Injector/Fuel issues (Stock harness issue)
 

Preface:
Running an N332 rtek 1.7 ECU
720 CC secondaries
no emissions
walbro fuel pump
ALL 87 wiring harness
Two weeks ago I finally finished my project (that had been sitting for 7 months) and went to start it. Zero fuel pressure (with a 1 year old walbro). Replaced walbro. Good Fuel pressure now. Now the injectors are not firing. The car has 115 compression on front and rear rotors. It was rebuilt by kevin landers 5000 miles ago. Plugs are bone dry. Will injectors fail if they are run with 0 fuel pressure? My next step is to pull the injectors and test the ohms on 'em. I just can't understand why this is happening. The only other thing that stands out, is that I've got a cream colored wire with red stripes on it with a (non stock) spade connector on it :confused: It's running off the same wire that runs to the ground on the top of the manifold. I don't remember seeing this on my other harness (I replaced the harness with a better looking one since the old one melted from the turbo heat.)

WTF.

Check and see if they are getting a signal to turn on before suspecting the injectors.

Injectors can stick shut if left sitting for a time, especially if allowed to dry out or if moisture is present in the fuel.
I have had to spent an hour or more getting some of them working again that were stuck, and even then some didn't pull thru.


Good luck,

Gordon
WitchHunter Performance
Fuel injector cleaning & flow testing service

If you check the resistance on them with an ohm meter, and it's out of spec, can that be a sign that they are stuck?

up?

No, that just tests the coils. The only way to test them is to wire them into the fuel rail so they don't pop out under pressure, jumper the fuel pump relay (yellow two pin connector), turn the ignition to on and then pulse power into two prongs on the inject. When it gets power it should spray fuel. Don't give the injector power for to long might burn the coil only quick bursts.

OK, verified that the injectors are working, they are the correct (2ohm) impedence. Hooked up power and they were clickin and passing fluid. I am sure the problem resides in the ECU or wiring harness. Is it possible this could be caused by a bad CAS as well? Is there anything else that the ECU uses as input to fire the injectors that it may not be getting a signal from?

I also tested the fuel relay, and solenoid resistor, both were within spec.

At this point, to verify the harness and CAS inputs, you might as well get down to the ECU and start checking voltages. Should have battery voltage (12) at each injector "input" to the ECU with key on (ECU plugs on, also). The voltage should drop a bit while cranking, though good luck on trying to decipher whether the voltage is falling due to the starter draw, or the injectors actually firing...Needless to say, if one is falling much more than another, the one not falling as much (or at all) may be bad...This scenario could be due to a bad ECU, also...If both don't fall at all, check that rear rotor housing ground (resistance from the ECU pins, if you wish).

As for the CAS, you can either remove the plug (big one), and read the two coil circuits with a meter for resistance (should be around 150 ohms each circuit), or check the inputs for voltage (probably a little less than 1v) while cranking (plug ON)...

Oh lord, don't get Wayne started with the CAS :).

Excellent this is what I was looking for. Like I said I just swapped over to the rtek 1.7 ECU... There maybe an issue there with a solder joint or some such that's causing the issue. Checking the injectors... AT the ECU, i can just stick the neg on my multimeter on the body and put the pos right in the corresponding Injector plug on the ECU...

here is my diagram... just tell me I've got it right...
THANKS WAYNE! you rock.

http://www.cochran-racing.com/harness.jpg

Hey, that's kinda cool, I've never used the harness diagrams like that before. Just remember that the plugs on the harness sides might be mirror-imaged when looking at the backs of them while installed on the ECU. Of course, if you verify wire colors before you poke, you'll be OK. And, you might find it easier to use a small piece of hard wire, like a paper clip, instead of the actual meter lead when backprobing the ECU with the positive lead...And if you're doing all of this by yourself, having clips to hold the ground on/wire in/etc. will help immensely...

Holy shit I AM AN IDIOT. I forgot the ECU case WAS the ECU ground. I had it unbolted going through testing everything. Henrik (the pocketlogger guy that does the Rtek7 upgrades) Pointed this out to me. I'm going to replace everything and check and see if this was the issue. Hours of pouring over FSM, checking resitances, conspiracy theories and it boils down to this. Man I feel stupid.

