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Jeep won't start
- Thread starter Xjo90
- Start date
You need a fuel pressure gauge to screw into the fuel rail to tell if there is pressure. On thing you might want to do quickly....is swap relay in the relay bank....One of them controls the fuel pump. Also check coil and make sure all wires going to coil are secure. Another way to test the fuel pump for basic "it turns on" test is to turn the ignition key 3/4 forward. (almost start) and listen with the door open to see if you can hear the fuel pump initially spin up. (it only does it for 2 secs...but will do it every time you turn the key 3/4 forward)
5-90
NAXJA Forum User
- Location
- Hammerspace
If you have better than 150K on your XJ, and don't know how old the CPS is, plan on replacing it. Expect to pay about $40 at the dealer (only place it can be had) and have at least 3 feet of ratchet extensions on hand (as well as a 7/16" or 11mm socket with the inbuilt U-joint) to change it. A small magnet to hold the bolts in the socket will also be a huge help!
The Schrader valve on the fuel rail is standard GM, so any fuel pressure test gage that will connect to a GM fuel rail will work.
If you are not getting fuel, and you are not getting spark, the CPS is definitely the culprit. The CPS generates the base timing signal for both fuel injection and timing, and losing that one sensor will kill BOTH signals. If it's either/or, work back thru the systems.
Given the age of your XJ, I'd start with the CPS anyhow. It's due to fail in the first place (average service longevity seems to be 100-150K miles.)
5-90
The Schrader valve on the fuel rail is standard GM, so any fuel pressure test gage that will connect to a GM fuel rail will work.
If you are not getting fuel, and you are not getting spark, the CPS is definitely the culprit. The CPS generates the base timing signal for both fuel injection and timing, and losing that one sensor will kill BOTH signals. If it's either/or, work back thru the systems.
Given the age of your XJ, I'd start with the CPS anyhow. It's due to fail in the first place (average service longevity seems to be 100-150K miles.)
5-90
martin
NAXJA Forum User
- Location
- Huntsville, AL
XJo90,
Lets go back to basics, you need spark and fuel to make an engne run. How do you check these on our version of the XJ since we can not read error codes, since the computer does not store them, and there is no customer way to read the computer.
I highly recommend you get the factory manuals for you XJ, they will pay for themselves. If you need informaiton like today then sign up at www.alldatadiy.com and get a subscripition for your XJ. Either source should tell you how to check fuel pressure and what value it should be.
For FUEL you need to verify you have pressure in the fuel line and that the fuel pump does work.
For SPARK try to barrow a timing light and hook it up to #1 cylinder, actually any cylinder would work, and crank the motor. If it flashes then you are getting spark. If it not them my first supsect is the Crankshaft Position Sensor (CPS). With our XJs their are two versions of the CPS - standar and high altitude. They are the same price. The high alt gives you more advance which means more power don't worry you have a knock sensor so you will not have any pinging. Go to the dealer to buy it, either way I'd get the high alt - more power for no additional money that a no brainer
If you do have pinging then time to replace the knock sensor. Some people NAPA sells them but I know I got a new one at the Jeep dealer.
Lets say you do have spark that could confirm you have a bad camshaft position sensor. It is burried inside the distributor and is a Hall effect sensor. It tells the computer and 3 injectors fire fuel. The key question is "do you smell gasoline after you long cranks?" if you do then I'd say the camshaft positon sensor is good, it also called the sync sensor. If this sensor is bad then time ot install a rebuilt distributor to get a new sensor, either way you may have warn bushings. On my 69 Camero with the 230 straight 6 we changed the distriburor at 80,000 miles and 150,000 miles. So distributor bushings wear. It more important on a car with points and condensor but still is important for an electronic controlled engine.
Do those tests if you can but like 5-90 I think it most likely the CPS, doubt it the sync sensor. Either way with If you have over 100,000 miles on the engine then I'd consider a new/rebuilt distributor as preventive maintenance.
