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  #1  
Old August 5th, 2018, 21:29
crwdwg crwdwg is offline
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No Crank, No Fuel, No Start, All Sens Pwr'd

First of all, I am very new to this forum and if this issue has been addressed somewhere else...please let me know! Secondly, I am a seasoned mechanic in both air and ground vehicles, although, I have been known to become frustrated with an issue and miss the K.I.S.S. items. The problem: My daughters 88 XJ, 4.0 had been running with a wavering idle, slow shift response, and a sluggish take off with an very audible backfire. I diagnosed a faulty CPS, TPS, and IAC. All of them were replaced and the TPS was set correctly using an ohm meter. It ran great for a day, then the problem came back ten fold. Sans a fuel pressure tester, I replaced the fuel pump thinking a lack of pressure may be causing some of the issues. When I turned the key to start nothing happened at all. I have power to all engine sensors, lighting, and interior electrical items. All relays in the engine compartment have been checked, the start relay is functioning properly, the battery is less than 24 hours old with a good charge, all grounds have been checked and refreshed, the starter checks out with an external jumper switch, and I disassembled, cleaned, and reassembled the Neutral Safety Switch which ohm'd out good in all gears. I even had a spare ECU that I plugged in to see if that was the issue. Of course I also had a spare Ignition Switch that I threw in to no avail. I still have no power to the start relay! Today, I decided to buy a new ignition switch and after connecting it and turning the key, it cranked for less than a second.....then nothing...No power in the start position! Could a bad fuel pump cause all of this? If so, could that faulty pump fry an ECU? At this point, I'm ready to gut it and drop in a 350! Any help, idea, or kick start would be great at this point! Thanks in advance!
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Old August 6th, 2018, 03:13
Jim Malcolm Jim Malcolm is offline
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Re: No Crank, No Fuel, No Start, All Sens Pwr'd

You say "no power to the start relay". Is that to the battery hot terminal or coming from the ignition switch? I suspect it's a wiring issue. The components are good but there's a break in the wire or a loose terminal somewhere. You're going to have to trace it. Do the gauges move when you turn the key?

The computer is connected to the starting circuit only to know when it's being started. If the wire or input to the computer was completely grounded out, I guess it could prevent the starter relay from activating, but otherwise it has no input into the starting circuit.
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Old August 6th, 2018, 06:54
CJR CJR is offline
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Re: No Crank, No Fuel, No Start, All Sens Pwr'd

Here is something to try that worked on my 00XJ which had similar no-start problems. Take your jumper cables and clamp one end to one of the starter motor housing mounting bolts and the other end to the negative terminal of the battery. See if it starts when you turn the ignition key to start. If it does start, the starter motor has a bad grounding system. In my case, I made up a #2 welding cable and connected one end to a starter mounting bolt and the other cable end to the negative battery terminal. Problem solved.

Best regards,

CJR
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Old August 6th, 2018, 22:22
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8Mud 8Mud is offline
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Re: No Crank, No Fuel, No Start, All Sens Pwr'd

The starter relay circuit is really simple. Green wire "I" pin, power in, actuates the relay, comes from the ignition switch. The Black wire (with tracer) completes the relay activator circuit through the neutral safety switch in the auto trans to ground.

None of it goes anywhere near the ECU.

You'll get no fuel or spark unless the motor is turning over, safety feature- The fuel pump will prime for a second or two when you first turn the key to run, but the fuel pump won't really work continiously unless the ECU is getting a good pulse signal from the CPS during crank and/or motor running.

As far as your bucking problem goes, it could be many things, anything from some mechanical issue, to ignition crossfire or something in the sensor circuits.

The CPS wire has a tendency to cook on the exhaust manifold, you have to be careful where you run it and tie it up well out of the way.

The ground path from the TPS is a known trouble spot and has many possible choke points.

Slow shift points kind of indicates something with the TPS, but first you have to adjust your TV cable and ohm test the TPS ground or you are just wasting time. I had a TPS ground circuit fault in one XJ I chased for over a year. It was a non crimped splice just sitting in the crimp connector. Sounds easy, there are numerous splices in the injector loom, finding that one wasn't
as easy as it sounds. Not likely to be your issue, but it had nothing to do with the actual TPS. Side note, the TPS is seriously moisture sensitive, if it gets wet, bad things happen.

A tip, most people go straight to swapping sensors, I've been screwing with the early XJ's since 87, maybe one time in three or less it is the sensor. The wiring and connectors suck. And the system has the same problems as any earlier non sensor motor, spark plug cables fail, distributor caps get full of moisture or dust etc.
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Old August 7th, 2018, 12:44
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Flyfisher Flyfisher is offline
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Re: No Crank, No Fuel, No Start, All Sens Pwr'd

^^^ All good advice from 8Mud, but I've got to wonder. Consider the sequence of events, changed TPS, IAC, and CPS and it worked great for a day, then began to run poorly. What would cause that to happen? Poor connection to one of the recently installed sensors? Poor adjustment or fastener torque on one of those sensors. I mean, nothing else changed!

Then you changed the fuel pump and ended up with a no crank situation. I don't believe the fuel pump circuit has any effect on the starting circuit. Is it possible you bumped something, loosened a wire? Did you disconnect the battery during any of this work? If not, it may be possible you caused a short somewhere during the work that affects the starting circuit.

Then you changed the ignition switch and you got it to crank only briefly. Did you adjust the ignition switch? It needs to be adjusted to work properly on all key settings (acc., off, run, start). To at least get it to crank, I would suspect ignition switch adjustment first. Once you get it to crank, then you can see how it runs and chase down a poor running condition separately.

Good luck!
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