Ok got a Real good Electrical problem come on in

[phrogs]

Ok this is on a 90 ZR-1 I know what I am checking and how to check it but not sure of what else my problem could be other than the ECM so im posting here to see what some of you think.
I also have it posted on the ZR1netregistry.

I have known for some time my #6 Cylinder has not been firing. I finally got a chance today to open it up and verify that my primary injector for sure is not firing and double check all of my wiring.

The car runs like ****, I have a tech 1 and figured out how to turn off cylinders, when I pick #6 there is no change this is just another verification that 6 is not firing.


I have newer Injectors, Replaced all plugs, wires, and coil paks I have checked everything and all ohm within specs.

Compression in #6 is good as well.

I have good spark.

#6 spark plug is clean as a whistle no carbon at all while the other spark plugs do have carbon and have been firing.

I decided to pull the plenum and do an injector spray test.

I removed all of the injectors from the Injector housing's and unplugged all of them but #6.

For this to work the Ignition module must be plugged into the harness I just pulled it off of the plenum and pluged it back into the harness.

I placed a Container under the injector to see if it sprays fuel and low and behold #6 Injector is not spraying fuel.

I also tested the #1 primary injector the same way and it sprayed no problem so I know my troubleshooting method works.

I plugged in the #4 primary injector harness into the #6 injector and it sprays when doing the same test so the injector is fine it is something electrical.


I had checked the ohms on the injectors before I pulled the plenum just to see what they were reading, all were around 14-15 ohms.

#6 was in the 14-15 ohm range so its right there with the rest of them its fine I also know from the above test that it is in working order.
That also means that my wires and conections are good from the ECM yellow plug to the #1 inj fuse. They checked out fine.

I also checked the individual wires from the # 6 injector primary plug and the wires are at .005 ohms or is it .05 ohms I had my DVM set on 200 ohms just like when checking the injectors its one of those readings. I checked the ECM to injector wire and I also checked the injector ground to the fuse and it reads the same so the wire's are good.

So no breaks in the wires that would be to easy!

I removed the female wire for the #6 injector from the Yellow weather pack plug and checked it on the ECM pin by sliding it onto the male pin as if it was in the plug it is tight with a nice drag to it and fits nicely so I do not suspect that it is not getting a conection. Then re-installed back into the yellow weather pack.


The only thing left is the ECM in my eyes.

Is it possible that the ECM could have an issue and not fire one injector?

Does anyone know how I could check that the ECM is sending a signal to the Injector? Im sure there is a tool out there for it but I do not have one

Please help I need my car running



Fire away with your thoughts I feel I have checked what I can without a Extra ECM to verify that it is not the ECM.











**Ok UPDATE**


Just got this from Marc Haibeck so if anyone has any issues with your ECM try these guys out I will be contacting them today and will update the cost and if its a rebuilt or exchanged unit.



Hi Johnny,

You did a nice job covering all of the possibilities and describing it. I agree that the most likely suspect at this point is the ECM.

I have had good experience with K & B Products for ECM repair.
http://www.kandbcorvetteproducts.com/

They have repaired 5 out of the 6 ECM's that I have sent them. On the one unit we gave up trying to fix it and they did not charge me for a repair.

Best of luck.

Marc

[WB9MCW]

WOW This is a good one for sure - I think you are right time to do a ECM sub.

Let's see what the others say!

[ittlfly]

Does anyone know how I could check that the ECM is sending a signal to the Injector? Im sure there is a tool out there for it but I do not have one.

I think you are talking about a noid light. It plugs into the harness at the injector. You crank the engine and the light flickers to show that the ECM is sending the fire pulse to the injector....Napa carries them....or any of the tool truck..ie: Snap on, Mac etc

[phrogs]

Does anyone know how I could check that the ECM is sending a signal to the Injector? Im sure there is a tool out there for it but I do not have one.

