Intermittent no start condition

[Kirk Morgan]

Check for battery voltage in the injector harness when you have a no start condition.

Kirk

[Rich Biebel]

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

[John Boland]

The battery is something to consider before you spend real money. It could be failing in a way that it is generating electrical noise.

[ss3011]

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.

[John Nechiporchik]

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

[countrypuppy4865]

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.

[ss3011]

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.

[Rich Biebel]

Originally Posted by John Boland

The battery is something to consider before you spend real money. It could be failing in a way that it is generating electrical noise.

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....

[John Nechiporchik]

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.

[ss3011]

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.