98 Limited No start.

Jeep turns over but does not start. First thought was the CPS. Replaced it with a Rock Auto unit and still no start. Looked at the wiring from the FSM and this is what I have found. No voltage to the coil in key on or trying to start. Fuel pump relay does not engage when key on or trying to start. No voltage to the CPS at the CPS connector at key on or trying to start. What is going on with my jeep? 98 limited auto 242. Suggestions?

I just went through this with my 98 Limited.

Try swapping the fuel pump and ASD relay to rule out a relay problem. The ASD relay will not pass power from the ignition switch to the coil or fuel pump if it is bad.

When you're KOEO, do you have a fuel gauge reading or voltage reading at the dash gauge(s)? If you don't, then your network BUS may be down, which could still be the CPS. This can sometimes be verified by attempting to connect a scan tool to the DLC. If you can not connect or communicated with any modules, then that's an indicator the network is down.

For my problem, it ended up being an internally shorted PCM that stopped supplying 5 volts on the shared line. I would get a meter on it and verify you're getting battery voltage and ground to the PCM, and make sure you're getting 5 volts out of the PCM to the shared sensor line. I believe the CPS, TPS, MAP, CMP, and VSS are all on the shared line. In my search to locate a short and restore 5 volts I pulled the primary ignition coil as well along with the injectors. When I never found the 5 volts I put an ammeter on the battery and found it was drawing 1.5 A with the key off. This was the internally shorted PCM which took down my network.

You have some testing to do. Keep us posted and good luck. I can help with PCM connector pins if you need it, along with a good replacement PCM source if it comes to that.

How old is your battery? Are your connections clean and tight? How old is your tune-up hardware?

98NWCherokee said:

I just went through this with my 98 Limited.

Try swapping the fuel pump and ASD relay to rule out a relay problem. The ASD relay will not pass power from the ignition switch to the coil or fuel pump if it is bad.

When you're KOEO, do you have a fuel gauge reading or voltage reading at the dash gauge(s)? If you don't, then your network BUS may be down, which could still be the CPS. This can sometimes be verified by attempting to connect a scan tool to the DLC. If you can not connect or communicated with any modules, then that's an indicator the network is down.

For my problem, it ended up being an internally shorted PCM that stopped supplying 5 volts on the shared line. I would get a meter on it and verify you're getting battery voltage and ground to the PCM, and make sure you're getting 5 volts out of the PCM to the shared sensor line. I believe the CPS, TPS, MAP, CMP, and VSS are all on the shared line. In my search to locate a short and restore 5 volts I pulled the primary ignition coil as well along with the injectors. When I never found the 5 volts I put an ammeter on the battery and found it was drawing 1.5 A with the key off. This was the internally shorted PCM which took down my network.

You have some testing to do. Keep us posted and good luck. I can help with PCM connector pins if you need it, along with a good replacement PCM source if it comes to that.

How old is your battery? Are your connections clean and tight? How old is your tune-up hardware?

Click to expand...

I know the ASD relay is working because I swapped it with the starter relay. The fuel gage says empty and I know there is fuel in there. Electrical work is not my thing. So I need to check the voltage into the PCM and see if the PCM is grounding? Happen to remember what pins on the PCM they are? BUS? I don't have a scanner and have been waiting for an excuse to get one. Any suggestions on that?

Went in the garage and pulled the C1 connector on the PCM and A22 Fused B(+) has 12 volts. The A31 and A32 are showing continuity to ground. How do you test if there is output? DO the plugs backs come off?

My guess would be your fuel sending unit is not functioning properly. On my 98, my gas gauge would constantly switch from empty to the correct amount and back again. I swapped in a new unit (which controls the level of fuel displayed as well as pumping it to the injectors) If you did not notice this prior to the issue you speak of, I would check to see if you are receiving power to the sending unit. If you do not back track from there. Check post #16 here:
http://www.cherokeeforum.com/f2/cranks-but-no-spark-no-fuel-pressure-154471/index2/

I hope this helps
cpefy3

Ghost said:

Went in the garage and pulled the C1 connector on the PCM and A22 Fused B(+) has 12 volts. The A31 and A32 are showing continuity to ground. How do you test if there is output? DO the plugs backs come off?

Click to expand...

