I had a problem finishing the fuel test. I clamped the return line and repeated the test. I couldn't get any reading at all. So I removed the clamp on the return line and started the car to make sure everything is OK. Then I decided to start the test again from the beginning. The gauge still did not budge. I wonder if I messed up the gauge somehow. If I can find out what's wrong with it, I'll complete the fuel test.

Meanwhile I had to drive 150 miles yesterday. I stopped off at a friend's on the way home when a miss became very noticeable and the SES started flashing. A P0175 code showed up too. The SES was not flashing any more by the time I got home.

Next day: the O-ring on the fuel test connector was damaged and maybe didn't get a proper seal. Also I wasn't getting the connector tight enough, because the spark plug wire was too close to the connector. I disconnected the spark plug to give me more room and finally got a reading. The pressure was at most 50 and it dropped immediately to 0. I may have to fix the O-ring and try again when I have time tomorrow.

 

Alright I switched the bushing on the test gauge with one in an adapter in the kit. What a relief to get the gauge working again. Repeating the tests gave the same results as earlier. Before blocking the return line, the pressure might have reached 55 or so (I didn't wait too long, because I wanted to clamp the return asap). After blocking, the pressure was already on the way down to zip. This is a failure, right Captain?

I'll pull the plenum and take a look.

 

Yup, pull the plenum. We know the pump is good, and the regulator is not leaking past the valve plate. The regulator and or metering block could be leaking externally, a spider line could be leaking, or a poppet nozzle, that's all that's left.

 

I got the plenum off just before the rain came on. There's not much black left so that suggests major leaking in there from somewhere, right? Is the pressure regulator part of the spider assembly? How do I confirm where the leak is? Would it be jumping to conclusions to assume an external leak from the regulator?

Edit: The oval ring/gasket around the metering unit came off when I removed the plenum. It looks stretched. I practiced on my parts blazer and this gasket was securely fastened. Is it normal to have to replace it? I was washing the practice unit with solvent and that one stretched too.

2nd edit: After further review, the yellow o-ring in the return line hole was broken. Does this sound like something that would cause my test results? Explains why the engine starts immediately when cold and needs longer cranking after driven.

 

The oval shaped gasket should be replaced when the plenum is removed. It will not cause a fuel leak, but it will cause a vacuum leak. The O rings where the fuel lines attach to the fuel metering block would definitely cause excessive leakdown. The only way you're going to see it leak, is to attach the fuel lines to the metering block and activate the fuel pump. If an O ring is broken, it needs to be replaced. This kit has all of the parts to reseal the metering block: Item Details Most auto parts stores either have it, or can get it. Another option is to upgrade the injector assembly: This assembly comes with the injectors relocated to the intake ports and eliminates the poppet valves. Also comes with the regulator, (and the o rings already installed). Noticeable improvement in engine performance.

 

I reconnected the fuel lines to the metering block as you said. The fuel regulator was leaking.

Then I did a dumb thing. I took a chance on a spider which I had previously removed from an old Blazer same year as the one I'm working on. The fuel regulator was good on that one. Anyway, I put everything back, started her up and got a P0301 code with a flashing SES. I never had any problem with a specific spark plug before. Could it be the injector on that cylinder was no good? I should have just switched the regulator. I wasn't trying to be cheap, just trying for a quick fix.

Edit: I pulled the #1 plug and it was dark. I switched it with #5 which was white. Same P0301 code, no difference in how engine idles since changing spider. Looks like I'm going to be doing the spider replacement again? Before I do that, I'm going to replace a lot of vacuum hoses. I noticed cracks and rotten ones all over the place. Don't know how that could affect a misfire, but several threads mention it.

BTW, this forum is awesome for learning what's going on. And thank you, Captain.

 

You can swap the regulator. If you weren't getting the P0301 before swapping the injector assembly, chances are the #1 injector or poppet has a problem. Generally, if there's a problem with the injector assembly, chances are that something else is about to fail too. If that's the case, you're better off replacing the entire assembly. The regulator is ~$60 and each of the 6 injectors are ~$60. The whole assembly is under $200.

Swapping the spark plug confirmed that the plug is not the problem.

 

O Captain! my Captain! My dreadful work is done,
First pull on plenum really sucked, but second time was fun,
The codes are clear, the engine purrs, to you I am indebted,
I followed close your sound advice, and thus I was rewarded;
So take heart! heart! heart!
All with Blazers flashing red,
If you’re helped by Captain Hook,
No tear must you shed.

 

LOL, You have more time in the poem than you did fixing the truck! Glad you got her fixed, thanks for the kind words, and for posting back.