You do know the led is polarity sensitive. Did you do it with the plug off the injector? It does sound like you did a valid test...but I'm pretty wary..A regular filiment I get...the LED is "black Magic!" I just can't answer for sure.

Btw right now my hood is up and I have #2 injector unplugged. I tried a small marker bulb, (1156 type socket, with a .6 Amp bulb, round about the diameter of a penny) , And saw nothing. It needs a smaller bulb than that, at least in daylight.

Without me reading back through...it only takes a couple minutes, double check the AC output from the unplugged CPS. I have .4 ACV. Shortly after seeing .3 on my last one I had problems.

Cruiser has written about removing the ECU and going over the springs in the contacts with a dental type tool to make sure they are fitting snug. Myself, I think I would do that before buying a replacement. a "vicious circle" . A bad connection can make heat. Heat can ruin the temper of the spring/contact, then more resistance and heat.

I think you have a C-101 connector there by the brake booster? There is actually a factory part to re-rout your CPS wires to the ECU around that. > http://www.bc4x4.com/faqs/yj.cfm?cat=5&faqid=164
You can even check for the CPS signal right at the ECU plug. Someone here might know which one it is!

 

Ill double check the connections tomorrow morning and give them a good cleaning. Ill also double check my reading on the cps but i belive i was around .35.

When i checked the injector pulse i had it unplugged, and tried both polarities. I only got the one single flash with one polarity. When i reversed it, i got nothing.

 

Sheez...that's a little borderline I think. I get .4. Hey! You have a Coil to put under the seat for a rainy day. If it's under .35, cranken well, throw it in there with that coil and install Napa# CSS980....I'm on my third CPS if you count the one it came with...(since 02), if you keep it, at some point you might be glad you have a spare.

Not that I know from personal experience, but the ECU's in these seem to be pretty hardy from what I've read here. Wires and connections and things like the CPS come up often though. You DID do Cruiser's C-101 cleaning? (well)

I'm in and out working on a few projects.....watching for a little dash bulb for that niod light. Only 30 acres to check...I'm sure there is one here somewhere! (I DID try that before and got ZIP, but I want to double check) Also I might try a regular two cell (3 V) flashlight bulb. I would expect it would blow that though.

 

Im going to run to the local junk yard and grab a ecu out of a jeep and a cps tomorrow. What models of jeeps have interchangeable ecu's? Would any renix 4.0 ecu work? Does it have to be out of a 5 speed jeep since mine is?

Ah i love electrical. Not.

 

Im going to run to the local junk yard and grab a ecu out of a jeep and a cps tomorrow. What models of jeeps have interchangeable ecu's? Would any renix 4.0 ecu work? Does it have to be out of a 5 speed jeep since mine is?

Ah i love electrical. Not.

 

I'd make sure it's not the CPS or it's wiring before I spent more $ on parts. Btw I did check injector power with Led's. (I have hundreds of them here, UV, bright and soft). I couldn't log on to U tube for some reason. Anyway with three in parallel, one would blink while it idled. Edit...I deleted some incorrect diode wiring.

Cruiser once posted, (and it's about 7 lines down in my sig), " If you're going to the JY, get one out of a 1989 or 1990 with the part number ending in 428" I'm sure that applies for 87&88. The later are better. Do make sure if you have an auto trans, get one for an automatic. I'm not sure about a manual trans.

If the CPS and its wiring are not right, you could try a dozen ECU's with the same result.

Cool you are homing in on the problem. Victory is at hand!

 

Well my trip to the junkyard failed. Couldn't find an ecu out of a jeep that would work. But i did stop by the parts store and grab a new cps just in case. After about 2 ours of wrenching in the rain in my driveway in the dark, still no fire. I didn't get a chance to check the new cps though because my neighbor threw a hissy fit and called the cops because the music coming out of my phone was too loud. People these days.

Also i haven't cleaned any connections yet. Its on my list before i buy anything else. Cant hurt i guess.