I think you are talking about a noid light. It plugs into the harness at the injector. You crank the engine and the light flickers to show that the ECM is sending the fire pulse to the injector....Napa carries them....or any of the tool truck..ie: Snap on, Mac etc


Yeah thats it!

[XfireZ51]

If the wires are good, could be an injector driver. I would do an ECM swap.

[phrogs]

Yeah Now that I'm fresh out of ECM's

:o

[bdw18_123]

Sounds like there is a good chance it is the ECM, especially after all the extensive troubleshooting you have done already.

My '90 Z had the same issue, although the only reason I found out there was even an issue (car wasn't running then) was because I loaned my ECM to Tom (tccrabs) for troubleshooting he was doing at the time and his car ran crappy just like you describe with yours. He also took it to Jeff Flint (jeffvette) and his car ran the same crappy way with my ECM. They even swapped out PROMS and that didn't help.

So obviously it was the ECM itself that was causing the misfire (probably a bad injector driver on the board or something, I don't know. I sold it to Haibeck for the $100 he was offering for bad ZR-1 ECM's), it wasn't the original computer though, it was a rebuilt one that was put in sometime in 2001. I am now running an original ECM that I bought from sgreg back aways with the PROM that came with my car and it is running great.

[Pete]

If the wires are good, could be an injector driver. I would do an ECM swap.


:sign5:

That's the only thing i can think of.
Isn't there any other Z boys by you to try one of there ECMs.

Pete

[tomtom72]

:o I have an ECM that has a DTC 61, secondary vacuum fault code. It is an internal issue. It does let the car idle fine, it just restricts the driving rpm to 3k. I'll ship it to you as I think it would be okay as a test swap @ idle if you think it would help?

The ECM is the original one from my 90 btw. I just don't have a EPROM to put in it.

A noid light would do the same thing though.:o

:cheers:
Tom

[tccrab]

Johnny:

I had a similar misfire, although mine was intermittent.
http://www.zr1.net/forum/showthread.php?t=10828&highlight=probe+plug
If you've never stuck the probe from your volt meter into the ECM plug, then I wouldn't worry about it.
But if you have...............
:censored:

TomC
'Crabs

[GOLDCYLON]

Johnny:

I had a similar misfire, although mine was intermittent.
http://www.zr1.net/forum/showthread.php?t=10828&highlight=probe+plug
If you've never stuck the probe from your volt meter into the ECM plug, then I wouldn't worry about it.
But if you have...............
:censored:

TomC
'Crabs

I remember that TC what about a bad quad driver Johnny? Or that coil base as a possibility as well?

[phrogs]

TomC I remember your issues and I checked the pins they grab onto the male pins on the ECM with definate drag so I have conection there.

What im going to do to day is swap the pins from #6 into another injectors wire spot on the ECM and see if it fires that cylinder just for grins.

Im going to get the Noid light and see what that tells me.

As for the Coil pack base Does that signal to the ECM that the spark plug is sparking before it allows the injector to pulse?

[tccrab]

As for the Coil pack base Does that signal to the ECM that the spark plug is sparking before it allows the injector to pulse?

Johnny:

I don't have schematics here at work, but I would suspect that there are independent circuits that control the coil pack and the fuel injector functions.
My thinking is that the coils are "waste spark" and fire twice per rotation where as the fuel injectors only fire on the intake stroke.
It's possible that the same trigger is used to fire both functions, but the control circuitry are most likely different.

TomC
'Crabs

[XfireZ51]

Johnny:

I don't have schematics here at work, but I would suspect that there are independent circuits that control the coil pack and the fuel injector functions.
My thinking is that the coils are "waste spark" and fire twice per rotation where as the fuel injectors only fire on the intake stroke.
It's possible that the same trigger is used to fire both functions, but the control circuitry are most likely different.

TomC
'Crabs

Firing the coils packs is controlled by the Ignition Module, not the ECM. ECM controls the timing.

