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Vortec 7.4 injector and regulator replacement plus bonus

This is a discussion on Vortec 7.4 injector and regulator replacement plus bonus within the Technical / Maintenance forums, part of the General Discussion category; Already posted this over on Chevytalk but what the hell...here it is again: The subject is a 1996 Vortec 7.4 ...

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    Loves GMT400 haters someotherguy's Avatar
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    Vortec 7.4 injector and regulator replacement plus bonus


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    Already posted this over on Chevytalk but what the hell...here it is again:

    The subject is a 1996 Vortec 7.4 with 240K hard miles on it, transplanted into a 1994 3500HD. It's had a whole list of problems that previously were just annoying, but recently got bad enough to cause major grief.

    It's had the hot restart issue where it cranks forever then blows out a bunch of unburned fuel, typically leaking injectors or bad fuel pressure regulator. I picked up a Standard Motor Products # PR217 regulator from Summit - made in USA. Got a set of Bosch injectors that are a bit of an upgrade over the stock Delphi Multec design; Bosch # 0280150973 from Five-O Motorsports. Plenum gaskets and new fuel rail O-rings round out this segment of the job.

    Additionally, had hoped to silence some serious valvetrain noise due to excessive wear on the factory nonadjustable rocker setup. Ditching these in favor of Comp Cams roller tip 1.72 rockers # 1411's, which are available in a kit with conversion rocker studs (must be 3/8" thread on bottom, 7/16" on top, to fit these late model heads that previously had the nonadjustable rockers simply bolted in) and pushrods. Rocker and pushrod kit w/o studs is # RPR205; stud kit # 4514-16 - they offer it combined under part # RPS302 saves you about $8 but wasn't in stock.

    Fuel injectors: first big hassle was getting the EGR tube off the plenum; they tend to seize, and the backup nut on the fitting is very slim so you don't have room for two large wrenches. Used some PB Blaster, a Channel-Lock brand skinny profile adjustable, and a 1-3/8" on the coupling nut - using a 2x4 block of wood on the valve cover to let the Channel-Lock wrench shove against. (Some anti-seize lube on the fitting is a great idea for reassembly.)


    Simple to get the plenum off; just a bunch of wiring to disconnect and then 8 bolts come out, it lifts right off. Helps to tie-wire a bunch of junk out of the way so you have a clear path to remove.


    COVER THE PORTS RIGHT AWAY; you don't want anything falling down in there at all! I used a paper towel with brake cleaner to get any oily residue off the surface first, so the tape would stick:


    To disconnect the harness from the injectors, the round wire part of the clip pushes towards the connector; you can squeeze it with your index finger and thumb, and lift it off. Once they're all disconnected, unhook the fuel supply and return lines from the fuel rail (helps to remove the distributor cap for working room.) Then unbolt the fuel rail completely from the intake. Gently pry the injector out of the intake with a screwdriver if necessary; the O-ring will have it kind of tight. The rail comes out with all the injectors attached. Take care not to knock any crud into the holes in the intake for the injectors.


    Here's the rail with the injectors removed; getting the hold-down clip off is a little tricky as they're shoved down over plastic nubs in the rail. I used a small flat screwdriver to go under them and carefully twist the tangs away from the plastic nub, working them up the nub as I went. The regulator has been removed too; takes snap ring pliers to get it out. Be sure both its O-rings come out too; large and tiny.


    When removing the injectors be sure to get each O-ring out of the fuel rail with a pick. Here's the old injectors with the O-rings popped back on so I can be 100% sure I have them out of both the fuel rail AND the intake. Note the regulator doesn't have its smaller O-ring in place; I hadn't picked it out of the fuel rail yet. You can also see the one plastic nub I broke for the injector clip.


    Wipe a small amount of clean motor oil on each O-ring where the injectors go into the fuel rail, before installing. I did the same with the FPR O-rings. You don't want to tear any of these; by the time it's all assembled and you discover you have a high pressure fuel leak, you'll be pissed. I left the protective caps on the new injectors until it was time to reinstall the fuel rail.


