swaped in motor,having relay problem and no start condition

swapped an 87 motor into a 90. installed everything, motor cranks, and im going to checkfor spark in a min, but the relays are clicking on and off. and the car doesnt start. the fuel pump is on off on off(because of the relays)


what would cause the relays to be on off on off. what could cause this problem? i didnt swap electirical parts, used all the stuff of the 90. need help asap!!!!!!!

Well, when you turn the key to ON the B latch relay is going to provide power to the fuel pump for about 3 seconds and then cut it off. When you turn the key to the START position the fuel pump will get power from the starter relay. When the key returns to the ON position, the fuel pump will get power from the fuel pump relay.

Most of the motor start issues after a swap have turned out to be the grounds. Often the one from the head to the firewall.
Best guess would be a bad ground or maybe a short that is sucking the voltage down.
A weak battery may also be an issue, but that often affects the starter first.

I am a getting power through the grounds. Electrical backfeed I think but I didn't change any wireing. I even added a body grond and still have the same issue. I turn the key to the on position and the relays absolutely freak out the click back and forth a bout ten times a second .

Maybe try unplugging one sensor at a time and see what happens. Maybe even unplug the ECU eventually. Try to isolate it to a sub system or at the very least, try to sort out if it is a power issue or short in the sensor systems.
Try unplugging one relay at a time. The O2 sensor (if memory serves me correctly) is a dual position relay, it operates two systems, it may be a prime candidate for a chattering relay. Check the B+ latch relay, charred or burnt contacts in relays can make them chatter.
I still tend towards it being a ground issue of some sort, when grounds get interrupted the power can take odd paths. The relays may chatter because they have current on both sides of the activator coil or not enough current is passing to ground to keep the coil and contacts activated.

ok, i just woke up. last night the relays quit freaking out(dont know how or why, but they did.) i checked for spark. nothing. checked the coil, nothing. swapped it from the donor rig, and nothing. so ive narrowed it down to a no spark condition. im thinking it has something to do with the little box thats conected to the battery(i call it a power distribution box, dont know its real name). it has wires bolted to it, and i believe theres four fusible links plugged into it as well.

when we put the motor tranny and tcase in we swapped the alt, knock sensor, distributor, power steering pump, water pump, therm, intake man, new exhaust man.

From the 87 we used the motor, tranny, tcase, starter, o2 sensor, crossmember, and cat back system.

the only thing electrical wise we put on the truck thats not off the 90 is the 02 sensor from the 87.




ALSO. when we put the starter on, i accidently put the power wire on the wrong post of the solenoid. then when i went to put the ground on the batt, it cranked and it sparked. so im thinking i might have sent too much current through the ground circuit, and either burnt a fusible link, or damaged that box that i call the power dist. box. any help is welcome.

thank you soo much

Motor can crank on less than the 9V minimum needed to power electronics. I didn't catch the part where we eliminated a weak battery (dead cell, etc.)

newer battery. tested it. its fine

basically. i go to school in sacramento. im studying diesel/auto mechanics. my motor has seen better days and i got a sweet deal on a better jeep (d44, , bottom end rebuild, new rad, shocks, and other parts., but it had 500 dollars in dmv fees.) i towed the donor rig and drove mine down to salinas where im from. my buddy and i swapped the motor and what not. we didnt touch anything electrical except unplugging connectors and plugging them back in to the new motor.
one thing i did wrong is at 10 oclock pm when the starter was going back in i wired it wrong. so i think its and electrical issue somewhere in that box or i burnt up a fusible link, but i left my dmm in sacramento so im useless. and i cant see any burnt wires.

but i dont know if the trans has different sensors or is controlled different. remember, this is out of an 87 and went into a 90. maybe the tcm isnt allowing the pcm to let the coil produce spark.
also, if my linkage was misadjusted, my nss might not allow the car to start. problem there, i bypassed it over a year ago. so it cant be misadjusted linkage.


i dont have an fsm for these vehicles, and dont have a chiltons. if someone could post up a diagram for the power distribution box, or tell me which wires do what id be greatful. theres two green wires plugged into it, and a orange and a black with white strip. there fusible links if im not mistanken, and i need to know whats what. plz help. ill be searching

The power distribution box is the starter relay on the Renix XJs.

The B latch relay provides power to the coil--do you have power to the coil?

http://www.lunghd.com/Downloads_and_Links/Jeep_Renix_Fuel_Injection_manual.pdf

page 40 shows the starter relay connections

i dont have power to the coil.. i checked for spark out of the coil and had none, so for kicks and giggles i swapped in the one from the 87, and still no spark. also, starter will crank the motor over.

thank you sooo uch 89xj for that link. im looking at the starter relay on page 40. if the systems are the same on the jeeps, why do i have to different starter relays? the one on the 87 is a 3 prong. on the 90, four prong. i guess there is slight variations.

now my question. if my fuel pumps kickin on, and my starter cranks, does that mean my ground terminal is good? and does that also mean the starter relay is good?

also, im looking at the diagram of the b+ latch relay , could i have damaged my ecu? i see thif i did are they they same on the two vehicles( i think tyhey are, but i dont know) okay. im going to check the fuse line to the relay

what prong is it missing?

are you getting power(trigger) to the coil from the icm? if not, it could be a bad cps. maybe a bad cps wiring harness or it was damaged when installing the engine/trans combo. the icm get a signal from the ecu when the ecu receives a signal from the crank position sensor.

norcalchris said:

thank you sooo uch 89xj for that link. im looking at the starter relay on page 40. if the systems are the same on the jeeps, why do i have to different starter relays? the one on the 87 is a 3 prong. on the 90, four prong. i guess there is slight variations.

now my question. if my fuel pumps kickin on, and my starter cranks, does that mean my ground terminal is good? and does that also mean the starter relay is good?

Click to expand...

Sounds like your starter relay is Ok. Have you tried swapping the relays around?

You should be getting 12v out of the B latch (ASD) relay to the primary side of the coil.

i do not know if i am getting power from the icm.(ignition control module??) unfortunetly all i have with me is a test light, so i cant do too much. i do have a spare cps( from the 87) and as too what prong is missing off the starter relay, i am not sure. i will check.

joe peters, i have tried switching the relays around. when i get a multimeter i will definetly be posting up voltage readings.

i do not know what prong is missing.i do not know if the icm(ignition control module??) is supplying power to the coil. do you know what prong it is and what connector to the coil it is on? i do have a spare cps, and i will go swap them. on the zjs ive been told the cps is to be adjusted when installed, is my cps to be adjusted when installed?

and joe peters, yes i have swapped relays around. no difference.

opps, didnt think the first post went through. haha

Ok, when looking at the ICM there are three connectors. Three on the left, two in the middle, and three on the right. The right connector is not used.

Looking at the first three pin connector, C is first on the left, B is in the middle, and A is on the right.

The first pin, on the left, C, is the Tach.

The second pin, in the middle, B, is a ground.

The third pin, on the right, A, is positive and is hot in the START and RUN positions.

Note: The ICM/ECU/o2 sensor grounds are those grounds at the dipstick tube.

Check pin A--if you have no power there work your back through the B latch relay, etc., until you find the open circuit.

okay, i swapped the cps. no difference. the icm is it the coil too? i was looking through the manual 89xj gave the link to, and they are refering to the coil as(ipm) ignition power module. are we talking about the same thing? if not, where is the icm. i will go test and be back