Random shutdowns

[Dunedain15]

Yet another tale of woe. About a month ago, my wife was driving the Burb. She was accelerating up a hill from a stop, and the truck just shut off. She pulled to the side of the road, and it fired right back up as if nothing were wrong. She started driving again. About a half mile down the road she came to a stoplight. When it turned green, she stepped on the gas, and it accelerated as normal for a couple seconds then shut off again. Again, it fired right back up. Haven't had a single problem with the truck since.

Fast forward to last night. Driving home from a beer run, I accelerated from a stoplight. Accelerated normally for a couple seconds then died. Fired right back up as if nothing were wrong. Made it home with no other issues.

I got a new Stanadyne PMD, heatsink and extension cable from Leroy in March of last year, and it's currently mounted behind the front bumper. Physically, everything looks fine in that area. The PMD that was on the truck when I bought it was a black one that was zip tied to a hunk of aluminum and bolted to the intake manifold. That one never had an issue, but I wanted to replace it because it was zip tied to a heatsink with no heat transfer pad. I replaced the lift pump with Leroy's pump/filter kit in August of last year. I have not dropped the tank to remove the sock yet. The Burb has 157,000 miles on it, and AFAIK, it's the original injection pump. I have a fuel pressure gauge, but the GlowShift sending unit is dead again (2nd one in a year), so I don't know what the pre-injection-pump pressure was when it died.

I said all that to ask two questions:
Is there a sending unit I can get from somewhere else that will work with the GlowShift gauge?
The problem is super-sporadic which is frustrating. So, where do I start troubleshooting?

 

[rlb]

The problem is super-sporadic which is frustrating. So, where do I start troubleshooting?

Fuel pump grounds and relays?

 

[SnowDrift]

I had very similar symptoms when my ignition switch was bad. Several times, just driving down the road and it shut off, just like someone turned off the key. Fired right up afterward, usually. The only way I found it was when I was sitting in the garage when it was dead one time and happened to wiggle some wires on the column and everything started working. I could duplicate the problem, at will, by moving the wires a certain way.

 

[Burning oil]

There is a chance its the PMD too. Do you have another to try? Sounds like PMD to me?? Also temporary plug PMD to truck harness and eliminate ext cable as a potential problem.

 

[Dunedain15]

There is a chance its the PMD too. Do you have another to try? Sounds like PMD to me?? Also temporary plug PMD to truck harness and eliminate ext cable as a potential problem.

I knew somebody was gonna bring up the PMD. It's classic PMD behavior. The only other one I have is the one that's zip-tied to the aluminum block. I'll move the Stanadyne from the bumper and secure it somehow under the hood temporarily to eliminate the cable.

Is there any chance it could be the IP? That's my real fear at this point.

 

[NVW]

Anything is possible, I would hook up the zip tied one and see what happens.

 

[GM Guy]

do you tilt the steering column often? that would be my first guess is the ignition switch.

dont "rape" a lifetime bumper mounted PMD, leave the PMD in its current location, and switch to your old one without the cable, and see if it keeps doing it. any replacement history on the ignition switch?

 

[Dunedain15]

do you tilt the steering column often? that would be my first guess is the ignition switch.

dont "rape" a lifetime bumper mounted PMD, leave the PMD in its current location, and switch to your old one without the cable, and see if it keeps doing it. any replacement history on the ignition switch?

I don't think the steering column has been moved since I bought it. Maybe when I put the gauge pods on the pillar. As far as I know, the ignition switch is original.

There was some slight hesitating while driving at speed last night. Didn't shut off, but definitely hesitated a couple times. I'm currently talking to GlowShift about getting a new sending unit under warranty so I can watch my pre-IP pressure. I'm gonna switch to the old PMD tonight and see what happens. Thanks to everybody for your input. I'll keep you updated.

 

[Dunedain15]

All right, Gents. I've had the old PMD plugged in for a week now, and I haven't had a single hesitation or shutdown. I'm gonna move the old PMD to the heatsink on the bumper to check out the cable. Question at this juncture: Can I take the #9 resistor out of the Stanadyne PMD and put it in the black one I have? The difference is slight, but noticeable. My power went down when I switched back to the old PMD. Thanks.

 

[Burning oil]

You can swicth the resistor.

 

[JayTheCPA]

Refresh my memory . . . Doesn't the resistor have minimal actual effect on the fuel delivery once the ECM (eventually) re-learns what is going on?

 

[JMJNet]

Refresh my memory . . . Doesn't the resistor have minimal actual effect on the fuel delivery once the ECM (eventually) re-learns what is going on?

It may or is. However, the effect may be different with different trucks.

The condition of IP is different with different truck.
So that extra small addition to the fuel rate can feel some difference.

 

[Dunedain15]

I made the switch Friday night. The black PMD under the hood has a GM part number on it, and it had a #4 resistor in it. I had been driving with it for a week under the hood. When I switched to the #9 resistor and put it behind the bumper, there was an immediate increase in power. Not a ton, but noticeable. Also, GlowShift replaced my fuel pressure sending unit under warranty, so now I can monitor that if it shuts down again. Thanks for all the input, Guys.

 

[JMJNet]

#4 resistor is actually a negative compare to the standard.

IIRC, #5 is the minimum/standard, greater is an increase and lower is a decrease.

At this point, you should experience a better/increase of power.