[phrogs]

Firing the coils packs is controlled by the Ignition Module, not the ECM. ECM controls the timing.


so what signals the ECM to fire the injectors?

something must tell it that it is time to fire. Is it the Camshaft sensor?

I am trying to reduce the possibilities of other things being broken other than the ECM but it looks like it is the ECM all day long..

[GOLDCYLON]

Firing the coils packs is controlled by the Ignition Module, not the ECM. ECM controls the timing.


This was my understanding as well which is while my money is still on the coil sytem or the module under the plenum

[Demps]

JP,
Have you changed the coils around to rule out a partial failure?
Trd

[phrogs]

I just took the #6 and #1 injector wires and swapped them in the ECM weather pack so I could double check my harness I installed the harness and with the Noid light checked the harness The #1 injector worked with #6 wire pluged into the #1 spot. Its just the #6 not working. It seems to me that the ecm is my problem since it controls the primary injectors.

[tccrab]

Johnny said he had good spark in his original post.
Just no fuel from injector.

My bet is that it's ECM related.

Beg, borrow or steal another ECM, plug it in and start 'er up.
I'll bet dollars to donuts that the problem goes away...

TomC
'Crabs

[Demps]

Johnny said he had good spark in his original post.
Just no fuel from injector.

My bet is that it's ECM related.

Beg, borrow or steal another ECM, plug it in and start 'er up.
I'll bet dollars to donuts that the problem goes away...

TomC
'Crabs

Oops, saw the "not firing" and ran the wrong trail. Hopefully the ECM will fix it.
Ted

[Corbusa]

For the 1990z are there aftermarket ECM's ? or where would a person get one to keep on the shelf? Expensive.? The reason for my questions are I hope to keep my ZR for a very very long time and I need all the education I can get and slowly get parts I can afford.
At BG this year is there anyone that brings parts etc for educational purposes? Thanks Sorry I didnt mean to Hi-jack the thread..

[GOLDCYLON]

My money is on the quad drivers which control the injectors. In MY92 these became part of the ECM and chip circuity. We are however talking about Johnny's MY 90. Johnny swap your drivers (They are identical) then tell us which side is firing incorrectly after the swap


I sent you a PM as well. GC

[Paul Workman]

My money is on the quad drivers which control the injectors. In MY92 these became part of the ECM and chip circuity. We are however talking about Johnny's MY 90. Johnny swap your drivers (They are identical) then tell us which side is firing incorrectly after the swap


I sent you a PM as well. GC

Mine is a '90, and I wuz thinking about them too (I assume we're both talking about the two quad relay modules?). But, looking at the schematic in the FSM, the primary injector current does not pass through them; only the secondaries (two quads = 8). Based on what I've read has been done - not actually being there - the ECM is floating to the top of the suspect list for me too. (Note the cautious tenor, as I (we all) have been wrong once or twice when it comes to 'lectrik chit!)

I seem to recall there are at least two schematics in the FSM touching on the ECM, DIS, and injectors... I'll keep looking, but my money is on the ECM (at the moment).

Thinking out loud, I know Marc Haibeck provides ECM service (sends them out, if I recall), so if it is the ECM, then there is a solution to that problem.

I tell ya...dealing with GM to get information on repair parts - or even just spec sheets - is a real PIA. I'm just sayin...

P.

[GOLDCYLON]

Mine is a '90, and I wuz thinking about them too (I assume we're both talking about the two quad relay modules?). But, looking at the schematic in the FSM, the primary injector current does not pass through them; only the secondaries (two quads = 8). Based on what I've read has been done - not actually being there - the ECM is floating to the top of the suspect list for me too. (Note the cautious tenor, as I (we all) have been wrong once or twice when it comes to 'lectrik chit!)

I seem to recall there are at least two schematics in the FSM touching on the ECM, DIS, and injectors... I'll keep looking, but my money is on the ECM (at the moment).

