Why and How to clean your fuel injectors

If you own an injected 308 or Mondial (non-T), your car gets its fuel through a relatively simple mechanical injection system made by Bosch. (There are many threads and references on the finer details of how this system works). The system essentially pushes a steady stream of fuel through the injectors mounted in the intake manifolds anytime the car is running or cranking to start. The injectors are always spraying fuel, unlike electronic injection where the injectors shoot little "spurts" of fuel on demand.

To work, they have a little spring inside the injector, and a spray tip. When the fuel pressure inside the injector reaches about 3.5 bar (around 50 psi) it overcomes the spring pressure and fuel squirts out. The nozzle is designed to make a fine mist to aerosolize the fuel. Think of a Windex bottle turned to "spray" mode (not "stream" mode!)

When your injectors get clogged up, several things can happen. Most common, is they stop opening at the right pressure. The spray pattern becomes "stream-like" (again, imagine the windex bottle, but this time on stream....not doing a lot of aerosolizing) and the other thing that can happen is that the nozzle sticks open a little, so it dribbles when it shouldn't.

These issues have various symptoms. When they drizzle, it causes "run-on" (the car hiccups a few times as it continues to try running after you turn the key off). When the spray pattern is streamy, you get bad fuel economy and poor combustion (and high emissions....cars can have a tough time passing emissions in this condition). When they open at too high a pressure, the car runs lean (and the headers can run hot...ask me how I know.)

Anyway, I'll bet that 75% of the people on this board have never cleaned their injectors the whole time they have owned the car and I'll bet 75% of those people don't realize just how bad their injectors are and how much better the car will run with clean ones. I'm happy to say that I am no longer one of those 75% and I'm going to share with you how this little procedure is accomplished. In theory, it is really simple. In practice, there are a couple important things to know that can complicate it.

I must back up here and say that sometimes it's great to be a member of the FFIC ("Ferrari Fix It Club" the goofball name we have given to our New England group of Ferraristi that get together to work on our cars). Not only do we have a great time drinking beer and working on Ferraris, but between us we have something like 5 lifts, a ton of tools and a lot of technical know-how including fchatters Verell and Bertocchi. Bertocchi, who mostly posts in the vintage section, is a factory trained Ferrari guru who operates an independent shop in Massachusetts focusing on Italian cars, mostly Ferrari and Maserati. His shop to me is like a candy store...milling machines, big lathes, and chock full of rare vintage cars in various stages of restoration including a one-of-a-kind Ferrari 212 from the 1950s that is nearing completion. And a 348 getting a major.
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Anyway, I was over at Bertocchi's shop one day basically making it hard for him to concentrate and asking dumb questions about why my WIFE's Mondial was running poorly, and he asked me if I had done something simple like cleaned the injectors. (Hey, we clean the jets on carb cars, why not the injectors on injected cars?) Not only did he have all the tools to clean and test them, he would show me how it's done. SWEET!

So I went home to pull my injectors out. Now this is where it should be easy, but it might not be. To explain why, I need to back up a little and show you an injector which is disassembled.

This shot shows the three pieces of an injector assembly. You have the injector itself (long skinny thing), the threaded piece that holds it in the manifold (cylindrical aluminum piece which I am going to call the "carrier" for lack of a better word) and the rubber seal which goes between them. Inside the seal is a lip that goes in the groove on the shaft of the injector to make it air tight. (See next picture). The the injector/seal slides into the carrier. The hole in the top of the carrier is a hex cut-out so the 12mm hex part of the injector can pass through it.

Pics below: injectors in various stages of disassembly.
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Here is what the injector looks like installed. To get it out, first remove the fuel line (14mm flare nut) using either a 14mm a flare nut wrench if you have one or an open end wrench.

Now you ought to be able to put a 12mm wrench or socket on the injector and remove the whole threaded carrier from the manifold because the injector is seated in the hex-cutout of the carrier and the injector should turn the whole assembly. Should is the operative word.

Only it almost never works out that way because of several things:

1. The carrier is stuck like nobody's business in the manifold.
2. The injector is brass and soft and shears in the carrier.
3. The rubber seal has swollen over time and pushed the injector up a little so it doesn't grab the carrier well. See number 2.
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So what actually happens is you put a wrench on that injector and as soon as you put a little torque on it...the injector just spins within the carrier.

What you need to do now is pull the injector straight out. (Remember, only the lip in the seal seated in the groove in the injector actually holds it in.) To do that, you need a puller. The one I used was made by Verell. (I believe that he will build more if there is call for them.) This is where the FFIC comes in handy again. I asked "Hey, who has Verell's injector puller??" and soon I had it in my hot hands. Kenny was cleaning his TR injectors the week before.

