LT1 install - No Spark

[TFagan]

My questions continue. The motor turns over great and the fuel pump is on, but no spark. The motor did run before I installed it. I t might be a ground. My harness is one from LT1Wiring harness for my application. I thought that I was very careful on the grounds connections. Any help would be very appreciated.

[youngrodder]

Originally Posted by TFagan

My questions continue. The motor turns over great and the fuel pump is on, but no spark. The motor did run before I installed it. I t might be a ground. My harness is one from LT1Wiring harness for my application. I thought that I was very careful on the grounds connections. Any help would be very appreciated.

Test with a multimeter that you are getting 12V to the computer while trying to start the engine. My motor ran on temperary wiring. Once I fully wired the truck the motor would no longer start. My issue was the power feed going to the computer. Once I turned the key the power feed that was reading 12V dropped to 0V during cranking. Without 12V the injectors would not fire and there was no spark as the computer will not come on.

I also invested in a noid light that you can hook to one of your injectors to confirme that they are getting a pulse which proves that they are firing.

I betting is not a ground issue as much as a power supply issue.

Good luck
Marc

[ricott]

If you are not getting spark, chances are it is the Opti Spark. I have replaced two on my 1992 Corvette, and one on a 93 camaro we owned. I would use a noid light to see if the injectors are pulsing. If so, I would then focus on the opti spark.

[whammer33024]

I agree on the optispark. If you didn't replace that with a new unit before the install then that's where I'd start. Also, go for a GM replacement unit. A lot of the aftermarket optisparks are hit and miss and this isn't something you want to do multiple times.

[youngrodder]

In my opinon the OptiSpark seesm to be a catch all for most people trouble shooting a no spark issue. In most cases it is something simple. Before throwing $$ at the problemm really test with a multi meter and a noid light. If you dont have a noid light these can be rented from some auto parts stores.

It's frsutrating but you will get it.

Marc

[TFagan]

Thank you all very much. I will follow these suggestions. Probably wont get a chance until Thursday. ( I dont want to get grounded from the wife) Merry Christmas to all

[1project2many]

Is the pump wired up using only stock electronics? Did the donor car have VATS / Anti-Theft? Was this disabled in a custom tune?

[TFagan]

LT1wiring harness reset the computer when they built my harness to meet my needs

[1project2many]

So for now we'll assume they reprogrammed the pcm correctly and disabled VATS.

First test I'd do at home is to see if the pcm is triggering the injectors. If the ecm is not receiving a low resolution signal it won't trigger injectors. Connect a test light from B+ to the - side of the injector connector while the connector is disconnected from the injector. Crank the engine and watch for blinking. No blink means test opti. Blink means head toward ignition primary (coil and ignition amplifier module).

These pages are for an early system. They may be appropriate for the OBDII engine also. It's been a *few* years since I've had hands on an LT1. Use the "cranks but won't start" page. It asks you to verify fuel pressure & etc. If you're sure the fuel supply is Ok and the injectors are being triggered you can skip to the ignition system diagnosis in chart C4. It's found about 3/4 of the way down the page.

http://camaroforums.com/forum/lt1-lt...t-start-65637/

These steps can also be used to diagnose the opti: http://shbox.com/1/4th_gen_tech2.html#opti_test

Sorry if this seems a bit short. I'll help with specific questions if you have them.

[whammer33024]

awww, i used to be a moderator at camaroforums, lol.

that shbox site is absolutely awesome. i can't tell you how many times i've used that site myself, and especially referred people to that site.

[TFagan]

Here is the latest - noted below is what I get with power to the switch. I have the power from the fuse box to the power spade and the power wire for the computer. I wired the fuel injection wiring to the IGN-1 spade (it loses power at crank position), I have the coil wire to the coil spade. How do I get power to the injectors?

The wiring harness that I have comes with its own fuse box for the harness. With the key in the on position, I show power to everything except the injectors.

Spades on the back of 1958 IGN switch
Spade | Key off | key on | key to strart
BAT | 12v | 12v | 12v
ACC | 0v | 12v | 0v
COIL | 0v | 0v | 12v
IGN-1 | 0v | 12v | 0v
IGN-2 | 0v | 0v | 12v

Hope this chart helps.

[1project2many]

Great chart!

First, if your harness isn't set up this way, I'd consider using relays triggered by the IGN-1 circuit to supply power to the injectors, coil, and other ignition powered circuits to help reduce the amount of current draw through the ignition switch. But the following will apply even if your ignition circuits are direct wired.

You need to supply power to IGN-1 with the key in start, but you also need to restrict power to the starter solenoid when the key's in the on position. If you have a separate starter solenoid terminal on the switch check for continuity between IGN-2 and the starter terminal. If no continuity you can bridge IGN-1 and IGN-2 with a jumper.