Sorry, but the ECU case is a ground for ...nothing. You can put the ECU on a piece of rubber and the thing will work just plenty good fine and never miss a tick. Right now I'm driving my 87 turboii arond with it not bolted to anything. Just sort of hanging around......like a hanging chad. (election season humor).

Well whatelse do you think it could be? I mean... it makes sense that this is the problem... it worked fine when it was bolted down prior to the rtek7 chip.

Perhaps a solder joint that is slightly broken on the circuit board and when the ECU is bolted down the break in the solder joint closes together???

Maybe when you get it bolted down and running right you can press down on the ECU with you hand to see if the engine starts to sputter or whatever the bad symptoms are. It sounds like a bad solder joint. Just guessing. Don't know.

Ok Bolted the ECU down, Still same issue. Measured voltage at the ECU on the primary injectors is 12VDC, at the injector itself .... a slightly different story... If I ground the black wire of the multimeter to the bell housing, I get good voltage, If I test the two wires together I get some really wierd fluctuating results, this is with the key in the ON position. Should I just reground the B/Y Wires right to a solid ground on the chassis? Also, Where can I find good injector grommets to replace the stock ones? I got some Pepboys ones and they do not seal correctly and it's leaking a small amount of fuel.

I also checked the resistance at the CAS, it was 153 ohms which is in spec.

Ok I can answer some of my own questions now. When injectors are pulsing they complete the circut and make 12vdc between the two wires. I'm going to assume that the CAS provides the signal to make the "pulse" on the B/Y wires shown above on the emissions harness.

This is kind of strange because when you run from the cas, through the front harness, to the emissions harness, and RIGHT to the injector. Bypassing the ECU. All the ECU is doing is Providing 12v and the cas signal from the front harness is making the link. If you look at the E.G.I Control unit plugs in the diagram. There are no B/Y wires.

Can anyone tell me where the B/Y wires are getting their signal from so I can run new wires to that point and verify this is the issue?

In the mean time I'm going to radioshack and building an LED with a resistor to simulate the injector firing. (thanks to swivel for this advice)

A picture is worth a couple words...

http://www.cochran-racing.com/wiring.jpg

The black/yellow wire supplies 12v to the injecotr coils.

The ECU makes the injectors pulse by applying and removing a ground on the other wire to the injectors. It does this on/off in milliseconds.

The CAS wires go from the cas to the ECU. The ECU uses that cas signal to pulse the injectors by putting a ground on the injectors.

So? What's the problem?

Have you tried swapping in the stock E-Prom in the ECU? I would imagine you socketed your ECU when you changed chips?

To answer your question with the picture. You can do it but you would need a resistor to get the impediance back up for the ECU. You probably would want to cut the wire on both ends and splice the wire in as a replacement. You should really try and find another ECU to test with before you go crazy.

Something is screwy here. You said the injectors are 2 ohm resistance. Then you post a jpg of a car that has high resistance injectors. So? Which is it? IF its a early 87 the proper diagram is the one I'm posting with this post.

And, do you now know how the injectors work???? And that you'd NEVER ground the black/yellow wire any more than you'd ground the positve wire on your battery? Say YES.

I was confused as hell when I wrote most of this post. What I was understanding is that 3F and 3E were constant 12v and the ground came from B/Y to pulse. NOW I understand it's the other way around. The pulse to ground is on 3F and 3E and B/Y should also be a constant 12V. When I take voltage at the injector harness B/Y is fluctuating from 5-6-0VDC with the key in the IGN On.

I didn't realize that diagram was high IMP. It's the only wiring diagram I have in my copy of the FSM for a turbo car. I have the online version of the S4 FSM, which is probably from a High imp 88 car.

I believe this is the problem since I can't measure out constant 12VDC at the injector harness on the black yellow wire.

I didn't know this earlier. I do now. Thats why I posted the diagram.

I can't isolate the CAS as the problem yet because I'm not getting 12VDC constant on the Black yellow wire yet. Where can I splice off this wire and run a clean wire to each injector?

I'm still not sure what type car you have. Theres one way to find out. Pull the air filter/afm out of the car. Look directly below it. If its a low impedence car you will see an aluminum covered resistor package with one large plug on it, mounted on the fender.. IF you have a high impedence car you will not have that item. It would be mounted on the fender with two bolts.

