{ "formatVersion": 1, "title": "No-Start Diagnosis: Crank, Spark, Fuel", "description": "A structured diagnostic walk for a vehicle that will not start, designed to be worked in order rather than jumped around. It splits the problem in two at step 3 (does the engine crank or not), and then follows one branch instead of throwing parts at both. Bring a multimeter; bring no parts at all until the end.", "category": "diagnostics", "subcategory": "Starting and running faults", "difficulty": "intermediate", "tags": ["diagnostics", "no start", "electrical", "battery", "starter", "troubleshooting"], "language": "en", "estimatedMinutes": 205, "estimatedCost": 15.0, "currency": "USD", "author": { "name": "Trackara", "bio": "Official Trackara blueprint template", "url": "https://trackara.app/blueprints" }, "vehicleCompatibility": [ { "make": "Any", "notes": "Written for a 12-volt, negative-earth petrol or diesel vehicle with an electric starter. The reasoning applies to almost anything from the 1970s onward; the code-reading steps assume OBD-II, which in the United States means model year 1996 and later. Hybrids and EVs do not follow this procedure at all. Their high-voltage systems require model-specific training and equipment." } ], "requiredTools": [ "Digital multimeter", "OBD-II scan tool or Bluetooth adapter", "Wire brush or battery terminal cleaner", "Socket and wrench set", "Test light", "Insulated gloves", "Safety glasses", "Flashlight", "A helper to turn the key" ], "parts": [ { "name": "Battery terminal cleaner / brush", "kind": "consumable", "quantity": 1, "estimatedCost": 6.0 }, { "name": "Dielectric grease or terminal protectant", "kind": "consumable", "quantity": 1, "estimatedCost": 6.0 }, { "name": "Replacement battery terminal clamps", "kind": "optional", "quantity": 2, "estimatedCost": 12.0, "notes": "Only if the existing clamps are cracked, badly corroded or have been over-tightened out of shape. Cheap insurance when you already have the battery disconnected." }, { "name": "Can of starting fluid", "kind": "optional", "quantity": 1, "estimatedCost": 6.0, "notes": "Only as a diagnostic aid in step 11, and only with the caution noted there. Never as a routine way to start an engine, and never on a diesel with glow plugs or on any engine with a compromised intake." } ], "steps": [ { "stepNumber": 1, "title": "Write down exactly what it does", "description": "Before touching anything, record the symptom precisely, because the words matter and they will point you at the right branch. Silence when you turn the key. A single loud click. Rapid machine-gun clicking. Cranks slowly. Cranks normally but never fires. Fires briefly and dies. Each of those is a different fault with a different first test.", "estimatedMinutes": 10, "tools": [], "parts": [], "warnings": [], "tips": [ "Rapid clicking is nearly always inadequate current (a flat battery or a poor connection) rather than a bad starter.", "One solid clunk with no rotation points at the starter, the solenoid, or a very high resistance in the main feed.", "Silence with dead dash lights is a battery or main connection problem. Silence with healthy dash lights is a control circuit problem: ignition switch, relay, neutral safety switch, clutch switch or immobiliser.", "Note whether anything changed just before it started: work done, a jump start, a flat battery, wading through water, a fuel fill." ], "checklist": [ "Exact symptom written down", "Dash warning lights behaviour noted", "Recent events or work noted", "Fuel gauge actually checked" ], "imageUrls": [], "videoUrl": null }, { "stepNumber": 2, "title": "Make the vehicle safe to test on", "description": "Park on level ground, apply the parking brake, chock a wheel, and put an automatic in Park or a manual in neutral. You will be cranking the engine with the bonnet open and hands near belts and fans, so remove rings, watches and anything hanging.", "estimatedMinutes": 5, "tools": ["Safety glasses", "Wheel chocks"], "parts": [], "warnings": [ "Cooling fans on modern vehicles can start with the ignition off. Treat the fan as live at all times.", "Never lay tools across the battery. A spanner bridging a battery terminal to the body welds itself in place and can burst the battery.", "Batteries vent hydrogen. No sparks, no smoking, eye protection on." ], "tips": [ "If you are testing alone, a long-handled remote starter switch saves a great deal of climbing in and out. A helper is easier." ], "checklist": ["Parking brake on", "Wheel chocked", "Transmission in Park or neutral", "Jewellery and loose clothing removed"], "imageUrls": [], "videoUrl": null }, { "stepNumber": 3, "title": "Split the problem: does the engine crank?", "description": "Turn the key to start and listen. If the engine turns over, meaning the starter spins the engine whether fast or slow, you have a crank/no-start and your fault is in fuel, spark, compression or