I'm working on someone's 1990 sedan he had a no start issue but the only code was throttle position sensor. Anyway he decided he wanted to do a mpfi swap so we did. We have a p06 obd1 ecu, an obd2 distributor, and obd2 injectors (no resistor box needed). So we wired the obd2 distributor and injectors as they needed to be and we checked the wiring on every part from distributor, injectors, main relay, all the way down to the ecu at least 4 times each so like over 10 times total and nothing is wrong. We even have one car thats set up the exact same way in the shop that runs.

But for some reason all except one of the injectors only squirt barely enough to make one little drop but the injector on the left is spraying enough to fill up about an 8th of a water bottle just by priming not even cranking.

So after I found that I moved that plug to the other injectors one at a time and they all work with that one plug. All of the other plugs are getting about the same voltage as that one. Any ideas what could cause this?

 

Are you using adapter harnesses for everything? If you rewired the injectors as an obd0 MPFI, then I'd triple check the wiring on the three injector positions that aren't working. Sounds like the signal is too weak for the solenoid to properly actuate.

 

yea when something like this happens its always good to make sure the wiring is in the right place

so heres my little check list for obd1 fuel injectors

there all in the 26 pin connector for the ecu

what i want you to do is check for continuity, this means make sure that electricity passes threw the wires

this is how your pin wires are numbered
1 3 5 7 9 11 13 15 17 19 21 23 25
2 4 6 8 10 12 14 16 18 20 22 24 26

ok so the first one

is pin one
this is injector 1 and it should be a brown wire
check and make sure this wire goes to injector 1
this in the cyl closest to the timing belt

next is pin 2
this is injector 4 and should be a yellow wire
do the same test

then pin 3
this is injector 2 and should be a red wire

now we skip pin 4

pin 5
this is going to be injector 3 and it should have a light blue wire
now do the test on this one

hope this helps

 

Marcos Barrios,
we have a harness for obd0 to obd1 at the ecu and I just checked again everything is good there.

On this harnes its left to right starting with the brown/white becauase its the other side of the connector but i followed each wire back to the ecu and it lines up with the ecu pinout a1-inj1 a2-inj4 a3-inj2 a5-inj3

From right to left is injector 1-4 1red-2red-3yellow-4yellow starting by the timing belt.

 

Just did a test with little 12v leds I plugged them into each injector plug and it seems they're not grounding to the ecu because I'm getting voltage but they only light up momentarily when the key is first shut off or turned on but not while cranking. I've done that test on my b swap ef and it usually flickers with the pulse. I don't think the ecu is bad because we've tested 4 different ones and same thing

edit: I just tested the ecu I've been using in another car and confirmed its good

 

If you're confident in the fuel system wiring, then check all your grounds. I've lost count of the weird, dumb, confusing problems I've seen that were solved by cleaning up a ground.

 

Where are all the grounds located I only know the thermostat ground and main battery ground and trans. Then sensor grounds but not getting any codes unless I crank too long

 

Two grounds on each front corner by headlights - IIRC the driver's side is tied into some of the under-dash components, passenger ties to the ECU somehow. Ground point under the dash by the steering column, though I'm not certain if that can screw with the fuel circuit. There's also a ground at the back of the car - don't remember where it is on the sedan but that's the main ground for the fuel pump.

 

All of the grounds are good I'm at a loss for what it could be. Does anyone know what else could control the injectors besides the ecu/main relay?

 

The main relay doesn't control each injector individually, it ties into all 4 with the same feed. So if the main relay is an issue than it would effect all 4 injectors, unless the wiring is somehow wrong.
Since you have removed the resistor box, how did you bridge those connections?

 

I tied all 4 of the yellow/black wires together and ran them down the the power pin on the ecu I think its a25. I don't remember which pin it is exactly and I'm not at the shop right now so I can't check but I'm certain it was the same one they use in all the writeups

 

Those wires go to the main relay. They should not connect to the ECU.

 

they just need 12v and the ecu powers the main relay from a25 so idk what you mean because it works just fine that way and we have one thats running thats wired the exact same way not to mention almost every write up I've seen has you do it that way but its hooked up to the power wire that powers the main relay so it's the same thing essentially. 12v before or after the main relay doesn't seem to effect it

 

I'm curious to see these write-ups. None that I have used suggested this.
Regardless, voltage is not amperage. The Main Relay is fed by a 15 amp circuit from the under-hood fuse box and the ECU provides only a signal voltage to the main relay to cycle the pump and injectors off that 15 amp. That is the function of a relay. It is anything but "the same thing essentially." Assuming you've grabbed that signal wire and run it to the injectors, then you've removed the signal to the relay, and thus the fuel pump. Apparently you must have modified that as well. Sadly, one cannot troubleshoot circuits that are not defined or explained.

 

These are for obd0 but a15 is the same pin on obd0 main relay as obd1 a25 also keep in mind k didn't use the resistor box because it's obd2 injectors. But still the same wiring just without the box and obd1 ecu