Connect and Cruise start up issue

[Alphatrev]

Wondering if anyone can help. I have the GM LS427/570 engine with the 6L80 transmission connect and cruise package. I am not a tuner, and I bought the package so I wouldn't have to get into software tuning and diagnostics etc.

I have everything connected and can start the engine on the key, but it cuts out immediately. I wondered if it was fuel pressure, but if I leave the starter engaged (accidentally) for an extra second, the engine keeps running, and will blip on the throttle, until I release the key back into the regular run position. It feels to me like the power is turning off as soon as I release the key. I have tried swapping the pink wires (painless kit with an idiot column) but to no affect. It feels like the power sent to the unit is good when I engage the starter, but shuts off when I release the key. I have checked and double checked my grounds.



Anyone have any experience of this?

[Alphatrev]

I read that it could be VATS, but why would GM program the connect and cruise package with VATS when it is supposed to be factory setup to run its a stand alone system in old vehicles, and I have no way to check or deactivate that system.

[130fe]

Check your pcm ign source is ign powered all of the time and not just in the run position.

[Alphatrev]

I did. If it was powered in the run only position, the engine would not start. I have the opposite problem. The engine starts, but will not continue to run when I release the key.

[icemanrd19]

If it’s a 69 check into the ignition switch wiring with the idiot column. I remember some issue would that

[Alphatrev]

The Ididit column was spec'd for I believe 70-75 Camaro. The whole car is custom, so it doesn't really matter what year it is. I do suspect the Ididit relay pack, as it definitely feels like the engine is being switched off when I release the key. I will call Ididit tomorrow and see if they can advise.

[wfo guy]

My thought is you don't have power in the run position from the switch. If you don't have a memory wire going to the ecu, that will cause problems also. As a short cut, run a hot wire to the power feed on the ecu and see if the problem goes away.

[Alphatrev]

Surely the ECU is already directly connected to the battery? Can you explain what you mean by a 'memory wire'. Thanks.

[dhutton]

If that is the Ididit column with the relays you will need their update kit to keep power from dropping out between start and run. Give them a call.

Don

[wfo guy]

Most ecu's have 2 power wires. One is connected to power at all times and it keeps the memory "alive" all of the time. The ignition wire powers up the relay that sends power to the ecu for it to operate in "run" mode. Without power going to the "run" side of the ecu in the run position of the ignition switch, the ecu is still in the "off" mode. Ecu's only control the ground circuits of relays in case you were unaware. I looked up the cruise and connect instructions. This is what I believe to be important: Attach a 12 volt ignition switch feed from the vehicle to the pink ignition
switch wire in the harness (this is required to enable the proper powerup sequence of the ECM). This can be routed into the passenger
compartment with the accelerator pedal connector and diagnostic
link connector. Next, connect battery power (minimum 8 gauge wire)
to the horizontal stud on the fuse relay center The other two studs are
for accessories and are 50 amp fused), and the harness installation is complete.
The run wire from the ignition switch needs to go to the pink wire and be hot when in the on position. My guess is that yours is only hot in the start position.

[Alphatrev]

Most ecu's have 2 power wires. One is connected to power at all times and it keeps the memory "alive" all of the time. The ignition wire powers up the relay that sends power to the ecu for it to operate in "run" mode. Without power going to the "run" side of the ecu in the run position of the ignition switch, the ecu is still in the "off" mode. Ecu's only control the ground circuits of relays in case you were unaware. I looked up the cruise and connect instructions. This is what I believe to be important: Attach a 12 volt ignition switch feed from the vehicle to the pink ignition
switch wire in the harness (this is required to enable the proper powerup sequence of the ECM). This can be routed into the passenger
compartment with the accelerator pedal connector and diagnostic
link connector. Next, connect battery power (minimum 8 gauge wire)
to the horizontal stud on the fuse relay center The other two studs are
for accessories and are 50 amp fused), and the harness installation is complete.
The run wire from the ignition switch needs to go to the pink wire and be hot when in the on position. My guess is that yours is only hot in the start position.

Thanks for all the replies. I do feel like I am going around in circles with this.

The first photo is my double red (10 gauge I think) going from the battery to the GM fuse block. Its the one shrink wrapped in black. The red wire shrink wrapped in blue goes on to the Painless fuse block.

