HudsonN

Just put another transmission and TCase into my 99 XJ.

Drove it flawlessly for ~250 miles without a single problem.

Today it just randomly stalled while driving. Now it just cranks and cranks and won't start.

My guess is CPS for that issue but I've never seen the "no bus" before. Ideas?

DJeXeCute

Pull the instrument cluster and clean all the connections male and female.

CCKen

A defective CPS will cause a no bus situation.

Unplug the CPS and turn the key to RUN and see if the instruments work and the no bus goes away.

When you changed the transmission the CPS may have been damaged or it wasn't secured properly.

RTorrez1

I second that it's a problem with you CPS. If you do replace it go with an OEM.

tjwalker

Great advice as usual from Ken.

Although anything along the "bus" including all 5 volt sensors and the computer can cause a NO BUS - NO START, the most common cause is the crankshaft position sensor.

The above quick and dirty test noted by Ken will tell you if this is the culprit.

Roadking_

My 94 Cherokee had cps go out while driving. Was like a light switch. Killed engine. Was lucky after cool down it started and got me home. Replaced with one from dealer no problems last 4 years.

HudsonN

I figured it was a CPS situation, just didn't know if no bus and CPS issues were related.

Just unplugged the CPS. Gauges still don't work. Plugged it back in. Still just cranks and cranks no start.

I do have another OEM CPS sitting around but for some reason i'm almost 100% positive the CPS in there is a OEM CPS i bought from chrysler about a year ago. (Unless i mixed them up during the transmission swap.)

I also noticed that the firewall ground to the cylinder head bolt was broken in half. I re-grounded that and still nothing. Obviously i'll fix that as well, but that's not my problem either.

I'll throw a new CPS in tonight and see if that resolves my problem.

CCKen

Looks like there may be more than one problem afoot.

Crank but no start and no instruments.

Concerning no instruments: There have been several XJ's with no instruments and no bus due to poor ground connections in the engine bay. Before getting into cleaning all the ground points in the engine bay, do this simple test. It says it's for the braided strap on the firewall but it also checks the ground cable at the right fender. Tell us what you find.

XJ Body Ground Connection Test

This test checks the condition of the vehicle body ground connection (Braided cable on firewall to engine cylinder head bolt). This test should be performed with the battery positive cable removed from the battery.

Start: Disconnect both battery cables, the negative cable first, then the positive battery cable. Reconnect the battery negative cable and perform the test as follows:

(1) Connect one ohmmeter test lead to the vehicle fender. Connect the other test lead to the battery negative post.

(2) The resistance should be less than one (1.0) ohm.

(3) If the resistance is more than one ohm, check the braided ground strap connected to the engine cylinder head and the vehicle body for being loose, corroded, or damaged. Repair or replace the ground strap connection and replace bolt at firewall connection or nut at engine cylinder head bolt connection, if required.

Finish: Disconnect the negative battery cable. Reconnect positive battery cable, and then connect the negative battery cable.

HudsonN

Just replaced the CPS with another CPS. (a chrysler one but an older one i had. Not sure if it actually works.)

Jeep still doesn't start. Just cranks and cranks.

Cleaned the battery terminals and replaced the firewall to head bolt ground with a nice new ground.

Took out my fuel pressure gauge and put it on the port on the fuel rail. 0 PSI.

No Pressure at all. Don't hear the pump priming or anything. Swapped the ASD relay into the fuel pump one. Still nothing. No pressure at the rail.

Bad fuel pump or is this another sign of a bad CPS?

Still had a No-bus, engine light on, but my code reader can't establish a connection.

DJeXeCute

Last time my cps went out the pump was still priming. Might be changing a fuel pump.

HudsonN

I'm afriad you're right.

I just thought that the CPS was directly related to the fuel system? Like i thought it cut fuel if it went bad.

Maybe i'll just replace both. Haha.

CCKen

If you changed the CPS and still have No Bus, you have more problems than fixing it by changing the fuel pump.

Roadking_

If you have spark the CPS is working. Use an old plug with insulated pliers and remove a wire and connect to plug hold next to block or head and get assistant to turn over engine. You prob have spark. I'm betting fuel pump or a clogged line.

CCKen

Do you think a fuel pump or a clogged line causes a No Bus?

tjwalker

I'm with Ken on this. A NO BUS is a computer bus issue and should have nothing to do with the fuel pump circuit.