Flynbryn

I'm having a problem with my LT8. First some back ground information. The car is only used for road racing. It is a S4 TII with a 60-1 turbo 720 primary and 1600 secondary injectors. it is tuned to 403 RWHP at 14 psi (7500 rpm). The ECU has been in the car for 3 years with no issues. It's been tuned 3 times again no issues. On track I have noticed that during throttle modulation I was getting a slight hesitation at about 4.5 to 5.5 krpm. I attributed it to the 1600 CC secondary injectors and the S4 on off TPS. The ECU is mounted inside the car on the fire wall behind the glove box area. This area is water tight and insulated from heat. 3 weeks ago at the track I had an alternator take a crap. After replacing the alternator the car fired right up and was making almost 14v. I then ran a 20 minute session with no problems. It started to rain the next morning (the car never got wet) about 9:00 AM after several hour of a light drizzle it was time to get on track. During the warm up lap I went through a puddle at about 80MPH . Almost immediatly after that the car just died. I tried to re-fire it but it wasn't happening. While turning it over initially I could here the fuel pumps and I saw that the combustion chambers were full of raw fuel because there was a cloud of smoke (smellled like gas) emitting from the exhaust. I quit trying to start it and turned the battery switch off and got towed in. After returning to my pit I turned the power on and flipped the ignition switch on and I noticed that the fuel pumps did not kick on. I tested the green wire from the ECU to the FP relay and nothing. switched the FP relay to the back up I have next to it just in case and still nothing. I though maybe my 12v switched power wire either got wet or pulled away from its moorings due to the force of the water from the puddle. This was a stretch but I checked the ECU light, the green light was on. I then decided to connect my laptop to see if there was an error code, but I could not get the ECU to connect. I got the same message you get when the ignition is turned off. "Unable to connect to COM #1". I figured that the ECU had fried and it was either time to send it back to the land down under or install a Motec and ditch the Microtech all together. We loaded the car up and took it home. the next day I figured what the hell I'll see if it will fire so I turned the ignition on and nothing. for some reason the following day I thought that I had left the ignition switch on so I went out to the garage and checked it was off. So again waht the hell I turned it on. Viola the pumps kicked on and after clearing the fuel out it fired right up. I was stoked to say the least. I let it run for an hour and then 15 min each day for 4 days. I decided that something in the harness must have gotten wet so geared up to replace it with all mil spec wires and weatherpack plugs and while I was at it I'd throw in LS1 coils and a Ford style TPS. My reason for these upgrades is that hesition I spoke of earlier. Well I replaced the harness installed the coil packs and the TPS and not really liking electrical work I was meticulous with the pin outs and labeling of each wire. So I cross my fingers and hit the switch AHH no fuel pumps. I check the relay it isn't working. I found the ground was off. Feeling good I put the ground back and ARRRRGHHH nothing. I see the green light on the ECU is on I start to get Deja vu!!! I am 99% sure that everything is connected properly. Especially the constant and ignition power. I tested these several times! The only other thing I was unsure of was the coil pack harness but I got the diagram from the internet and it is perfect. I thought maybe low battery voltage but I have at least 11v. I'm currently charging the battery as a precaution. I'm at wits end with this. I'm copying this to the microtech forum as well. any sugetions or items to check will be appreciated. HELP!

rx72c

iTrader: (8)

sounds like the Fuel Pump circuit in the microtech is damaged(shorting out somewere will do it). Anyways. You can either send it back to microtech to have it repaired OR, if you look at the relay, the pin that the green wire goes, take this wire(stop it from going to the microtech), ground this wire to the chasiss somewere. See if the fuel pump starts working and post here.

Flynbryn

thanks for the advise. I was thinking the same thing. If I gound the wire (85) from the relay the pumps do start, but I don't get a yellow light on the ecu. if I connect the green wire to pole 85 on the relay the pumps start, but the relay starts clicking and the green light does come on. it seems that the ecu is being powered by the green wire. I checked voltage from the relay at pole 85 and it HAS voltage. so it must be back feeding the ecu somehow. What really concerns me is that I can't get the laptop to connect. I'm going to hook up my ecu in a m8s dune buggy who also has an LT8 on an 13BRE and see what happens before I send it back to MT. thanks again I'll keep you posted