the immobiliser: work steps 4, 5, then jump to step 9. If the engine does not turn over at all, you have a no-crank and your fault is electrical or mechanical seizure: work steps 4 through 8 in order.", "estimatedMinutes": 10, "tools": ["Flashlight", "A helper to turn the key"], "parts": [], "warnings": [], "tips": [ "This split saves more time than any other single decision in the whole procedure. Everything after it is branch-specific.", "Do not crank for more than about ten seconds at a stretch, and let the starter rest a minute between attempts. Starters overheat quickly." ], "checklist": ["Branch identified: crank/no-start or no-crank"], "imageUrls": [], "videoUrl": null }, { "stepNumber": 4, "title": "Measure the battery's resting voltage", "description": "With everything off and the vehicle having sat for at least an hour, measure across the battery posts themselves, not the clamps. Note the reading. As a rule of thumb for a 12V lead-acid battery, around 12.6 volts or a little above is fully charged, around 12.4 is roughly three-quarters, and around 12.0 or below is significantly discharged and will struggle to crank a cold engine.", "estimatedMinutes": 10, "tools": ["Digital multimeter", "Safety glasses"], "parts": [], "warnings": [ "A battery reading well under 12 volts may be sulfated or have a shorted cell. Do not fast-charge a visibly swollen, leaking or very cold battery.", "If the battery is frozen, do not attempt to charge or jump it." ], "tips": [ "Measure on the posts, then on the clamps. A different reading between the two means the clamp connection is the fault, and you just found it in thirty seconds.", "A battery that reads fine at rest can still fail under load. Resting voltage tells you state of charge, not health." ], "checklist": ["Resting voltage measured at the posts", "Same reading confirmed at the clamps", "Reading recorded"], "imageUrls": [], "videoUrl": null }, { "stepNumber": 5, "title": "Clean and secure every connection in the main circuit", "description": "Disconnect negative first, then positive. Clean the posts and the clamp interiors back to bright metal. Then follow the two heavy cables to their far ends: the negative to the body and to the engine block, the positive to the starter and the fuse box. Clean and tighten each of those too. Reconnect positive first, then negative.", "estimatedMinutes": 20, "tools": ["Wire brush or battery terminal cleaner", "Socket and wrench set", "Insulated gloves"], "parts": [ { "name": "Battery terminal cleaner / brush", "kind": "consumable", "quantity": 1 }, { "name": "Dielectric grease or terminal protectant", "kind": "consumable", "quantity": 1 } ], "warnings": [ "Negative off first, negative on last. Doing it the other way round is how spanners get welded to bodywork.", "Disconnecting the battery may lose radio codes, learned transmission behaviour and stored fault codes. Read your codes BEFORE you disconnect anything if you can." ], "tips": [ "The engine-to-body ground strap is one of the most frequently corroded parts of the whole system and one of the least frequently checked. Find it and clean both ends.", "Corrosion hides under the insulation of an old positive cable. If the cable feels stiff or the insulation is swollen near the terminal, the copper underneath is probably green." ], "checklist": [ "Posts and clamps cleaned bright", "Negative-to-body ground cleaned", "Engine-to-body ground strap cleaned", "Positive feed to starter and fuse box checked and tight", "Reconnected positive first, negative last" ], "imageUrls": [], "videoUrl": null }, { "stepNumber": 6, "title": "Watch the voltage while cranking", "description": "Leave the meter connected across the battery posts and have a helper crank. Watch what the voltage does. A healthy system holds up while cranking; a battery or connection that is failing collapses. A common trade threshold is that cranking voltage should not fall below roughly 9.6 volts on a 12V system at normal temperature. Much below that and the battery cannot deliver the current the starter needs.", "estimatedMinutes": 15, "tools": ["Digital multimeter", "A helper to turn the key"], "parts": [], "warnings": [ "Keep the meter leads and your hands clear of the fan, belts and pulleys while the engine is cranking." ], "tips": [ "Voltage that collapses to almost nothing AND rapid clicking is the classic flat-battery-or-bad-connection signature.", "Voltage that stays high while the starter does nothing at all points the finger at the control circuit or the starter itself, not the battery.", "Most parts stores will load-test a battery free. If your cranking voltage looks marginal, get that test before buying anything." ], "checklist": ["Cranking voltage observed and recorded", "Behaviour compared against the symptom from step 1"], "imageUrls": [], "videoUrl": null }, { "stepNumber": 7, "title": "Voltage drop test the starter