Fuel Injector Blow Out! - Alfa Romeo Bulletin Board & Forums
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post #1 of 66 (permalink) Old 10-08-2019, 05:11 PM Thread Starter
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Fuel Injector Blow Out!

Last June I had a shop pull and send in my 10 year old injectors to flow test them, the test results where horrible with 3 out 4 injectors failing, they all were way way down on flow and dripping and the 4th was only able to get a fair rating with no drips but was lower then the rated flow rate. They were all repaired to flow like new and all was great. These are Bosch injectors!

Fast forward to today when I was pulling into my garage after a spirited hwy drive and all of sudden I heard soft knocking, turned the ignition off and pulled off the airbox and open the throttle bodies butterflies to find the #3 throttle body filled with bubbling boiling fuel on top of a closed valve.

Since I was wasn't at speed, just pulling into the garage I'm hoping nothing got bent, the engine didn't die or suddenly stop.

Inspecting the cylinder with a borescope everything looks fine, the cylinder was in the compression stroke with both intake and exhaust valves closed.

I have not tried to start the engine or turn the motor over by hand yet.

I did turn on the ignition to see if any codes came up on the ECU and when I did fuel shot out of the #3 injector till the fuel pump stopped, like the injector is stuck open acting as an open spicket.

I called the shop that did the work but they won't be able to look at it for 3 weeks. In the mean time about the only thing I can do is change the oil that's diluted with fuel now.

What all should be done to check that nothing got bent?

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Last edited by msiert; 10-08-2019 at 05:22 PM.
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post #2 of 66 (permalink) Old 10-08-2019, 05:18 PM
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Originally Posted by msiert View Post
Last June I had a shop pull and send in my 10 year old injectors to flow test them, the test results where horrible with 3 out 4 injectors failing, they all were way way down on flow and dripping and the 4th was only able to get a fair rating with no drips but was lower then the rated flow rate. They were all repaired to flow like new and all was great. These are Bosch injectors!

Fast forward to today when I was pulling into my garage after a spirited hwy drive and all of sudden I heard soft knocking, turned the ignition off and pulled off the airbox and open the throttle bodies butterflies to find the #3 throttle body filled with bubbling boiling fuel on top of a closed valve.

Since I was wasn't at speed, just pulling into the garage I'm hoping nothing got bent, the engine didn't die or suddenly stop.

Inspecting the cylinder with a borescope everything looks fine, the cylinder was in the compression stroke with both intake and exhaust valves closed.

I have not tried to start the engine or turn the motor over by hand yet.

I did turn on the ignition to see if any codes came up on the ECU and when I did fuel shot out of the #3 injector till the fuel pump stopped, like the injector is stuck open acting as a opens spicket.

I called the shop that did the work but they won't be able to look at it for 3 weeks. In the mean time about the only thing I can do is change the oil that's diluted with fuel now.

What all should be done to check that nothing got bent?
I don't have a good answer for your problem, but I've never heard of an engine being hydrolocked with fuel.

Chris

1990 Spider Veloce
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post #3 of 66 (permalink) Old 10-08-2019, 05:52 PM
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I would pull the plugs and spin the motor to clear everything out and as you suggest change the engine oil. Then maybe it is just a case of replacing the bad injector.

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post #4 of 66 (permalink) Old 10-08-2019, 05:56 PM
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Shoulda sent them to Cruzin Performance!!! Teasing aside, without a compression gauge and turning over engine at speed, I would try getting #3 at the bottom of the compression stroke and turning the engine over with your finger over the plug hole and see if you feel pressure. That would assure your valves are seated.... from your description though I would lean toward a bad injector with no real damage, but I'm kind of a newbie to the Alfa scene!
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post #5 of 66 (permalink) Old 10-08-2019, 08:06 PM Thread Starter
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Been reading up on stuck open injectors, some say it could be a grounding short that would cause it, others are saying its a mechanical failure in the injector?

It's unclean right now if it fixable or if I need to buy a new one. From what I read you dont just replacing one you replace them all?

Sure glad it didn't happen at speed, the engine would be a goner. Fuel can hydro lock just like water.

