When it comes to starting Jeep engines, the three basic elements needed are air, spark, and fuel. There are a variety of issues that can affect whether or not your rig cranks including heat, cold, fluids, and wear and tear on Jeep parts and cables.
Here are a few scenarios and remedies for getting a Jeep started. Keep in mind, there are different fixes for different models – what works for a contemporary 4-liter Cherokee won’t necessarily work for an older YJ. And before you go through too many diagnostics, always make sure you have fuel.
Jeep Won’t Crank
#1 Turn the key to start position, with your foot on the brake. Rock the gearshift back and forth until it fires up or starts to turn over (then you know it’s your neutral safety switch). The neutral safety switch tells your starter you’re not in gear and it’s okay to start.
#2 Check the battery cables at the battery. Wires can get corroded and may need to be bent or manipulated to break up corrosion.
#3 If you know the battery is good, hit the starter with a hammer. This resets the brushes. Don’t hit it with all you’ve got, but give it a good whack. You can do this with alternators, too, but it’s tougher to get to them on a 4-liter engine. V8 engines are generally accessible.
Jeep Cranks Slow
A slow crank means you are not getting enough amps through the starter, through the cables, or the starter is failing.
#1 Same as above, check the battery cables at the battery. Wires can get corroded and may need to be bent or manipulated to break up corrosion.
#2 Check for burns – the shielding on the cable can get burnt.
Crank, But No Start
#1 Spray a whiff of starting fluid into the intake – if it cranks and starts to sputter then you know you have a fuel problem. If you have a fuel problem, open up the fuse box and examine your relay panel – shuffle one into fuel pump position
#2 Hit the fuel tank with a hammer (not too hard) – you’re trying to cause a high frequency vibration to get it to start running.
#3 If someone is with you, have them turn the key in the run position (not the start position). Position yourself near the tank, listen and feel for fuel pump running.
To determine if you have fuel pressure, check the Schrader valve (it looks like a valve stem). On the fuel rail, check for fuel pressure – a dribble is bad, a spray is good.
If You Are Not Getting Spark
#1 Look for the CPS – crank position sensor. It’s a wire and magnet that tells the computer what position the crankshaft is in to know when to fuel and the rpms of an engine
#2 If you crank it over and have a tachometer that doesn’t move, you have a dead CPS
#3 Put a brand new one in – crank position sensors are very heat sensitive
#4 Pour a bottle of water (air temperature) over the CPS, which is on the driver’s side in the transmission bell housing