circuit", "description": "This is the test that finds the faults an ordinary resistance check misses, because it loads the circuit. With the meter on DC volts, put one probe on the battery positive post and the other on the starter's main terminal, then crank: the meter now reads the voltage being lost in that cable. Repeat on the ground side, from the battery negative post to the starter body or engine block.", "estimatedMinutes": 25, "tools": ["Digital multimeter", "A helper to turn the key", "Flashlight"], "parts": [], "warnings": [ "You are working close to a live, high-current cable with the engine cranking. Keep the probes steady and stay clear of moving parts." ], "tips": [ "The trade rule of thumb is that a good connection loses very little, commonly quoted as under about 0.2 volts across any single connection and under about 0.5 volts across the whole feed or the whole ground path. Anything markedly higher than that is your fault.", "A cable can look perfect and still be corroded internally. Voltage drop is the only test that sees it.", "Test both sides. Ground-side faults are at least as common as positive-side ones and are much more often overlooked." ], "checklist": [ "Positive-side drop measured while cranking", "Ground-side drop measured while cranking", "Any connection with an excessive drop identified" ], "imageUrls": [], "videoUrl": null }, { "stepNumber": 8, "title": "No-crank branch: control circuit and starter", "description": "If the battery and the heavy cables are good and it still will not crank, work the control side. Confirm the vehicle is genuinely in Park or that the clutch pedal is fully depressed, then try starting in Neutral instead of Park. If it starts in Neutral, you have found a neutral safety / range switch fault. Check the starter relay and the starter fuse. Check the immobiliser or security indicator on the dash. Finally, check for voltage arriving at the starter's small trigger wire while the key is held at start.", "estimatedMinutes": 20, "tools": ["Test light", "Digital multimeter", "Socket and wrench set", "A helper to turn the key"], "parts": [], "warnings": [ "Never bypass a neutral safety switch to 'test' it while the vehicle is in gear. Cars have run people over doing exactly that.", "If the engine will not turn by hand at the crankshaft bolt either, stop. That is mechanical seizure or hydrolock, and cranking it further will cause damage." ], "tips": [ "Trigger wire has voltage but the starter does nothing: the starter or its solenoid is the fault.", "Trigger wire has no voltage: the fault is upstream, in the relay, the ignition switch, the range/clutch switch or the immobiliser.", "A blinking security light while cranking is the immobiliser refusing the key, and no amount of starter testing will help." ], "checklist": [ "Tried starting in Neutral as well as Park", "Starter relay and fuse checked", "Security/immobiliser indicator observed", "Voltage at the starter trigger wire confirmed or ruled out" ], "imageUrls": [], "videoUrl": null }, { "stepNumber": 9, "title": "Crank/no-start branch: read the codes first", "description": "Plug in a scan tool and read stored and pending codes even if no warning light is on, because a no-start often stores codes without illuminating anything. Look particularly for crankshaft and camshaft position sensor codes, fuel system codes, and immobiliser or communication faults. Note whether the scan tool can talk to the engine module at all; a module that will not respond is itself a major clue.", "estimatedMinutes": 15, "tools": ["OBD-II scan tool or Bluetooth adapter"], "parts": [], "warnings": [ "A code names a circuit, not a broken part. A crankshaft position sensor code means that circuit is faulty: the sensor, its wiring, its connector or its reluctor. Replacing the sensor on the strength of the code alone is guessing with money." ], "tips": [ "Write down every code and its freeze frame data before clearing anything.", "If the scan tool cannot connect at all, check the diagnostic socket's power and ground fuses. A blown fuse there often shares a circuit with something else that has failed.", "A crankshaft position sensor failure is one of the classic causes of 'cranks strongly, no spark, no injector pulse'." ], "checklist": ["All stored and pending codes recorded", "Freeze frame captured", "Module communication confirmed or noted as absent"], "imageUrls": [], "videoUrl": null }, { "stepNumber": 10, "title": "Check fuel delivery", "description": "With the vehicle quiet, turn the key to on without cranking and listen at the fuel filler for the two-second whirr of the pump priming. No whirr means no pump, and the cause is often the pump relay, the pump fuse or the inertia/impact cutoff switch rather than the pump itself. If the pump runs, check actual pressure at the rail's test port if it has one, against the specification for your vehicle.", "estimatedMinutes": 