
✅ New crankshaft position sensor (CKP)
✅ New camshaft position sensor (CMP)
✅ RPM signal visible in OBD live data (approx. 120 rpm while cranking)
✅ Aftermarket RPM limiter from previous owner has been electrically bypassed and completely removed from the circuit
✅ Spark test

• Spark plug removed and grounded to engine block
• Occasional, sporadic sparks observed, at most one per test but not during every crancing attempt
• No consistent or repetitive spark pattern during cranking

✅ Ignition coils (COP)

• 12 V supply present
• Ground OK
• ECU trigger signal tested with LED test light (difficult to verify reliably due to sealed connector)

✅ OBD live data shows reasonable values for:

• TPS
• MAP
• ECT
• Battery voltage

❌ Still no start

Wiring / electrical observations

• Previous wiring repairs found in the harness to the COP coil on cylinder 2 (all three wires spliced)
• No similar splices found at coil for cylinder 4
• No clear correlation to the current fault found so far, but noted

Grounds / voltage drop

• Voltage drop measured between battery negative and engine block during cranking: ~0.19 V
• Starter still feels sluggish despite this
• Suspicion remains around grounds, main cables, or starter motor condition

Questions / help needed

• Are there known ground points or main cables on the Jimny M13A that commonly cause slow cranking and no-start issues?
• Common faults that give an RPM signal but unstable or no ignition?
• Next logical steps:
  • measure voltage drop on positive cable to starter?
  • mechanical inspection / bench test of starter motor?
  • ECU or immobiliser related issues?
• Any Jimny-specific quirks I may be missing?

All advice is greatly appreciated – including suggestions on how to proceed systematically or what is worth handing over to a workshop.Thanks in advance!
John

Wel om to the forum.
First port of call have you checked the immobiliser is reading the key and behaving itself?

Most important question- Was it running perfectly when you parked it yesterday, or did it last run for you ages ago, did someone else last use it or even did you buy it and have never had it running yourself?



It could just be cranking too slowly.

Is there any oil in it?  (We though SIL's BMW mini had a lazy starter until we noticed no oil on the stick- BMW minis empty the sump in a few thousand miles)

Is the alternator or power steering seized? Easy enough to drop the belts off to check.

It could be a lazy starter motor. I'd remove it (allow half a day, it is not easy) and strip it down for inspection, replace if there is any doubt, you don't want to take it off again.

Sometimes people drive these cars through deep muddy water that gets into everything causing rusting and seizure of bearings

Once it is cranking nicely, if there is still no sparks you can start checking all the wiring around the coils, and maybe swapping coilpacks.