If there is no separate solenoid terminal or if you have continuity then I think the best method is to use a relay triggered by IGN-2 to supply power to IGN-1. When power is available on IGN-2 it should close the relay. When the relay is closed it will connect BAT to IGN-1. When you release the key from "start" power will be removed from IGN-2 and the relay will open. Power will be supplied to IGN-1 by the switch but it cannot get to IGN-2 because the relay will be open.

However, to be fully safe, you should probably check to ensure there is no overlap period when IGN-1 and IGN-2 might both be on.

Wiring at the relay terminals would be:

85: IGN-2
86: GND
87: IGN-1
30: From Battery +

HTH

[butchp]

First let me say I have no experience with this system. I have always wired my control boxes direct to the battery hot and ground also ( msd, chrysler silver box ). Your start and run position on switch will be wired to have 12v on both positions when it starts and the switch is on run and the start wiring is off.

[1project2many]

Please disregard previous post as it's not thorough enough and I can't edit / delete it.

So to summarize, using the chart (thank you!):

The coil is connected to COIL.
The EFI is connected to IGN-1.
No power is supplied to IGN-2 or COIL with key "on."
No power is supplied to IGN-1 in start.
There is no information supplied (in your post) as to where the injectors are getting power.

Is this correct?

Looking at the above, does it also seem like there's a potential problem with power to the coil?
I'm wondering of the coil and the injectors are both supplied power by the same circuit.

So you need to supply power to IGN-1 with the key in start, you need to supply power to the coil and the injectors with the key in "on" and "start," and you also need to ensure that you do not accidentally supply power to the starter with the key in "on."

First test. Check for continuity between the injector power wire and the pink power wire to the coil. If they are conected, all is good. If not then you'll need to determine where the injector wires connect to the rest of the harness.

Next test: Do you have a separate starter solenoid spade (I'll call this SOL)? If so, check for continuity between COIL and SOL. If no continuity you can bridge IGN-1 and COIL with a jumper. This would be the preferred method. If there is continuity between COIL and the SOL then a jumper between IGN-1 and COIL will not work.

Next test: If you show continuity between COIL and SOL, check for continuity between IGN-2 and SOL. If there is no continuity, move the coil wire to IGN-2, install a jumper between IGN-1 and IGN-2. This will supply power to the coil and IGN in "on" and "start." If there is continuity between IGN-2 and the SOL then a jumper between IGN-1 and IGN-2 will not work.

If there is no separate solenoid terminal or if you have continuity between these terminals then you've got more work to do. In this case I think the best method to get power to IGN-1 in "start" is to use a relay triggered by COIL or IGN-2 to supply power to IGN-1. When power is available on IGN-2 (or COIL) it will close the relay. When the relay is closed it will connect battery power to IGN-1. When you release the key from "start" power will be removed from IGN-2 (or COIL) and the relay will open. Power will be supplied to IGN-1 by the switch but it cannot get to IGN-2 (or COIL) because the relay will be open.

You will also have to move the coil wire to the IGN-1 circuit to make sure it gets power whenever the key is in "run" or "start." And if the injector power supply is separate from the coil power supply, you will also have to connect that to IGN-1.

Wiring at the relay terminals would be:

85: IGN-2
86: GND
87: IGN-1
30: From Battery +

Finally, with all these circuits powered by IGN-1 it would be a good idea to use a relay to supply power to the EFI circuits instead of powering everything through the switch. Maybe your harness already does this but if not, you might want to consider making the change. I'd expect it to be more reliable long term especially if you plan on adding other accessories such as electric wipers, heater, and maybe more modern conveniences such as power seats/windows/stereo, etc.

HTH

[TFagan]

Thank you - great detailed info. I will try when the new years get togethers slow down. happy New Year to all

[TFagan]

The weather finally warmed up enough I could brave the cold in everything noted in the post above was right on. Speed and performance has a diagram on that I needed to do with my ignition. I am closer but it is not running yet. I have power at crank and on positions but no fire. I checked an injector on each side to see if the is 12volts with the key in the on position. each injector has 12 volts with the key in the on position. I check the write up the street and performance has on 94 LT1 will crank but not start write up. I just do not know where to start.

[youngrodder]

Originally Posted by TFagan

The weather finally warmed up enough I could brave the cold in everything noted in the post above was right on. Speed and performance has a diagram on that I needed to do with my ignition. I am closer but it is not running yet. I have power at crank and on positions but no fire. I checked an injector on each side to see if the is 12volts with the key in the on position. each injector has 12 volts with the key in the on position. I check the write up the street and performance has on 94 LT1 will crank but not start write up. I just do not know where to start.

You have 12v in the on postion. Make sure you have 12v in the start postion. This was what tripped me up. The way I had mine wired to the EFI terminal on the fuse panel. My 12v would drop to 0v when I went from on to start.

Good luck
Marc

[TFagan]

I will double check. The write up from Street and performance showed an illustration of adding a jumper wire on my stock 1958 chevy truck ignition switch.