25, "tools": ["Flashlight", "Digital multimeter"], "parts": [], "warnings": [ "Fuel systems hold pressure long after shutdown. Relieve the pressure per the manufacturer's procedure before opening any fuel line, and have a fire extinguisher within reach.", "No smoking, no sparks, no work lights with hot bulbs near an open fuel system.", "Fuel on hot exhaust is the most common cause of engine bay fires in home garages." ], "tips": [ "Some vehicles have an inertia or impact cutoff switch that trips after a knock and needs manual resetting. It is often in a footwell or the boot, and it has stranded a great many people.", "Old fuel is a real cause. If the vehicle has stood for a season or more, suspect the fuel before you suspect the electronics.", "Listen for injectors ticking during cranking with a long screwdriver against the rail as a stethoscope. No tick with good codes usually means no crank signal." ], "checklist": [ "Pump prime heard or ruled out", "Pump fuse and relay checked", "Inertia/impact cutoff switch checked if fitted", "Rail pressure measured against spec if accessible", "Fuel age and quality considered" ], "imageUrls": [], "videoUrl": null }, { "stepNumber": 11, "title": "Check for spark (petrol engines)", "description": "Pull one coil or plug lead, fit a spark tester, ground it properly, and crank. You are looking for a strong, consistent spark rather than a weak intermittent one. If there is fuel and spark at the right time and it still will not fire, the problem has moved to timing or compression.", "estimatedMinutes": 20, "tools": ["Insulated gloves", "Safety glasses", "A helper to turn the key"], "parts": [ { "name": "Can of starting fluid", "kind": "optional", "quantity": 1 } ], "warnings": [ "Ignition systems produce tens of thousands of volts. Use a proper spark tester and insulated pliers. Never hold a lead in your hand.", "Never test for spark near an open fuel line or a fuel spill.", "Starting fluid is extremely flammable and is a diagnostic of last resort only. Never use it on a diesel with glow plugs, and never spray it into a running or hot intake. If a brief spray makes the engine fire and die, you have proved a fuel supply problem. That is all it is for." ], "tips": [ "Spark on one cylinder does not prove spark on all of them, particularly on coil-on-plug systems.", "No spark AND no injector pulse together points strongly at the crank position signal or the engine module's power and ground, not at the ignition parts themselves." ], "checklist": ["Spark tested and characterised", "Injector pulse checked", "Result cross-referenced with the codes from step 9"], "imageUrls": [], "videoUrl": null }, { "stepNumber": 12, "title": "Sanity-check compression and timing", "description": "If fuel and spark are both confirmed good, the remaining possibilities are that the engine has lost compression or that the valve timing has jumped. A cranking compression test across all cylinders, compared against each other, tells you quickly which it is: uniformly low across every cylinder is the classic signature of a jumped or broken timing belt or chain.", "estimatedMinutes": 20, "tools": ["Socket and wrench set", "A helper to turn the key"], "parts": [], "warnings": [ "A snapped timing belt on an interference engine may already have bent valves. Do not keep cranking to 'see if it catches'.", "Disable fuel and ignition before running a compression test, and remove all plugs so the engine spins freely." ], "tips": [ "Relative numbers matter more than absolute ones. One cylinder much lower than its neighbours is a mechanical fault in that cylinder; everything equally low is a timing fault.", "An engine that cranks unusually fast and quietly, almost freely, has usually lost compression across the board." ], "checklist": ["Compression compared across all cylinders", "Timing marks verified if compression is uniformly low"], "imageUrls": [], "videoUrl": null }, { "stepNumber": 13, "title": "Write down what you proved, not just what you replaced", "description": "Record every measurement (resting voltage, cranking voltage, voltage drops, codes, fuel pressure, spark result, compression figures) alongside the date and mileage. A no-start that recurs in six months is solved in minutes if you have the previous numbers to compare against, and in hours if you do not.", "estimatedMinutes": 10, "tools": [], "parts": [], "warnings": [], "tips": [ "Note which tests came back GOOD as well as which came back bad. Ruling things out is most of the value of a structured diagnosis.", "If you handed it to a shop at any point, log what they found too. It belongs in the same history." ], "checklist": [ "All measurements recorded with date and odometer", "Codes recorded", "Conclusion and the evidence for it written down", "Parts actually replaced logged with part numbers" ], "imageUrls": [], "videoUrl": null } ], "coverImageUrl": null }