Brian P

I've been trying to sort of some of the problems with a friends car, 86 FC, Today I discovered that the secondary injectors aren't firing. I did as the service manual says and disconected the vacuum line to the boost sensor, unplug TPS etc, and they don't fire, run the car to 3500+ RPM and nothing.

So, the manual says check the CAS, did that its fine, the injectors have a resistance value of about 2 ohms...so I think their ok..

The manual then says replace resistor if necessary. What resistor are they talking about? Variable Resistor?

Tomorrow I'm going to check continuity between the injector harness and the ECU.

Is there anything else that I'm missing?

HAILERS

There is a solenoid resistor and its located below the air flow meter and filter. Remove the air flow meter and filter and you'll see it. Its covered by a shiney piece of aluminum and has one large round plug going to it. You should try ohming out the wires from there to the ECU. There is a factory manual and wiring schematics at http://www.iluvmyrx7.com Its for a 88 but should fit your car. The ECU, located under the passengers feet. The plug is the smaller of the three plugs. If the 88 manual does not work for you write back. Now help me. What manual were you refering to? I've missed the test that you refer to. Somewhat interested. Just for some info....the ECU supplies a groung to the injectors. They have a constant 12v going to them all the time. You problably know that.

Brian P

The info I got was from page 4a-69 of the FSM, it says if operating sounds aren't heard then check resistance of crank angle sensor(checked ok), wire from CAS to ecu for continuity.(would the car still run if it wasn't??), replace resistor, does resistor control primary and secondary injectors?

I'm going to go start doing some more checks, I'll write back to update my progress,

BTW, is there any way to test that the ecu is grounding the injectors?

*EDIT* I can't find any info on how to check the resistor, any idea?

HAILERS

The resistor data is in the fsm in section 4a and if you have a 87 manual its on page 4a-72. What ever you do do not by-pass the resistors. I have been led to believe that will zap the ECU. Also you might want to go to go to section 4a Control Unit. Page 4a-30 to 4a32. It has the ECU signals for the cas and the injectors. No I'm not sure how to tell if the ECU is puting a gnd on the injectors. I vaguely remember putting a meter on the ECU for one of the secondaries and while driving could'nt tell much of a voltage drop. But thats just me. I could have been missing something. There is a fellow who is Keith's father named Irv and another fellow Six Rotors who I hope add some information to your questions. Each injector has a resistor dedicated to it (my understanding). There is a 12v input at the resistor assy that feeds alll four injectors. If you want to compare resistances from the resistor assy to the ECU, I would be willing to do so, but I'm off to work in the next hour.

HAILERS

Back. I am looking at the wiring schematic and it seems if you would take the small plug off the ECU and checked pins 3E,3H,3c,and 3F for 12v then there is probably nothing wrong between the resistor assy and the ECU(yeah I know there is no load). It can't be a lack of voltage if the primaries work. You could swap the primary and secondary injectors to confirm they work. Here is a site that has some rx info http://www.k2rd.com/FC3S/fc3s.html Have fun.

HAILERS

Want to try something a little different? Take the injector plugs off the secondary injectors. Go for a drive. If they are really not *firing*, when you hit 3800 in second or third gear, you should be thrown towards the windshield. Around 3800rpm I have heard is when the secondaries come into play and at the same time the duty cycle of the primaries is cut back. If the secondaries plugs are off and the primaries cut back at 3800 the car should radically slow down. A true shade tree mechanic. I am what I am.

HAILERS

Just another notion. I see at the bottom of your post that you have a 87turbo. You could swap resistor assys b/t cars to verify that it is good or bad.

HAILERS

Here's a good article on ignition http://www.teamfc3s.org/info/articles/demystifying.html I'm like you in that I do not understand how, if the signal from the cas was not getting to the ECU, how could the engine run? The article just confirms that the signal from the cas is used as a trigger for the injectors.

HAILERS

And now something useful. I went out to my car and put a *tap* on the wire to 3F on the ECU(Rear Secondary).Put a digital meter on it. Drove the car. Regular slow driving it read 12.5v give or take .3v. Now in thrid gear, pedal to the metal and over 4000 rpm I read 8.5v. So I'm saying you could do the same and check out whether or not the ECU is putting out.

Brian P

Ok, heres what I check before I smoked my knee on a 12 side housing

Oh yeah, my car is a T2, this is a friends GX. I'm thinking that because we swapped the car from auto to std there might be some things that aren't required by the ecu anymore and they are screwing things up.

