Anyone have experience with 98 or newer 4.3 vortec? (1 Viewer)

[Mark W]

We've got a '99 SFI vortec that is got gremlins. We had a clogged injector (at least that is what we surmise at the moment. Missfire on #5 with all other problems eliminated).

We removed the spider and ran it through an ultrasonic cleaner. Seems to have solved that prblem. BUT... upon reasembly we only have fuel flowing to #3 and #6 injectors.

We tossed another injection unit on the rig off of a good running engine. Same symptoms.

We've got good ground and good voltage to the system. No codes showing except tranny codes (it came out of an auto). But those were present before we pulled it down and they had no effect on anything.


If you have any experience, knowledge or other background with this system, sound off. PLEASE!

Thanks,

Mark...

 

[Medusa]

Strange that you are not generating any codes, Mark. What pressure do you have going into the injection unit? I would put a pressure gauge on the line and see what the input pressure is. One thought is that the input pressure is marginal and some of the poppit valves are simply not opening.

 

[Mark W]

One of the first things we checked. 60 PSI.

We figure that it has to be related to something we did . But there really isn't that much impacted by removing the injection unit. I don't really believe in coincidences like this really being coincidences. But everything seems to be the way it should be. Except for the small detail of fuel coming out of the injectors.


Mark...

 

[kirk]

Did you swap injectors around to see if the problem follows the injector? Also there are huge grounding loops in the GM system. Make sure the wiring is ok and you are getting a signal to the injector. Since you tried another computer I am inclined to believe the wiring or injector is the culprit.
Was the 60 psi coming from the tank? The fuel rails are supposed to be 36-38 psi.

Good luck
Kirk

 

[cruiser88]

my father had grounding troubles also with his 98 it cost him a fortune to find good if memory serves me right start checking grounds at the fire wall good luck

 

[Mark W]

Did you swap injectors around to see if the problem follows the injector? Also there are huge grounding loops in the GM system. Make sure the wiring is ok and you are getting a signal to the injector. Since you tried another computer I am inclined to believe the wiring or injector is the culprit.
Was the 60 psi coming from the tank? The fuel rails are supposed to be 36-38 psi.

Good luck
Kirk

We swapped the entire injection unit, injectors included. This setup doesn't use a fuel rail. The pump pressure goes right to the central control unit in the middle of the plenum and for there is distributed to the injectors via short (individual) lines).

Grounding is high on my list of suspects. About the only thing that I can think of tight now. But all the ground streaps are good and we even added additional jumpers to make sure.

???????


Mark...

 

[curious1]

There was an upgrade available from the dealer regarding the spider poppet nozzles. They were having problems with the original spider disign. I upgraded mine on my 2000 4.3L vortec. I don't know if this may be you problem.

 

[Mark W]

Do you remember any further details about what sort of problems they were having or what the upgrade was?


Mark...

 

[DHONDAGOD]

Was the 60 psi coming from the tank? The fuel rails are supposed to be 36-38 psi.

Good luck
Kirk

min pressure on a 98 vortec is 60 psi. 60-66 is specs. i aggree with jack, if the pressure isnt high enough it will not open the injector "poppet valve".... 36-38 psi is for a conventional injector that a vortec is not. depending on guage accuracy you may be below the min pressure that your injectors will work at. id get the fuel pressure up before going any further. if the pumps stock and has any time on it (especially if it normally runs with low feul in the tank) then id suspect that. keep us posted as to what you find..


chris

 

[curious1]

Do you remember any further details about what sort of problems they were having or what the upgrade was?


Mark...

The poppets were leaking IIRC. The upgrade was a new new spider with injectors instead of poppets. I agree that you need to confirm you are getting 65 psi before moving foward.