You thread the injector puller onto the injector, then just tighten the nut on the top while holding the bolt from turning with another wrench and voila! It pulls the injector right out.

Next you get a 12mm Allen socket, put it on a breaker bar, stick it in the carrier and pop that carrier loose. Pull the seal out of the carrier and you are disassembled. (It is recommended that you replace the seals. They are around $12 each and available from Ricambi.)

Below: The injector puller
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The next thing to do is take them to be tested. In my case, Bertocchi has the cool Bosch injector tester. It's a pump with a fuel line on it and a reservoir to fill with solvent (mineral spirits) along with a pressure gauge. You install an injector on the fuel line and put a cup under it to catch the solvent. Now pump the pressure up and see if the thing opens at the right pressure. Mine all opened way too high (4 bar+) and then when they did open, I got these nasty streams of solvent, not a nice aerosol. "Pissing ropes" as Kenny put it. Not good! Well, keep pumping....and soon the solvent does its job, removing the crud, and within a dozen more pumps of the handle, a nice aerosolized squirt along with the characteristic chirping sound the injector makes when the thing is working right. It's actually really fun!

Shots:
1. Bertocchi setting up the tester
2. What the tester looks like
3. Tester gauge
4. Proper spray pattern (look carefully, hard to see. Took me a lot of shots to get that with the shutter delay on this crappy point-n-shoot POS!)
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The next part of the test is to pump the pressure up to just under 3.5 bars, making sure it doesn't open too soon, then closing the valve on the gauge to do a pressure test. You let it sit for 90 seconds to be sure the pressure holds. This insures no dribbles. The injector should open at 3.5 bars, not 2.5 and not 4. It should hold 3 bars with no loss of pressure for a few minutes, then open at 3.5 and squirt.

Once you have done all 8 injectors, cycle them through again. I actually had one that stuck a little again even after being cleaned the first time.

What do you do if I don't have access to a tester/cleaner unit? Well, you could probably mail them to someone to clean them for you. (I'm sure Bertocchi would do that or someone else might....sounds like a business opportunity to someone if you ask me!) You can also buy new injectors for $20 each from here. (I'm pretty sure those are the right ones, but double check because I'm not 100% certain!) This might be the easiest way to do it but more expensive than cleaning perfectly good injectors. It's really cool to clean them and see them go from dirty to clean and know how crappy they were and how much better they are now.


Now you can put them back in the car. This is easy.

1. Install the seal on the injector (use a little silicone spray to make them slide together easily.
2. Now push the injector/seal combo into the carrier.
3. Put high temp anti-seize on the carrier threads so you can get the damn thing apart in a couple years when you do this again. (You will thank yourself later!)
4. Thread the carrier back into the manifold and tighten the injector. You should not torque them down too hard. Let me say that again: take it easy on the torque! They aren't lug nuts!

Don't get any dirt into the nice clean injectors while installing them.

Now hook up the fuel lines. Start it, check for leaks in the lines, and go drive.

Hey wait a minute, now my car won't start!!

It's true, if you get air in the lines and injectors, sometimes the thing can crank a long time and not get the pressure to blow out the air and run. Here's what you do.

Behind the fuel distributor there is a connector that connects to the switch on the flow plate inside the fuel distributor. (see diagram from the service manual). This switch prevents the fuel pump from coming on unless the car is running or cranking over. Pull this connector off. Now when you turn on the ignition, you will hear the fuel pump. (Don't try to start the car, just turn on the ignition switch to the first position). Let the pump run for 30 seconds and build up fuel pressure. Now gently push down a little on the flow plate in the fuel distributor. (You will need to pull off the airbox). This pushes fuel to the injectors. DO NOT push it for too long or too much. You can severely flood the engine. Bertocchi says that his technique is to crack open the fuel lines a tad at the injectors and let the air bleed out. I found that it was not necessary...the fuel pump would push the air out the injectors when I pushed on the flow plate. When I heard one of the injectors start to make that "injector sound" (you heard it when cleaning them), you know there is fuel in there.

Now put the connector back on the fuel distributor, replace the airbox and star the car. It should start fine but may take a minute to run well as all the injectors get bled out.

Ta da! I'll bet it runs a lot better!

Illustrations below from the service manual:
1. The flow plate and switch connector in the fuel distributor
2-3. The electrical schematic of the relays and description of how it works.
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And this is the important part....my disclaimer....

I am in no way an expert in anything related to working on cars. This write-up summarizes my experience with injector cleaning but does not represent expert advice! I am not liable if you blow yourself up!

Birdman

P.S. When I have a little time I will put this in a print friendly format on my website.

 

This all sounds like a good way to do it if you have the tools but...

