Runs ruff at idle and when excellerating sounds like its missing. had fuel presure shecked its bleeding off after shut down?? new fuel pump.
Good chance that your fuel pressure regulator has gone bad and needs to be replaced. Sorry you have not indicated what year your Jimmy is so going to take a guess it's of the 1996 and above.
You may may have a leaky fuel pressure regulator.
Double check cold start cranking fuel pressure. If under 63-62 lbs you have problems. Run the full fuel pressure test and post back pressures.
Here is the guide lines on testing:
Check cold start fuel pressure.
Check engine running fuel pressure.
Check engine running on the road fuel pressure.
Then shut it off and watch for fast leak down.
Pinch off at rubber part or block off return line and check full pressure.
Later V6 and V8 gm engines should have 60-66 fuel pressure.
Cold start should be 64-65 lbs of pressure.
If you do not have full fuel pressure on a cold start the injectors will not squirt fuel.
Engine running should be 60-66 lbs pressure depending on engine load.
Full pressure with return pinched off should be 75-85 or more.
And if it has a fast leak down after shut off you have a leak.
Post back fuel pressure readings.
The 75-85 is only a check on the capable full pressure of fuel pump.
If you can not find the rubber return line check full pressure by
plugging return line or just or the true full pressure can be taken
direct at the end fuel filter. What are the pressure readings that you have done. Good luck and be glad to help you get your Jimmy running 100% again.
You can pick up the new upgraded MFI system to replace the SCPI system in your jimmy, for around $300.00 at Auto Zone or NAPA. If your injection system is still good and it's your fuel pressure regulator that has gone bad, it's around $60.00 Keep me posted.
MFI is the Multi Fuel Injection system like the 2003 and up blazer and jimmy fuel system which is more reliable and efficient. You can update your fuel system to the new system out there.
Auto Zone Fuel injector system for GMC Jimmy and Chevy Blazer 1996 to 2003
Part Number:
800-1512N
Notes:
New SCPI conversion to MFI. Replacement poppet nozzle available.
Contents:
Includes Instruction Sheet
OEM Replacement:
Yes
Quantity:
1 Assembly - 6 Injectors
Type:
Sequential Cental Port Injection Assembly
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Yep change the pump! and new filter too!!!
well the injector and spider rail is a exspensive adventure i got one in my drive now that a guy doesnt have the money to by the rail the fuel pressure regulator isnt that expensive and eask anuf to change there is just one torx security screw you got to mess with! outside of that its easy enough also common problems is the o-rings around the main injector are bad about leaking too might want to change them also
the plastic rings you found go around the fuel injector thats! why your loseing pressure
http://www.alldatadiy.com/alldata/AFI~G~...
go to this link and read this service bulletin this will give you a easier and better understanding as to what is going on
just tell them you need the injection rail for that model and thats all you need to tell them if they still don;t know then ask them the number to there D M. district manager and tell him or her that LOU that used to work in corporate said they hired some dumbazzes at yout store and they need to fire em so you can get parts
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its a 96 jimmy. had it tested guys at shop say presure is fine starts up every time but then bleeds off quickly want to replace spider injector and presure regulator. it has a new fuel pump 4 days ago.
got it off and found 2 plastic rings dont know where they came out of any idea does it go in the regulator hole?
replaced fuel presure regulator and now it barley can start and it sounds worse...
MFI system to replace the SCPI system what is this??
what do i ask for at auto zone? i called and they dont know.
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