Wrecked '90 XJ

I just picked up a '90 XJ that had been wrecked and parked. Decent project, and for $100 I can't complain a bit. Body damage minimal, but the kid that owned it decided to take stuff apart to see how it works :twak:


Anyhow, all the wiring was disconnected under the dash. Got it all back together and the engine cranks but won't run--no fuel. Have power at the relays, but it's not getting back to fuel pump. Is there anything between the relays and the pump itself that would fail, or am I looking for a short?

Going over the wiring diagrams, I've found the diagnosis ports under the hood, but I have a large cluster harness on the passenger side laying in the floor. Everything's plugged into the computer, but it looks like the end to a computer cable. It's a blue/grey housing with C and D 1-16 markings. Is this a diagnostic cable, or is something supposed to be plugged into it that's missing?!?


Thanks--

dubby

dubbyx said:

I Everything's plugged into the computer, but it looks like the end to a computer cable. It's a blue/grey housing with C and D 1-16 markings. Is this a diagnostic cable, or is something supposed to be plugged into it that's missing?!?


Thanks--

dubby

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I believe that's the TCU plug for the transmission...........shoud have a module there for the transmission to work correctly.
Are you the dubby from SFT?

Yup. That's me.

TCU huh? Crud. Happen to know where it mounts under the dash? Maybe it's still there and just unplugged... *I hope*


I havn't seen it on the wiring diagram pack I'm using, but its for an '88. Might be an issue here, but it's been dead on everything else so far. I did see a number of sensors and switches that are associated with it running, but I wouldn't think they'd completely cut off the fuel supply.

dubbyx said:

Happen to know where it mounts under the dash? Maybe it's still there and just unplugged... *I hope*.

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It should be mounted to the back of the passenger side dash.
I had to remove the complete under-dash piece across the bottom to gain access to it. It is mounted on two bolts that are affixed to the dash panel.

B Raider, where are you in texas?

Check for a big white ballast resistor on the front drives side inner fender wall. Some years had one and if it dies it kills the power to the fuel pump. Not expensive, less $10 probably. You can test it by shorting across the wiring harness connectors to see if the fuel pump turns on. Or ohm the resistor if there is one. Should be real low like less than 100 ohms, maybe even 10 ohms.

Check the fuses too.

From what I've been able to find on the TCU, it doesn't necessarily have to be plugged in?

I'm pretty sure it's missing from my truck, but it does have the Comfort/Performance switch on the dash so I'm guessing it'd be of benefit to have that. Do parts stores carry these? I havn't found anything but a specialty shift box so far...


There is a big white chunk of a thing on the driver's side inner fender. Two orange wires do indeed hook up to it, so I'll give that a shot. I'm sure my neighbors think I'm crazy walking back and forth with a flashlight trying to solve this.

dubbyx said:

From what I've been able to find on the TCU, it doesn't necessarily have to be plugged in?

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That statement is true....when it is unpluged you can manually shift the gears. When mine was plugged in, it defaulted to first gear only .... until I found real demon lurking in a cut wire and missing trans fuse.
That's how I found out there was nothing wrong with my transmission and it was an electrical not mechanical problem.
The information found here on is amazing to say the least.

I tried the white chunk. It was indeed less than 10 ohms, 5.3 to be exact. I went ahead and jumped it and tried anyhow with no result.


The wife doesn't know it yet, but when she gets back into town she's got a lot of helping out to do. Seems like everything on these rigs is spread to one end or the other, and sitting in the middle does no good .

It's been fun for the last couple weeks though, and the upgrade parts pile is growing steadily. And to think, the only reason I originally bought it was for the front axle...

Try reading the "How to Troubleshoot a No Start XJ" thread to see if anything in there that might head you in the right direction.
It's in the FAQ section at the beginning of the forum.
Here's the link:
http://www.naxja.org/forum/showthread.php?t=101119

Was this thing roled in the wreck. Not sure about the 90, but newer cars have anti roll over switches in the fuel pump circuit. I see the 91 has one for sure.

The first one to check is the fuel pump relay, also check the ignition switch, fuse box and fuse link. You should be able to hear the fuel pump kick on, its loud, when you turn the power on (run position, not the start position. IF you do not hear it, and / or there is no power to it (tested with a meter when you first switch the power on note that it cuts off after a few seconds, so the ECU must have an internal timer setting for shutting it off) then it is a wiring or relay. or ignition switch problem (assuming the fuel pump is good). This means the ECU must have power too, in my opinion. Yes, I see the wiring for it!

