Murk 'EM

92 civic dx
B16a (jdm)
heres the problem.. i had this engine in another 92 hatch and it was fine i get a new (stock) shell and it had a ZC DOHC and it ran fine
i get the car drop my B16a in it and the fuel pump wont prime, tested and replaced the main relay i have 12v going to the "hot while cranking" wire on the relay and on the ground side your suposed to have 0v while cranking.. i have 12v then it drops down to 9v (still while cranking..
i checked resistance thru the ground wire from the relay to the pcm (thinking it was a short) and i have no open in the wires
so im thinking the pcm isnt grounding out the relay to prime the pump
if i jump the relay harness with a wire the pump primes.. if i ground out the ground side of the relay (with the relay in the clip) the pump primes
PLEASE HELP iv been trying to figure this out for like 3-4 months and im stuck

Murk 'EM

bump
no one has any idea?

iliv2xlr8

Replace the relay...

Murk 'EM

i have 3 relays all are working and none of them prime the pump its not the relay

Murk 'EM

anybody have an idea why my pcm isnt grounding out the relay for the fuel pump?

Former User

Do you also lack spark?

Have you already thoroughly cleaned and tightened the critical ground wire located on the thermostat housing?

Have you checked whether fuse 31 (hood), 24 (dash), or 18 (dash) is blown?

When the key is in ON(II), does the CEL remain on? If so, are you able to retrieve any CEL codes?

Murk 'EM

i havnt checked for spark cause i would like to have fuel first and i gotta find my spark tester..
teh fuese are fine the only one blown is my backup light fuse
(im not sure if it matters or not but iv done it both ways) my dash isnt in the car cause im messing with the wires under it and its easier when i had my cluster in the car there was not MIL and i couldent pull any codes

Former User

Even if there is a sensor problem, the ECU can't store CEL codes when the BACKUP fuse is blown. Replace the 7.5A fuse with a good one.

Knowing whether or not you have spark may help to troubleshoot the problem.

Murk 'EM

ill check the spark.. but im 99% sure its cause the pcm isnt grounding the relay for the pump, cause when i tested the ground side (of the relay and the pcm) while cranking i had source voltage and its suposed to be 0v being its the ground..
i just need to know what i should check or do to get the pcm to ground the relay

Former User

Let me explain my questions. The thermostat housing provides ground for the ECU which in turn provides ground for the main relay and distributor. Hence, if the ground on the thermostat housing is loose or disconnected, the ECU will not be grounded, resulting in the lack of both fuel and spark. In addition, the CEL will turn ON but will not blink a CEL code when the service connector is jumped.

Murk 'EM

the ground on the thermostat is tight and clean.. how ever i did get alot of resistance thru the wires from the ground to the pcm
which would explain the little amount of voltage (mVs) going to the fuel pump with the key in the "run" position
im going to go over the ground wires to see if i have a loose connection or GFS on the wires if so ill replace those wires and hopefully my problem goes away

Jackal6042

If you cant seem to find any wiring issues maybe see if a friend can borrow you a "known good" pcm to see if that itself is the problem.

x1xofakindx

I did a swap and didnt hook my transmission housing ground to the frame rail and my fuel pump wouldn't work...but I am sure you probably got that but thought I would add my two pennies if it helps ya.

Murk 'EM

thanks yeah my engine grounds are all there, clean and tight