Only getting spark when i let off the ignition

[bmwracing_6]

first off i had the hardest time to get a spark and have checked the cas and ignition module, and it has a new ignition coil and new ecu and this is what happens... i will turn the key and i do not get a spark and when i let off the ignition it will throw a spark.. i am lost and so confused to why this would happen.... somebody please help me thanks!

 

[steve]

I heard that it could be the mfi relay that is cutting off and on very quick thus preventing spark. Is this true and what could make this happen?

You'll have to tell us if it's the MPI relay chattering or not. It's possible for it to do so and if that's the case the ECU won't really stay running long enough to start the car.
Either low voltage or a bad ECU can cause the relay to chatter.

Steve

 

[bmwracing_6]

I'm willing to bet if you keep bumping your thread it will be put under lock down. Be patient everyone here knows how it is to have the dsm down for a while and I'm sure who ever can help will help. This is not a area of normal knowledge for most. Does It turn over while not sparking?

yeah it turns over just no spark

 

[bmwracing_6]

You'll have to tell us if it's the MPI relay chattering or not. It's possible for it to do so and if that's the case the ECU won't really stay running long enough to start the car.
Either low voltage or a bad ECU can cause the relay to chatter.

Steve

well actually i think it is coming from the ecu... is this normal or what because i know for a fact that the ecu is good because it is a new one

 

[sniver]

Things can be defective, possibly cross check the ecu in your 92. As far as i can tell i don't see any relays in the ecu..so i doubt the sound is from the ecu. the mpi relay is just inches away, put your finger on it while you turn the key on,you will be be able to fell it click. It should click once when the key turns on and once more after you turn it off. If its chattering it'll click several times very rapidly while the key is on. again you could feel with your finger.

 

[bmwracing_6]

ok i will do that tommorow and see where it is coming from and report it back on here

 

[steve]

There is nothing in the ECU to make noise. Since the only "new" ECUs come from the dealership and cost $1200 I have a hard time believing yours is new, that means it's questionable.

What do your check engine light and boost gauge do when you turn the ignition on?

Steve

 

[bmwracing_6]

i mean i did not mean "brand" new but used and should be in working condition. new to mean i guess i should say but i guess that it is coming from the relay then if it is not possible... however i will check tomorrow so i will be 100% sure of the problem and i will post back on here. i had to splice the wiring harness for the swap because i did not have a complete harness from the car or the engine i bought. Could this cause low voltage because it may not have a 100% good connection? So if the relay clicks on and off repeatedly then the ecu is bad? cause if it is i am going to get the company to replace it. by the way steve your the man you have helped me further my knowledge about dsms thanks for the help but i guess that is why you are a "Dsm Wiseman" i will post up here tommorow so look out for it.

 

[bmwracing_6]

oh whoops almost forgot umm yeah the check engine light comes on and the boost gauge sticks at 0.... but i will check on that for you so i can be 100% sure.

 

[toybreaker]

I'm getting a little confused here...

You have a 91, that you're working on, and a 92 for parts, right?

Put the ecu from the suspect car into the running car, and that's that. It either runs or it doesn't.

Please, slow down a little, and lets approach this logically.

You've got a whole bunch of threads running about this right now, and I don't have any idea where we're at, or what's what.

I just re-read this whole thing, and I'm somewhat confused as to where we actually are with this.

Is this a motor swap that hasn't run yet?

Have you been making major wire harness changes?

Also, are ALL the grounds in place? There's several mission critical grounds in the engine compartment, and inside the car near the ecu as well. If any of these has been corroded/damaged/left off you will get all kinds of weird symptoms, including exactly what you're describing.........

Edit; just saw your pm. I am happy to help, but I'm still a little groggy from new years sneaky: ), and the fiesta bowl, , so please, let's slow down some, and approach this in a logical step by step fashion, or you're going to be performing a lot of extra work checking things that don't need to be checked, and quite possibly skipping right by things that do need to be checked.

Us old guys have problems understanding you young'uns at times. Correct grammar, spelling and punctuation will go a long way towards getting your problem solved, as the people with the answers will understand the questions mo' better.

I'm actually quite suprised your thread didn't get locked during your bump-a-thon. (Defiant must be on vacation... )

Capische?

(//old man with a hangover rant off// )

 

[ECLIPSE4x4]

Stop bumping your thread, if it is bumped one more time it WILL be closed.

If you have to add to something, edit a post, do not post a new one everytime you want to add a comment.

 

[bmwracing_6]

Ok sorry about that I am just very egar to get the car running. Ok here is what I have done toybreaker first off I have a '92 gsx that I bought running for myself the '91 is my brothers project car we bought it as a roller just no engine.