I had one clogged injector recently. Just as a "quick fix" I pulled the whole assembly and got my trusty can of carb cleaner. I inserted the "straw" [perfect fit BTW] into the top of the injector and pushed the trigger...after a few shots of cleaner the pattern changed to a spray and I re installed the injector...problem solved [temp]. I plan to do the same to the rest but change the seals, soak the injectors overnight in Techron and then shoot them with the carb cleaner.

Of course unless someone replies here that I will do harm by injecting them with the carb cleaner [too much pressure?]

 

ok, Q: I understand that the system remains under pressure while off. How does one relieve that pressure before applying that first 14mm wrench on the injector lines?

 

Take off the gas cap [joking, but it does release pressure]

I had a very small amount of weeping when I pulled mine. I do it on a cold motor with a shop rag wraped under each...worked for me

 

Nice write up Birdman, thank you very much!

Few questions:

1. From your Ferrari tech acquaintance, what would be the recommended frequency to do this, mileage and/or years?

2. Would the frequent use of injector cleaner in the gas tank increase the needed time between cleaning? What would be the best cleaner to use?

3. Would replacement be recommended over cleaning at certain intervals as well? Expense isn't that great to replace.

Jeff

 

Birdman,
Thank you a lot. Just a info, is the p/n of the injectors you mention applicable to euro 328 as well?
Thank you again.
Ciao
Eugenio

 

Birdman,

Thanx allot. Awesome post! I think I can get started on this maybe this/next weekend.

mwr4440

 

Isn't it a lot easier to just do an "Italian Tune-up"?

 

The carb cleaner trick is clever and probably a good way to clean them! You can't test the the opening/holding pressure though. Soaking overnight in Techron may or may not do anything....I'm not sure if soaking in cleaner without pressure to force cleaner through it will actually do anything.

 

Tillman, my experience was that if you wait a day, there isn't enough pressure in the injection lines to worry about. The pressure doesn't hold forever. Only a tiny dribble of fuel will come out when you pop off the injector fuel lines.

Birdman

 

1. I'll ask him to chime in. I don't know.

2. I'm sure that occasional Techron use would be a good idea.

3. I'm not sure it matters if you clean them or replace them, as long as they work right. There isn't much to go "bad" in an injector. Unless it gets dirty, it should last a long time and work fine.

 

I'm not sure if they are even right for the 308! LOL! But yes, I think they use the same injectors. There are people better qualified to answer that question around here. Someone tell us!

 

Yes, but it doesn't always work. I tried it! And if the car is running very poorly because of a severely plugged injector, the Italian tune up can do more harm than good. Imagine your car running very lean in one cylinder because of a plugged injector...high RPMs will severely overheat the exahust valves and header. Bertocchi believes this is the issue in the 355s that melt headers: a problem in the fuel delivery design that causes certain cylinders to run lean at some RPMs.

Priced headers recently? Ugly! Don't want to melt one!

 

BTW...no mention of the seal residue left behind whan you remove the injector...I used a small shop vac first to suck out any particles in the manifold [and there will be some]. Then take a Qtip and drop some WD40 on the end. Go in and dab around the base and pull out the residue. Once you have it all just blast it clean with some carb cleaner and your all set the re install the assembly.

 

I too am a member of the FFIC and did this cleaning service a month or so ago at Bertocchi's shop for my Tr's injectors during an intake powercoat project. In fact my results were what lead Birdman to do his and his excellent write up however wordy as it might be! I could not believe the difference in smoothness in power and in fuel economy. The Tr is now getting 15mpg at a steady cruise of 3k rpm. I had been getting around 10-12 at best. Best bang for the buck service that can be done for an older injected car for sure.

A BIG plug must go to Verell, however, for manufacturing the injector puller. That thing worked flawlessly and made the removal of the injectors an absolute piece of cake. I know he would be will to manufacture more for those interested.
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I take it this is better than running injector cleaner for a tank or 2? Did you try this before pulling the injectors?

Is there adjustment in the 3.5BAR valve? If it doesnt open at 3.5BAR once cleaned must it be replaced?

thanks for the write up!! I think Ill put this on the list of things to do

Aaron

 

How did you know which injector was clogged?

 

No fire in that cylinder

BTW...if you use this method make sure the can is at least 1/2 full or it won't have enough pressure to blow thru and create the spray pattern confirming it is funtioning properly. I used Gunk Carb Medic in the yellow can with red straw. I also took some Techron and put it in the top of the injector and let it soak a bit, then shook it like a cocktail and shot the cleaner thru. So far, so good.

I imagine this could be done with the injector in place and just the fuel line removed. You just wont see the spray.

 

I found soaking the new seal in hot water makes it easier to install. 1/2 cup water nuked for 60 seconds worked for me. Let is soak for about a minute or two for expansion.