hippydippy

So my jeep suddenly doesn't start, have done spark test and can smell gas when it turns over. I did get it stuck in a 2+ foot mud puddle last week and ended up having to leave it for the night! however it started right up after getting it out and has drove fine this past week. Only other thing i can think of is I took it to a automated car wash the day before and that night it was single digits. Suggestions? Possibilities ?

hippydippy

And today sprayed starter fluid right into throttle body while jumping it and got it to fire once a few times but nothing more

tjwalker

The two primary suspects for water intrusion are:

1. The throttle position sensor

2. The distributor cap

I'd suspect the TPS before the cap, but either are a possibility and should be ruled in or out. I'd start by removing the distributor cap and putting it in an oven at a very low temperature for an hour. Also remove the connector from the TPS, spray it thoroughly with electrical contact cleaner, add a small dab of dielectric grease to the connector and reconnect.

hippydippy

Opened up the distributer and it looks clean and brand new so I don't think that's it, I'll look up the tps though

hippydippy

Sprayed the connections today and did the dielectric grease, still no start. Is there any way to test if the sensor is good?

tjwalker

Below is more on the TPS. But before digging into that, I'd verify if you have spark and the quality of that spark. You need a snapping, BLUE, spark to start the engine. Yellow/orange/white indicates a weak spark which may not be strong enough to start the engine.

Pull a plug, keep it attached to the plug wire, place the plug electrode near a good engine ground. Have a buddy crank the engine while you watch.

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The throttle position sensor is connected to the throttle shaft on the throttle body. It sends throttle valve angle information to the PCM. The PCM uses this information to determine how much fuel the engine needs. The TPS is really just a simple potentiometer with one end connected to 5 volts from the PCM and the other to ground. A third wire is connected to the PCM. As you move the accelerator pedal with your foot, the output of the TPS changes. At a closed throttle position, the output of the TPS is low, about a half a volt. As the throttle valve opens, the output increases so that, at wide open throttle, the output voltage should be above 3.9 volts. Testing can be performed with an electrical meter. Analog meter is best. You are looking for a smooth sweep of voltage throughout the entire throttle band. While slowly opening and closing the throttle, take note to the movement of the voltmeter needle. There should be a direct relationship between the needle motion to the motion of the throttle. If at anytime the needle moves abruptly or inconsistently with the movement of the throttle, the TPS is bad

You should have 5 volts going into the TPS. At idle, TPS output voltage must be greater than 200 millivolts. At wide open throttle (WOT), TPS output voltage must be less than 4.8 volts.. The best is to use an analog meter (not digital) to see if the transition from idle to WOT is smooth with no dead spots. With your meter set for volts, put the black probe on a good ground like your negative battery terminal. With the key on, engine not running, test with the red probe of your meter (install a paper clip into the back of the plug of the TPS) to see which wire has the 5 volts. One of the other wires should show .26V (or so). The other wire will be the ground and should show no voltage. Move the throttle and look for smooth meter response up to the 4.49 at WOT.

Perform the test procedure again and wiggle and/or tap on the TPS while you watch the meter. If you notice any flat spots or abrupt changes in the meter readings, replace the TPS.

The TPS is sensitive to heat, moisture and vibration leading to the failure of some units. The sensor is a sealed unit and cannot be repaired only replaced. A TPS may fail gradually leading to a number of symptoms which can include one or more of the following: -

NOTE: The throttle position sensor is also DIRECTLY involved with transmission shifting characteristics! It should be verified early in the troubleshooting process, when a transmission issue is suspected!

• Poor idle control: The TPS is used by the ECU to determine if the throttle is closed and the car should be using the Idle Air Control Valve exclusively for idle control. A fault TPS sensor can confuse the ECU causing the idle to be erratic or "hunting".
• High Idle Speed: The TPS may report faulty values causing the engine idle speed to be increased above normal. This is normally found in conjunction with a slow engine return to idle speed symptom.
• Slow engine return to idle: A failing TPS can report the minimum throttle position values incorrectly which can stop the engine entering idle mode when the throttle is closed. Normally when the throttle is closed the engine fuel injectors will be deactivated until a defined engine RPM speed is reached and the engine brought smoothly to idle speed. When failing a TPS will not report the throttle closed and fueling will continue causing the engine to return to idle very slowly.
• Engine Hesitation on Throttle Application: The TPS is also used by the ECU to determine if the driver has applied the throttle quicker than the Manifold Air Pressure sensor can read. The fueling is adjusted accordingly to cope with the sudden increase in air volume, however a faulty sensor can cause the ECU to ignore this data and the engine will "hesitate" when applying the throttle. In extreme cases with the engine at idle, a sudden application of full throttle can stall the engine.
• Engine Misfire: A fault TPS can report values outside the denied acceptable range causing the ECU to incorrectly fuel the engine. This is noticeable as a slight misfire and can trigger the misfire detection software and/or Malfunction Indicator Lamp (MIL) light on the dashboard. Extreme cases can cause excessing misfires resulting in one or more cylinders being shut down to prevent engine and catalytic converter damage.

hippydippy

Checked spark again and it was a weak orange. So I took the coil off my parts car and swapped it in , still weak orange. Did some research and found it might be cps?? Seems lik a major pain in the *** to change though. Seems to be one of the main possibilitys though

highmileage

MAP sensor?

hippydippy

im pretty shire that alone doesn't cause no start

highmileage

On our lovely XJs' yes it can.
Loads the motor pig rich with fuel making it so if you can get it started lots of accelerator + lots of black smoke, lift off the accelerator it dies.
Brought it up because you said you could "smell gas", if it is the CPS there should be a no spark no fuel scenario... Yah?

hippydippy

ok thats a good point, reason i think its cps is that 1. it happened completely randomly (no warning) 2. Its not getting spark. it lit up faint orange on the test light. doesnt fuel pump still prime with a bad cps?

hippydippy

We'll replaced cps and still no spark, and I'm starting to miss the jeep and will prauly just go to a shop...

highmileage

No.
No "fuel" no "spark", bad CPS. As far as I know.
Pending on where you got the CPS from(AUTOZONE) it could be bad from the box.

scheetz_21

What year Xj?? Mine was doing the same thing could smell fuel but didn't even try to fire , bad cam position sensor but that is only 2000 up so if not maybe bad ECM ???

hippydippy

it's a 92, tomorrow I'm going to check the fuse box and ignition grounds. I have a fresh tune up , and have changed the coil and cps so far. It shows weak spark before distributer