The 3 pink wires are Painless 920, GM ignition and Ididit relay box. I checked with Painless to make sure I was using the correct wire, as I was alternating between the 920 and the 931. They say 920 is on in both run and start modes. The reason the pink wires are currently (pun intended) unprotected is because I have been swapping back and forth to see if one makes a difference vs the other. But no difference. I am now relying heavily on the new ignition switch coming from Ididit. I should get that tomorrow, but probably too late to get installation assistance from Ididit this week. Hopefully I can figure it out on my own, as I don't want to waste another weekend on this. I am moving house in 3 weeks, and I expected to have the car running weeks ago, but it looks like it is going down to the wire on that. When I move, I lose my 1700 sq ft shop until I can build the new one. The car is really close to done, and I don't want to put it on hold for a year while I am tied up with a building project.

[Alphatrev]

Thanks for all the replies. I do feel like I am going around in circles with this.

The first photo is my double red (10 gauge I think) going from the battery to the GM fuse block. Its the one shrink wrapped in black. The red wire shrink wrapped in blue goes on to the Painless fuse block.

The 3 pink wires are Painless 920, GM ignition and Ididit relay box. I checked with Painless to make sure I was using the correct wire, as I was alternating between the 920 and the 931. They say 920 is on in both run and start modes. The reason the pink wires are currently (pun intended) unprotected is because I have been swapping back and forth to see if one makes a difference vs the other. But no difference. I am now relying heavily on the new ignition switch coming from Ididit. I should get that tomorrow, but probably too late to get installation assistance from Ididit this week. Hopefully I can figure it out on my own, as I don't want to waste another weekend on this. I am moving house in 3 weeks, and I expected to have the car running weeks ago, but it looks like it is going down to the wire on that. When I move, I lose my 1700 sq ft shop until I can build the new one. The car is really close to done, and I don't want to put it on hold for a year while I am tied up with a building project.

Just as an experiment, I separated all the pink wires and connected the Painless 931 to the Ididit ignition box and the Painless 920 to the GM ignition wire. It may be my imagination, but the engine seems to run for half a second longer upon start up.

[Alphatrev]

Painless say it is normal for accessories to shut down during start up. So all good there.

[wfo guy]

I would run a jumper to the pink wire from the battery and start it. If it still doesn't run, we're looking at the wrong place. Removing the switch from the question is the quickest way to see if that is the problem.

[Alphatrev]

I would run a jumper to the pink wire from the battery and start it. If it still doesn't run, we're looking at the wrong place. Removing the switch from the question is the quickest way to see if that is the problem.

A great suggestion, thanks. I tried it with both pink wires but no change. The engine fires but will not run. What did I just prove?

[Alphatrev]

The car has a Ricks Tanks fuel tank and fuel pump. I think it is a Walboro 340 which Ricks told me was plenty of pump for the engine I am using. It also has the Corvette fuel pressure regulator mounted close to the pump. I currently have no way to verify fuel pressure. What is the easiest way to do this?

[andrewb70]

The car has a Ricks Tanks fuel tank and fuel pump. I think it is a Walboro 340 which Ricks told me was plenty of pump for the engine I am using. It also has the Corvette fuel pressure regulator mounted close to the pump. I currently have no way to verify fuel pressure. What is the easiest way to do this?

You can rent a fuel pressure testing kit from a local parts store and measure the fuel pressure at the rail. There is a valve on the rail specifically for this purpose.

Andrew

[Alphatrev]

You can rent a fuel pressure testing kit from a local parts store and measure the fuel pressure at the rail. There is a valve on the rail specifically for this purpose.

Andrew

Thanks, that's the next thing I will do. So, would low fuel pressure prevent the engine from idling? Wouldn't it start, but not make max revs? Or does the operating system check fuel pressure internally and prevent the engine from starting if pressure isn't high enough?

If there is an internal fuel pressure sensor, can I install a fuel pressure gauge that reads off of the CAN BUS system?

[wfo guy]

In regards to the pink wire, I believe you have proved the ignition switch wasn't the problem.

[andrewb70]

The ECU assumes 58.5 psi at the rail, no matter the load and it does not have a sensor to monitor the fuel pressure.