Random loss of ignition signal to ECU?

[portmod7]

I have an MS-II v3.0, 2.905 code. It is on a Gen-I small block Chevrolet 5.7L. I am running an MSD Street Fire distributor (http://www.street-fire.com/GM_EFI_distributor.html) with an 8-pin module and "Dual Connection" (PN 5526) external coil. I have also done the MSnS-E Modification.

The thing had been running fine other than fuel/air tuning issues up until 2 weeks ago. I was out running around town, came home, and then tried to leave a short time later. When I tried to leave, the engine fired up and died immediately. It did not want to start after that, like it had no spark or fuel. I cranked on it for a minute or two, then tried holding the throttle wide open while I cranked because I didn't know what else to do. Then I let the throttle closed, and it fired right up with the next turn of the key. So I thought it was somehow flooded....

I don't drive this truck every day, once every 3 days maybe. The next incident happened 4 days later, I was cruising over to a friends house, I had just turned left at a stop light, and the engine died on me with no warning. I let the truck roll in gear, hoping it would fire back up, and after a few seconds it picked back up and ran. I made it to my friend's house, stayed there for a couple of hours, then headed home.

On the way home I stopped at the store, and at the drive through for food. I shut the truck off and started it multiple times, no problem. Then as I left the drive through, turning left from a stoplight again (I think it was just coincidence) the thing died on me, only this time it would not start again. I pulled into the median, then had to push it into a parking lot and come get it with a trailer later. I had my wife try to start it while I looked and listened under the hood and noticed I had no fuel pressure while cranking, so obviously the fuel pump wasn't running.

I towed the thing to my shop and dropped it off. The next morning I came to work on it, it fired right up. I had been having a fuel pressure issue (10psi low, 35psi.) for a couple weeks, so I shut it off and started diagnosing that thinking maybe that was my problem. I found out the fuel line connection from my in-tank pump to the bulkhead fitting was loose. So last night, I dropped the tank and I fixed my fuel pressure problem. I ran the pump with the engine off by jumping the pump relay, I've definitely fixed the fuel pressure problem. So I went to start the truck up to reset the fuel pressure, it won't start, won't even try. I haven't done anything since idling it in the shop except drop the fuel tank, pull the pump out, and put it back together and now it won't run.

I hooked up TunerStudio while cranking and noticed the "Cranking" indicator does not come on. That leads me to believe I am not getting an ignition signal to my ECU. Does that sound about right? And whatever is causing it is random. It's happened after it's been running and hot, after it's been sitting and cold, and during short drives that barely get it to "running" temperature.

Sorry for the LONG post, but hopefully some of you have made it through.... Any ideas what could cause this? Like I said, before now, everything has been working flawlessly for a couple months. I hadn't even had my laptop connected for a week or two previous to this starting.

Thanks!

[Matt Cramer]

If you are seeing no RPM signal, my first thought is a dead HEI module.

[portmod7]

Thank you for the suggestion Matt. I will check it out. You think it could be going in and out like I describe?

Anything in particular that would cause that? It's a new distributor/module, or new a couple months ago I mean.

[Matt Cramer]

I've seen HEI modules flake out like that before.

[portmod7]

Thank you for your help Matt.

When I went back to the vehicle to investigate, it still didn't want to run. So I tapped on the distributor a little with a screwdriver handle just so see if it would make a difference.... fired right up!

So I pulled the module out, and went to the parts store and got a replacement. However, the replacement wouldn't work. I'm not sure if MSD does something different with their pickups so you have to buy parts from them or what, but a CarQuest replacement module wouldn't register an RPM, just like what originally started all of this.

With nothing better to do I decided to put the original module back in. The CarQuest module had slightly larger prongs for the pickup connection, so they kind of enlarged the cavities in the plug and it wouldn't make a tight connection to the original module. When I took it all apart the first time I didn't like the way that connection looked anyway. The plug looked to be a little crooked an maybe not seated properly. So I used some needle nose pliers to "adjust" the cavities in the plug so it would grasp the prongs of my original module a little tighter.

Once I got it all back together, it fired right up, and has the few other times I've tried it since. I've been busy with other stuff, so I haven't driven it at all or really done anything to confirm that its fixed, but right now I'm thinking it was just a bad connection between the pickup and the module. I will keep my fingers crossed!

[portmod7]

Just an update on this, I ditched the MSD Street Fire distributor for a new GM unit because I was still having problems. I haven't had this issue since!