4.5 and 4.9L Injector replacement/upgrade HOW-TO GUIDE

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  • 2 Post By Lithorian
  • 2 Post By eddie262
Cadillac Tech Tips - How to fix it Discussion, 4.5 and 4.9L Injector replacement/upgrade HOW-TO GUIDE in Item Specific Cadillac Discussion; 4.9 Liter injection replacement. What I used for this repair was the 19lb Bosch Type III injectors from a 1998 ...
  1. #1
    Lithorian's Avatar
    Lithorian is offline Cadillac Owners Enthusiast
    Automobile(s): 1995 Deville 4.9 Liter, 1988 Camaro Iroc-Z 5.0 Liter
    Join Date
    Dec 2007

    4.5 and 4.9L Injector replacement/upgrade HOW-TO GUIDE

    4.9 Liter injection replacement.

    What I used for this repair was the 19lb Bosch Type III injectors from a 1998 For explorer 5.0 Liter.

    if you are good with your hands this is not a hard fix, all you need is a 7mm socket, a 10 mm socket with a 3 inch extension, a deep socket 15 mm and 2 inch extension, a shallow 15 mm, many rags, and a flat head screw diver, alot of patience, and the most imprtant, knee pads, you will be kneeling on the car, alot.

    First pull the 20 amp fuse for the fuel pump, run the motor, this relieves some of the pressure in the fuel lines, then open the cap on the end of your fuel rail, use a screwdriver and a rag to relieve the rest of the pressure. once that is done we can begin. start by disconnecting the negative battery terminal, then remove the upper half of your air cleaner. then open your throttle plates and remove your throttle and cruse control cables, (this is a great time to clean your throttle body as well as rod out your EGR tubes.) next pull back on the tensioner and remove your belt, now look at your power steering pump, there is 4 bolts holding it in, remove the 2 15mm bolts on the corner that go through the braket, the remove the 15 mm bolt on the top of it, then pull the 15 mm bolt that goes through the P/S pump bracket and olternator, (its right next to the tensioner) next take the bolt out of the back of the alternator, andthe loosen up the alternator bolt closet to the fire wall, slide the alternator up and carefully lift up on the P/S pump/ tensioner bracket, and slide it up and and away front the motor, there will only 2-3 inches of movement, be very carefull not to damage the P/S lines, this extra 2-3 inches will give you the room you need to wrk on the last injector on the front bank.

    next get yourself some rags and remove the coolant line coming out of the thermostat houseing and heading toward the heater core, be careful to soak up all the coolant you spill and soak up some of he coolant sitting int the houseing, you dont want it running into the open ports on accident. now carefully remove the vacuum lines comeing off the EGR solenoid, EGR valve, map sensor, FPR, and brake booster, check the FPR hose for signs of fuel while you have it off, (good ol' sniff usually works, if it's been sucking fuel you'll smell it) now take yer good ol' 7mm and remove the backet holding the EGR solenoid and Map sensor and set it aside. now its time to start getting to the fuel rail, unplug the injector harness that sits right above the transmission, if your rail conects to the fuel rail at the top of the valve cover dont worry about it, if the fuel line run in at the transmission, disconnet the 10 mm bolt holding it all down, then pull the bolts out of the holder for you throttle cables and set it aside, puull the two rail bolts in the rear out, pull the bolt by the FPR out, then the one near the P/S Pump, get a pry bar and GENTLY pry the fuel rail up,

    *intermission* go grab a coke, take a piss, whatever you gotta do now**

    take an old hanger and bend it so you can fish any of the old o-rings out of the ports, and stuff rags over the open ports, now carefully pull all the injector clips out, dont lose them. prepare your new injectors first, put NEW orings on them, do NOT remove the pintle caps if they are the bosch type threes, if u break the caps you are up shit creek, they are not available (PM me if u break one, ill help you make one) so cut the old orings off and slide the new ones OVER the pintle cap, set them aside

    one by one start removing the old injectors, make sure to unplug them THEN remove them, you do NOT want to ripp that harness, MY price from GM is 300 bucks, YOUR price is around 450, be sure to pull the old o-rings out of the fuel rail. now lubricate the o-rings on the new injectors with either clean engine oil, or a silicone compound, if u use the silicone be very carefull not to get it where it can invade the injector, it WILL clog it. slide them into the fuel rail one by one, clip em, and plug em in, nowonce you have all 8 in, hook up the battery ad run the fuel pump a few times to check for leaks, no leaks? of course not, you followed my instructions. turn the fule pump off an line up the injectors to their respective ports, make sure that the bottom o rings are lubed, and push them into their respective ports then screw the fuel rail back into place, now what i do to make sure they seat is to take a flat head screw driver and push them down further into their portss, as long as they are all clipped into the fuel rail the wont fall out, visually inspect to make sure that the o-rings didnt sock or pinch on the way in, if you see no problems put it all back together. again, leak check it with the fuel pump.

