Leaking Fuel Injector(s)

1991 Buick Regal, 3800 V6

I posted a few weeks ago about having a rough idle on a cold start. After some research and closer inspection of the vehicle, I’m quite certain I have at least one leaking injector that is flooding a cylinder and causing the car to misfire on a cold start. I’m also not at the gas mileage I should be at.

So I’m wondering, is fuel injector replacement as straightforward of a job as it looks? Any major issues I could run into in doing a replacement?

I’m planning on replacing all six injectors (I can get them for $50 each buying online with a discount code), but given that the vehicle is so old am I better off just replacing the faulty ones? I’m assuming pulling the spark plugs and seeing which cylinder is wet will tell me which I need to replace.

And one more question: Is there a way to depressurize the fuel system when I park the car for the night, thus preventing fuel (or most of it) from leaking into the engine until I get this fixed? I’ve read that just unscrewing the gas cap can depressurize the system.

Thanks all.

Don’t buy them until you are SURE you need them…


You car is 23 years old…It has LOTS of miles…This must be a labor of love…

It only has 113k and was garage stored for most of it’s life (got it from a friend).

It runs perfectly otherwise and you would think you were standing in the mid 90’s looking at it.

Also, the auto part store said that diagnostic tools won’t work on a car this old. He gave me a little metal key to stick into the diagnostic plug and said “listen to the beeps and flashes then start googling. It’s like Morse code.”

What’s the way to determine for sure that it’s the injectors?

The fuel rail should have a test fitting, looks like a tire valve…You can connect a pressure gauge there (a dial-type tire gauge will work) and see how fast fuel pressure drops when you turn off the key…

Could dirty nozzles cause a small leak? Any merit to the injector cleaner additives?

In most cases if an injector is leaking off it’s due to a worn or deformed pintle. The pintle is the needle in the injector that opens and closes the tiny port of each injector.

In an engine 23 years old, I’d change all six. A Haynes repair manual from the parts store will tell you how to depressurize the fuel system. I’d get a manual, review the process, and be sure I had everything I needed before starting. Tools you can buy, but the biggest problem might be access to the injectors on the rear bank. The manual should address these issues, and it’ll also give you a good idea whether or not to attempt the job.

In the interest of full disclosure, I’ve never changed the injectors on this engine, but the guys that wrote the manual will have.

Unscrewing the gas cap will not relieve pressure in the fuel lines. You could remove the fuel pump relay, start the engine, and allow it to die; which it will do very quickly.

If the injectors do not come with new seals for some unexplicable reason then be sure to get a full injector seal kit. This will prevent both air and fuel leaks after assembly.

Any idea how tough the rear three will be to get at?

The rear three are clearly visible and accessible under the plastic head cover.

My only concern is seating them all in on the rail properly.

I found that applying a light coat of grease on the o-rings helps to seat the injectors when re-installing. I’ve not had a leak or any problem with doing that. Anyone have comment on that?

I lubricate injector o-rings with clean engine oil

So far, so good

I always lubricate any o-ring before installing. Keeps them from chafing during install.

Yes seating in the rail and the intake can be a pain but you can do it.And yes, you’re right in that leak down can cause flood condition in one or so cylinders.Old cars are good but they wear out.Replace all the injectors,use some assembly lube on the o-rings to make it easier.(silicon grease may be compatible).Replace the fuel pressure regulator(on the fuel rail),there’s a check valve that keeps fuel in the line, that could also be your problem, I believe it’s part of the sending unit in the tank.After replacing the injectors a pressure leak-down test will tell if check valve is working.Specs in the books.Don’t worry about fuel pressure, it’s not alot, you can soak it up with rags make an obvious fuel line disconnect w/ rags around it to keep it from spraying everywhere.