Re: Intermittent no start condition
The sensor outputs a very low voltage and it would be millivolts......
A Fluke can read this accurately.... I just had some trouble with the ABS sensors in my GMC.... They do the same thing.......and can easily lose low speed output from rust building up under them. I found the info readily available online as to what they should read just by turning the wheels by hand......and a little work with a file and a wire brush.....and Viola....all better... That was after I had already replaced both sensors and they were probably good..... |
Re: Intermittent no start condition
Mike/Joe/Kirk,
I did the test of the crank trigger as Joe stated. Simple and effective. Next, I spoke to MSD and the tech rep indicated the ohms reading of the MSD pickup (test leads on purple and green wires) should be between 65 and 85 ohms. This is for the non magnetic pick-up.....magnets are in the wheel, not the sensor. Will test mine tonight along with using my newly acquired noit light to test injectors. Also got a few other areas to check (connections, grounds etc) tonight. |
Re: Intermittent no start condition
Rich , I believe there is a special coverage for the wheel speed sensors you can check with your local GM dealer as it varies year to year. We clean and apply a compound to the knuckle so rust doesn't redevelope. John, good deal testing this stuff is not hard at all, but does require a few items, sounds like you're on top of it. Joe Oh and sorry bout that wrong resistance spec, I was shooting from the hip on that, which is the spec GM uses withtheir sensors must have got stuck in my head.
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Re: Intermittent no start condition
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Re: Intermittent no start condition
FED 387....after testing every circuit I could test....it appears that the only logical conclusion I can come to is the coil is the problem, as you stated a few days ago.
Tonight, I checked the ohms on the crank trigger sender....78.2 (MSD said between 65-85)...OK Tried to start....fired right up. Repeated 2 more times and fired up. 4th. try....no start Grounded coil wire (dist. end) to block in two different locations approx. 1/16 gap......no spark Tried again about 15 minutes later....spark like 4th of July. Replaced coil wire.....fired right up. Gotta be the Friggin coil..... Going to get one tomorrow. |
Re: Intermittent no start condition
Went through test process again this morning.
I believe when I tested the coil last night (metal screw in dist end of not) I did not have a proper connection.When I use a spark tester, it gives me a signal. Throw out last nights test. Tried to start car this AM....fires right up Second try ...no start. put spark tester on coil AND noid tester on injector simultaneously...Result...no start, spark at coil, NO light at noid tester. Repeated several times same result. HELP AGAIN!! |
Re: Intermittent no start condition
John....It sounds to me as I said before.....You have an intermittent wire connection problem between the ECU and your MSD or possibly your battery connections to your ECU.
It has been to long for me to recall the exact wiring connections needed between the MSD and the Accel ECU..... Accel still shows the wiring diagrams and tons of info on their website. The ignition connector on the Accel unit and all the connections related to it are where I believe your trouble may be. Your ECU needs to be switched on and also gets a tach signal from the MSD.... Without actually seeing your car and wiring it's impossible to tell you how to fix it. You have isolated the problem and now know it IS the injectors are not turning on and supplying fuel to the engine......so the ignition system is not the problem..... |
Re: Intermittent no start condition
Check for battery voltage in the injector harness when you have a no start condition.
Kirk |
Re: Intermittent no start condition
This is for a Gen VII Accel ECU and may be helpfull
The connector labeled IGNITION is what powers up the ECU.... http://data.prestoliteperformance.co...ng_diagram.pdf A lot of info available here.. http://info.accel-ignition.com/dfi/a...-download.html |
Re: Intermittent no start condition
The battery is something to consider before you spend real money. It could be failing in a way that it is generating electrical noise.
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Re: Intermittent no start condition
I may have asked this before, but does the crank trigger supply the signal for the injectors, or is it the Opti-Spark ? My DFI box used the Opti-Spark for the injector signal, and the crank trigger for the ignition.
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Re: Intermittent no start condition
John, battery is brand new.
SS3011, The way I understand it, the tach signal from the MSD fires the ECU and the injectors get the signal from the ECU....I may be wrong on this....cause I don't understand all the intricacies of this unit. I spoke with an Accell dealer in Alabama....He suggested isolating the ground and running it all the way to the negative terminal on the battery.I did this today.....no start. I'm pulling my hair out!! John |
Re: Intermittent no start condition
I don't know if you are considering updating, but if you are I highly recommend calling David Page at FAST. He can get you hooked up with a Fast system.
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Re: Intermittent no start condition
Why I ask about what triggers the fuel injectors is the Opti-Spark has a connector that goes into the top of the cover, opposite side from the coil wire. Is there a connector attached to that terminal ? Should be a 3 or 4 wire connector.
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Re: Intermittent no start condition
SS 3011, I just checked...There is NO connector going into that slot on the cap.
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Re: Intermittent no start condition
Cooter, I will look into the FAST system as well as BIG STUFF.
I think as a last ditch effort, I'll borrow a known good coil and give it one last try before I conclude it is without a doubt, the ECU. Carburetors are starting to look real good!!!!(LOL) |
Re: Intermittent no start condition
I would strongly recommend the FAST.
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Re: Intermittent no start condition
If and when I have to replace the Accell, How big of a task is it to switch to the FAST?
Does it come programmed with a base tune-up, or is it a start from scratch? |
Re: Intermittent no start condition
It comes with several base tune ups. Pick one close to what you have, and program it with that.
