Refurbishing fuel injectors

Gentleman …

I thought I’d post something that I ran into during my recent cylinder head rebuild … dirty fuel injectors.

Since I still had the original Bosch injectors that were installed in 1989 I decided to either replace them (expensive, around $380) or send them off to be refurbished (less expensive around $160).

Then I thought why not do it myself ? So after researching the internet I decided it was very doable. The main culprits I found are the fuel filters that get clogged up and rusted, and hardened, leaky O rings.

A rebuild kit for 6 injectors cost me $17. This included new filters, O rings, and pintel caps …


I used a car wheel valve stem and removed the schrader valve. The large end of the rubber valve stem fits nice and tightly over the intake end of the injector. The other end of the stem has the plastic screw on cap. I drilled a very small hole in the end of the cap just large enough for the plastic straw that come with a can of carburetor cleaner. I pushed just the very end of the straw through the hole and super glued it in place being careful not to get glue in the end of the straw. I then energized the injector using a 9v battery to allow the cleaner to pass through it …


First sprayed injectors as is. Ragged and dripping fuel patterns on several and none had the fine atomized mist that I was looking for.

Tested again with filters removed. Even atomized misty spray, like new.

Tested again after new filters installed. Same even atomized spray. Mission accomplished !

Removed and replaced O rings.

Did not replace pintel caps, they were just too difficult to remove. I did get one off by literally tearing it apart and since there was no difference in the spray pattern between that one and the same ones with the original caps I left well enough alone


Grooveman your ingenuity never ceases to amaze me. You are an inspiration to us all!

Grooveman, Maybe you have stated this before, but how many miles on your car?

This is the correct way to handle it on any car with some miles. Nice work.

They’re pretty easy to rebuild, so it just makes sense to do it while they’re out.

Gentleman …

Mike thanks for the compliment but I did see bits and pieces of this on the net.

John I just rolled over 160K on the clock.

I agree that while everything is apart is the perfect time to do this job, but removing the rail and the attached injectors is simplicity in itself. It’s a project you might want to consider if you have an hour or so and $17 :smile:

Thanks, I guess I’m still good, less than half that on my 1990 XJ6 and running well.

Fantastic. I am just about to remove the loaner head and put back mine rebuilt, so great opportunity to refresh the injectors, like you did (300k miles on mine, injectors never touched, at least not in most recent 180k). Where did you get the injectors rebuild kit?

Another way is to put them in an ultrasonic bath cleaner and use paint brush cleaner. The dirt literally just falls off.

Just make sure that your cat/dog is not within range when you do this, as “ultrasonic” translates to “loud deafening scream” for them.

kind regards

Zigmund …

Here’s a link to the company I purchased my kit from. They’re located in North Dallas …

I called them and talked to Mr Big Dawg himself just to be sure this was the correct kit for our injectors.
Very nice people to deal with. I think you’ll be shocked when you pull out the filters, mine were really nasty. They are made of a fine metal mesh and were full of corrosion.

By the way there’s a bit of a trick to getting the old filters out. I used a sheet metal screw that was just big enough to screw into the end of the injector with the filter. Now take the head of the screw and put it in a vice. Use an open ended wrench that’s just big enough to slide around the body of the injector and tap the side of the wrench with a hammer pulling the old filter out. The new filters just tap in.