    Here's a repair I did with two zip ties for the nub I broke. It's on an injector right next to a fuel rail hold-down bolt so I'm not worried, plus the zip ties held it very well, looped through the clip.


    NEXT UP...stock NONADJUSTABLE junk rocker setup:


    And the Comp Cams adjustables in place...unfortunately, had to use the old factory 5/16" pushrods instead of the nice new 3/8" that came in the Comp Kit; the factory guideplates are for 5/16" and there wasn't much I could do on short notice. This is the kind of stuff the guys on the tech line don't warn you about. I almost swiped a set of 3/8" guideplates off another older big block sitting here but then the stud holes will be too large - 7/16" instead of 3/8", because they're coming from an engine that was adjustable valvetrain from new. Fuel rail re-installed with the new injectors and FPR; again I wiped some clean motor oil on the O-rings where the injectors seat into the intake. Also lots of clean oil dumped on the rocker parts during assembly. Moly lube would have been better but again, in a pinch...


    Plenum reinstalled, MAF etc. all hooked up so I can do the running adjustment on the valves, after doing initial adjustment with the engine off. It's a pain to get to several of them with everything in place but it's not going to run without the MAF...


    Zip ties/tie wire used to keep everything out of the way, especially the plug wire loom brackets:


    Truck fired up great on first try; I had more oil ready with a squirt bottle tip on it (pirated from a gear oil bottle) so I could keep drenching the rockers until the pushrods began oiling. Most of them began oiling right away but a couple were stubborn so I just kept soaking them down.

    After some running adjustments I got it to where it sounded mostly quiet, even using my stethoscope - after a test run though I've got a pretty significant tick. All the miscellaneous clattering is gone which is a nice thing, but that heavy tick is still in there - figuring at this point that's going to be something bigger like a collapsed lifter or other problem. Not running perfect so there's still some dragons to slay but oh well; running much better now.

    Richard

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    Registered User 454cid's Avatar
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    Re: Vortec 7.4 injector and regulator replacement plus bonus

    Richard the engine will run without the MAF. It will take a couple of tries to get it started, before the computer figures out that is needs to run in Speed Density. That was something I learned just this past year in the big 454 thread.
    454cid
    1999 K3500 RCLB

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    Registered User rockien's Avatar
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    Re: Vortec 7.4 injector and regulator replacement plus bonus

    Richard, thanks for posting the pictures. I just removed my plenum last night to change the FPR on my 1998 k2500 Suburban, but found the intake was seeping antifreeze out the back, so I am going to get gaskets and change the intake gaskets and order new injectors as well. It has had the hard start problem for a couple of years now, so I'm pretty sure this will fix it, after reading all of the post about this exact problem.

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    Registered User 454cid's Avatar
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    Re: Vortec 7.4 injector and regulator replacement plus bonus

    I can't beleive you still have the quick mis-connect fitting on the heater hose!
    454cid
    1999 K3500 RCLB

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    Registered User rockien's Avatar
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    Re: Vortec 7.4 injector and regulator replacement plus bonus

    454cid, what options are available to replace that connector. I still have that quick connect fitting, but it is not leaking, YET. FYI, I replaced all the same stuff (other than rockers) as in this post plus the intake gasket and the Sub runs perfect.

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    Registered User 454cid's Avatar
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    Re: Vortec 7.4 injector and regulator replacement plus bonus

    Quote Originally Posted by rockien View Post
    454cid, what options are available to replace that connector. I still have that quick connect fitting, but it is not leaking, YET. FYI, I replaced all the same stuff (other than rockers) as in this post plus the intake gasket and the Sub runs perfect.
    I used a brass hose barb that I got through the dealer. It was listed for use on the water pump, I think. It was expensive, Though. I wish it were a little longer, but it seems to hold ok with a hose cut off as straight as I can and a decent stainless hose clamp. You can get that type of thing at the parts store, but it might not be brass.
    454cid
    1999 K3500 RCLB

 

 

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