Thinking out loud, I know Marc Haibeck provides ECM service (sends them out, if I recall), so if it is the ECM, then there is a solution to that problem.

I tell ya...dealing with GM to get information on repair parts - or even just spec sheets - is a real PIA. I'm just sayin...

P.


Yeah Paul, Johnny said he has already tried (swaping the drivers) so its on to the ECM I guess. Also the QUAD drivers only affect the secondaries and not the primary injectors. Its hard to believe only one injector out of one bank is effected by the ECM although. I know he said the harness was good but maybe there is a micro break somewhere in the harness. Anybody have an ECM to loan him. I dont? GC

I really hate electricial problems

[ittlfly]

so what signals the ECM to fire the injectors?

something must tell it that it is time to fire. Is it the Camshaft sensor?

I am trying to reduce the possibilities of other things being broken other than the ECM but it looks like it is the ECM all day long..

FWIW... even with a bad cam shaft positioning sensor the engine will run and fire all 8 injectors. If it was a bad sensor it would be coding out #31. I have a new GM OEM cam positioning sensor if you are interested. A new Gm one can be hard to find. I scored a new one fron Chris over at Superior Chevy in St Louis awhile back. Cheapos are a dime a dozen....

[ScottZ95ZR1]

I have a new GM OEM cam positioning sensor if you are interested.

I think I'd like to buy the sensor if Johnny doesn't need it, Steve.

[ittlfly]

I think I'd like to buy the sensor if Johnny doesn't need it, Steve.

PM sent..

[Pete]

FWIW... even with a bad cam shaft positioning sensor the engine will run and fire all 8 injectors. If it was a bad sensor it would be coding out #31. I have a new GM OEM cam positioning sensor if you are interested. A new Gm one can be hard to find. I scored a new one fron Chris over at Superior Chevy in St Louis awhile back. Cheapos are a dime a dozen....

Yeap,what he said.
Try it yourself unplug the cam sensor she will start and run but will get SES light.

Pete

[XfireZ51]

Yeap,what he said.
Try it yourself unplug the cam sensor she will start and run but will get SES light.

Pete

The cam sensor is used by the ECM for sequencing the injectors. Basically it tells the ECM where #1 cylinder is. After that the ECM "knows" what the firing sequence is. I like the idea of swapping harness connectors and seeing if the "new" #6 now fires.

As for the primary/secondary operation, recall that the LT-5 ECM is essentially an L-98 ECM since it was too costly to develop and certify a purpose built engine control system. The L-98 has 8 injectors. To drive the additional 8 injectors the LT-5 uses the primaries to provide the firing signal to the secondaries. The secondary relays are used to provide the power. In a way, its a bit like the operation of the LSx coils. The ECM only provides the firing signal, the power comes from the BATT.

[phrogs]

Yeah the Secondary Modules have been swaped sometime ago just for giggles and it didn't change anything but again they are for the secondaries. The ECM controls the Primarys.

It might be a problem finding a replacment ECM. Plus Im about to be moving again since I got my Job offer out in New Mexico. Working on CV-22s for the Air Force. Never thought I would be a Military Contractor LOL

[phrogs]

Ok See UPDATE in my first post!
From Marc Haibeck


Hi Johnny,

You did a nice job covering all of the possibilities and describing it. I agree that the most likely suspect at this point is the ECM.

I have had good experience with K & B Products for ECM repair.
http://www.kandbcorvetteproducts.com/ (http://www.kandbcorvetteproducts.com/)

They have repaired 5 out of the 6 ECM's that I have sent them. On the one unit we gave up trying to fix it and they did not charge me for a repair.

Best of luck.

Marc

[GOLDCYLON]

How much does the repair service normally cost ?

[phrogs]

Well,

$325 and ten days to fix your ECM.
Comes with a one year warrenty.

[VetteVet]

so what signals the ECM to fire the injectors?

something must tell it that it is time to fire. Is it the Camshaft sensor?

