Hey everyone. I just was dealing with another issue with my truck and was searching for information. In this search I noticed that I never updated everyone on what went on with the issue I wrote about in my previous post, so I'll start with that.
The issues with my truck were a little beyond plain and simple because of the computer firmware issues I had, but the rap was one of those dumb overlook things that really made me want to turn in my wrenches. I did try measuring transfer pressure with the engine running using a home-made fitting with an Ashcroft pressure gauge I had kicking around. The pressure pulsates pretty heavily and it makes it difficult to read, but averaged around 150 psi IIRC. I figured that there was something else up with the pump so I swapped it with another used 5521. The truck sounded the same. After the swap a friend listened to my video and insisted that I double check my firing order. I had carefully labeled the lines and installed them back where they came from but checked anyways. The previous owner had put a (assumed good used) 5521 pump in the truck in their attempts to get it running (without installing the right firmware, but that was another issue). Apparently in the process they switched the lower two lines and the firing order was incorrect. I straightened it out and have been driving the truck ever since November 2014.
Lately I had a couple stalling issues and it wasn't PMD or computer (I had both in the cab and swapped them on the side of the road, no luck). It was always tough to start and beat was a little uneven so I decided to put another pump I acquired into it - a -5521 I stripped off a mud-covered engine that threw a rod, with the stock black Stanadyne PMD still on it and connected (which is now next to the GM/FS one in the glovebox). I got it all set up and timed with GMTD ScanTech (which I highly recommend to others) and noticed that it was leaking fuel, in addition to the occasional code 36 (fuel solenoid response too long). I pulled the manifold back off (and made some block off plates to cover the exhaust crossover ports so that it could be run like that) and found that the leak was coming from somewhere in the rear half of the fuel solenoid. The rubber boot was full of fuel and it was dripping off the back of the solenoid. I read somewhere that these can be finicky but despite my searching I couldn't figure out much about what lie under the hood - most specifically, how the fuel is supposed to stay in the pump at that point.
So I did an exploratory on another pump and there are the results:
There are two shoulder screws with threaded studs on the backs of them that make up the electrical terminals. 6mm heads and self locking nuts hold the wires onto them (also 6mm). These tighten against a white plastic (probably nylon) spacer with a flange on one end. Below the spacer is an O-ring which expands when the shoulder screw is tightened and seals against the shaft of the shoulder screw and the screw hole in the anodized aluminum end cap of the fuel solenoid. Below the O-ring is another white plastic spacer which bottoms against the body of the solenoid itself, where the shoulder screw threads into the electrical contacts of the coil.
These were snug in my truck so I left them alone.
There are two Torx head screws also installed in the end cap. These are what actually hold the end cap to the solenoid body and they use copper crush rings of some sort to seal against the head. A T-10 is a somewhat sloppy fit and a T-15 is too big, so I'm guessing that they may be a T-12 but I didn't have anything between T-10 and T-15 so the T-10 got the job.
I have seen some testimony of others having had these Torx-head screws back out of their fuel solenoids, causing a horrid fuel leak and other issues. The ones I took off the exploratory cadaver were fairly tight. I did a finger feel of the torque on them and then checked the ones in my truck. Sure enough, they were loose. I gave them a good guess at torque (didn't go nutso on them, they aren't very big, and I don't want to distort the housing and cause issues with armature stroke).
Not only did this fix the fuel leak, it also seems to have gotten rid of the DTC for "fuel solenoid response too long" (or something to that effect). I'll see if I can put up some photos for the group later on which provide more detail of the fuel solenoid assembly. Tonight I have to put it all back together so I can really test it out and make sure that the DTC doesn't recur, but I ran it for a while last night after resetting it and the history is clear.
