Gstoltz

Ok,bare with me on this:

I have a 95 Z28 M6, 159,xxx miles. About a month ago i was driving down the road, and the cars stalled out on me. I pulled off too the side of the road, let it set for two minutes, and it cranked right up. I pulled out, and it stalled out again. This time it didnt crank up after a brief waiting period, and I had it towed back to my place. The next day I came out (after it had cooled) and it cranked up the first time I tried it, but never after that.

Since that time I've done the following in order: took the ignition control module in to AZ to get it tested (passed). found out the fuel pump wasnt priming when the car was turned into the "run" position so I replaced the fuel filter in hopes it was clogged (still no luck). Swaped out the fuel pump relay with no differinf luck Replaced the battery as it was almost five years old and ready for replacing. After this, the car started! So I drove it around the block for about five minutes until it stalled out in the exact same fashion as earlier referenced. (note: when the car stalls, the fuel gauge jumps well past the F level, for what that's worth). I then ordered a walbro 255 from treperformance.com for $100 and installed it correctly via the trap door method. Before sealing it up, I turned the key to run and I could hear the new pump priming. Turned the key further and it started up strong. I drove it for about five minutes around the block, waiting for it to stall and it never happened. I parked, let it set for ten minutes and started it up again, drove it to pump gas (89 grade), filled it up. Still no problems until I started it up drove off, and within two hundred yards it stalled out in the same fashion. I then let it set for thirty seconds and it started right back up strong and I drove it home (note: the fuel gauge stayed far to the right of of F).

When I parked, for some damn reason antifreeze started leaking from the front of car, not the radiator though. This may be unrelated completely, but I thought I'd throw it in. This is my hugely annoying issue, any help would be greatly appreciated.

OBE1 95Z28

Suggest you install a fuel pressure gauge and verify that the fuel rail holds pressure after the fuel pump has primed the system. Your coolant sounds like your waterpump is leaking out its weep hole. This could potentially get your opti wet which can lead to starting issues.

Gstoltz

thanks for the reply... i'll give the fuel gauge a try.

as an update... the same "stalling" issue happened again... i'd driven the car about twenty miles today with no issues at all when it stalled out completely as i was driving about 40 mph down a street... i pulled over, turned the key off and turned it to "run" immediately... the fuel pump primed and the car started right up. i drove it home another 4 miles without any problems at all. could a faulty fuel rail cause this unexplained, intermittent stalling? could your other explanation of moisture hitting the distributor cap be causing this as well? i'm at a total loss... please help.

Gstoltz

Update 2: I started my car just to let it idle while I was messing around in the garage. It idled fine for twenty minutes and then just died... The temp gauge was at the halfway point and after it died, no antifreeze was spilling from the reservoir as it was before (I replaced the radiator cap so I think that is fixed). I started the car back up and it ran for about two minutes and died again... Does any of this add up!?! Please help!

Injuneer

When they tested the IC Module was it hot? They have a tendancy to break down when they heat soak. Using Shoebox's method to space the module off the head will sometimes help:

4th Gen LT1 F-body Tech Articles

Gstoltz

Thanks for the mod idea. I tried it and I still have the car stalling out after twenty minutes of idling. The temp gauge is around the halfway mark when the stall happens. Any ideas? Should I check the fuel pressure even though it seems like this is heat related? Should I try the thermostat?

jproz1167

the fuel pump is dead, my 97 3.8 did the same thing start/die ... Then it went totally dead. Just replace the pump and it will run fine again.

Gstoltz

I've already done that... i replaced the stock fuel pump with a walbro 255. the pump works beautifully, so the only part of the fuel system that may be suspect would be the fuel rail system from what i understand.

Injuneer

There is nothing in the fuel rails to go bad. Doesn't sound like the fuel pressure regulator.

Heat soak can affect the fuel pump, but if it did it with the stock pump and with the Walbro, it would seem to rule that out. Heat soak can also affect the optical cam position module in the Optispark distributor. If that was the problem, it would be setting codes. Another remote possibility would be the fuel pump relay suffering an intermittent problem, but you replaced that.

Have you scanned it for codes? Have you monitored the fuel pressure?

Gstoltz

How can i check if the water pump is leaking out of the weep hole? i've put a fresh ICM and Fuel Pump in and after the engine gets warm, the engine dies on me and the fuel pump refuses to prime until the engine cools. so its not the ICM, its not the fuel pump (this is my third pump i've tried)...

bobdec

Do you have a volt meter. If so install the positive lead on the fuel prime connection under the hood ( http://shbox.com/1/fuel_pump_prime.jpg ) and the negative lead to chassis ground. If possible run the leads into the car and leave the meter attached till it craps out again and you can see the meter. This is the output of the fuel pump relay going directly to the pump. The PCM monitors the ignition key and will pick the FP relay. The meter should read positive +12 v for two (2) seconds whenever the ignition is switched from off to on (pump prime cycle) and stay at +12 whenever the PCM sees opti pulses indicating the engine has started.. If this line is +12 and the pump is not running it's a wire problem from the FP relay back to the pump , or the pump (I know you already replaced it). If the line is NOT +12 volts for 2 seconds when key is switched on then its the FP relay, +12 v supply/fuse to relay, PCM wiring to relay or the PCM (very rare). I know this is a PITA, but we need to isolate the failure between the relay to PCM, or relay back to pump.. may have missed it, but has FP relay been replaced.. here is a schematic ref shbx.com http://shbox.com/1/1995_pcm3.jpg

Blueangel73

I am not sure how much this could help, but it seems that your car stalls when you get to the point of your thermostat opening up. Are you running the stock 185/190 degree thermostat? You could try installing a 160 degree thermostat and seeing if the same thing happens when the thermostat opens at the lower temp. I use the 160 in my car and the car runs at a steady 180/185 degrees, the stock one keeps the car around 200-210 I believe. If nothing else this will help with keep the ICM cooler along with the rest of the engine.

Also, have you checked along the bottom side of the water pump for leaks that could leak on to your opti, the leak might only happen at the high temp when the water pump gaskets might loosen up a little.

Again, just thinking outside the box.

4montecarlo

you need to determine when the car dies, did it die from no spark or no fuel.
matt