I have a 1990 4.0 Auto, fresh rebuild. I cranked it up right away and ran it for 20 mins no problem. I restarted it again 2 or 3 times but it would die if I didn't keep on the gas. Now I have a weird no start issue. The engine cranks, but no spark. I replaced cap+rotor, coil, and CPS sensor already. I was going to get a new ignition control module, but I don't wanna buy one until I narrow it down. When the key is turned "on" the 2nd relay (if looking from front of engine towards back) clicks rapidly. I think it's the ASD relay or a fuel pump relay, but I'm not sure. I also notice a very similar clicking/buzzing in the fuel pump. If i unplug the fuel pump wiring clip it stops. I played musical relays and switched them around, still clicks. I DO have fuel pressure in the line whenever I crank it, but I can't really tell if the pump is priming right because of all the buzzing noises... I don't have a gauge to read the exact fuel preassure, but I may be able to get one.
I'm stumped. I'm very suspicious it's something to do with the ASD relay or a fuel pump issue, but it has fuel, just not spark. The only other things I could think of is a bad CAM position sensor(in the distributor,not the other cps!) or a bad Ignition control module(the thing the coil sits on top of). I dont know how to test the ASD relay or whatever it is. I'll see if Advanced can test my ICM tomorrow. I looked a bunch but I only found info for 1991+ HO enginees. Any sugguestions? Can I Jump the relay or test resistence at the relay?Any help is appreciated. Thanks.

 

Bump..

 

surely there should be a way to test resistence on the fuel pump at the relay, I know how to do it on some other vehicles but don't know the correct contacts or reading you should get on the jeep.

 

I'm 99% sure its something to do with ASD because the relay buzzes with the key on, but do get fuel, just no spark. The other only things I could think of is Cam position sensor or ICM. I know it's not gonna fire unless the ASD functiong right- but I have absolutely no clue what the ASD really does or how it works-and most importantly how to test it!

 

actually the relay that clicks is the fuel pump relay, which makes sense becausew of the buzzing noise in the tank. I'm still stuck here.

 

You've said that you already switched relays around but the same one still "clicks" which should tell you it's not a relay.

My understanding of the ADS relay is that it cuts power to several things, such as ignition and fuel, when the computer senses a major problem (and I assume this would be like if the vehcile was in an accident). I believe it gets a ground trigger from the ECU. I'm wondering if you just have a ground problem somewhere, and this is not letting the ASD relay activate and is only partially triggering the fuel pump relay.

And what do you mean by a buzzing noise in the tank? I think I would start there, checking all the wiring to the fuel pump, making sure there are no loose connections and unplug the connections where you can to check of corrosion. If the vehicle sat for a while in a damp climate while the motor work was being done you may have gotten some corrosion somewhere. Or the fuel pump just failed, which could happen.

 

Freshen your grounds!

 

Get it running? That clicking relay is the clue. It should click on and off stay on until the keyv is turned to off. Same for fuel pump. The ecm controls the asd relay... If the ecm doesn't see the ignition stator cps and the ignition switch power in 2 seconds it shuts down that's the relay ...you can't listen you have to feel it unless you have a stethoscope.