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Last edited by msiert; 10-08-2019 at 08:09 PM.
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post #6 of 66 (permalink) Old 10-08-2019, 08:12 PM Thread Starter
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I'll rotate the engine tomorrow and do a leak down test to check things out further.

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post #7 of 66 (permalink) Old 10-08-2019, 09:38 PM
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You need to get some oil in the cylinder. The gas washes all the oil off the cylinder wall and surface rust can start within a couple of days.

1969 1750 Spider Veloce w/dual webers, 1969 1750 Berlina, 1971 1750 Spider Veloce w/ dual webers, 1985 Spider Veloce 23,000 orig. miles, {Two} 1986 Spider Veloces, 1987 Spider Veloce bought new, 1988 Quadrifoglio, 1991 164S, Plus several more. I think they are breeding.
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post #8 of 66 (permalink) Old 10-08-2019, 10:21 PM
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Since all the injectors fire at the same time, just swap leads with another and see if it just sprays continuously too, then you will know whether it is the injector or electrical lead...
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post #9 of 66 (permalink) Old 10-09-2019, 12:51 AM
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Since all the injectors fire at the same time, just swap leads with another and see if it just sprays continuously too, then you will know whether it is the injector or electrical lead...
Are you sure all injectors fire at the same time?

Sounds wrong to me. Would be very fuel inefficient.

I've heard of spark plugs firing on the exhaust stroke as well as compression stroke, but never fuel injectors ...
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post #10 of 66 (permalink) Old 10-09-2019, 01:23 AM
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normally if I wanted to "try" unstick a stuck injector I'd remove the connector and touch the injector on/off with current (9V DC battery)....see if that makes it click on and off....maybe in between some short sharp taps to help it along!

I seem to recall your S4 has a completely modified injection system ('black spider project' thread of 10+ years ago!), so not quite sure what you have.

Dom - Alfa Spider 1990 S4 - formerly: Alfa 101 Sprint, 2600 Sprint, Montreal - family classics: Jensen Interceptor II, '58 Hooper RR Silver Cloud I, Shadow II, '60 Corvette.
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post #11 of 66 (permalink) Old 10-09-2019, 03:58 AM
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Since all the injectors fire at the same time, just swap leads with another and see if it just sprays continuously too, then you will know whether it is the injector or electrical lead...
Are you sure all injectors fire at the same time?

Sounds wrong to me. Would be very fuel inefficient.

I've heard of spark plugs firing on the exhaust stroke as well as compression stroke, but never fuel injectors ...
Pete
Possibly. I overlooked the fact he has the Motronic fuel injection. The Bosch FI fires all injectors simultaneously.
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post #12 of 66 (permalink) Old 10-09-2019, 05:46 AM
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motronic injectors all fire same time.

Dom - Alfa Spider 1990 S4 - formerly: Alfa 101 Sprint, 2600 Sprint, Montreal - family classics: Jensen Interceptor II, '58 Hooper RR Silver Cloud I, Shadow II, '60 Corvette.
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post #13 of 66 (permalink) Old 10-09-2019, 06:03 AM
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Murray's car has programmable engine management.

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post #14 of 66 (permalink) Old 10-09-2019, 02:54 PM
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Quote:
Originally Posted by skibum
The Bosch FI fires all injectors simultaneously.
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motronic injectors all fire same time.
Are you guys serious? Are you meaning that they all squirt fuel together, or the same time in the 4 cycle combustion process?

If they all squirt fuel together, then for every revolution of the engine they would ALL have to squirt 4 times with only 1 time being actually when wanted per cylinder (i.e. when the inlet valve is open and air is being sucked in). Fuel would be pooling on the back of the closed inlet valve.

What is the advantage of fuel injection then? A carburetor or a single injector into the manifold would be more efficient. Crazy design. Cannot believe it. The fuel wastage is enormous
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post #15 of 66 (permalink) Old 10-09-2019, 03:05 PM
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Are you guys serious? Are you meaning that they all squirt fuel together, or the same time in the 4 cycle combustion process?
Yep, that's how it works. There isn't one "fuel injection event" per cylinder. The ECU controls the fuel volume by varying the duration (percentage of time each injector is held open) but they all fire in parallel. Read the Probst book on Bosch FI: it has a good explanation.
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