So, check for a bad ground wire!!!!!!! The ECU grounds the fuel pump relay, if I am reading this right. May be a bad Renix Ground issue, which is common. Check the firewall to engine head ground strap and the firewall to engine block, near the oil filter - oil dip stick tube, ground that runs to the battery too. It has several sensor / ECU grounds there at the block also. If that ground is bad it will kill the fuel pump and the realy itself. Lastly it could be the hot wire from the ignition switch to the fuel pump relay. Its the yellow wire at the ignition switch!!! That same wire also powers the ECU in the Renix years, 87-90.

Also note, for later trouble shooting, that WOT at the TPS shuts of the fuel injectors.

Nope, wasn't rolled. Just smacked on the driver's side front corner. Took out everything from the radiator to the corner, back to the shock bracket. All I had to do was replace the fender, inner fender, and the airbox/hoses in that area. Really, really minor as far as wreck damage goes. I made it disappear in under 2 hours. The parking and digging around has been more of a headache.

I took today off from it, but I'll go over that thread BR, and will check your suggestions as well tomorrow Ecomike. I appreciate the help.

Well I just routed a new wiring harness and on the 99's the ground for the fuel pump was in the back behind the spare tire mount. Check that out maybe. Sounds like a bad ground. Have you checked your fuel pump relay? You could try swapping one of the other relays with it and see if you can at least get fuel.

Just on the off chance, unplug and replug the CPS connection at the rear of the intake manifold and see if it doesn't try to start.

I sure hope it's that simple - bad CPS for whatever reason.

CPS? I'll just unplug 'em all and for lack of knowledge on that one.


Now, I did find another "plug" under it today. Appears to hang off the back/driver's side of the block. 3 prong, too covered in greast to tell any colors. It's been that way for a LOOONG time by my guess (unplugged). I can't see where it goes, either up or down, nor can I tell exactly where it comes out. No voltage detected.


I havn't made it out to our XJ piles yet to scavenge a TCU, but I'm tracing back over everything I've already done to make sure I havn't missed something.

dubbyx said:

CPS? I'll just unplug 'em all and for lack of knowledge on that one.

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LOL......:banghead:
What are you using for a reference as to help in finding where stuff goes and whatnot?
There are several web sites that have tech downloads and tech tips that help out a lot.
I have found these to be of some help.
http://www.lunghd.com/
http://jeepgarage.free.fr/ownersmanual.html

I'm using the second link you posted up above--jeepgarage


Progress today, and more setbacks. With a little help from my lovely assistant (who after a trip to the parts store became b****y-redhead-wife) I was able to do a full check of all the voltages from the front to the rear, and go over many of the already suggested ideas and tips. I learned a lot about how this thing is set up and where all the parts are located. Indeed, the pump was getting juice at first startup and then cutting off as suggested. I disconnected the fuel line at the filter, routed a hose to a jar, and ran power directly to the pump. It worked, for a second, and then cut off. So, pump's bad after all.

When we pulled it out, the screen had fallen off, and the inlet was 20 kinds of nasty. Tried putting in the suggested E7006 fuel pump with no luck. Wouldn't fit. It was too big, and the included rubber isolators wouldn't begin to fit into the assembly. The only way that I could've possibly made it work was to trim them down, and even then the inlet wasn't long enough for the screen to go back in place.

Returned the pump, thinking maybe it was boxed wrong, or for some reason the assembly had been replaced with the E7001 pump. No luck. Cross-referenced every number under the sun to still come back with the E7006. I had enough for the night, and decided to just buy a whole new assembly--$15 more and I have to wait a day for it to show up...

Well, these darned XJ's aren't that difficult. Once you figure it out, they're actually pretty simple, huh?!?

Got it going today. Sounds good, bad exhaust leaks (busted header too) and still needs a good hosing off. Nothing painful though. Tranny shifts fine, wheels spin. T-case does it's thing. Once it fired up, it took a couple seconds of tuning and you wouldn't have ever known it was broken down for 3 years...

Now, to make it stop...


Thanks again for all your help guys. I'll be coming back more and more I'm sure. This truck was acquired to be a test bed for some of my welding and fabricating ideas without jeopardizing the family SUV.

dubbyx said:

Well, these darned XJ's aren't that difficult. Once you figure it out, they're actually pretty simple, huh?!?

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I'm finding that statement to be true for sure. But ya gotta know where to look and what to look for ........but thanks to sites like this one....help is out there.:clap:
Now if I can just figure out just where the Part Time light problem is on mine I'll be a tad bit happier...:dunno: but that's what the search button is for ...huh? LOL

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