So this is a good thing. This means the PCM is receiving a good power and ground signal. The next step is to determine whether your network is active and whether you have an operational BUS. The BUS, or CCD BUS (Chrysler Collision Detection) refers to the network of computer modules within the XJ. If the modules cannot communicate with one another, the XJ won't start and you'll get a crank but won't start condition. The PCM provides 5 volts as an output to the engine management sensors (mentioned in my previous post) Since you're not getting any gauge readings it sounds like, I would be trying to determine if the PCM is providing the output 5 volts. I'm not certain which pin this is as I'd have to look at a wiring diagram and I'm at work for the next 10 hours. You can pull all the sensor connections and then check the PCM. If the PCM is providing 5 volts, my next step would be to re-connect, then pull sensors one at a time to hopefully isolate the circuit that contains the short. If you pull a sensor, and the 5 volts returns, then you've isolated a circuit with a short. If you don't find a short, and you never find 5 volts, you might be looking at a PCM too. Mine made it 165k before crapping out. I was hesitant to pull the back covers off the PCM connectors as I felt this might cause more harm than good. You can backpin with a T pin at the connector if you need to do further testing at the PCM.

One thing you might check that's really easy......is your PCM warm to the touch with the key off? When mine went the PCM was very warm to the touch......my first indicator to put a meter in series and find the current draw.

Just something else to consider......the wiring for the CPS is prone to failure along the transmission bellhousing. If you're not confident in DVOM testing, you can always begin with a thorough visual inspection of the wiring harnesses to make sure you don't have a break anywhere, although it sounds like you are competent with a meter.

Scantools are as varying in price as they are in function. For the average DIYer I would say spend no more than $350 on a scantool. You can spend $25,000 if you want, but the basic units will do what you need. Make sure you get one that is updateable via online, and records live and freeze frame data. If you can get one with graphing or a scope function, then all the better. I've been looking at an Autel unit that runs around $325. Craigslist is also a decent place to find these as they typically work or don't.

Here's my thread if you want to read through my diagnostic process. Hopefully it will help save you some time and frustration:

http://www.naxja.org/forum/showthread.php?t=1106580

Looks like the 5 volt ouput is at A17 at Connector #1 at the PCM.

Before you worry too much about a PCM, or continue with any testing, you haven't answered the question about the health of your battery and tune-up hardware. Jeeps do NOT tolerate low voltage, and a marginal battery and/or poor connections can cause ALL kinds of problems. Remember KISS......."Keep It Simple Stupid"

98NWCherokee said:

So this is a good thing. This means the PCM is receiving a good power and ground signal. The next step is to determine whether your network is active and whether you have an operational BUS. The BUS refers to the network of computer modules within the XJ. If the modules cannot communicate with one another, the XJ won't start and you'll get a crank but won't start condition. The PCM provides 5 volts as an output to the engine management sensors (mentioned in my previous post) Since you're not getting any gauge readings it sounds like, I would be trying to determine if the PCM is providing the output 5 volts. I'm not certain which pin this is as I'd have to look at a wiring diagram and I'm at work for the next 10 hours. You can pull all the sensor connections and then check the PCM. If the PCM is providing 5 volts, my next step would be to re-connect, then pull sensors one at a time to hopefully isolate the circuit that contains the short. If you don't find a short, and you never find 5 volts, you might be looking at a PCM too. Mine made it 165k before crapping out. I was hesitant to pull the back covers off the PCM connectors as I felt this might cause more harm than good. You can backpin with a T pin at the connector if you need to do further testing at the PCM.

One thing you might check that's really easy......is your PCM warm to the touch with the key off? When mine went the PCM was very warm to the touch......my first indicator to put a meter in series and find the current draw.

Just something else to consider......the wiring for the CPS is prone to failure along the transmission bellhousing. If you're not confident in DVOM testing, you can always begin with a thorough visual inspection of the wiring harnesses to make sure you don't have a break anywhere, although it sounds like you are competent with a meter.

Scantools are as varying in price as they are in function. For the average DIYer I would say spend no more than $350 on a scantool. You can spend $25,000 if you want, but the basic units will do what you need. Make sure you get one that is updateable via online, and records live and freeze frame data. If you can get one with graphing or a scope function, then all the better. I've been looking at an Autel unit that runs around $325. Craigslist is also a decent place to find these as they typically work or don't.

