CPS Replaced, No Spark Still......

[ihscoutlover]

I am going to start backprobing/checking the fuel system, since I now have the spark figured out, and the check engine codes are showing clear. I have been working on charging the battery overnight, so that I can have a true 12 volts in the system to continue testing. I think next I am going to jumper the #2 and #4 pins on the relay and check the voltage back at the connector by the fuel filter and see what I get there. I think too, I am going to change the filter(since I am already back there), and see what comes about with that changed out, and see if I still have good pressure, as well as correct voltage/power by then. I will report back my findings. Also my other ECU came(thanks Matt), and we will go from there, as I will still be using my current one, in case there is a short/problem that I cannot locate, so I don't F up the replacement one.

Jeff

 

[Milhunter23]

Im sure you have checked this already but if not check the tip of your rotor that spins around. I have found that some of those tips like to fall off pretty easy. Make sure that it has that small Tee tip at the end of it. This would cause you to have no spark as well. happened to me and I went nutz trying to find out the prob when it was something so simple

 

[ihscoutlover]

Yup. The rotor that was in it was dirty, and I just cleaned it up enough to do my testing, since I am going to be replacing all this stuff for now till I can get my performance coil, wires and cap rotor combination. I got all of that stuff clean enough to get me a spark, so I know that its sparking now, but its the fuel issue I need to get licked. Should be posting up my results within the next 24 hours, as I am letting the battery get a full charge, and then I will pull some wires and get started on the fuel pump issue.

Jeff

 

[Jalves619]

I'm in almost the exact same situation right now. After a week of poking around with a multimeter, I gave up and took mine to a mechanic who scanned it and came to the conclusion that the ecu was fried, but when I gave him another to try out it didn't change anything. I'll be keeping an eye on this thread and if I come up with anything useful I'll interject again.

 

[stockli]

It starts if you spray ether in the tb?

did you do a pressure test on the rail? Im sorry for asking stupid questions but I got a headache reading the thread lol.

Did you see if your fuel filter is plugged up? Bad regulator?

 

[Matthew Currie]

I'm still betting that at least one problem, if not the only one, will be a bad ground at the fuel pump and sender.

 

[stockli]

I'm still betting that at least one problem, if not the only one, will be a bad ground at the fuel pump and sender.

Good point. Has the fuel system been isolated as a cause? I mean a mechanical or electrical issue been ruled out in the fuel system?

 

[ihscoutlover]

Update. I back probed the wiring for the PCM. I found that the incoming voltage on the #9 pin was system voltage(12V). I then turned the key on, and found that the voltage on the coil feed was beween .01 and .04 volts. But after realizing that I still had my plug tester on the coil wire, I cranked it from under the hood and the blue and white sparks were a great sign. I went ahead and hooked the coil wire back up, and put some starting fluid down the TB, and it fired up, then died pretty quick. Now its not getting fuel. I am going to diagnose the fuel pump circuit and see whats going on there. I got spark now, however I think that the PCM is still acting up. So once the replacement one gets here I have a way to try and see if my PCM is bad or not. That's all for now, and thanks Ron for the advice.

Jeff

It starts if you spray ether in the tb?

did you do a pressure test on the rail? Im sorry for asking stupid questions but I got a headache reading the thread lol.

Did you see if your fuel filter is plugged up? Bad regulator?

No pressurization of the fuel rail at this time. I am still working on checking out the grounds on the pump assembly, and the harness to verify voltage is either there, or not, and how good or bad the ground is. I am going to pull and change the fuel filter first to make sure the pump doesn't have to work as hard to get fuel to the fuel rail. I am also going to direct wire the pump to 12v to make sure it works as well. This testing should yield me some results. I am still looking to possibly replace the ECU, as it has been intermittant on its operation, as I have checked all grounds and probed the wiring and I am getting different results each time I test it or the other components. I will post up my results as soon as I get some.

Jeff

 

[stockli]

Try turning the key to run and listen for the pump to pressurise then push in the schraeder valve and see if gas comes flying out. It should.

 

[ihscoutlover]

It's not doing either. BTDT. I am trying to determine if the ECU isn't doing its part correctly, or if the actual pump is intermittant or bad. I'll post up when I have more information.

Jeff

 

[ihscoutlover]

Ok here is an update. I swapped the computers to see if my results changed. Well they did, sort of. First, it still shows empty on the fuel gauge, with at least 5 gallons in the tank. I am still not getting the fuel pump to engage, either with a jumper in the relay slot or not. I haven't direct wired the pump to 12 volts to verify its operation yet. However, I consistently get the check engine light to operate correctly with this computer ALL the time. It was intermittent with the OE one that was on the Jeep when I got it. Everything else seems to be ready and operating correctly so now I am concentrating on the fuel pump. I will post more once I have tested the pump, and I am wondering if there is some kind of problem with the sending unit/pump assembly, so I may be going back to the JY to get another complete assembly for testing/comparison. Thanks Matt, I think the intermittant computer issue is fixed, now I can concentrate on the fuel side and make sure that I have the pump and other parts operating correctly.

Jeff

 

[Ecomike]

Just for fun, try running a ground wire from the battery negative post to the Gas tank and ground wire on the fuel pump, at the fuel pump. The fuel pump and sensor may be using a common ground?

 

[Matthew Currie]

Just for fun, try running a ground wire from the battery negative post to the Gas tank and ground wire on the fuel pump, at the fuel pump. The fuel pump and sensor may be using a common ground?

Yes, the pump and sensor do use a common ground, and in case it was missed (I tend to run on, I know), since the gauges on this vintage XJ work backwards from the traditional way, if the sender is shorted or if the pump is seeking ground through it, it will pin the gauge at empty. Ground would be my first suspect.

 

[ihscoutlover]

Update: Its Alive!!!!

I got it to fire up and run on its own finally. I changed out the fuel pump, as the pump failed to run with 12v directly hooked to it. The new pump works as it should. It died on me initially, but I think some air was in the lines from replacing the filter, pump and stuff. Now its put some fuel in the tank, and some fuel system cleaner in it and I should be good from this aspect. Now its change and flush coolant, tranny fluid, and xfer case fluid. Then diffs and some brake work. Seems strong, a little more hesitant than my last '94 on starting(takes longer to crank over to start). Otherwise then the exhaust needs to be replaced from the manifold back, but I am contemplating the header also being replaced. Thoughts or suggestions?? Thanks for all the help I have learned a great deal of new testing and such, and even having the FSM has taught me stuff as well. I will try and post up a video later of it running and you all can hear it and advise me if I am barking up a good or bad tree based on the upper noise I am hearing. Oh and the AC seems cool too, so that's probably in excellent shape, which means I actually have a vehicle with AC now(till I can find another '94 as well).

Jeff