Cleaned and good injectors now dead

[Philip Lochner]

It is a personal requirement that before I 'squirt an engine, I require for the injectors to be cleaned (expensive) in order for me to have the confidence that the injectors are delivering equal amounts of fuel.

So, I had 24 LoZ injectors cleaned (about 1 month ago - might be more) by a Bosch approved outlet, for the Cobra V12 I'm building and V12 E-type that I will convert to EFI.

Last night I wanted to measure the opening times of each injector so that I could group them into "slow" for the left bank and "fast" for the right bank and found that 5 of the 24 injectors were now dead (would now not open).

I had heard before that one should not let cleaned injectors lie unused for long due to the cleaning agent in the injector evaporating and leaving a sticky goo rendering the injector inoperable. Seems like this is exactly what happened to me.

Previously I had success on a dead injector by BRIEFLY applying 24V (two 12V batteries in series) to it but this time, this technique would not work.

I then "baked" them in the oven at 95*C and this resulted in 4 of the 5 coming to life. Some needed encouragement by tapping them upside down (ie on the fuel supply side) on my bench vice. "Baking" the 5th injector at 125*C brought it to life as well.

[EWflyer]

I'm a newcomer to the fuel injection retro-fit game. I've got a project I'm slowly working on, just a little 250cc motorcycle. I've been gathering parts and information from various sources for about eight months now.

Because I started out from absolute zero knowledge, and I'm not a "re-invent the wheel" type of guy, I'm always looking for information from other people who've already got it all figured out.

A comment you made in your post really jumped out at me because I've recently had the tiny injectors from my motorcycle project professionally cleaned (the motorcycle they came from ended it's days in a wreck that involved a car, a fence, and a small pond in Bristol, England). You said you tested your injector by briefly applying 24 volts. This started my mind into recall mode and about an hour later it came up with this:

The following quote is from the website of the WitchHunter Performance Fuel Injection and Flow Testing Company in Bothell, WA (just North of Seattle, WA). Here's the website: http://www.witchhunter.com/index.php4 Under the website subheading of "Injector Tips - keeping injectors healthy" you'll find this statement:

A 9 volt battery can be used to check for stuck injectors, listen for a click. Don't use the car's battery for testing, it can overheat the injector coil, (especially low impedance injectors). Just because an injector "clicks", it doesn't mean that it flows correctly, it just indicates it's not stuck.

I've tried this 9 volt battery method on my injectors and it worked great, both before and after they were cleaned.

So if the WitchHunter website is right, you shouldn't use a 12 volt car battery to test an injector, and it specifically mentions not doing this to low impedance (low Z) injectors. And I'm guessing that if 12 volts isn't a good idea then doubling the voltage to 24 volts is a really bad idea.

All that said, I'm still just a "new guy" to the fuel injection world. Is there a reason or generally accepted principle of fuel injection work that guided you to test your Low Impedence injectors with 24 volts? Are the Witchhunter guys wrong in their statements about the 9 volt battery test? Did you start out with less voltage and eventually work up to 24 volts while trying to unstick them?

[Philip Lochner]

Is there a reason or generally accepted principle of fuel injection work that guided you to test your Low Impedence injectors with 24 volts? Are the Witchhunter guys wrong in their statements about the 9 volt battery test? Did you start out with less voltage and eventually work up to 24 volts while trying to unstick them?

Please note that I did not "test" the injector with 24V. I only used 24V as a "last ditch" effort at getting it to break loose. Injectors should NOT be tested with 24V. I would not even advise that what I did be done on an injector UNLESS you accept that the injector might really be dead ie not much to lose.

I did do an experiment with HiZ injectors to determine the change in opening time as a function of voltage and applied a flat battery producing almost 8V to MS and the HiZ injectors still worked fine with just less than 8V. For some reason it did not work with LoZ but I did not bother to find out why.

The 9V battery test therefore sounds quite feasible.

No, I did not have a variable power source and merely used two 12V batteries to apply 24V to the stuck injector (in situ) when the car's own power feed would not work.

[kritip]

Wouldn't a soak in petrol in an ultrasonic bath cleaned them back up? I picked up an ultrasonic bath for free that was being chucked out. Would have been kinder than baking and overvolting.

HAving tested them professionally, and then getting them working again as you have, I'd be concerened and have them sent of for testing again. PITA and expensive for sure though.

Kristian