First I thought it was the coil and I took the coil off and tried to clean the connections on the bottom. I wired it back wrong and it blew the ecu. I got another used ecu from the place I bought the engine from. The engine is a JDM engine (just for reference).

Then I checked the CAS took it to the 92 (running car) started right up on the 92. I did the same thing with the coil pack ignition module and the MFI relay and intend on doing it now to the ecu (just to make sure).

Right now I am into looking at the MFI relay that you wrote about earlier. So how can I check this I do have a manuel and have been looking how the wires lay out but that wont help me with my problem. I am going to get a Voltmeter today so if you can walk me through the MFI check procedure that it would help me alot. If the test comes back bad then would I be in need of a new wiring harness? I will also look out for those ground wires.

Thanks guys for the help and sorry for bumping the tread so many times I am just so frusturated with it cause I have been working on it for a month now.

 

[toybreaker]

Hey, it's cool, I know what it's like to have the jones to be rallying, not wrenching...

Thing is, this is one of those rather complicated issues that will most likely have a very simple cause.

So many things were changed, swapped around and field tested that we really need to slow down and focus on one area, finish with it, and then move on to the next step with the information from the last step guiding us where to go next.

I am trying to write a how-to on how to check the mfi relay, if you can bear with me for a bit, I'll see what I can do for you later today after work.

If you could take some time and just check over everything you had to remove/change/install it would be very helpfull.

You might find a forgotten ground, or unplugged connector.

At the very least, it will give you a little more confidence that it's not something really simple. Maybe run the fuse box with the testlight/voltmeter again, just to be sure everythings good to go. If you melterfied an ecu, that current had to come from somewhere.

Could you post a pic of the ecu damage, please? I'm sure Steve could tell us exactly what happened during that episode, and what to look for as far as possible collateral damage that could have happened to the other components connected to the ecu.

Hang in there man, I know that you'll get to the bottom of this.

 

[bmwracing_6]

Ok all the fuses are good to go i forgot about the grounds so i am going to have to check again. The ecu was already diagnoised by steve however he did not tell me exactly what it came from but here is the picture again.

http://i132.photobucket.com/albums/q28/bmwracing_6/porject91gsxburntecu.jpg

I saw that there is a black cylinder in about the middle of the ecu that has a wire comming out of both ends that I have noticed it lay on it side too i did not tell steve about this cause I just noticed it. Well I will go check the grounds and I will wait you man thanks again your saving me from giving up... my friends here think I am crazy and think it is waste of my time but I know these cars can be fast.... I just cant wait to see it when I get it running. Yes I said "when" cause I want to keep a confident state of mind.

 

[toybreaker]

It's cool you got a voltmeter It's a very valuable troubleshooting tool.

In order to check the power into and out of the mfi relay, we need it to be plugged in and accessable. I put a mailing envelope down to ensure I wasn't going to short anything out against the dash, and then just pulled it out to the side..

You probably won't be able to put the red positive voltmeter probe into the mfi relay connector far enough to touch the wires. You can use a bent paperclip held in the alligator tip to backprobe the connector Please, be carefull you don't touch anything except what you're trying to test.

Put the black voltmeter lead alligator clip on a good ground. The one I have mine attatched to in the picture is where the ecu and mfi relay receive their ground to the chassis.

Plug the two leads into the voltmeter, Turn the voltmeter on to volts, dc, and you're ready to rock.

In this picture, we're testing the battery supply voltage on the black and red wire, terminal 10 of the mfi relay. We will test the rest the same way.

 

[bmwracing_6]

What do your check engine light and boost gauge do when you turn the ignition on?

Steve the CEL binks a couple of times and then goes off and the boost gauge stays at 0.

Does the car need to be on? also is it suppose to read 12 volts? also it is 10:30 here in Virginia so I will be doing this tommorow. and i do this for all of the postive wires? do i look for a certain reading on each one? I am also learning how to use this voltmeter as I am doing this so it may take me a while to use it correctly as dumb as it may sound. However if you would like you can procede to the next step of checking th mfi relay.... Thanks again man

 

[steve]

Steve the CEL binks a couple of times and then goes off and the boost gauge stays at 0.

The CEL shouldn't blink at all. When you say that the boost gauge stays at 0 do you mean it moves to 0 and stays there or the gauge doesn't move from where it sits at below -7

The ignition needs to be on for most of the tests of the MPI relay.

