How to get the fuel pump to start working

HOW?, well diagnosis it. (toss coin 4.0L)
I guess you mean fuel pressure is 0, ?cranking?
here is how to diagnose RENIX.
It really is not Jeep,its French EFI.
Must have power 12vdc to the ECU. (fuses)
10v to 12v cranking, key out battery is 12.6vdc or more, is it?
cranking, be sure to be cranking,..!!!
to CHECK pumps.
you then check for 10-12vdc out of the fuel pump relay using a volt meter (DMM) cranking.
if that dead 0v, you have bad inputs to the ECU.! OR RELAY IS BAD.(check all 4 pins to learn that)
check them per FSM (or ask)
if the fuel pump relay closes now cranking (there is no ASD relay till 1991)
and 12vdc exits at the top red arrow seen above. Juriy post
then the ECU is doing its job and is happy.
the CKP sensor dead my kill the pump on RENIX systems.

there are no scan tools (sold OTC) that fit this jeep , so RENIX is very hard to diagnose.! but we can. using meters.

ask? how. owned 2 . MJ/XJ 88s
then we check that 12vdc line.see 2nd red arrow aBOVE.
the voltage there to the pump.
10-12v cranking, got that?, good.
if not the wires are bad there.
if that checks out?, measure the pump black wire if its 12v (NOT 0) CRANKING
THAT MEANS PUMP GROUND IS OPEN OR RUSTED.
I POST THIS FOR ALL RENIX OWNERS.

NOW I BACK UP.:
Really this is engine no start.
first check fuse.
2nd check that there is spark.
if all 6 are dead the CKP is dead.
got spark good, try test fuel. ah it runs for say 3 seconds on test fuel. sounds nice.
we then check fuel pressure.
if its bad we check voltage to pump.
(both wires)
if pressure ok , then we do NOID light testing on the injectors.

like that.
The ECU cuts fuel for many reasons.
loss of spark
loss of CKP
sees TPS stuck wide open throttle.
TPS ground wire cut. (open)

see some Renix facts here.
its very old EFI.
http://jeepdied.com/

has no flash codes either then....
very hard to work on,. HOW?, well diagnosis it. (toss coin 4.0L) I guess you mean fuel pressure is 0, ?cranking? here is how to diagnose RENIX. It really is not Jeep,its French EFI. Must have power 12vdc to the ECU. (fuses) 10v to 12v cranking, key out battery is 12.6vdc or more, is it? cranking, be sure to be cranking,..!!! to CHECK pumps. you then check for 10-12vdc out of the fuel pump relay using a volt meter (DMM) cranking. if that dead 0v, you have bad inputs to the ECU.! OR RELAY IS BAD.(check all 4 pins to learn that) check them per FSM (or ask) if the fuel pump relay closes now cranking (there is no ASD relay till 1991) and 12vdc exits at the top red arrow seen above. Juriy post then the ECU is doing its job and is happy. the CKP sensor dead my kill the pump on RENIX systems. there are no scan tools (sold OTC) that fit this jeep , so RENIX is very hard to diagnose.! but we can. using meters. ask? how. owned 2 . MJ/XJ 88s then we check that 12vdc line.see 2nd red arrow aBOVE. the voltage there to the pump. 10-12v cranking, got that?, good. if not the wires are bad there. if that checks out?, measure the pump black wire if its 12v (NOT 0) CRANKING THAT MEANS PUMP GROUND IS OPEN OR RUSTED. I POST THIS FOR ALL RENIX OWNERS. NOW I BACK UP.: Really this is engine no start. first check fuse. 2nd check that there is spark. if all 6 are dead the CKP is dead. got spark good, try test fuel. ah it runs for say 3 seconds on test fuel. sounds nice. we then check fuel pressure. if its bad we check voltage to pump. (both wires) if pressure ok , then we do NOID light testing on the injectors. like that. The ECU cuts fuel for many reasons. loss of spark loss of CKP sees TPS stuck wide open throttle. TPS ground wire cut. (open) see some Renix facts here. its very old EFI. http://jeepdied.com/ has no flash codes either then.... very hard to work on,.

got a voltmeter , a DMM?
we can find the cause easy.
the meter will never lie to you.
ask how. it's not difficult, but
on my 88's the (even both new) the pump was real loud on the pick up truck, sounded like ball bearing ball landing in the pickup bed.
fists full dropped.
Key on for 3 seconds.
Learn this, some ECU, run the pump key on
others do ,not, most jeeps do.

but back in the 86 to 93' time frame, lots of ecu's used, RENIX, AMC, then Chrysler.
93 is the best of them all, older. !
Best first good EFI.

Given these facts, i'd do all pump tests
cranking (on a dead engine , symptoms no starts and spark good, and test fuel works.)

I just sold a car that (1996) that the ECU when updated "flashed", the update changed this rule (TSB'S).
to cranking only pump rule (from key on run)
see?
It's best (when working on all cars) to assume you dont know the rule. (it's pure ECU software logic inside)
see? (unless you do know, for a fact this)
(you owned it and know)
when i fix cars not mine, i never assume this.(rule) i Assume worst case
I hope this help you.

my new jeep is dead silent, key on.
but does spin, key on. got a voltmeter , a DMM? we can find the cause easy. the meter will never lie to you. ask how. it's not difficult, but on my 88's the (even both new) the pump was real loud on the pick up truck, sounded like ball bearing ball landing in the pickup bed. fists full dropped. Key on for 3 seconds. Learn this, some ECU, run the pump key on others do ,not, most jeeps do. but back in the 86 to 93' time frame, lots of ecu's used, RENIX, AMC, then Chrysler. 93 is the best of them all, older. ! Best first good EFI. Given these facts, i'd do all pump tests cranking (on a dead engine , symptoms no starts and spark good, and test fuel works.) I just sold a car that (1996) that the ECU when updated "flashed", the update changed this rule (TSB'S). to cranking only pump rule (from key on run) see? It's best (when working on all cars) to assume you dont know the rule. (it's pure ECU software logic inside) see? (unless you do know, for a fact this) (you owned it and know) when i fix cars not mine, i never assume this.(rule) i Assume worst case I hope this help you. my new jeep is dead silent, key on. but does spin, key on.

he dont. in 1986, not one does. (ASD) in Renix systems. he dont. in 1986, not one does. (ASD) in Renix systems.