    start your motor, take a can of car cleaner and check for leaks, you can USUALLY hear them, those leaks are quite loud, but the carb cleaner is extra insurance, no leaks? again, of course not :P

    for the best results i re calibrated my ISC motor.

    before this repair I had a rough idle, lean codes and poor gas mileage, all 3 solved now.

    Oh and people, i know a guy that smokes while doing this kind of shit, if you smoke and blow the hell out of yourself you deserve what you get, please do not EVER smoke while working on a car, ESPECIALLY with fuel sysems.

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  3. #2
    eddie262 is offline Cadillac Owners Member
    Automobile(s): 85&88 SEVILLES, 90 DEVILLE'S (2)
    Join Date
    Jul 2008
    Washington DC metro area

    Re: 4.5 and 4.9L Injector replacement/upgrade HOW-TO GUIDE

    4.9 Liter injection replacement.

    I recently followed the directions above and was pleased to discover that yes it IS possible for someone with modest mechanical ability to replace all 8 fuel injectors, the fuel pressure regulator, and the fuel filter.

    Many thanks to Lithorian for taking the time to jot down the original directions. The following notes are meant only as additional insight and in no way meant as criticism. I am such a scared cat when it comes to breaking things, that I am assuming others would benefit from these hints.

    Lithorian said he used the 19lb Bosch Type III injectors from a 1998 For explorer 5.0 Liter. The injectors fit perfectly and are available on eBay from a seller named “precisionfuelinjectors.” I bought a set of 8 refurbished injectors on sale at $109 plus shipping from that seller. Fast, smooth transaction.

    Below are notes I took while replacing the injectors, regulator, and fuel filter on my 1990 Sedan deVille, with 64k miles on the odometer. The car was presented to me with rough idle, no power (car would barely climb the smallest hill!), and terrible gas mileage. Using the on-board diagnostics showed that 3 injectors were non-reactive when turned “off” using the E.5.4 override. This means the engine did NOT run even rougher at idle when I turned off the offending injectors, using the COOLER button on the HVAC panel (see FSM for complete directions).

    OK, here are my notes.

    Fuel filter:
    1) Replace the fuel filter while the fuel system is de-pressurized. You’ll need 16mm and 20mm flare wrenchs to disconnect the fuel filter. And you’ll want to loosen the fittings first before removing the filter completely. Then working quickly, orient the new filter so the end marked OUT is facing the front of the car, and completely remove the old filter. GAS WILL POUR OUT OF THE LINES because the gas tank is higher than the filter and the gas will run to the lowest point.
    2) Insert the fuel lines into the filter and begin tightening the nuts; the flow of gas will dribble to a stop once you have the lines in the filter.
    3) You may want to wear thick rubber gloves and have a box fan running on high to blow the gas fumes away from you. I did both things and it worked fine; but the gas pouring out was nerve wracking!

    Fuel pressure regulator:
    1) This part is hard to change UNLESS you remove the entire fuel rail from the manifold.
    2) You’ll need a TORX socket (I forget what size but it’s a 25m or 30mm I think) to remove the regulator from the fuel rail. You’ll also need a large wrench to undo the flare fitting that connects the regulator to the fuel line – it’s 15/16 if memory serves.
    3) I found that I had to crack hard on the big flare nut to get it loose and it loosened with an audible CRACK. Yours may also. Also, I had to pull fairly hard on the fuel line to get it out of the old regulator; in fact I had to bend the line a little to get it out. Bending it back and tightening the flare nut worked ok to seat the line in the new regulator without causing any leaks.
    4) Be sure and use the new O-ring supplied with the new regulator.

