Ok, been helping a friend with his mpfi swap, he did all the wiring except for a jumper harness I made for his dizzy.

The car cranks and sounds strong like it really wants to start but wont. Only throwing code 20 which after reading shouldnt keep it from starting. I went over his wiring with 4thgens site and its good.

Has spark in all 4 and his timing is good, set slightly retard until it starts then he'll go back and set it right.

We dont think its getting fuel in #3 and #4 based on smell and the fact that both spark plugs are still brand new, while with the other two you can tell theres combustion.

So, running through the helms we get to testing signal at the ecu, with ignition on test between A2 and A1,3,5,7 for current. Using a test light we get nothing, then heres the weird thing, we've been uing a multimeter on setting 0.5 DCmA to read for current on everything as its the only thing where anything will even register on the needle....when we test the A2 with the injector wires the needle actually moves negative?!?! wth is this?

Also we tested the injector resistance and the resitor box and they came up clean so we're left with the signal from the ecu. Any clues?


Modified by blah13 at 12:42 PM 2/24/2004

 

i would check and check and check the wires you ran from the ecu to the additional 2 injectors......and also did you get an mpfi ecu? cuz if you are using the stock dx or std it only sends signal for 2 i believe.......

 

Yeh, I sat in there and yanked on each wire (theyre all blue that he used) and traced each one and he did it right. The 2 yel/blk together and to the resitor box. The 4 red/blk to each of the injectors, then the 2 wires he added to 2 and 4 and then the stock dx main and aux injector signal wire to 1 and 3.

And we know the injectors are getting power, we tested for current with the red/blk wires then to a ground and they all registered the same. So thats why were trying the ecu signal but getting weird readings, but weird as they are theyre the same reading on each injector wire. So with #1 and 2 definately firing were left with clogged/stuck injectors. We're gonna try swapping 2 and 3 and see if its the injectors or the wiring.

He's got an auto like I do but mines still dpfi so its hard to find another PS9 ecu to try on it.

 

Bump with update.

Ok, after getting off work last night I call my buddy and ask how things were going and he says he has no fuel at all. So after getting over there I grab my multimeter and heres what I did/got.

I pulled all the injector clips off, hooked the multi up to the 2 wires inside and had him crank the car. Every time hed crank it the meter would spike, so this means the inj are getting power right?

I then went to the ecu and used a2 as the - and a1,3,5,7 as the +. Hooked to each one and every time he cranked, it spiked.

So this means the inj are getting power I assume? So I had read that if you take 2 wires, run them directly from the battery to each post on the inj itself that it should fire or click. Does it click once or constantly? I think we got 1 click but it could simply be the sound of the spark/power. Its this way with all 4 connectors and all 4 injectors.

The only thing I can think to try now is taking the blk/yel wire out of the connector at the driver side shock tower and wire it directly to the resistor box, but I dont see how that would help as I'm pretty sure the inj are getting power. Or do you think hes somehow fried all his injectors? This really makes me not want to try this swap with my dx. dpfi power, heh...

edit : oh yeah, theres also no code 16, so I dont think theres a break in the circuit.

 

Yeehaw, more updates. I think I may have found the problem, after searching my ***** off it seems that the injectors receive a constant 12v power source, then the ecu simply decides when to ground the circuit for each injector so that it will fire.

When I was testing for power at his injectors the helms simply says "Is there battery current?" It never says how much there should be so seeing the needle move I assumed, yes it has current. So going back again and testing at the injector clips using DC mA.5 I got 1 whole freaking volt, actually a little less bc it fluctuated a little bit. And with the resistor box testing ok at 6-7ohms I went to the shock tower connector and tested both blk/yel wires and got less than 1 volt at each. But why does it spike up each time we cranked it over? I read in other posts that it usually drops from 12 to 10ish.

So through the helms I see that the power comes through the main relay but where does it come from to get to the main relay so I can test the power before it hits the main relay? Is it possible for the main relay to activate the fuel pump (which it does) but not provide enough power to the injectors? Is there a resistor inside the relay? I think I've found the problem but I want to test the power going into the relay before I send my buddy off to buy a new one. So please mpfi guys, I know theres an assload of you out there, whats your opinions?