A-Dub

iTrader: (6)

Im running an LY6, GM Dual Plane intake, Holley 770 street avenger, aeromotive elec pump and MSD 6LS2 controller. Cold starts are easy. Turn on pump, pump accelerator pedal, and it fires right up. Hot starts are more difficult. I seem to have to crank it 3 or 4 times to get it to start. Runs good once its started. Currently its on MSD pill #2 with MAP attached. I have not done any timing programming yet.

Is this an ignition or a carb prob?

speedtigger

iTrader: (16)

It may be heat saturating. If so, one possible cure would be to run a carburetor spacer made of wood, plastic or phenolic resin. Their insulative properties may cure the issue.

A-Dub

iTrader: (6)

I don't think thats the deal. The truck has a 160 thermo and efans keep it cool. I've only driven the truck once now and ran it in the driveway a few times finishing the build. I'm leaning towards the MSD. Found a post a couple years ago with another member having the exact same issue. Sent him a PM, but haven't heard back yet.

bad67ls

iTrader: (2)

sounds like a cam sensor issue to me? or its flooding. i had a 750 dp on my old motor with those little red umbrellas for check valves in the accelerator pump wells and they swell and dont seal after a while. pull the aircleaner off when its hot and see if the squirters are dripping fuel.

A-Dub

iTrader: (6)

Well to make it more confusing, it started flawlessly on hot restart yesterday. Then this morning, it acted up like before. Except it was a cold start.

ZONES89RS

iTrader: (25)

What octane? What plugs? 87 octane and hot plugs are a possibility, but I would not imagine that too often. Does it ever diesel down when you turn the car off?

A-Dub

iTrader: (6)

93 octane, TR55 plugs.

I'm wondering if its a voltage prob. I wasn't paying real close attention when I fired it up first thing this morning, but I think it was at 11V. Should have charged on the drive to work. 13+ volts all highway for 30 min. Went out to start it after it sat for a couple hours and it was down at 11V again. Did not want to start.

Gonna test/replace the battery today.

ZONES89RS

iTrader: (25)

Interesting, would make sense.

GNCLONE

I was thinking what Tigger said.

Don't know if you solved it yet, but vapor lock is possible when the fuel line runs close to exhaust components, not necessarily the coolant temp.

A-Dub

iTrader: (6)

Since it has done it on a cold start now, Im further doubting vapor lock. Didn't get a chance to replace the battery yesterday. Hopefully this afternoon

A-Dub

iTrader: (6)

So I replaced the battery last weekend and I also removed MSD pill and put in my own tune with 15deg during cranking and 20 at idle. That seemed to make a big difference. The problem wasn't gone, but it was very infrequent.

This morning (cold start, truck sat overnight), it would not start. Crank crank crank. Occasional exhaust backfire, occasional intake backfire. Checked all the MSD connections, checked fuel pressure. Walked away, came back and it started.

I'm completely stumped. Crank and Cam position sensors are new GM parts.

Pop N Wood

iTrader: (1)

I have an intermittent cam sensor connection. Every now and then the motor gets hard to start and backfires through the carb. If you go to the FAQ section of the MSD site they say the cam sensor is not needed for the motor to run, but there is a 50-50 chance of the spark coming in at the right time. That means 50% of the time it comes in 180 out of phase. That almost certainly causes the backfires

A-Dub

iTrader: (6)

Yea I called MSD. They said if you run the MSD box without the GM Cam sensor extension harness, you have to swap the two outside wires on the MSD connector. Funny their instructions never mentioned the extension harness. Going to try it out this evening.

ZONES89RS

iTrader: (25)

That is correct on the front cam sensor setup. Had to swap mine on the TA with a 08 5.3.

A-Dub

iTrader: (6)

So Im sure there are different extension harnesses out there, but you can't use the LY6 extension harness with the MSD harness because the female on the LY6 is a 6 pin and MSD is a 3 pin.

I swapped the position of the two outer wires on the msd connector like msd said and hooked it back up. Working so far. I will update the thread if it acts up again

A-Dub

iTrader: (6)

Prob was gone until about halfway through Power Tour. Talked to MSD since they were on tour. They suggested changing a setting in the software that will average signal during cranking. That setting doesn't exist, so I will have to give them a ring this week.