Sounds like a plan. I just got done removing the fuel tank and fuel pump assembly and I must say, you are definitely right about how much it sucks to take off. I'm working on it sitting in a clearing in the woods, so it especially sucked to remove. It took me a long time to figure out how the heck I was supposed to get all the hoses off, but lots of twisting and turning at weird angles finally got it all off. Everything looks in good shape on the assembly, so I'm just going to get a pump and be done with it.

Thanks everyone for your help, and let's hope that after I replace the fuel pump, this Blazer runs on start up!

 

Fingers are crossed

 

Okay, we have a success and a new problem.

I changed out the fuel pump and put the tank back on. I added some fuel additive that is supposed to clean out your injectors and also raises the octane at the same time. I poured in about a third of the container to only one gallon of gas because the directions just said "used for up to 25 gallons of gas per container." I figured it was a lot, but there was nothing that said that I couldn't.

So we turn the key to the ON position a few times to get the fuel in the lines and then try to start the engine. VROOOM! It starts up, but immediately revs to a very high RPM and stays there so I shut it off quick. A few more attempts and it continues to happen. The fuel pressure did go to 58-60 psi, so it seems the fuel pump was at least some part of the problem.

Now we have another problem, it won't lower the RPM level. We figured it was because of the stuff we put in, so we diluted the additive with more gasoline (about 15 gallons, the tank is basically full). We then bled probably about half a gallon of fuel out of the fuel line, figuring this must have purged the line. Same problem on start up. Is there fuel stored after the fuel pressure testing port? Would that even be the problem?

As far as I can tell the accelerator is not stuck, nor is the throttle. My assumption for this is because the accelerator pulls up easily and I assumed the little open/close device in the air intake being closed means the throttle is closed. As we know I did take off the air plenum and replace that FPR, which requires removing the throttle cables (which I'm assuming, from above). Could my problem be anything other than far too much additive which is still in the lines?

Oh, and the gas tank is leaking too. Lovely. The o-rings in the two screw on lines were scuffed up and I hoped for the best. I'm going to go to a local hardware store tomorrow and find those o-rings so that the tank won't leak again... I can't wait to remove the fuel tank again and then put it on again!

Throw me ideas on what could be causing the high RPMs.

 

First, you can get to the lines and o-rings through the driver's side rear wheel well. If you loosen the straps to giveyourself a little more room and jack up that side of the truck so the wheel just starts to come off the ground, you can reach in there and play with the lines.

Second, check the throttle cables for binding. They shouldn't be tight. If they are tight, check for misrouting.

Then check for vacuum leaks. Are the vacuum lines securely on the ports on the upper manifold? Are those lines securely attached to the check valve (smaller line) and brake booster (large line)? How about the other lines that attach to the check valve? Did you install a new upper intake manifold gasket and torque the bolts correctly?

 

Yeah it sounds like a loose or missed connection. Go over all your plugs and vacuum lines when you were taking the plenum off. There's a vacuum line directly under the throttle body that I sometimes miss, due to it being underneath the plenum, out of sight, out of mind type of thing.

Glad to hear that your truck is up and running now. Those pesky fuel pumps can be a pain.

 

good luck!

 

I just thought of another - do you have the PCV valve hose hooked to the port on top of the plenum?

 

Well, we got the fuel tank off again (it took us only an hour instead of 5 hours this time!). We found the fuel tank leaks and have sealed them up. The gas tank sealant (QuickSteel) is still drying, and hopefully we will have sealed all the rust-throughs. I also bought new o-rings for the connections, so hopefully the fuel tank won't leak any more.

Now, to talk about the high idle. I checked the throttle cables and they all seem fine. When I try to pull them sideways there is some give and none seem tight. As I said before, would it be possible for it to have the throttle open without the little rotating disc open?

When we replaced the upper manifold we did replace the gasket. We just tightened it down to no specific torquing. We have a torque wrench, is there a specific number it should be at other than... tight?

When you talk about the vacuum lines, are those the two lines that come out of the back of the upper manifold (a smaller one on the passenger side, the larger on the driver side)? Are there any others I should be looking for?

Also, the PCV valve hose is connected into the top of the plenum, but the hose did have a tear in it (I am not 100% sure, but I might have torn the now brittle hose while removing the upper manifold). I just sealed it with some electrical tape when I checked it earlier today. I figured that would be sufficient because the old PCV valve was just sitting in whatever that thing is it goes into (about halfway between the spark plug area and upper gasket, on the passenger side - is this the crankcase?). It took no effort to pull it out. I just replaced it and it now sits in there tightly. Does that PCV valve require a tight fit? From my bit of research just now, it seems a leak in that could act like a vacuum leak.

I'm going to go check the stuff that I think you all just suggested, keep the help coming, we're getting very close now!

 

Well, another step in the right direction and more issues. Re-attached the fuel tank and it holds gas, however, the connections are still leaking. There are two that have attachment points with no o-rings and a double sided bolt that screws into both ends of the hose. They are leaking. It's more like the lines are sweating rather than pouring out. Nonetheless, do I simply need to get a new sending unit?

Next, even though the fuel tank was leaking slightly, I figured I should try to start the vehicle. The vehicle started right up and now it appears to idle at a much lower RPM. It was well within an acceptable "keep on" state, so I went and took a look at connections. Everything appeared fine (but what do I really know? haha). I knew the coolant reservoir was empty, but didn't really think about it with the higher RPM and suddenly the coolant cap on the radiator started gushing out fluid (the cap was still attached). I assume I was overheating the engine with the lack of fluid. Could that be attributed to anything else other than an empty reservoir?

I might as well mention that the oil dipstick is almost completely dry, except for about a centimeter on the end of it. I figure since I'm only trying to get it to run right now, it shouldn't be an issue with vehicle start up. Once the vehicle runs I will be changing the oil.

So assuming I have some sort of vacuum issue, is there any way to test vacuum leaks and things of that nature? Let me know!

 

Still looking for insight on these matters. Specifically if anyone knows of any way to check for vacuum leaks.