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Re: Intermittent no start condition
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This is just not true and I have no idea why you would think this could be true.... A Battery stores energy.....and is a DC device...it has no components that can create noise and this mans' problem is either a wire connection issue or his ECU is at fault..... I had an Accel Gen VII ECU with a piggybacked add on datalogger in my '97 LT-1 Firebird.....It is probably still in that car and the car was number 2 in Division 1 last year....narrowly losing the Division title.... I ran it as I mentioned earlier.....with a Crank Triggger that ran outside of the Accel box.....and that is what was mentioned here as how this problem car is run.....The fuel pump and ignition run independent of the ECU......The ECU needs Battery connections.....and a switched B+ to turn it on.....It also needs a Tach signal from the ignition box..... If the ignition spark was confirmed to be there when the engine was not starting and the Noid light showed NO light at that time.....the problem is the ECU or the wiring that connects to the ECU to signal it to run..... Spark is useless without fuel...and the injectors need the ECU to turn them on..... The Optispark is not used...and the distributer is in there just to send the spark out from the coil.......just like any crank trigger fired race engine..... Sorry if I sould bitchy but too many cooks spoil the pot....and when I see someone suggesting that the battery is causing this problem I get a little cranky.....LOL If you want to really satisfy yourself as to what the problem is... When the engine is in the no start condition.....spray carb cleaner in the Throttle body while someone else cranks it and if you are able to get it to fire or even run with a steady stream of cleaner going in the t-body.........you have proved it is a lack of fuel.... |
Re: Intermittent no start condition
I have done the test you described....Sprayed some starting fluid into the throttle body.....it started and ran for about one or two seconds.
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Re: Intermittent no start condition
Thanks for the info John. Now we know that none of the trigger electronics in the Opti-Spark have anything to do with your no start condition. It is so hard to track down intermittent problems. Since you have spark it is a good bet that you have a connection or wiring problem. Usually ECU's either work or they don't. Have you tried disconnecting the main injector connector and reconnecting it ? Most all the terminals are crimp connectors. If you know which wires are the power leads, then when you have a no-start condition leave the power on and probe to see if indeed you have the 12v power to the injectors. The ECU provides the ground to pulse the injectors. If you don't have it set up for sequential , which I don't think you do, because the Opti-Spark trigger is not hooked up. Then your system fires 4 injectors at once. Everytime the ECU sees 4 pulses from the crank trigger it fires a set of 4 injectors, usually bank to bank. It doesn't know when, since it has no particular cylinder reference, just every 4 pulses. Your ignition works, so the ECU is getting the pulses. If the injectors aren't firing then check the simple things first, like the connector connections, 12V supply to the harness, etc. You will figure it out, that DFI system is very reliable.
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Re: Intermittent no start condition
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Re: Intermittent no start condition
SS3011 and Rich,
This morning I read your post again and went back to the drawing board. I have the wire pin out list and started looking for the power feed circuits(+12v) to the ECU. I found a power feed that had an in-line fuse in a Packard fuse holder with a cover on it. I looked at this previously and thought it was a connector....not a fuse. Well, I popped the cover and found a blown 30 amp fuse. Replaced the fuse, car fired right up. I started it 7 times and each time it fired up. Recall this started as an intermittent problem, then a full blown no start. So, the fuse got the car running again. I'm hopeful that running the ground back to the negative battery lug solves the intermittent issue. I will continue to start it randomly throughout the day and validate that the problem is solved. I will also replace the coil as the MSD 8261 seems to have a history of problems. I hope this is the last I need to post on this issue. I want to say "Thank You" to all of the help you guys have given me as we walked through this thing. I learned more about this electronic fuel injection system in a week then I thought I would ever learn!!! |
Re: Intermittent no start condition
Great news John and I was pretty sure you would find something if you dug into the wire connections.
I work on electrical equipment everyday.....Nothing worse than an intermittent problem but I get them all the time... We have a little Joke saying at work that covers this.... A good visual inspection will often reveal the problem... I work on Miller Welders and that saying comes from them and has always been true... With all the electronics these days that is not so true anymore but you have to start with the basics.... I am glad something I wrote may have helped you I kind of wish I had my Firebird back....I really loved the wheelies.....LOL |
Re: Intermittent no start condition
Good deal John, glad you found it.
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Re: Intermittent no start condition
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Re: Intermittent no start condition
Mike, happy to help, that's what makes this site so great...lot's of good info. I personally love the tech discussions, always seem to learn something.
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Re: Intermittent no start condition
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Been following this with some interest after talking with a guy at a cruise night near me who installed a tuned port Chevy into his Avanti and he mentioned some issues he was having. That 30 amp fuse is pretty big, maybe see if you have a loose connection somewhere which popped it when contact was re-established. A 30 amp breaker would reset but you'd need to have some type of indication it tripped, such as a light which illuminates when that circuit becomes open so you would be aware of potential issues. |
Re: Intermittent no start condition
Bobby, After I got the car running, I tried to carefully reconstruct the test process that I followed and determined the following: The intermittent condition turned into a 100% no start condition as I was testing the various components. When I got to testing the injector connector, the homemade noid light ( a line lock light with two 6" leads with the correct terminals) .......I plugged one lead into the connector and the second lead momentarily touched the intake, resulting in a quick spark. I subsequently realized that this spark was the indicator that the fuse blew.
So, I'm pretty confident that I have isolated the root cause of the blown fuse. Also, I believe isolating the ECU ground circuit from the stud with 6 ground leads stacke up (ran ground to - battery lug) took care of the intermittent condition. This was based on advice from an Accell service rep. Thanks for your input. |
Re: Intermittent no start condition
jon --sent u a PM--FED 387
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Re: Intermittent no start condition
Got it.
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