tiggrlance

Just bought my first jeep yesterday. A very nice 98 cherokee. started up fine many time yesterday but will not start today. Turns over with no problem but acts like its not getting fuel to the carb (injected) or is not getting spark.

I read a thread on here that the Grand Cherokee has a security feature that can cause it not to start - wondering if this might also be the case on the 98 Jeep Cherokee?

I'll be digging into it tonigh so if you have any ideas please throw them my way.

Thanks.

Lance

mack1

Hi tiggrlance and welcome to TSF

The security feature thing probably keeps some from offering help. I know it has caused me to pause. I've never had a vehicle with that feature, so I'm not equipped to help in that regard. There is, however, a couple of things that you can do to localize the problem that are simple and apply to all vehicles. Solve the basic problem of "is it fuel, or ignition".

Pull a spark plug or get an extry one and lay it on the block and hook a sparkplug wire to it. Crank the engine over and see if there is a strong blue spark across the plug gap. If you get a good blue spark, the problem is probably fuel, though it could be ignition timing if the spark is there.

Solve the fuel question next. Pull the large hose off the intake manifold and use a can of starter fluid. Spray small bursts of spray directly into the manifold and see if the engine will start. If so, you should be able to keep spraying bursts into it to keep the engine running. If this is true, then the problem is fuel.

Post back and tell us if it is ignition or fuel. We will be better able to help you in the problem area.

Best regards,
Mack1

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tiggrlance

Thank you for the response. I checked the spark last night from the coil and didnt get any so I checked relays and fuses which are all good. I'll check the coil voltage tonight and see if I get anything.

Hopefully it doesnt go as far as a fuel pump issue because I have to take the tank off to check it (needs a new gas guage anyway!).

Thanks for the tip on checking spark - much easier than pulling the sleeve off of the distributor plug wire.

mack1

Hi tiggrlance,

Normally on checking the fuel, a pressure gauge is used. GM and Ford use a circulating fuel system where the pump in the gas tank pumps fuel to the engine and around a manifold from which the injectors take fuel. The excess fuel is pushed through a pressure regulator and returns to the tank. The gas is pumped in a circle. There is a valve on the supply line at the engine where you can connect the gauge. The injectors require a certain amount of pressure to spray fuel into the intake. There is normally a filter in the supply line at the tank. It sometimes gets stopped up causing low pressure at the engine. You'll have to look up the pressure for your system, they vary from Manufacturer to Manufacturer and model to model. Some are as low as 40 psi and some above 60 psi.

If you are going to do much work on your vehicle, you should buy a volt/ohm meter and a fuel pressure gauge. They can save you a lot of time.

If you suspect the coil, the resistances on it are about 0.90 to 1.5 ohms on the primary coil winding and about 1300 to 1400 ohms on the secondary. The primary wires are the two small wires going into the coil. The secondary can be measured from one of the primary wires to the highvoltage output at the top.

You can get data on your jeep at www.autozone.com. I got the coil resistances from there. I didn't look up the fuel pressures. If you need shop level data, autozone also has Alldata, where for a fee, you can get very good prints for your vehicle.

Hope this helps,
Mack1

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tiggrlance

ok.. took the coil off and it tested ok via the ohm meter. Went to Autozone and picked up a computer error code reader and found that there was an error that deals with the tranny. Researched the error further and found that it pertains to the Crank Position Sensor. If the CPS is bad it shuts off power to the pump and to the coil. unfortunately the pins on the CPS are not labeled so Im going to pull it off tonight and ohm it out against a new one at the parts store to see if its reading open or not. Will let you all know!

mack1

Hi tiggrlance,

Hope that is the problem. That would be a low expense repair.
Also, thanks for posting back. Any time someone fixes a problem and posts back, it helps others with the same problem.

Best of luck,
Mack1

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"If you like yourself others will like you also" me
"Don't drink downstream from the herd" Will Rogers

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tiggrlance

That was it. The CPS (Crank Position Sensor) was bad and shut down power to the fule pump and spark. $77 for the part and about 30 minutes to install and started right up. The error checker that I got on loan from Auto Zone saved the day!

mack1

Great, glad you got it.

Have a nice day
Mack1

__________________
"If you like yourself others will like you also" me
"Don't drink downstream from the herd" Will Rogers

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