"N8"

Hi guys I swaped a D16z6 into my girlfiends 1990 crx and am having a weird issue with the fuel injectors. I used a boomslang wiring harness kit, and the fuel injectors from the d16z6.

while I was troubleshooting it i put a multimeter across the leads on the fuel injector wiring harness and found that im only getting 3 volts to the fuel injectors.

I did some searching and found people saying that the main relay supply's power to the fuel injectors, and the computer switches ground to fire them.

Would a bad relay give you low voltage as opposed to no voltage to the injectors? also would a bad relay allow it to crank over and run the radio and headlights and junk? (cuz it does all that)

I assume its a ground issue im going to have to hunt down, and the car is a little rusty... Could you guys help me figure out which ground is associated with the fuel injectors, and where I could find it? (or maybe just help me locate all the grounds so I can clean them up and re-try)

Thanks guys

4drEF

The fuel injectors have individual grounds from the ECU. They are different color wires for each injector. That's what triggers the the fuel pulse. They do not use the engine ground and actually are isolated from engine ground somewhat through rubber seals and such.

The power wire is the yellow/black on all injectors.
All 4 join together (where the stock OBD0 resistor box would have been).into a thicker wire that runs to the main relay.
The main relay supplying low voltage would be very unlikely. It is a relay and with either work or it won't.

What trim is the CRX (DX, Si?)
Was the engine that was in the car before the swap running?

"N8"

I believe it was a 1.5L DX

either way it was a dpfi system and I had to convert it to mpfi. I did splice all those yellow wires together as well as ran two new wires for the extra two fuel injectors that are now in the system.

any idea why I would get a consistent low voltage across all four injectors?

4drEF

How are you taking your voltage reading?
Are you getting a constant 3volts?

The proper way would be to have the ignition to 'ON'
Disconnect all 4 injectors for this test only since you are having problems.
Hook your voltmeter neg probe to neg battery/chassis ground.
Hook your voltmeter pos to the yel/black wire in the injector clip.
All 4 injectors should have 12volts.

You should NOT have any voltage reading at all if you probe between the two wires in the injector clip.
The ONLY time that it would ever have a voltage reading is when the ECU closes the circuit by sending a ground pulse to the injector to fire it.
Other than that split second while the car is running (which is not something you can readily test), it should be a completely open circuit with 0 volts.

"N8"

hmm well I made some assumptions that were wrong I guess, I was reading across the two connectors and it read 3 volts while the engine was cranking, and 1.5 ish volts with the key in the on position.

4drEF

So you get 1.5 constant with the key in 'on' and with the probes going to both prongs in the injector clip?
That would signify a short someplace.

Go through the test I posted above and make sure you have 12v with all 4 clips disconnected.
If you do NOT get 12v (or something near that) then you have a short on your yel/black wiring.

"N8"

ok i'll do so. if it turns out yes ive got a short do I just have to look for the short in between the yellow/black wires at the fuel injectors and the main relay, or does it go elsewhere?

err that almost makes sense so ill just ask how hard it is to track down a short at the yel/black fuel injector wires, and or where do I start looking for said short?

4drEF

Looks like it goes to the fuel pump too.
http://www.justanswer.com/uploads/RI...10245_fuel.gif


I would see if you get that 12v first.
The short could be internal to one of the injectors or even with your other 4 wires that go to ECU.
You won't know that until you check for the 12v though.

If you have all 4 clips disconnected and don't get that 12v then;
- Take all 4 yell/black wires out of loom if you added any yet
- Inspect them carefully looking for any bare wire (use solder and shrink tubing - electrical tape and crimp connects will lead to failure)
- Check the 4 wires to the connection to the one thicker wire for any bare wire.

If all that check out to be fine then do a continuity check from any of the yel/black to chassis ground to see if you do indeed have a short.
Next would be to dig up the main relay from under the dash... let see how far you get with the 12v though.

"N8"

Cool thanks a bunch. I'll check it out

sanimalp

wait.. z6 injectors are high impedance. If you are using an injector resistor box, and those injectors, that may be your problem.

can you confirm if you are using the resistor box or not? I am guessing you are as every mpfi conversion tells you to use one, and doesn't talk about high vs. low impedance injectors, which matters in a big way depending on injector resistance.

"N8"

Yea its a good thought, but i wired it without the resistor box from the start.
Thanks for the input tho.

"N8"

Ok guys I've been back in and out of this car and now im still stumped. I chased the 12+ wire all the way back to the main relay. When I found no voltage at the relay I assumed that the relay was bad. For starters I just made a jumper and jumped from pin 3 to pin 7 to mimic a working relay. Both these wires were yellow/blk The fuel pump came alive and it started to catch and stumble a little as if it were going to start, but never actually started. So now im back with a new relay and getting the same failure. It would seem that whichever lead is on the other side of the switch in the relay isnt supplying power to this circuit. I checked every single fuse with my multimeter and they all seem to be fine.

Does anybody know wich wire I should check that would feed pin 7?
Dono really where to go from here. I just drove all the way out to work on this car hoping that this would fix the problem and now im stumped.

Any help would be much appreciated.