93 TBI 5.7 Pouring tons of raw fuel when key turned on

[Oldschooltruckdude]

On 1st cold start, injectors give the correct little spray to help start engine. Let engine run a minute or so, not enough to completely warm up. Shut engine off. Turn key on but do not crank engine. Hear loud clicking noises from engine area and injectors pour tons of raw fuel out, fills up the throttle body to the top and actually runs out the sides here and there lol Major fire hazard here.. This problem started kind of gradually, I noticed last few times I used the truck it didnt start correctly, sounded like maybe an injector had seeped a bit of fuel while sitting after being driven to the store, for instance - come back out of the store and it sounded rich.. had to kind of rev it a bit to get it cleared up. Windsheild wiper motor was bad and linkage messed up, so I replaced the wiper motor and had to re-adjust the wiper linkage which meant turning the key on and off several times. I then noticed fuel leaking considerably out the sides of the throttle body but air cleaner was still on, so I didnt realize what it was actually doing. I also heard this loud clicking sound when the key was turned to run but not crank over. When I went to start the engine, it had dumped so much fuel it would not crank lol Luckily it did not catch on fire. I figured I probably needed a new throttle body so I took the air cleaner off and was going to pull it, but decided to have a look at what it was actually doing and oh wow so much fuel being dumped! Whats causing this throttle body to do this?

 

[PlayingWithTBI]

I'm not sure what the clicking sound is.

Just off the top of my head, there's a few places it can leak -
1.) Bad O-ring(s) on fuel line connection to the TB. This would normally leak out the back.
2.) Cracked top plate or bad gasket(s). Fuel should be coming out between the housing and the top plate.
3.) Leaking O-ring(s) on top and/or bottom of injector housings. That should drip or run off the bottom of them.
4.) Cracked or leaking fuel pressure regulator diaphragm. This would be dripping out the vent hole at the bottom or side of the pressure regulator.
5.) Bad injector(s) internally which can't hold back the fuel pressure built up inside.

I'd start it and shine a flashlight behind the injector pods to see if they're spraying a nice cone and not dripping. Look for where the gas is coming out too. If the injectors are dripping it could be a bad O-ring or injector, needs further investigation. If your injectors are bad make sure you order "flow matched" replacements, OE ones can vary up to 10% from advertised so, a 61LB/HR injector can vary up to 6LBs either way.

Then get a rebuild kit that includes the fuel pressure regulator diaphragm, pull the TB, take it apart, inspect the fuel line connections and adapters, check the top plate for cracks and flatness. Check the injector housings for cracks too. HTH

 

[Oldschooltruckdude]

Those injectors work real good. They are doing a great job of filling the whole engine with fuel. Nice cone shape spray. The leaking is the excess fuel running out the top and splashing out of the barrels. They are POURING the fuel to it, actually filling the throttle body and intake with fuel. Something is telling them do that, I need to find out why.

 

[PlayingWithTBI]

Something is telling them do that, I need to find out why.

Well, unless the ECM is telling them to or, their wires to the ECM are being grounded out, then they're leaking somewhere. So, what you're now saying is you don't see any leaks, just the injectors spraying? If so, look at the insulated part where the wires go up through the TB/air filter spacer, maybe they're grounding out there?

 

[PlayingWithTBI]

The only time the ECM will tell the injectors to fire is when it sees DRPs (Distributor Reference Pulses) from the ICM, maybe something's going on with it? Maybe the pickup coil in the distributor is momentarily sending pulses to the ICM?

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[someotherguy]

This is a somewhat notorious issue but for the life of me can't recall what all steps to take on it, because it's been YEARS since I've heard of it. However:

#1 first and foremost try disconnecting both injectors from their harness at the top of the throttle body. If they still leak when you turn the key on, 100% you can rule out any cause related to the ignition module, CTS (coolant temperature sensor), PCM, etc. etc. ya follow? Issue will be strictly mechanical at that point if they leak with the injectors unplugged.

#2 if they're leaking with key on/injectors -unplugged- I would suspect the o-rings where the injectors mount into the pod, or possibly the (FPR) fuel pressure regulator has failed. Also possible injectors themselves have failed.

#3 if they are NOT leaking while unplugged, issue could be bad ignition module (pretty sure this failure mode is kind of rare, usually a failed one will not trigger spark, sometimes will not trigger injectors)

Richard

 

[someotherguy]

Well, unless the ECM is telling them to or, their wires to the ECM are being grounded out, then they're leaking somewhere. So, what you're now saying is you don't see any leaks, just the injectors spraying? If so, look at the insulated part where the wires go up through the TB/air filter spacer, maybe they're grounding out there?

Right where they bend coming up through the grommet, I've seen those wires get chafed and ground out against the air cleaner spacer ring. Might be why GM switched from metal to whatever type of plastic they used on later TBI's.

Richard

 

[Erik the Awful]

Right where they bend coming up through the grommet, I've seen those wires get chafed and ground out against the air cleaner spacer ring. Might be why GM switched from metal to whatever type of plastic they used on later TBI's.

That sounds like a hot item to check. The injectors are fed 12v when the key is on. The ECM controls the ground. That said, how likely is it that only the two ground wires are chafed through?

 

[Oldschooltruckdude]

A few people have said try replacing the coolant sensor, so I'll try that 1st and see what it does. I should say here that when I say the injectors are "leaking" I mean to say they are SPRAYING at an enormous rate. They do a beautiful job with a nice cone shape spray, very fast pulse, etc - but they fill up the motor very quickly... I have to change the oil and filter, replace the plugs, and roll the motor over to get the excess fuel out of the cylinders.

 

[PlayingWithTBI]

A few people have said try replacing the coolant sensor, so I'll try that 1st and see what it does

I don't think a new CTS is going to stop them from spraying with engine off as you said here.

Turn key on but do not crank engine. Hear loud clicking noises from engine area and injectors pour tons of raw fuel out, fills up the throttle body to the top and actually runs out the sides here and there lol Major fire hazard here.