    Fuel injectors:
    1) No amount of tugging or prying removed the fuel rail from the manifold until I squirted WD-40 onto the lower end of each injector. The entire rail came right after 5 minutes of letting the WD-40 do its magic.
    2) Wiring removal is pretty straight forward.
    3) You’ll have to pull and wiggle hard to remove each injector from the fuel line. Again, a little WD-40 made this task easier!
    4) I noticed that the fuel lines that run across from front to rear fuel line are somewhat loose in their moorings when the fuel rail is out of the manifold. But no leaks when the rails were re-installed. Just an observation here.
    5) You will have to disconnect BOTH rear fuel lines to remove the fuel rail from the manifold. Note hard to do, but a MUST-DO if you are removing the fuel rail from the manifold. DON’T FORGET to connect them again before doing your leak test (I did and had gas all over the place!)
    6) Drop the #6 and #8 injectors in place first – then the other ones will follow. Be careful of #1 and #3 as there is not a lot of room to work, even with the power steering pump loosened up. I put a long strip of 1x2 wooden furring strip (parallel to the valve cover) under the power steering pump to hold it up as far as possible.
    7) Removing the alternator entirely makes it so much easier to remove the entire fuel rail.
    8) Laslty, when re-installing the fuel rail, note that 2 throttle cable go above the rail and one goes below it; be sure and route the cable correctly BEFORE bolting down the fuel rail – I learned this the hard way!

    Huge positive difference in the running condition of the engine after all this work and well worth it!

    I could hardly believe the difference in how well the engine ran compared to the shaking, rattling, no power engine that came to me!

    Definitely want to do this repair if the symptoms indicate weak fuel injectors.

    Best of luck,
    Ed in Maryland

  4. #3
    primerib is offline Cadillac Owners Member
    Automobile(s): 95 Deville
    Join Date
    Aug 2009

    Re: 4.5 and 4.9L Injector replacement/upgrade HOW-TO GUIDE

    just did this today. works like a charm. thanks Lithorian

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  6. #4
    Texan4Life is offline Cadillac Owners Fanatic
    Automobile(s): 1990 Deville w/ 250,000 mi
    Join Date
    Jan 2008

    Re: 4.5 and 4.9L Injector replacement/upgrade HOW-TO GUIDE

    Got done putting new injectors and FPR. I wasn't impressed by fuel injector prices from rock auto or local auto parts stores. So with eddie262's advise I went and checked out the seller "precisionfuelinjectors". By simply browsing through his selection I found 8 "upgrade" injectors for a 91 fleetwood. In the auction he listed the compatible applications of which 1990 deville 4.5L was one of them. These were the new bosch injector (type III?) with a 4 hole nozzle giving a finer spray pattern. I picked up mine for $129.

    Fast shipping and great packaging. I loved how the injectors were vacuum sealed with a light coating of oil. New orings were already installed on the injectors. These babies were rubbered, lubed, and ready for installation!!

    Here is a pic of my fuel rail with new injectors and FPR installed:

  7. #5
    travellinmike's Avatar
    travellinmike is offline Cadillac Owners Member
    Automobile(s): '90 Sedan Deville, '06 CTS-V
    Join Date
    Sep 2009

    Re: 4.5 and 4.9L Injector replacement/upgrade HOW-TO GUIDE

    I have a set of 8 matched injectors coming hopefully by the weekend. I have the usual rough idle, no power and 4 mpg symptoms. My mechanic has replaced 1 bad injector at a time 3x in the last year and a half at $450 a pop. thought I'd tackle a complete replacement job myself this time.

    in on of the earlier posts it mentioned being able to use the diagnostic system to determine which injectors are bad. can anyone post the steps to get this to display? My Haynes manual details all the standard E and F codes but doesn't cover this procedure.

    I've got my fingers crossed that everything works out with no issues this week-end. is the FPR and filter recommended cheap insurance while things are apart?


  8. #6
    Submariner409's Avatar
    Submariner409 is offline If it won't run, chrome it
    Automobile(s): 2002.5 F55 STS - 67,500 miles, 2014 Explorer XLT FWD
    Join Date
    Feb 2006
    MD Eastern Shore, Kent Island

    Re: 4.5 and 4.9L Injector replacement/upgrade HOW-TO GUIDE


    Your fuel injector questions have been moved to the 4.X engine forum. Please read the forum title bar for Tech Tips.


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