Here's my thread if you want to read through my diagnostic process. Hopefully it will help save you some time and frustration:

http://www.naxja.org/forum/showthread.php?t=1106580

Click to expand...

Yea funny thing there. I use to work as a TSM for a one hour photo lab chain and the millimeter was something I eventually learned how to use. I got brave and noticed the backs came off. I have the pin out from the pdf fsm I have for a 97. I need a t pin but used a paper clip to probe the back wires and all the ones on the pin out that said 5 volts had no output or very low. It's late and I was getting tired so I've called it a night for now. I need to research scan tools while at work tomorrow. lol! Thanks for the info.

Ghost said:

I need a t pin but used a paper clip to probe the back wires and all the ones on the pin out that said 5 volts had no output or very low.

Click to expand...

I mentioned to a nice older lady I work with that I was looking for a T pin as I knew she did crafts at home. The next day there was a small plastic container with about 300 of them in my box at work! I have T pins for 100 lifetimes if you're near the Portland area.

98NWCherokee said:

I mentioned to a nice older lady I work with that I was looking for a T pin as I knew she did crafts at home. The next day there was a small plastic container with about 300 of them in my box at work! I have T pins for 100 lifetimes if you're near the Portland area.

Click to expand...

Yea I use to build RC planes so I've had them in the past. Never thought of them as a probe. Always just used a paper clip. I see there are some companies on ebay that sell computers. I have to replace the starter wire harness and am hitting up a pull a part Sunday. If I see a PCM is it worth a shot to grab one? I was told by a mechanic friend/wheeler that the silver PCM have a lot of problems. Apparently he has replaced a few. Also what company makes the repairs and does it right?

98NWCherokee said:

Before you worry too much about a PCM, or continue with any testing, you haven't answered the question about the health of your battery and tune-up hardware. Jeeps do NOT tolerate low voltage, and a marginal battery and/or poor connections can cause ALL kinds of problems. Remember KISS......."Keep It Simple Stupid"

Click to expand...

Battery is fine. I also put a optima I know to be good in it and still same issue. As for tune up parts I assume you mean the dist cap and plugs. I have not checked that simply because I know the FP relay is not engaging. It seems more of a electrical issue. I missed this part of the post last night. Hopefully I can make some headway tonight after work. A friend with a snap on scan toll is suppose to come by.

Had a friend/mechanic bring his snap on scanner over. No Bus. Looks like my computer is dead. We also did some more tinkering. The ASD relay and the FP relay were not kicking on. Voltage in was confirmed and all grounds were working. Found a computer repair service on eBay that I'm going to try out. I believe this is the company: http://www.ecudoctors.com/

I would check your local junkyard for a replacement ECU. Depending on where you live you should be able to get one pretty cheap, and be able to make sure this is your issue. If your local emissions laws are strict, you may need to have it reprogrammed with the correct vin from a company like Hot Wire Auto. If you do go this route, try and make sure the ecu you grab is from a vehicle with a similar setup (engine, transmission, etc). Just a thought....

cpefy3 said:

I would check your local junkyard for a replacement ECU. Depending on where you live you should be able to get one pretty cheap, and be able to make sure this is your issue. If your local emissions laws are strict, you may need to have it reprogrammed with the correct vin from a company like Hot Wire Auto. If you do go this route, try and make sure the ecu you grab is from a vehicle with a similar setup (engine, transmission, etc). Just a thought....

Click to expand...

We have no such laws..... I'm trying out a ECU repair service out of Florida. Plan is to hit up a pull a part and see if they have one to have around as a spare. Local mechanic friend says this particular ECU has problems and goes out a lot. Or at least he has replaced them on more then one occasion.

I paid $268 I believe for mine with express shipping. I think they were out of Florida too. My replacement has been working perfectly for 6 months.

Any possibility this Jeep has the factory anti theft system? I wouldn't be surprised to find it in a limited.

conejocherokee said:

Any possibility this Jeep has the factory anti theft system? I wouldn't be surprised to find it in a limited.

Click to expand...

Not sure. I would not even know how to tell. The build sheet is in a thread in the SEC chapter. It did have a key fob listed for keyless entry.

Computer it was. Thanks guys!