Electrical gremlins. Complete random voltage drop causes car to shut off..

[ForcedInduction]

Hi there! 

I have a dilemma on my hands. I replaced the battery to an Odyssey 1200 a year ago and the car ran great with no issues. Then I stored the car for about 9 months without a trickle charger and only starting it once in the middle of winter. Car started up no problem and ran fine, even after I came back in June. First time I started it, it ran great without problems. Second or third time I noticed my odometer wasn't working, then a different time it came on for like a few secs before starting the car and hasn't worked since.

I then removed my headers to wrap them and put them back in. At the same time I replaced my plugs. Car ran great for two weeks until one day during some hard cornering on an on-ramp, the car cut out for a second or so. I thought it might have been from my fuel sloshing around too much in the tank cause I was only 1/4 tank. On the way back home that night, the car stumbled a couple times on the highway just cruising. The next day it ran great during my 10 mile drive, I parked it for a couple hours and went back out again. It stumbled mid corner on an on-ramp on me again, this time with a full fuel tank. When I stepped on it to clear the corner onto the straightaway, it just stumbled and backfired with my RPMs dropping completely in the process like power was completely shut off to the car. I limped the car back home with it running either rich or lean all the while backfiring and not wanting to go, also barely idling and wanting to shut off.

I later hooked up my logger to see whats going on during another drive and noticed that my ignition voltage dropped to 9.5 volts a couple times during a 5 minute drive and then completely lost power which caused my logger to disconnect and car to completely shut off. I restarted it and limped it back home again.

Today as I cycled the key to the ON position, my fuel pump and accusump sounded like they were struggling as in the case of a dead battery. Car wouldn't start while battery voltage was 12.4v. I kept cycling to the OFF and ON position and then it sounded like I got power back, so I started the car. It idled for about a minute and then as I started pulling out of the driveway, it completely shut off on me and wouldn't start again like it had a dead battery while the battery showed 12.3v.



Has anyone had a similar issue before or know where to start? I checked all my engine to chassis grounds as well as my battery terminals and connections to my alternator. Everything seems ok.

[largeorangefont]

what are you doing for chassis grounds?

[ForcedInduction]

I have 4 or 5 2 awg connecting from the chassis to the motor. I believe all of them are hooked up to my heads.

[digitalsolo]

Either grounds or main power.   Make sure you don't have any loose crimps.

[halfspec]

I agree with the others. I'd put my money on a grounding issue. Sounds like you've got the engine grounds covered. How is your battery grounded? Have you tinkered around with it to see if you can improve it?

Also, how are you measuring your battery voltage? Are you measuring while you're cranking?

Lane

[wompa164]

Check your +12v constant and switched to your ECU.

[bimbleuk]

I gone through a similar issue recently where my Odyssey was not holding a charge and I'd noticed a voltage drop to the injectors under load etc. You might not want to go to quite the lengths I did but basically I pulled all the conversion feeds and earths to a common distribution box in the (RHD) passenger footwell.

Also worth checking any earths you can see up under the dash. The are a couple of large ones in the old ECU/emmisions/dash wiring harness which after I stripped out all the unused wires and cleaned them helped with power in the cabin area. After I did this I started to notice other side affects such as how much faster my windows were going up and down

Of course you may also have bad connections on the ignition assembly as there's a lot of power feeds running through it. Immobilisers can also affect this area as mine has burnt out a track previously.