A car with high impedence injectors will have one wire at EACH injector that is Black/Yellow and no solenoid resistor package under the afm/air filter. Sooooo....if you have the black/yellow wires at each injector plug....and no solenoid resistor package.....the injectors should be about 11-13 ohms each.

If you pull the plug off the ECU, pins 3E is the front primary and pin 3C is the rear primary. IF you leave the plug off and put your meter on the PLUG side of 3E and 3C....you should see battery voltage and it should be a steady reading. That is if the injector plugs are attached and the key is to ON.

Yes IT IS a low impedence ECU, Harness and resistor pack. It's an 87 Turbo. And yes, I did measure out 12VDC constant on 3E and 3C. What should the Black/yellow wire test out as?

The Black/Yellow that feeds the Solenoid Resistor???? Battery voltage...approx 12v.

The Black/Yellow comes from the Main Relay and a Black/Green wire at the Main Relay feeds that B/Y when the Main Relay closes. It (B/G), originates from the 40amp fuse in the engine bay.

It's the same black/yellow that feeds the Lead and Trail coil assy's

I'm saying, what should the Black Yellow wires measure AT each injector plug. Because it's measuring out to be (fluctuating) 5-7-0VDC. It's not constant. And I understand it should be 12VDC constant.

See, that's where your confusing the issue. If you had a series four with the solenoid resistor package, you would not have a black/yellow wire at each injector plug. You would have one wire at each injector with battery voltage, but those wires would be colored .......Lg/R....Lg/B......Lg/W.....and just Lg

There are two wires at each injector... Regardless of what color each one is... your saying only ONE wire should have voltage? Because that IS the current situation.

I'm sorry for confusing you. I was assuming the wire on my harness was B/Y because I was going based on the 88 High IMP diagram. I know that I can pull 12VDC Constant off the LG wires... but the other wire has no voltage.

Only one wire at each injector should have voltage. It should be approx 12 or whatever your battery voltage is at that time.

The other wire on each injector goes to the ECU. The ECU only puts a ground on that wire when the engine is running. It pluses a GROUND to that wire to cause the injector to pulse. It does this in milli seconds. Only happens when the engine is turning.

If you put the injector plugs back on....and go to the ECU and pull the smallest plug off....and put your meters neg lead on a good ground like the ECU attach bolts....and the positive lead on the plug that you just pulled off at either pin 3C, 3E, 3F, 3H.....you should see battery voltage of approx 12v.

YOur not going to see any pulsing unless the small plug is put back on and the engine is running. You backprobe one or the above wires and you should see a voltage drop from whatever the alternator is putting out to the battery. Only the primary will have a voltage drop. The secondarys should remain a steady reading. Usually at idle you'll only see a one to two volts drop from about 13v. In other words maybe down to 10-11v or so at idle.

Ok. Thanks. It's back to the drawing board for me. I guess I'll try a different harness or ECU.

Well, if you have approx 12v at each of those four wires, it ain't the harness.

It's also unlikely the injectors are bad. I've taken injectors that have not been in a engine for over a year and they work just fine and dandy.

If the cas is connected up, and you have 12v on each of the pins at the ECU for each injector......and the fuel pump is running.....they should be injecting when you crank the engine over.

Another AND is ...and if you have not been moving the fuel lines around on the engine. Sometimes the return and pressure lines accidently get crossed. Won't work like that.

Ever pull the plugs out and crank the engine to see if you have a mist of fuel coming out the plug holes?

Maybe swap in another ECU and try it.

Look and see if you have 12v on the black/yellow wire on the white, two socket connector at the LEAD coil assy. It should be there since you have 12v at the injectors. But check anyway.

Yeah. I'll test that out. I mean the big changes I made here.... New ECU and a different harness... That's what started this problem with no fuel.... I can't figure it.

-Mike

Where is the DIFFERENT harness? Is it what they call the EMISSIONS harness? The one that runs on the right of the engine bay and feeds the injectors and solenoids?

Yes, Emissions harness. My old one looked a bit chewed up So I swapped one over from another n332 ECU car and heat wrapped it so It would last a bit longer (hah).

