Cleaning of MFI injectors?

Paul Thomas · 03-03-2003, 03:54 PM

I remember someone a while back had good luck with this and wanted the how-to. A dentist friend said he would put them in the ultrasonic cleaner but that is a pain. Has anyone heated the solution on stove top?

Thanks,
Paul

pwd72s · 03-03-2003, 04:33 PM

Sounds dangerous to me....on a stovetop? Isn't there a risk of ka-boom? I'm kind of puzzled that you think they may need cleaning. MFI injectors are subject to much higher fuel pressure than more modern injection systems...this tends to make them "self cleaning". I'm passing on info as told to me by a mechanic I trust...when I asked him how often I should use an injection cleaner...

Paul Thomas · 03-03-2003, 04:53 PM

I know that Gus at Pacific will clean them for something like $8 a piece. I remember some on the board saying a while back that they had had good results with cleaning them. The tech article says use a mixture of turpentine, paint remover, and acetone in a ultrasonic cleaner that can heat the fluid to 150 degrees. Like i said, i thought that someone had accompished this on a stove top.

High pressure or not, there is a little screen in there and it is bound to get some sediment in it. If no one chimes in, i'll just take them to my buddy's office and put them in the ultrasonic machine.

Paul

pwd72s · 03-03-2003, 05:06 PM

"The tech article says use a mixture of turpentine, paint remover, and acetone in a ultrasonic cleaner that can heat the fluid to 150 degrees. Like i said, i thought that someone had accompished this on a stove top"

NOT MY STOVE TOP! KA-BOOM! Seriously, $48 to have them all looked at and cleaned by a pro isn't that bad.

derek murray · derek murray's Garage

I realize I'm a little late here... so for what its worth, you can buy your own ultrasonic cleaner from any good arts supply or drafting supply store (cheap)... they are used to clean the heads of inking pens (aka rapidographs or technical pens) used for ink drawing, drafting (old school) or plotters...

Paul Thomas · 03-04-2003, 03:22 PM

Ok, i must have dreamed it. To be honest, it never seemed like a good idea to heat that concoction, but i swear someone said they did something like that on a hotplate.

Back to reality. The devise that mechanics used to use for cleaning and evaling injectors was basically a hand pump with a fluid reservoir, T'd in pressure gauge and a fitting for one injector.

To clean,you can pump solution through the injector at high pressure or to evaluate you are to hold the injector pressure just below opening pressure and see if droplets appear.

I have been trying to come with a way to build such a devise. I f anyone has ideas please post them here.

Thanks,
Paul

Rot 911 · 03-05-2003, 05:29 AM

You realize you will have to be able to get a pump that can reach pressures over 220 pounds? John Walker I believe has a pressure tester, not sure if it is home made or not.

Rot 911 · 03-05-2003, 05:31 AM

Here's a picture of John Walker's tester or at least it is a picture he posted of one:

Paul Thomas · 03-05-2003, 06:27 AM

That is basically the design i was thinking of. All of the hand pumps i have seen so far reach at least 200 psi. The injector opens between 15-18 bar (213-256psi). To test the injectors you should hold the pressure 2 bar below opening pressure and wait. If no droplets, ie: leakage, occurs in 15 seconds then the injector is ok.

Paul

Zeke · 03-05-2003, 07:25 AM

Don't heat acetone or anything containing acetone ever. It has a very low boiling point and would be lost anyway. IMO, ultrasonic does the same thing as heating, it excites the molecules.

BK911 · BK911's Garage

I use berryman in an ultrasonic cleaner with good reults. My cleaner does not have a heat option, but it still gets pretty hot. I've put rusty injectors in and got new LOOKING injectors out. I've never tested them, but they sure look nice! And they have to be better than what they were before.

BK

wprater · 10-03-2025, 09:04 PM

Has anyone had success with the readily available ultrasonic cleaners? They are able to hold a temperature and seems like a safe approach to clean the MFI injectors. Im going to try a back flush method as well.

nickelplated5s · nickelplated5s's Garage

The dyno shop my motor is going to when the pump gets back said just buy new ones. They are from 69 after all.

wprater · 10-06-2025, 07:34 AM

The Bosch MFI injectors are about ~$140 in 2025. Regardless of price, I like to save as many parts as I can. I just got a backflush tool and have 10 injectors that are in poor shape and hope to get another 20 hours of hard driving out of them.

r lane · 10-06-2025, 08:11 AM

A company called Mercedes Source sells a cleaner similar to the Bosche system. Bob

wprater · 10-06-2025, 08:15 AM

I have their gasoline MFI tester and backflush kits. I was curious if others have had any success with the uptrasonic method as well. I've yet to try the backflish, but I've had little luck cleaning with the pressure tester. Only tested to see if they're holding pressure and spraying properly at the operating pressure of 130-140 psi, if I recall.

gled49 · 10-06-2025, 03:00 PM

Not sure how u back flush injectors, I just flush them, check for leaks and opening pressure, which is more like 230-240 psi.

wprater · 10-07-2025, 06:54 AM

Back flush with a hose and plastic bit to hold open the pintle. Then use a the pressure tester and attach a hose. There was a kit at Mercedes Source that should arrive today or tomorrow. I will try it and report back.

I did about 3 hours of ultra sonic in B12 at 120F today and it did not seem to help with the first two injectors I tried. There are 8 more soaking overnight and I hope I get at least one recovered.

porschedude996 · porschedude996's Garage

Quote:

Originally Posted by Paul Thomas

I know that Gus at Pacific will clean them for something like $8 a piece. I remember some on the board saying a while back that they had had good results with cleaning them. The tech article says use a mixture of turpentine, paint remover, and acetone in a ultrasonic cleaner that can heat the fluid to 150 degrees. Like i said, i thought that someone had accompished this on a stove top.

High pressure or not, there is a little screen in there and it is bound to get some sediment in it. If no one chimes in, i'll just take them to my buddy's office and put them in the ultrasonic machine.

Paul

Remind me to not charge my dentist. 😉 Wait, what city are you in? My dentist is a porsche guy, supplemented his tuition flipping 914’s before flipping was a word.

wprater · 10-07-2025, 07:14 AM

Found this from Warren and this is what I was trying yesterday.

https://forums.pelicanparts.com/35448-post2.html