Thanks for the help again

 

I DID mean IF it tests low. Also it's smart to go with a CPS from Jeep or Napa. Anyway the CPS signal needs to make it trough that C-101 connector to even tell the ECU to do anything. Myself, I wouldn't be buying anything until that's known not to be the problem.

You did do Cruisers sensor ground test I hope! Anyway sounds like the CPS, it's wiring, or the ECU. BUT! If the CPS (and wiring), gets the injectors firing but still no spark, then I'd suspect the ICU.

You following me? The ECU can do nothing without a signal from the CPS. If it's getting a signal and firing the injectors, I'd think of the Ignition Control Module (on the coil), before I'd invest in an ECU.

I hear one ECU bolt is tough, and can be left off re-installing.

 

Haven't bought anything else yet, but now i have i different problem.

I pulled apart the c-101 connector and gave it the best cleaning i could. Now when i crank the engine, theres no injector "pulse". I just have a solid light, and a strong smell of fuel.

Im thinking about chopping it out to eliminate that being a source of my problems.

My new cps is at .3 volts when cranking. And has resistance of 215ohms. But then again i dont know for sure if thats true or not. I don't trust it because my multimeter got left out in the rain. Whoops.

Ive found a diagram to use that tells me what connectors i need to test at the ecu for the cps signal, but for the life of me i cant understand it. Would it be the white/black and violet/black?

Thanks for the help again.

 

I'm looking> http://www.bc4x4.com/faqs/yj.cfm?cat=5&faqid=164


About 1/2 way down ;
Locate "C1" (violet with a white tracer). Using pliers gently pull out the wire at terminal "C1". With the wire towards the center of the terminal block slide the new wire labeled "C1" (White with a black tracer) into the hole until it seats.

OK, that's confusing because he's swapping in the bypass harness which is also color coded.

 

It looks like C1 and D1. I need great light and magnification to see some of that stuff.

Listen, I'd check my harness for any sign if anything burnt. If one wire shorts and gets hot, it will cut right through the insulation of other wires next to it and short to them. I'm thinking when you worked on the C-101 something was jostled. That could be why you have full time power to....wait "all injectors"? Idk, that doesn't sound right.

I'd hazard a guess that full power to all injectors is not the CPS... Hit the ecu with a (small) hammer!"

You are going to need a CPS signal to the ECU, weather that one is toast or not. Likewise you can't have melted, shorted wires....

I might see if that noid light stays on when I jiggle the wiring around that c-101 you worked on.

If my grounds tested good, and I had .35 or so to my ECU, and no injector pulse, and no spark I'd probably be looking for an ECU. In your case since the welder might have killed anything, the ICU could be suspect as well. (but with no injector pulse, she is not even trying is my .02)

 

Heres another mystery for you.... I found c1 and d1 just now. Thieve been tapped into at the ecu. Cut and twisted together. I followed those wires into the engine bay. The go up towards the brake booster, then stop at a 3 pin connector. Their zip tied to the c-101. I never did that and it was running without that connector plugged in. Hmmmm

 

I don't know whats going on with my phone. It said it didn't post those pictures. So i tried a couple more times and it kept saying the same thing. Sorry

 

If you cared you could "delete attachment". I cared once when it waz a private photo of my GF! (click edit> then "go advanced" > remove attachment)

This has come up a couple of times. Those who already have a bypass will have that 3 plug connector (with only two wires), left hanging there. (is my thought.)

I might check continuity (ohm's of resistance) , from the cps plug to those two, then if good connect them right, (or maybe solder them)

Or just run new wires. Even though we test for AC, I'd try to respect the polarity. Since the color code on the new CPS likely doesn't match I'd use the position on the three wire connector as a guide.

 

She lives!! Plugged that other connector into the cps and it fired right up. But now I'm confused. Why did it run before?! Oh well. That doesn't matter as long as shes running now!

Thanks again for all the help! I really appreciate everything you've done to help me out. And thank you for sticking behind a noob with electrical. I know i was probably a pain. Thanks!