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Upper Intake Manifold blew apart

F

forumsKDC

New member
Hello,
The intake manifold on my 2001 Grand Prix GT 3800 engine blew apart and started a fire. Fortunately the fire damage is easily repairable.

See the red arrow in the picture, a small vacuum hose is broken off. Not sure if that was done by the explosion, or broken before the explosion.
Blown UIM.jpg

Damage:
Back left fuel injector melted
All three back Fuel injector connectors melted.
Three Spark Plug wires
Small vacuum hose coming off the large vacuum to brake
Plastic return fuel line.
The back left part of the Fuel Rail is bent up.
So far, no wires are burnt!

Drove the car home and parked around 10pm, got up the next morning and as soon as I turned the key, it blew. I no not think the starter even had time to engage.

111k miles on car.

The internet is full of many thoughts about this; timing chain, stuck valve, fuel injector stuck open, ECU bad, etc..

When I logically think this through, the only way for this to happen is for an intake valve to be open when the spark plug ignites?
1. It this true?
2. Am I missing another way to blow apart the intake and started a fire?

Needless to say, I really want to find the why before I turn that key.

What I have done so far to check.
1. I looked down the intake ports and had someone crank the car to see if the value rods are moving. They are moving, so I assume that the timing belt is not broke.

What I plan to check today
1. do a compression test on each cylinder. Maybe a intake valve is not closing.
2. Use a NOID tester to see if something is wrong with the ECU to injectors.
3. get a code tester and see if there are any codes

Any other suggestions would greatly be appreciated.

Looking forward to your comments
Have a great Day!
kdc
 


I would check to make sure your ignition wires going to the spark plugs are in good shape, if they are cracked, voltage could leak from one wire to another wire and cause the plug to fire on the intake stroke, which would cause your manifold to blow off. There is a video of an impala in an oil change shop being started by the tech., and you can see the intake manifold blow and catch on fire the moment the started is engaged.
 
Ya that can happen with the plastic intake. You could change to the aluminum one now and use a gen V adapter plate w an l67 tb.
 
Thanks QUICKSILVER462 for your reply. The fire took out three of the wires, so all wires are going be replace, and we might as well do the plugs. Those back plugs are a pain.
kdc
 
Get a new fuel pressure regulator. That is what caused the explosion. What happens is fuel leaks around the diaphragm getting sucked through the small vacuum hose and igniting in the upper intake.
 


Thanks for the reply Nighthwk12. Replace the FPR will do.

I do not fully understand how having fumes in the upper intake cause the explosion. What was the ignition source to set off the fumes?

If all is working, nothing should be coming out of the intake valves back into the intake? What am I not understanding?

Thanks
Looking forward to your comments.
kdc
 
Hello,

Update to my progress!

I have repaired and all is running okay.

1. I purchased a fuel rail, fuel injectors and connectors from a Pick-a-Park used parts place for $109.
The fuel rail was bent from the explosion, two of the fuel injectors and three fuel injector connectors where burnt.
2. Return fuel line was burnt.
Autozone has a fuel line repair kit with a splice adapter for $20
3. Replaced spark plug wires because of being burnt. Decide to replace spark plugs while at it.
4. Replaced Fuel Pressure regulator
Autozone for $50
5. Replaced Upper Take Manifold
Autozone $139
6. A few vacuum hoses needed to be replaced
Some was used from the Pick-a-Part and some was new.
All for about $485

I used a high powered vacuum cleaner to vacuum out the lower intake ports. Need to plug the fuel injector ports.
Removed the spark plugs and cranked (remember to remove fuel pump fuse) the engine to eject any coolant fluids in the cylinders.
After getting the car running, I immediately took the car to a lube shop and had the engine oil flushed, new oil and fuel injector cleaning. $140
 
Thank you for the comment Nighthawk12. Engine is running very well and steady at idle.

Other things to mention. I had to splice in three fuel injector connectors. I soldered the wires instead of crimp connectors, used heat shrink tubing, then electrical tape. Also bought new wire wrap cover to replace the burnt ones. The hardest part was the splice kit for the return fuel line. It was very difficult to shove that brass connector in the old fuel line. At one point I begin to think it would been easier to fish the whole return fuel line out from behind the brake master cylinder and then down under the car.

We was very fortunate, it happen in our driveway and that my son quickly located the fire extinguisher in the house. He now has one in his car. Not a bad ideal to keep one handy.

But based on many internet searches, I was taking a big risk by not removing the lower intake manifold to do a better inspection for possible debris from broken manifold parts.

Thanks
kdc
 


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