I just bought a 1993 GMC S15 Jimmy with 190k, it is running really rough, like its missing a lot. It probably sat for at least a year because the tabs expired March 2010.

has new: fuel filter, Cap/Rotor, plugs, wires, and ICM.

It is still running rough though, did a cold compression test:

Rear
6: 150 5: 158
4: 149 3: 153
2: 149 1: 158
Front

Fuel pressure is 55PSI when running at idle.

still running really rough, not sure what I should check out next.

 

Are there any codes? Is the throttle position sensor functioning properly? How about EGR? Coolant temperature? Those are the things I would check after what you've already looked at.

 

Hello check this out it may just be that you need to replace your spider and fuel injector lines here is a sweet video on it check it out at You Tube put in
Vortec Chevy Problem and Fix! enjoy!!!

 

I watched the youtube video. I had already tested the fuel pressure to be 55, but I went ahead and tested it again today. What I found was shocking. I turn the key to the on position and it shot up to 65+ psi then once the pump shut off it plummeted to 0psi!! within 1 second of the pump shutting off. Did the same test only 30 mins later and the pressure jumped to 65+ then dropped to about 60 when the pump shut off and it HELD there... didnt budge at all. just held at 60.

So is this an intermittent problem im seeing? It pretty much runs rough ALL the time.

What made me decide to check the fuel pressure again is the last couple times when I go to start it in the morning I have to crank and crank and crank and crank till it finally starts. Sometimes it take cranking for a minute off and on other times it can take a good three minutes. (mind you I have not had this blazer long, maybe a week.)

Now once its warmed up, like if ive drivin it someplace. I dont have to crank and crank on it, it will start right up. Its only have to crank a lot to start it after its been sitting a very long time like hours.

for the fuel pressure to drop off like that I am thinking it could be the FPR OR a faulty pump. either that or the excess pressure is leaking off into an injector? That excess pressure has to go somewhere, either into the cylinders or back into the fuel tank. I am just at a loss right now. im almost leaning toward a fault pump because i do hear a whine when it runs and it sounds louder than my old blazer, but im not really sure.

I would like to find the faulty parts without a doubt in my mind. Theres nothing I hate more than just blindly throwing money at a vehicle till the problem is fixed.

 

Pull the Vortec cover off the top of the intake and then pull the round hockey puck looking thing (IMTV) - gently twist it to loosen, then pull it out. There's an o-ring you need intact for reinstallation. You might have to spray some WD40 to loosen it.

Peek inside with a flashlight - is one side washed looking, goldish? Are there puddles of fuel? If both sides look evenly black and gooky with no puddles of fuel, it's probably a fuel pump issue. If one side looks washed clean and there are puddles of fuel, it's internal to the manifold. If it's the driver's side, it's the nut kit (fuel pressure and return lines). If it's the passenger side, it's the fuel pressure regulator.

When you changed the plugs, did any of them look black or gooky or wet and smell of fuel?

 

I actually just pulled the upper intake manifold off. so I can see everything in there now, it actually kinda looks clean all over. but when i turn the key to the on position i dont see any leaks. (when the vehicle is running the fuel pressure gauge showed 55 PSI).

The previous owner said the engine ran like a top/great before it sat for about a year. The tranny went out and he parked it for about a year. About a month ago he replaced the transmission and then started it up and this is how it ran. So whatever went wrong, seems to have happened from sitting. I am thinking it must either be fuel related OR a lifter thats not working? The previous owner also said it could be a lifter or burnt valve which isnt out of the question with how rough its running but my compression test showed pretty consistent numbers which to me almost rules out a burnt valve.

TOBY: the check engine light is not on so im assuming no codes. Fully warmed up the dash shows the coolant to be just under 200 Degree F. I have not tested the TPS or EGR.

http://sites.google.com/site/jakejsite/in1.jpg
http://sites.google.com/site/jakejsite/in2.jpg
http://sites.google.com/site/jakejsite/in3.jpg

I would kinda like to remove the 6 spider legs and crank the car over with the ignition disabled or something so I can see if all the injectors are firing. This vehicle runs pretty darn rough like its missing though im not sure if its actually missing or not, all 6 spark plugs have spark.

if a cylinder were not getting enough fuel it would probably cause it to run rough like it is.

Leeann_Bravada: I will pull the plugs again and snap a pictures, im horrible at judging if a vehicle is burning right just by looking at the plugs. I will smell them though.

 

That's way too clean for there not to be a leak. It definitely looks like the FPR is leaking (see that the top is kinda dirty and the bottom and sides are clean?). Both sides should be evenly black and carboned up.

My FPR was only leaking under heavy load - like acceleration. It didn't leak when I pressurized the system with the upper intake off. But when I replaced the FPR, all my problems went away.

But in your case, it looks like the nut kit is also leaking. Also, lightly tug on the spider lines - make sure they're securely clipped into their ports.

In my pic below, both sides should look like the passenger side - with FPR - evenly black and gooky. The nut kit on that engine leaked and was replaced, that's why it's lighter and cleaner on that side.

 

Thank you and everyone else for the help!

with this Jimmy having 190k it probably wouldnt hurt to swap out the entire spider assembly. I am going to check the wrecking yards as soon as we get a day where its not raining so much.

 

I was just at my local u pull it yesterday, and every Blazer with a Vortes had the cover off and the parts out of it. People must wait in line for these things. Glad I dont have one on my TBi.

 

well I found one in a Van at the pick a part. the nut kit side was nice and black like no leaks but the pressure regulator side was almost comletely washed clean. who knows how long it sat in the yard though....

I am going to see about getting a really good aftermarket FPR to match up with this spider and nut kit that I pulled.

I was reading this post: https://blazerforum.com/forum/1st-ge...80/#post132745

swartlkk talks about the "Lindertech kit" replaces the stock FPR with the 96+ SCFI FPR which is a much better design.

Is this just a 96+ FPR because I dont see the kit listed on lindertech anymore so I am wondering if I could just order a FPR for a 96+ CPI 4.3L when i look the part up online it looks a bit different... so Im thinking there must be something special to the lindertech kit.