I am trying to reduce the possibilities of other things being broken other than the ECM but it looks like it is the ECM all day long..

Johnny,

Synchronous fueling is controlled by the ECM utilizing reference pulses from the ignition module to achieve the correct injector timing. The ignition module utilizes the crank position signal to generate the reference pulses. Sounds like you most likely have a faulty injector driver in the ECM, although it could be anything in the ECM involving that particular injector circuit.

For what it's worth, I am currently in the process of developing a schematic for the 1228331 ECM. I have identified all of the integrated circuits and am working to track all of the circuit board traces and account for the discrete components. I am also building an ECM test bench for ECM hardware and code testing.

My 1991 BFXB code disassembly is coming along quite well. I have over 80% of the variables and tables identified and more than 70% of the code commented. I'm at a bit of a standstill on the code until I can get the test bench finished so that I can identify the remaining I/O ports.

Jep

[VetteMed]

Thanks for posting this update, Johnny. Good to know of an option for ECM repair.

[GOLDCYLON]

Well,

$325 and ten days to fix your ECM.
Comes with a one year warrenty.


Thanks Johhny thats good to know. GC

I hope this fixes your issue it nice when members share.. it helps the whole community

[Tyler Townsley]

Johnny,

My 1991 BFXB code disassembly is coming along quite well. I have over 80% of the variables and tables identified and more than 70% of the code commented. I'm at a bit of a standstill on the code until I can get the test bench finished so that I can identify the remaining I/O ports.

Jep

I have a copy of the decodedd GMcalibration for the ZR-1. I have lent it out a couple of times to TodP and Corey H who have a completely commented calibration files for all versions. You might contact them to crosscheck what you have done so far.

Tyler

[VetteVet]

I have a copy of the decodedd GMcalibration for the ZR-1. I have lent it out a couple of times to TodP and Corey H who have a completely commented calibration files for all versions. You might contact them to crosscheck what you have done so far.

Tyler

Thanks Tyler! I haven't had much luck getting anyone to share much of anything. That's why I'm having to reinvent the wheel.

Jep

[Corbusa]

I guess I'm always the one asking the dumb questions. So here goes AGAIN:) Has/ does /can anyone shoot a video while working on the injection/ electrical on the ZR's ? I mean if someone could show the removal of the injectors and checking electrical with meters, checking the ECM etc etc Like vettevet is doing ..That sure would help us new people out and keep all of us up to speed .I'd sure buy one.. I guess my thought was people ( in general) are always posting vids. on Youtube. It cant be too hard to do. Thanks

[XfireZ51]

Thanks Tyler! I haven't had much luck getting anyone to share much of anything.

Jep

Jep,

Looks like you still haven't.

[phrogs]

I guess I'm always the one asking the dumb questions. So here goes AGAIN:) Has/ does /can anyone shoot a video while working on the injection/ electrical on the ZR's ? I mean if someone could show the removal of the injectors and checking electrical with meters, checking the ECM etc etc Like vettevet is doing ..That sure would help us new people out and keep all of us up to speed .I'd sure buy one.. I guess my thought was people ( in general) are always posting vids. on Youtube. It cant be too hard to do. Thanks



If I had someone to video me I could do that but Didn't really think about it when I was doing the work.

[XfireZ51]

If I had someone to video me I could do that but Didn't really think about it when I was doing the work.

Doesn't Haibeck already offer something like that?

Maybe this will help.

[phrogs]

he has something like that but probably doesn't show how to check them with a DVM.

[XfireZ51]

Maybe this will help. Don't need to remove injectors to test resistances.

[GOLDCYLON]

he has something like that but probably doesn't show how to check them with a DVM.


Your right he does not use a DVM. His Video shows the grounding a wire of Pack #3 on the ECM to verify secondares are engaged as well as direct power extension wire to the fuel pump to power up the fuel rails to check for leaks while the plenuim is off. He also how to reset the ECM without pulling the negative cable.