This is something that I probably should have addressed before, is the ECU the same for a standard shift car as automatic? This could be my problem right there.... I have a spare TURBO ecu.. I wonder, nah, it'll prolly **** it up

Thought I had a vaccuum leak so I pulled off the intake and replaced all the vacuum lines.. While I was under there I checked to make sure that the primary injectors weren't leaking (Doesn't start well at all when cold) They don't leak, and they have a very nice spray pattern.

Other things I did;

Main relay - checked ok
CAS resistance -checked ok
TPS - set to 1 volt
Timing - bang on
CAS to ECU continuity test - as per haynes manual, touch connector to a ground and if there is continuity then its ok,
BAC - I suspected this was causing problems, as soon as I cleaned it the idle went super high. I don't think it works, plus I think I broke it trying to get it to open more, It would only move 1/4" or so when you give it 12v. Shouldn't it move all the way open? Anyways I just ended up blocking it off and the idle has come down quite a bit. Now it sits at just under 1000 RPM.

When the car starts cold(after a lot of cranking) the cold start system does work. Probably not any more now that I blocked off the BAC,

Then I went to get a screw driver to tighten the screw back into the FP Reg before putthing the manifold back on and I smoked my knee bad, so thats where I'm at right now.

Thanks alot for all the help you are giving me, and for being patient enough to respond to my longass posts You have no idea how much I appreciate this,

Scott 89t2

ecu's are different from 5sp to auto. don't know if they would affect not using the 2ndarys though.

isn't there something in the truck that controls the injectors as well?

Keith

First check I would recommend is the resistor pack. The brown/yellow stripe wire feeds the rear secondary injector, the brown/white stripe wire feeds the front secondary injector. The Black/yellow stripe wire is 12V, which we know is good. After unplugging the resistor connector, meter the pins on the resistor pack connecting to the injectors to the 12V pin, you should read 5-7 ohms for each injector. If that is ok, you have power to the injector. To check wiring/injector function, I would suggest this: Ground the light green/red stripe wire for the rear secondary injector, the light green/white stripe wire for the front secondary injector to ground with ignition on (this can be done at the injector or the ECU - top left connector, small one, bottom row second and third pin from the left). If the injector clicks, the ECU is the problem, if the injector does not, either the wiring from injector-ECU or resistor pack-injector is bad. Good luck.

Irv, Keith's dad

HAILERS

Never messed with a auto. Pretty sure that manual and auto use the N326 ECU. The BAC probably did die tonite read the following url http://www.teamfc3s.org/info/articles/idle.html read the part about the bac. Its a vibrator. You can live without it until next summer or get one at the wreck yard. New cost way too much. I do know the auto uses one or two extra vaccum places on the rear of the r/h intake manifold. Did a vaccum port get left open? If it is just cap it off . Sounds a bit like a small vac hose, tube, whatever might be open. Hey, do get a digital meter and try to see if the secondaries are working. See the above post. I learned a bit while doing this. I don't know why, but I assumed that the secondaries opened at 3800rpm, period. I learned that its a relationship with the pressure sensor and the tps. I can get up to 5000 rpm in third if on level ground and ease the car up to that rpm. If I just floor it at say 3000, as soon as I get around 3800 the voltage drops on the secondary injectors meaning they opened. Have fun. By the way, does the screw on top of the dynamic chamber have any effect on the idle when you screw it in?

HAILERS

OOps. In the above post I meant to say I can ease the car up to 5000 in third without the secondary injectors opening probably because the throttle is just partialy advanced and there is no real load on the enginge if going on straight and level.

Brian P

Ok, I did check the resistor, but only a resistance check, and it was ok, I'll go and do the check that Irv suguested. Hailers: You should be able to fool the ECU into firing the injectors by removing the vacucm line from the boost sensor, this way the ecu sees 0 vaccum and at 2500+ rpm they should turn on. I've had the car reved to at least 5k without them turning on.

And no, the screw on the top of the intake doesn't lower the idle anymore, its screwed all the way in and it idles just under 1k.

I'm going to go recheck the resistor, I'm also going to pull up the carpet and make sure nothing was screwed with on the ECU (used to have an alarm, VERY poorly installed)

Well back to it, I'll write back on my progress

HAILERS

If you think about it, will you please tell me what the ECU number is on the top of the ECU? Making a list of the different ECU'S.