Jeepin2004

Hey Guys, I have a small issue that I hope someone can help with. I will admit off the bat, I haven't searched forum yet, but will if no one can help or you all say that its here and don't want to help another jeeper out.

Anyway my issue is, my 97 Cherokee, 6cyl, fuel injection, at times is hard to start, just cranks and cranks. Its happen twice right after getting gas, at the station yet, and few other times after driving for a bit and being parked. I manage to get it started every time, but I have to hold gas pedal to floor and crank it, it starts right up then. And I know with fuel injection you should never have do to that. Should I be thinking a fuel pump or something under hood like a senor or something. I thank you all in advance and appreciate all help.

sigsandjeeps

Check the CPS...Mine did the same thing. Replaced it and all is well.

Jeepin2004

ok, thats a point to start at and look thanks

RTorrez1

X2
CPS

copicatt

Mines is doing the same type thing. It is a 92 model. Cranks for 10 seconds, didn't use to do that. But runs fine/strong. By CPS, do you mean Crankshaft or camshaft. I find that confusing......thanks....

RTorrez1

Crankshaft

tjwalker

The throttle position sensor can act like this when it is going south. Below is more; they can be tested.

And I'd be darn sure that all tuneup hardware is fresh. Old ignition components raise havoc with starting. Fresh Champion copper plugs, new plug wires, cap and rotor.
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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 acordingly 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 deined acceptable range causing the ECU to incorrectly fuel the engine. This is noticable 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.

copicatt

Thanks for the reply, will pick up an analog meter tomorrow, All I have is a digital. I have replaced plugs (3 months ago), Injectors ( last week, one was leaking). Inspected distributor and rotor, look ok, but could be deceiving i Guess. No codes. Started cranking longer about a month ago. Afraid its finally gonna keep cranking. Patting the gas pedal does help it start for some reason even though it is fuel injected. Will test the TPS. Fuel pump hums like it is supposed to. Thanks.

copicatt

Havent gotten the meter yet, but just got a code 12, map sensor. Is there a way to check that. Its on the firewall, I know that much. Could that actually cause a hard start? Thanks

xjsnake

Off topic but Welcome! My former boss is from Jamestown, beautiful country up that way...

copicatt

I like it myself. Been here my whole 36 years. Lol. Thanks

tjwalker

Code 12 is not a map sensor code.

It merely means that memory to the controller has been cleared within the last 50-100 starts.

This is a code, but it is more "informational" in nature, not related to a problem.

If you have a 97 and have a check engine light, I recommend you get it read with an actual code reader or a scan tool. You need the full code, in
the P0XXX format. The full code is much more helpful than the 2 digit code that you can retrieve on early 97 vintage XJs.