So I recently got my '95 Jimmy back after originally purchasing it in 1997 and selling several years later. I am currently sinking a lot of time and money into it trying to get it back in shape. I think I have everything pretty much done but just can't figure out why it's so hard to start. The key has to be turned on and moved to the start position for short intervals only. It will eventually chug a few times, then a few more, then will start up. Continuous cranking does not work...it will only start if cranked in short bursts. The vehicle runs perfectly after it starts. Also, it has been sitting for about a year now but I start it every week or 2 and take it up the street to keep things loose. It started fine when I first got it but the starting issue has begun since it's been left sitting.

So with a lot of information and help from this forum, here's what I've done so far:

-replaced 2 freeze plugs (rusty/leaking)
-replaced rusted brake line
-replaced leaky trans cooler line
-replaced air intake boot
-replaced fuel pressure regulator (plenum appeared washed, see pics)
-replaced cap and rotor while plenum was off
-replaced spark plugs
-replaced exhaust system including cat and O2 sensor
-replaced egr valve and included new gasket with screen
-replaced fuel filter

That's all I can think of for now. Here's the latest info:
Checked fuel pressure at schrader valve, was about 52-54 with key on, engine off. I'm thinking this might be a fuel pump problem but not sure it they get weak or if they simply work or don't work. Any help would be greatly appreciated. Thanks!

 

Couple tests for you {based on others' experiences}

Do the key-on pressure test several consecutive. Does pressure build each time?
Check leakdown. After pump turns off, how long does it stay above 50psi?

Does engine start right up if you jump it from running car?

If answers are
yes
less than 5 min
yes
Any two or all of the three..
Then you are probably right. Fuel pump is weak and /or system still leaky.

Final test, go here.. scroll to bottom of post and test Fuel pump for head pressure/ leakdown.
https://blazerforum.com/forum/tech-a...agnosis-23038/

 

just replaced my fuel pump on my 96, had the same problem, it would never start on the first try no matter how long i held it or not, quick fuel pressure check, it didnt even hold for 5 sec, but once i got it running it ran fine. after the furl pump change, starts on a dime everytime, and since you allready changed the fpr, i would also point to the fuel pump.. but check to see if the fuel pressure holds or not..

 

The pressure isn't holding for sure. Could that be the fuel pump somehow? I turned the key on with the upper part of the plenum off after I changed the regulator and I didn't see any fuel leaking. Not sure what the problem is with it not holding pressure??

I hate to go through all the trouble of changing the pump and then still have it leak down and not be fixed....

Are there other causes for it not holding pressure other than inside the plenum? I don't see any external leaks anywhere.

 

Got this information from the link shared by Pettyfog...thanks.

3. A fuel system that drops more than 34 kPa (5 psi ) in 10 minutes has a leak in one or more of the following areas: 4. A fuel system that drops more than 14 kPa (2 psi ) in 10 minutes after being relieved to 69 kPa (10 psi ) indicates a leaking fuel pump check valve.

 

Another way to find out for sure is hook up a pressure gauge at the testing port, get it up to pressure, as soon as you hear the fuel pump stop, or see the pressure stop getting higher, have a friend pinch off the fuel line with the correct tool,(theres a rubber fuel line section a little after the fuel filter, starting to go up the firewall) if the pressure holds now, its the backside, if your sur
e its not a fuel line leak, change the fuel pump assembly.. should be good

 

I dont how true it is but I have alway been told a electronic fuel pump with just quit without any warning.

 

I like that idea...

 

They sometimes do.. but that is usually an electrical fail. Example being the OE 2x2 pump connectors as happened to mine.
Usually not if due to wear, though.

 

Pettyfog has posted valuable advice You should follow here - however ,to get it "running" the '95 CPI spider equipped engine can be coaxed to start and run by unseating and spray cleaning with a nylon bristle brush the poppet valve tips/injectors with some B-12 chemtool - NAPA has it - I got a '95 running that sat 4 years with it . And some sensor replacements ofcourse