Lets go back to basics, you need spark and fuel to make an engne run. How do you check these on our version of the XJ since we can not read error codes, since the computer does not store them, and there is no customer way to read the computer.
I highly recommend you get the factory manuals for you XJ, they will pay for themselves. If you need informaiton like today then sign up at www.alldatadiy.com and get a subscripition for your XJ. Either source should tell you how to check fuel pressure and what value it should be.
For FUEL you need to verify you have pressure in the fuel line and that the fuel pump does work.
For SPARK try to barrow a timing light and hook it up to #1 cylinder, actually any cylinder would work, and crank the motor. If it flashes then you are getting spark. If it not them my first supsect is the Crankshaft Position Sensor (CPS). With our XJs their are two versions of the CPS - standar and high altitude. They are the same price. The high alt gives you more advance which means more power don't worry you have a knock sensor so you will not have any pinging. Go to the dealer to buy it, either way I'd get the high alt - more power for no additional money that a no brainer
If you do have pinging then time to replace the knock sensor. Some people NAPA sells them but I know I got a new one at the Jeep dealer.
Lets say you do have spark that could confirm you have a bad camshaft position sensor. It is burried inside the distributor and is a Hall effect sensor. It tells the computer and 3 injectors fire fuel. The key question is "do you smell gasoline after you long cranks?" if you do then I'd say the camshaft positon sensor is good, it also called the sync sensor. If this sensor is bad then time ot install a rebuilt distributor to get a new sensor, either way you may have warn bushings. On my 69 Camero with the 230 straight 6 we changed the distriburor at 80,000 miles and 150,000 miles. So distributor bushings wear. It more important on a car with points and condensor but still is important for an electronic controlled engine.
Do those tests if you can but like 5-90 I think it most likely the CPS, doubt it the sync sensor. Either way with If you have over 100,000 miles on the engine then I'd consider a new/rebuilt distributor as preventive maintenance.
Can anyone explain where the CPS is located? The same thing hapened a year ago, changed cap, wires and plugs to start and the problem disappeared. I figured its the same problem, i guess I never fixed it. Can the CPS be a intermittent problem.
Thanks in advance.
Thanks in advance.
I
imma honky
Guest
CPS is on the bellhousing of the DRIVERS side tranny. Its in a tight spot. You will need at least a 10" extension, and at least 1 joint. I picked my CPS up at Adv. Auto for $30 in stock. You will most likely need to widen one hole on the CPS (i had to, one bolt was slightely bigger than the other). Easy swap once it is out, getting it out was the hard part for me......and gettign it back in til i figured one bolt was slightly (maybe 1/2 mili) bigger than the other. Hope this helps.
5-90
NAXJA Forum User
- Location
- Hammerspace
Hey honky -
What's the mfr and p/n on that replacement CPS, and what year XJ was it for? I've yet to be able to find one in the aftermarket!
As for location, the CPS is at 11:00 on the rear of the engine if you are looking right at the flywheel. A 10" extension isn't anywhere near enough, really - when I found a 36" extension used it cut the time ont he job for me from about two hours of fighting to about 10-15 minutes. Also, if you have a Dremel and a cutoff wheel (and a fairly steady hand!) you can simplify installation by doing the following...
(assume you are looking at the sensor in the "installed" position. Sorry, but I don't have any pix!)
1) open the "bottom" hole, as installed, straight out toward the end of the bracket. You may "flare" it slightly, but be sure NOT rpt NOT to actually enlarge the part of the hole where the bolt goes! The effect here will be to be able to slip the CPS bracket onto the bolt endwise.
2) Open the "top" hole stright out toward the bottom of the bracket (not the end.)
The idea here is that you will be able to have the bolts in place, put the sensor on the bottom bolt, rotate it down onto the top bolt, and tighten the bolts. This makes it far easier than fighting with the bolts and the sensor at the same time, and is worth the extra few minutes it takes to do the grind work. I think someone somewhere has posted how to do this, with pictures, but the location of such a pages eludes me for the moment. Perhaps someone else can help?
