I took the beast out for a long highway run today and was plagued with stalling problems. It seemed to occur randomly and could not be duplicated on demand. Any RPM, and speed; it didn't matter. When ever it felt like stalling, it would stall. It felt just like the fuel pump suddenly quiting. However, being that I have a manual transmission, if I left it in gear it would restart and it could keep going a little further. It made for a very jerky ride.

It seems that I'm suddenly losing spark or fuel but I can't tell which. The ALDL data doesn't show anything suspicious so I'm assuming it might indicate that it's a fuel problem. The fuel pump and filter are brand spankin' new so I kinda doubt it's the pump or filter. Perhaps the fuel pump relay? The relay I'm using is a junk yard special. However, I've never seen a relay go out intermittently. Got any pointers?

 

Check the resistance of the injectors. Much lower then 1.2 and they be drawing enough current to overheat the injector drivers. I saw the same thing on a 730 port setup. But, there still can be something else, ie ignition module. The ALD stuff will tell you what's being commanded, not what's actual other then the O2.

 

Resistance seems fine at 1.6 each. The ign module is less than 500 miles old but it wouldn't be too surprising for it to be bad already. I'm using a home converted 4 pin to 7 pin HEI. Yesterday I bought a new 7 pin HEI (comes with the module), it should arrive in a week or so. I'm also going to swap out the fuel pump relay and the ECM. I have a spare ECM so that won't hurt my wallet.

 

Update:

Looks like this problem might be related to battery voltage. I've noticed that my battery voltage starts out, when cold, around 14 volts. Then, after driving around a while, the battery voltage slowly decreases to around 12.4 volts and then the engine dies. Is this an alternator problem or is the decrease in voltage normal?

 

Yes, there sounds to be a charging system problem.
12.4 is kinda high to have an ecm shut off.

Start with the obvious, belt tension, battery cables, might even put a Volt Meter on the battery itself to see what the voltage is at the posts. There maybe a slight drop, but not too severe.

 

get your hands on an oscilliscope and check the alternator for a/c ripple. Sounds like the diode might be overheating during cruise modes. Otherthings like a bad coil can cuase this. I see lot of GM coils for HEI constanlty crack the towers and cuase all sort of nightmarish hard to find driveability woes. If in doubt dump some water on the igintion coil and wire and checfk for arcing out.

 

I was going back through my old posts and figured that it might be helpful to post the solution to this problem.

The stalling turned out to be a result of a bad ground.

 

Brennanw
Which one - on the back of the driver side head or the sensor ground???

//RF

 

This isn't a stock application. I'm using a Painless harness for my EFI and the system is installed in a 1956 ****** truck. I had all of my ground wires tied into a single heavy gauge ground wire that was molded into the lead (as in Pb) portion of my negative battery cable. Well, it turned out the the heavy gauge copper wire pulled loose inside of the lead (Pb) and was causing intermittent ground failures.