2ndthtsurplace

94 Honda Civic EX 2dr coupe swapped b20v

been running fine forever and one day on the way to work the engine shuts down like no power. cranks fine.......get it to shop......replaced main relay.....fuse 31 (15amp) fuse is replaced pops again during cranking....check wires for high resistance all check good from battery to fuse from fuse to relay from relay to ecu.....replaced fuel pump cus it had power all the way to it but no prime at key location 2......so cap, button, main relay, and fuel pump have been replaced....i have spark and during cranking the fuse keeps popping goin try an ignition switch tonite cus i am desperate and was told to try tht too from a bud....any extra input would be greatly appreciated will post wat happens after ignition switch is installed tonite also i have used a known good ecu and tried that just to verify it wasnt the ecu

Former User

15A hood fuse 31 powers the ECU via the main relay. The fuel pump and ignition switch are not on this circuit, so are not culprits.

Are you saying that fuse 31 only pops when the key is in ON(III) but never in ON(II)? If you leave the key in ON(II) for a while, does fuse 31 eventually pop?

By the way, when you have a short, as you do, you need to check the wires for continuity to body ground in order to locate the short. If the wires are fine (=no continuity to body ground), then the short may be inside the ECU. Pull it out and inspect it.

2ndthtsurplace

ok well i will try that so i need to put 1 end of my dvom to the wire and other to body ground correct and do each wire and find which one has high resistance correct and it should have like .02 or none right..??? also and if i find a wire with high resistance i can jus cut and run my own wire from the relay directly to the connector at the bottom of the fuse box (under-hood) and the colors and all should be the same right (nothing else in between i dont think)....???

Former User

You basically have it right, but you are looking for low resistance (continuity), which would be a reading between about 0-100 Ohms. Also inspect the main relay plug for any signs of a short (burnt). If the wires are fine, then the ECU may be fried.

2ndthtsurplace

well wat i got so far is on the black/yellow wire for the alternator as a reference is 1081 ohms and on the yellow/white (ecu fuse 31) i have 0 ohms as a reading so wat i need to do is run a new yellow/white wire from the main relay to the bottom of the under-hood fuse box correct? and the wire in the under-hood fuse box will be the same color?

PS i already tried a known good ecu and everything was the same

Former User

Yes and yes, but first carefully inspect the main relay plug. Also consider the short could be in the hood fuse box.

If you unplug the main relay, does the fuse still blow?

2ndthtsurplace

well i have a brand new main relay so i figure tht is all good and the thing is the yellow/white wire looks fine and not damaged at all hell one of the other wires look worse but idk i jus am not gettin a reading on tht one with or without a fuse in then i tested it at the bow and one side of the fuse contacts has resistance like 8000 ohms or something and the other has none

Former User

The fact that you must turn the key to get fuse 31 to blow suggests that the short in the wire that pins to main relay connector terminal 3 and runs to ECU A25 and B1 or that pins to main relay connector terminal 8 and runs to ECU A7 and A8.

2ndthtsurplace

well the wiring diagram i got says the yellow/white wire is the one that goes from the main relay to the fuse (31)....and is the one comes up with 0 ohms while the black/yellow (location 5 on main relay) says like 1100 ohms making the yellow/white the culprit since it has 0 ohms right?...cus i thought power went from the battery fuse to fuse 31 then to the main relay down the yellow/white and i guess the yellow/white is grounding out somewhere making the fuse pop...???? my friend is on the way with some butt connectors and stuff so i wanta make sure i cut and do the right stuff i been testin and doing stuff since tues and am goin crazy i hate wires lol

Former User

The Yel/Wht wire runs between fuse 31 and the main relay connector. If it had the short, fuse 31 would blow without turning the key, so I'm skeptical about your continuity to ground measurement.

The Yel/Blk wire that runs between the main relay connector and ECU A25/B1 and the Grn/Yel wire that runs between the main relay connector and ECU A7/A8 are where you should be looking.

2ndthtsurplace

on my DVOM i put the neg on ground and the pos lead on the yellow/black end on the connector and get a reading on 1100 ohms...

Former User

How about the Grn/Yel wire?

2ndthtsurplace

green/yellow location 8 has no reading on it

Former User

If you unplug ECU connectors A and B and repeat the main relay connector Yel/Blk wire continuity to body ground test, what Ohm reading do you get?

2ndthtsurplace

unplugged the biggest ecu connector and the middle one i believe the right ones and on the yellow/black i got no reading

Former User

You went from 1100 Ohms with the ECU plugged in to offscale with the ECU unplugged. Inspect the Yel/Blk wire ECU connector terminals at A25 and B1.

Here's how to locate the ECU pins:

http://www.phearable.net/tech/wiring...schematics.gif

2ndthtsurplace

so if i cut the 2 yellow/black wires coming out of the main relay (or depin it which idk how) and run new wires to the ecu and cut the yellow/black wires on that side and put them together basically replace the wires that go thru the harness would that work or do they go somewhere else in between

Former User

Your test is saying the Yel/Blk wire is fine because the resistance goes off scale when the ECU is unplugged.

2ndthtsurplace

ok so what that mean a different wire is bad (yellow/white to the fuse) or wat i took the ecu out of a friends car and tried it and the fuse popped right away when i tried to start the car and my ecu is chipped if that makes a difference or could it b the ecu ground i aint that great at wires man and i appreciate this alot more than u will ever know

Former User

2ndthtsurplace

the ends on the ecu side seem fine the wires arent loose and the pins look fine on the connector and the ecu but the yellow/black wires on the main relay connector side look a lil melted on 1 of them the other looks fine

Former User

There's only one Yel/Blk wire in the main relay connector, right? Plug in the main relay connector and unplug ECU connectors A and B. Measure continuity to body ground from ECU pins A25 and B1 individually.

Post pictures of the melted wire in the main relay plug.

2ndthtsurplace

both have no reading and i have 2 wires at the same location that are the same color as u can c in the picture the bad one is melted for about 6 inches and once it gets higher up looks fine b4 it goes into the big loom and i had it taped up with electrical tape for the time being

Former User

I don't see the main relay plug in your picture. There should only be one Yel/Blk wire in that plug (see below). Where do those two wires pin to the main relay connector? Does the melted one pin to terminal 3 of the main relay connector?

2ndthtsurplace

the main relay connector is in the bottom left corner the lil brown box u only c a lil part of it and thts where i have the 2 yellow/black wires at they both go into location 3 i figured 1 went to each of the ecu points