I think the principal reason the CPS is prone to fail eventually is heat - there isn't a great deal of airflow over it in its installed location, and the wiring and sensor proper are both awful close to the exhaust header. NOTHING electronic likes heat - even just something that's really a coil and core. Given time, heat will cause a component failure, and the location of this particular component is just really incomvenient. HESCO makes a kit that uses a modified crank damper and relocates the setup to the front of the engine, for your reference.
5-90
What's the mfr and p/n on that replacement CPS, and what year XJ was it for? I've yet to be able to find one in the aftermarket!
As for location, the CPS is at 11:00 on the rear of the engine if you are looking right at the flywheel. A 10" extension isn't anywhere near enough, really - when I found a 36" extension used it cut the time ont he job for me from about two hours of fighting to about 10-15 minutes. Also, if you have a Dremel and a cutoff wheel (and a fairly steady hand!) you can simplify installation by doing the following...
(assume you are looking at the sensor in the "installed" position. Sorry, but I don't have any pix!)
1) open the "bottom" hole, as installed, straight out toward the end of the bracket. You may "flare" it slightly, but be sure NOT rpt NOT to actually enlarge the part of the hole where the bolt goes! The effect here will be to be able to slip the CPS bracket onto the bolt endwise.
2) Open the "top" hole stright out toward the bottom of the bracket (not the end.)
The idea here is that you will be able to have the bolts in place, put the sensor on the bottom bolt, rotate it down onto the top bolt, and tighten the bolts. This makes it far easier than fighting with the bolts and the sensor at the same time, and is worth the extra few minutes it takes to do the grind work. I think someone somewhere has posted how to do this, with pictures, but the location of such a pages eludes me for the moment. Perhaps someone else can help?
I think the principal reason the CPS is prone to fail eventually is heat - there isn't a great deal of airflow over it in its installed location, and the wiring and sensor proper are both awful close to the exhaust header. NOTHING electronic likes heat - even just something that's really a coil and core. Given time, heat will cause a component failure, and the location of this particular component is just really incomvenient. HESCO makes a kit that uses a modified crank damper and relocates the setup to the front of the engine, for your reference.
5-90
5-90
NAXJA Forum User
- Location
- Hammerspace
I almost forgot - the CPS can be an intermittent problem, IF the wires have been melted clean and they are grounding out on the exhaust manifold. Start at the 3-pole Weatherpack cnx at the rear of the intake manifold and follow it back (that's the CPS harness cnx,) looking for melted/bare spots on the way. You can j-u-s-t see the CPS from the top of the enging with a little contorting and a good torch!
You still haven't mentioned how many miles you have, but going just from the model year, I'd plan on changing the CPS anyhow. It's either worn or starting to (finally!) melt. When you put the new unit in, make sure to add some sort of protection for the cable. I didn't have any "fire sleeving" handy, so I used the split loom for an extra layer until I can get some in. Every little bit helps...
5-90
You still haven't mentioned how many miles you have, but going just from the model year, I'd plan on changing the CPS anyhow. It's either worn or starting to (finally!) melt. When you put the new unit in, make sure to add some sort of protection for the cable. I didn't have any "fire sleeving" handy, so I used the split loom for an extra layer until I can get some in. Every little bit helps...
5-90
XJ-wheeler
NAXJA Forum User
- Location
- Phelan CA
I had a no-start problem on my 1990 and I wasn't getting spark. it ended up beging the plug on the coil mount. The coil sits on top of the mount and the plug comes out of the drivers side. Check that plug and make sure the points on it are not burned. that was my problem. It was not the coil its self but the mount under it. Tyson
I
imma honky
Guest
xj-wheeler, when you say "coil" which one do you mean? B/c my jeep is still not running and we checked the ignition coil, but its on the passenger side. It also sits on a mount that we think might be the culprit. Is this what your talking about?