Well I did some more work today. Wired the injectors in to the rail (so they wouldn't pop out under pressure) and tested them, No spray. Wired them to a 12v powersource and they were spraying fine (per the FSM instructions).

So I started messing around with the wires down by the ECU. On the front harness -> Emissions harness plug I found a loose connection.

http://www.cochran-racing.com/harness.jpg

That wire indicated was making a clicking sound on the relays under the driverside of the dash. I replaced this wire and made a good connection and now I can hear this relay click on when I turn the car on. It still did not resolve the issue however. My next step is new harness/ECU.

Another thing I should note for you hailers, This is an 88GXL with a 87 turbo 2 motor, drivetrain, ecu, and harness.

No telling when Hailers will be back on, so I'll try to help you a bit...I tried to speed-read everything since I've last posted, and one question pops up- Have you read the 3 grounds from the ECU pins to the chassis? Two of them are on the same small ECU plug as the injectors, the third is on the middle plug, IIRC. All of these three go to the rear rotor housing ground. If the harness is good, and the ECU is good, the only thing left for correct injector operation is that ground.

Turn off all power on the car, read the ECU pins to ground (whichever pins they are in your application). Meter to resistance. Should get a couple of ohms or less (zero being what you're looking for).

Ok, I'll take a look at that.

Wayne,

I read your post on ECU troubleshooting. Is it worth my time to check all the voltages at the ECU if I cannot warm the car up? I'll come back here and post all my findings and see if anything looks way outta spec...

-Mike

Anyone? any of the other electrical guru's care to chime in on this?

If you're at the point that you're "grasping for straws", so to speak, the ECU checks will be more of a peace of mind thing now. Even if you can't start (or warm up) the car, a lot of information can be gleaned from most of the sensor readings.

So, is it worth your time? I dunno, what else do you have to do?

I think alot of frustration here would allieviated if I was to work around the problem and jump a few months ahead here by installing an engine management system. I'll go through the ECU tommorow with the meter and give a reading on all the pinouts.

injector problems
 

Sorry to interrupt, just reading this thread, I'm going through the same problem right now.(no fuel in one rotor) I just found a worn wire(It was rubbing under my cold air intake) coming from the solenoid resistor. Could it have hurt the ECU in anyway?

If I read right, you have 12v at the injectors and AT the ECU pins with the key to ON.

So, the way I look at it, you need to determine if you have spark. IF you have spark, but the injectors are not injecting, my guess is that for some reason the injector drivers in the ECU have gone tits up. So go look for spark. Got spark? Then get another ECU. used.

yeah, spark is fine on all wires and the rear rotor has fuel. The front one is bone dry. I had the entire engine bay stripped. Also did a street port and removed all the emissionsions. Sorry if i'm being a bit vague i'm just trying to keep it short.
what I was wondering is if a shorted wire(grounded) at the solenoid resistor could cause any harm.

just another thougt, would it throw a code if the injector driver was fried? I have the led's wired in the dash.

Well, I do have spark, however the injectors refuse to fire. I'll get an ECU as my next step.

Shorted wire would probably blow a fuse, then nothing would be working...

No, the CEL won't show a dead injector...

Last time something like this happened to me (only one rotor working), it turned out that some injectors I had purchased from another forum member were rusted shut (yet the coils still read out good). Might want to check out that possibility also :)

Much appreciated. It seems i did way too many things at once and now I'm paying the price. LOL. Anyway, I guess I'll just have to sort it out one problem at a time. The cars been sitting for almost 2 years now. It ran fine when i pulled the motor.(just a coolant leak.o rings) Problem is I built another fc this summer so I didn't finish everything on the 86 at once. I'm gonna patch up the wire at the solenoid resistor and swap the injector and hope for the best. Do you know if ether will hurt the motor? Hoping it won't but I'm afraid to find out the hard way. I used to use it on my fb in the winter time and the car went 220 k before dieing

I'm going to swap ECU's. I think I found the problem. That one wire I was referring to earlier that I re-ran because it was making a clicking sound... That wire fried the injector driver in the ECU I'm pretty sure of it. I'm going to do an ECU swap, and an injector cleaning for my primaries. Then I'm going to try it again.

wish me luck.

-Mike