I have an 1998 GMC Jimmy 4.3L V6. I went into my local Super-Lube here in Florida to have an oil change done. They convinced me to get a "Fuel system cleaner" done. I drove it around town, turning the vehicle off several times to go into shop at various places with no issues. I made it home, and when I tried to go to work the next day, it didn't crank. Engine attempted to start, but didn't turn over. I contacted Super-Lube to let them know of the problem. Before I go into that explanation I should mention that when the engine cleaning was being done, there was lots of smoke coming from the engine. When I left the shop, there was an engine light on, which subsequently went off while I was traveling around town. It should also be noted that I had less than 1/4 of a tank of gas when I went into the shop. After I left, I filled the tank to FULL.
The guy at Super-Lube suggested a new fuel filter, and then spray starting fluid in the carburetor. We put a new battery in, as well as a new fuel filter. When disconnecting the filter, lots of fuel came out of the line, and the filter WAS dirty. We used the starting fluid to get the Jimmy running. It idled perfectly fine, engine light disappeared. No RPM fluctuation, voltage, or oil pressure fluctuation. I thought "Great it's fixed." I drove it to the store and really tried to gun it hard to help everything circulate properly, as well as hopefully burn off any excessive gunk left over from their cleansing. I came home, my parents drove it out and it stalled on them in the middle of the road. They were able to push it into a gas station where my dad was able to get it cranked, and bring it home. Since then, the vehicle hasn't been able to crank. I called Super-Lube to complain and had a tow truck driver come to take it to their shop. One hour prior to the driver coming, I attempted to start the vehicle. It just makes a noise of trying to crank, but seemingly no fuel supply to the engine. When the driver came, it started up just fine. The shop claims it is running fine and that the fuel pump is putting out 55 PSI to the engine.
I've read several articles stating sometimes fuel injection cleaner (which is what they did), can harm your fuel injectors. I asked on the phone if it could be the fuel regulator, in which he replied it couldn't be. I've read where there could be cracks in either the lines leading to the fuel injectors to/from the fuel regulator, which can cause not starting. I've also read that it could be the pump. If the pump is putting out the correct pressure when tested, and the starting of the Jimmy is intermittent, why would it be the pump? For the record, I have had NO issues at all with my Jimmy prior to entering their shop. My concern is that this cleaner has somehow damaged my fuel injectors, regulator, or pump.
You have a lot of misconceptions and misinformation. First of all you're confusing the description with "crank", "attempted to start", and turn over". Those are all the same thing. "It didn't crank. Engine attempted to start, but didn't turn over". If it didn't turn over, how could it attempt to start? And how is a starter problem related to the fuel supply problem?
Secondly, there had better be lots of smoke coming out of the exhaust while they're doing the cleaning. It's supposed to break the carbon loose and send it out the exhaust, otherwise, what good is it doing?
Third, you have to understand that GM does have a lot more injector trouble than any other brand and the cleaning services often have very good results. To recommend that service, especially at the mileage you listed, suggests your mechanic had your best interest at heart and thought he could provide a good value for you.
Fourth, you're suffering from what every mechanic dreads; that's the "ever since" syndrome. Ever since they did that repair, I have all these new problems, and of course they're all related. My car was running fine before so there's no way it could suddenly develop all the same problems every other car on the road will develop sooner or later. It's just a matter of WHEN those problems develop, then figuring out who we can blame.
By your own admission the car ran fine when you got it back from the shop. That would not be the case if their service damaged or plugged something. Stalling while driving is a real common problem on all car brands and that can show up anytime. It usually has nothing to do with any previous service, and in almost all cases your mechanic is not psychic and he can't tell when that is going to happen. Crankshaft position sensors often fail by becoming heat-sensitive, then they work again after the engine cools down for an hour. There is nothing anyone can do to cause that problem; it just happens. We replace the offending sensor or part and move on.
The first thing you need to do is have the diagnostic fault codes read. It's important to understand they never say to replace parts. They only indicate the circuit or system that needs further diagnosis. About half of the time the sensor referenced in the code will be the cause of the problem, but it's just as likely to find a corroded terminal in a connector, a wire rubbed through and grounding out, or things like that. Many auto parts stores will read the codes for you for free.
If you do indeed have a cranking problem, which I don't think is the case here, that is often related to a failed generator, and that can show up as elusive running problems too. If the battery is fully charged and the starter is working properly, we don't have to discuss GM's charging system problems until later.
I will never defend a dishonest mechanic or shop, but so far you haven't included anything to suggest they are to blame. With further testing and diagnosis, I could be proven wrong, but so far it's just a coincidence.