My sons blazer stopped on him, He calls and I go see whats up, It is spinning over like it is out of gas, but gauge says 3/4 tank, I put 3-4 gallons in it any way but no luck, then I pour small amount into plenum and it starts and I drive to gas station and it takes about 6 gallons to fill, I drive home, about 5 miles and it has a slight hesitation at part throttle, any suggestions, also no check engine light so far, thanks

A quick thought is that I would check for a partially clogged fuel filter...

replaced fuel filter and pump, can ran for two days then it stopped again,squirt fuel in plenum, it starts and run ok execpt for a slight hesitation sometimes

It definitely sounds fuel related. Possibly a dirty carb or throttle body? Could be as simple as a batch of bad gas. If this is a fuel injected car, some of the sensors could be acting up. If it's carbureted, it sounds like you've covered the easy stuff. I'd pick up a manual for the car that covers troubleshooting step-by-step. If you have all the right tools, you'll save a ton of money. If not, your local mechanic can probably sort it out in about 2 hrs. ($150)

95 4.3L Jimmys are CPI (Central Port Injection) injection motors.

The CPI Unit is located inside the upper intake plenum. It consists of the cpi which is connected (integrated) into the fuel pressure regulator. To see the system, you must take off the upper plenum. The unit is located in the center of the intake, with 6 poppet lines/nozzles branching off of it.

There is 3 things that tend to break with this system over time. They are

1. Fuel pressure regulator: this is the most common thing that breaks. There is a diaphram inside the fuel pressure regulator that breaks and will leak gas into the plenum. The fuel pressure regulator is in the center of the intake on the passenger side. It looks like a gold cylinder.

2. Inlet/Return fuel lines: There are 2 fuel lines that connect to the cpi unit. They are on the drivers side. They will weaken over time and can get pinsize holes in them that will leak gas into the intake.

3. The 6 plastic popett lines leading to each cylinder.

Common systems of these failing are: Bad idle, hard to start, shaky revs, low gas mileage, and most important I think is bad smell from the exhaust. Most of the failures seem to occur around 80K miles, and your lucky if they make it to 120K miles without replacing some part of the CPI system.

The best way to check for a failure is to remove the upper plenum. The plenum is the huge piece under the "vortec" plastic peice. Looks like 3 tubes going down on each side. There are about 9 or 10 bolts that you need to take out and also remove electrical things, etc. to get it off. I would suggest buying a haynes manual or chiltons manual. They explain it well. It really isnt that hard if you take your time. Shouldnt take more than 30 mintues or so the first time.

If you do this, and get the intake off, look at it from the front. If 1 side of the intake appears clean, this will be where the leak is comming from. If it is passenger side, it is probably the fuel pressure regulator, if it is on the drivers side, it is probably the fuel lines.

Heres a picture of a leaking fuel pressure regulator:

http://www.samscars.com/Sep25_01.jpg

There is also other ways to check for a leak, but arent as effective. One way is to disconnect the brake booster line and smell for gas. It comes out the back of the plenum and goes to the brake booster at the back right of the engine on the firewall, (if looking from the front.)

It is very easy to replace the CPI unit and fuel return lines. Heres the unit removed from the intake. If you have to replace the unit MAKE SURE you know which poppet line goes to which cylinder. If you screw it up, it's like getting the wrong spark plug wire on the wrong cylinder, only you can't check it out without taking the manifold apart again.

http://www.samscars.com/Sep25_11.jpg

I would suggest buying your parts at www.gmpartszone.com, (http://www.gmpartszone.com,) they have the best prices i found, and are very helpful.

The CPI unit gm part # is 17113673.
The fuel lines, called a "nut kit" are # 17112705
Prices are about $272, and $40 respectively.

If you want to go to the dealer, expect to pay $473, and $63. I've checked. If you want them to do the install, expect $700-900+. Rip off.

Its not hard to do it yourself just need a socket set, screwdrivers, etc. Basic tools.

If it's the pressure regulator you can adapt a 96 and later pressure regulator to the 95 and earlier CPI system with a kit from lindertech.com. Might be able to save some money over replacing the hole injector setup.

http://www.lindertech.com/4~3_regulator_adapter_kit.pdf

I have a 96 with the SPFI system which is similar but not exactly the same so I haven't used it, but I did have to replace my injector setup at about 130K miles.

I hope this helps explain all the problems with the CPI. Also, if you have replaced your cpi, and are still having problems, check to make sure the fuel lines were replaced also. If they have, i would think maybe fuel pump or EGR valve. But other people would probably know more than me.

[ 03-06-2005, 04:49 PM: Message edited by: Mark C ]

THanks Mark, great info, I have just about convinced myself it is the "spider" except for the no start and then running ok sympthon, From info on the net, seems they are a common problem so with 130,000 miles I will replace it tomorrow, my guy at the dealer treats me fair so I will use your price guide to keep him honest, ;) Again thanks guys for the help and I will keep you posted on the results. Man, give me the ole points and carb anyday tongue.gif Rick

Okay, went to my local parts guy, Woodie, and he fixed me up with the spider and nut kit. Installed it this morning and car is running better than ever. No hesitation, and so far no starting problems. Thanks everyone for the help and if anyone has a blazer 4.3 with the same problem maybe this thread will be of some help to them. I will post in about a week and let you know the long term prognosis of this ole blazer, thanks again guys. By the way my cost on the parts were 297.00 for the spider and 48.24 for the nut kit plus 7% tax. Rick

Hi guys, I know this is a old post... But I found it infomative and I just wanted to add some money saving tips. ;-) Since gmcpartzone.com whatever (link above) no longer works.
First of all the "Nut kit" (why the heck do they call it that anyway? ;-) ) Is made by Doorman Help! Almost all car part places carry this. The part number is 55163 and can be bought for $43.59
The regulator is also availalbe... it is part number 55162 and I'll know the cost tomorrow when I pick it up. ;-) I think it is about $40.00
--Edit-- the regulator was 42.99.
Andrew