Steve

 

[bmwracing_6]

it sits at -7 then goes to 0 when i turn the key... so if the CEL is blinking then what could that mean. I am guess many things but could it have something to do with a starting problem? By the way Steve i know you told me that

That's the resistor to limit the current on the +5v sensor voltage pin (pin 23). Somewhere you have it shorted to ground.

But what can this mean and where could it be coming from?

 

[toybreaker]

My apologies!

Had a nice artcle for the how-to's,. but I managed to lose it in the posting proccess.

Anyway....

The mfi relay is just an electrically operated switch. It receives power from the battery and the key, and when activated, sends that power out to the fuel pump and engine.

It has three coils controlling two circuits. Two for the fuel pump, and one for the engine sensors.

The black and red wire at terminal 10 should be hot and showing 12v all the time.
. this is the feed wire in from the battery for the engine sensors/ecu/injector resistors

The two red wires at terminals #4 and #5 should show 12v when you turn the key to the on (and start) position
. these are the wires out to the engine sensors/ecu/injector resistor pack.

The black and white wire at terminal 3 should show 12v, with the key in the on and start position.
. this is the feed wire in from the key to run the fuel pump.

The black with green wire at terminal 2 is the wire out to the fuel pump/ecu.
. It should show 12v when cranking the engine, as well as when the engine is running.

. If it does not, you can carefully apply ground to terminal #7 (white/red wire) of the mfi relay with a jumper wire, (with the key on.) This should turn on the pump.

That's the short version of how to test your mfi relay.

Please let us know what you find.

 

[bmwracing_6]

i will go work on this now however i know the fuel pump is working because it is spraying gas and there is gas coming out of the o2 housing... i will get back to you on what i find

 

[steve]

The mfi relay is just an electrically operated switch. It receives power from the battery and the key, and when activated, sends that power out to the fuel pump and engine.

It has three coils controlling two circuits. Two for the fuel pump, and one for the engine sensors.

The black and red wire at terminal 10 should be hot and showing 12v all the time.
- This is the feed wire in from the battery for the engine sensors/ecu/injector resistors

The two red wires at terminals #4 and #5 should show 12v when you turn the key to the on (and start) position
- These are the wires out to the engine sensors/ecu/injector resistor pack.

You must have lost pin 8 in the posting problems. (It runs to ECU pins 63 & 66)

If the 12v doesn't show up on pin 4 & 5 connect pin 8 to ground and see if that activates the relay and switched the power from pin 10 to pins 4 & 5.

Steve

 

[bmwracing_6]

Ok here is what I found all the wires I have tested came back 12v except for the last wire #2 black and green wire however I just got back and just noticed that I need to test wire #8.

Here is what happens to pin 2 when I turn the key to start the engine the volts will stick around 9v and when I let off the key it will shoot up to 12v but only for a second then it goes back to 0 like it should. Could this be my problem cause it seems to similar to the starting problem I had when I got spark when I let off the ignition.

Oh and Steve the CEL is not blinking anymore either I was half asleep or the car is playing games with me .

 

[steve]

Other than your cranking voltage being low (9v) the rest sounds good so I'd rule out the MPI, MPI and Ignition fuses.

Do you have a good ECU or just the ones you keep burning up? You've been through two of them now right?

Steve

 

[bmwracing_6]

steve nah I burnt one and the other one I got another one from the place I bought the engine from this one does work because I put it into the '92 (running car) and it work good.

I still need to check the pin 8 wire I will get back to you on that.

 

[steve]

Nope, think about it. If you don't have power at pins 4 and 5 with the ignition switch off and do whith it on then the MPI relay is working. And indirectly the ECU circuit for driving pin 8 is working.

Steve

 

[bmwracing_6]

Ok so I checked out pin 8 and I now see that I dont have to? But I only got a reading of 9v from pin 8 when i checked it. Is that good or bad? If good then what is the next thing I need to check?

Whats next on the list toybreaker?

Ok I was just fooling around and looking at the wiring I found 3 wires that were never connected... Now I never wired the harness together it was my friend that did that... I found a thin solid black wire that when I checked the volts on it the MFI relay clicked and the injectors made a noise this also happened when I grounded the wire. This wire was only putting out about 0.2v

There are also 3 more black wires that are already connected two thin ones and one thick one I checked the voltage one the thin ones and i got 0.9v for one and 1.1v for the other. When i used the test light i could not get a light from the black one i found that was not connected.

Here are some pictures of these wires
This first picture is of the three wires not connected at all Top wire is a Green/Yellow stripe middle is Black/ Green stripe and bottom is the solid black wire that made the MFI relay click when i ground it.

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This is one of the wires that were connected

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This is one of the wires connected

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