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Username Post: Vortec 7.4 injector and regulator replacement plus bonus        (Topic#257907)
Posts: 27003
Age: 45
Loc: Texas
Reg: 08-01-03
02-20-11 02:59 PM - Post#2049463    

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.

94 Chevy C2500LD / 06 Silverado SS / 06 Chrysler 300C SRT8 / 06 Dodge Magnum SRT8

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Senior Member
Posts: 1346
Loc: Houston,Tx.
Reg: 04-20-03
02-20-11 03:52 PM - Post#2049494    
    In response to someotherguy

Heads look clean under the valve covers for having 240k on it. At least it looks like someone too care to change the oil reg.

Senior Chevytalk Moderator -- Performance Subject Matter Expert --
Posts: 16468
Age: 67
Reg: 03-16-01
02-21-11 05:02 AM - Post#2049728    
    In response to GRUMPYK3500

the difference in the intake runner internal surface condition makes it obvious the there a huge difference between something going on it the ports,its probably either with injectors or valve timing as ones far cleaner than its companions, but bad valve guides, a vacuum leak or other factors like timing and intake runner reversion can effect the results

Posts: 27003
Age: 45
Loc: Texas
Reg: 08-01-03
02-21-11 11:58 AM - Post#2049896    
    In response to grumpyvette

Yep, I did note the difference in the ports. We suspected there were injector problems and regulator problems, as both items are well-known for being troublesome on these engines - even well before 240K miles.

The vacuum line to the fuel pressure regulator was rotted and slipped off easily, too - practically fell off when I touched it. It hides under the plenum though so it's very difficult to see it, much less replace it, without removing the plenum.

It's got some smoking that is likely bad valve guides, or at the very least, bad valve stem seals.

94 Chevy C2500LD / 06 Silverado SS / 06 Chrysler 300C SRT8 / 06 Dodge Magnum SRT8

Forum Newbie
Posts: 1

Reg: 03-31-11
03-31-11 09:28 AM - Post#2069915    
    In response to someotherguy

I have the same engine in a '97. I also replaced the stock rockers but with an adjustable GM stamped steel with 3/8 rods using Comp Cams OEM style roller lifters. I have had a heck of a time with them trying to adjust the lash out (noise). Actually had the ball ends break off on exhaust side. Changed to a solid 3/8 rod which has been better but still noisy. I have considered going back to the nonadjustable.
I have just purchased some Bosch injectors and new regulator to clear up the hot start issue also. I plan on pulling the entire intake and rechecking the lifters.
Any suggestions would be helpful.

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Posts: 2

Reg: 10-10-10
04-25-11 09:54 PM - Post#2081970    
    In response to LVan

can you get the regulator off without pulling the upper intake? Does the upper intake gasket look like its reusable?

Posts: 27003
Age: 45
Loc: Texas
Reg: 08-01-03
04-26-11 09:29 PM - Post#2082527    
    In response to tdale

LVan - if you read back through my post I think I gave a tip or two on the injector & regulator replacement; some of it is no-brainer and some of it is head-scratcher! Not a difficult job though. One thing to watch out for that I can think of off the top of my head is make sure both O-rings come out with the regulator, the large and the small.

tdale - no; you've got to remove the upper intake. You can just barely see the regulator with everything assembled, but there's no way you'll get the snap ring pliers in there to pop it out, without disassembly. Besides, you'll want easy access to replace the vacuum line as well. I don't think I would attempt to re-use the intake gaskets. They're not expensive, so why risk it?

94 Chevy C2500LD / 06 Silverado SS / 06 Chrysler 300C SRT8 / 06 Dodge Magnum SRT8

Posts: 68

Loc: Custer Park, IL
Reg: 12-14-02
05-03-11 07:53 AM - Post#2085504    
    In response to someotherguy

Earlier you said you had a "significant tick"?
I'm just wondering how that worked out for you?
I had a weird thing on mine - I changed to Comp Cams adjustable valve train setup also, but I have a tick coming from somewhere around #7 that I can't get rid of. I'd be interested to see how yours worked out. Thanks.
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Posts: 27003
Age: 45
Loc: Texas
Reg: 08-01-03
05-03-11 08:19 AM - Post#2085517    
    In response to axedental

Pretty sure what's going on in the engine I was working with, is that it's got a cam going flat, or a lifter seized in the bore and blew out a cam lobe. I've read about it a few times now, happening in the Vortec 7.4's.

94 Chevy C2500LD / 06 Silverado SS / 06 Chrysler 300C SRT8 / 06 Dodge Magnum SRT8

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Posts: 2253
Age: 32
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Reg: 08-29-12
08-09-15 05:55 PM - Post#2567577    
    In response to someotherguy

This is a great write up. I refrenced it several times when changing my dad's injectors. I would like to add a tip. Take a picture of all the brackets on the back of the plenum before you tear it apart. If you have to leave it set a couple days like I did, you'll forget how they went. I found it strange that the bolts going into the plenum were American and everything else is metric. Even the studs had American on one end and metric on the other. I just wish they'd do away with metric.

Again, great write up. We didn't mess with the rockers, but if we ever do I'll look this back up.

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