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Old 09-14-2019, 01:42 PM
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GMC 3500 454 engine flooding out when warm

I just got a GMC 3500 with a 454, TBI. It runs fine when cold and floods out when it warms up. You can smell the fuel as it keeps flooding out. Any suggestions.

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Old 09-15-2019, 08:48 AM
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Someone should have an answer for you.


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Old 09-15-2019, 11:03 AM
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Pull your intake and look at the injectiors. They should be pulsing steadily. Run it for 2-3 minutes then shut it off. Your injectiors should be wet but not dripping.
Move your hand to the back and feel around the regulatior which has 4 screws there should be no wet fuel from a leaking regulatior gasket/ diaphragm.

If you have any dripping rebuild the tbi unit. It is the easiest carb you will rebuild. Just take note of the fuel regulatior spring as that will take you out if your not careful.

Next possible fuel smell comes from egr issues. The egr solenoid on these will cause all kinds of fun issues without throwing a code. In order for it to work the thing needs to have clean hoses, a working egr valve, a intact foam filter, intact wiring, and a working o2 sensor.

I have bought entire trucks with "junk engines" that needed nothing more then a new egr solenoid. If yours is bad the thing will "bog" bad, be down on power and choked. This is followed by a heavy fuel smell as the computer is just dumping fuel in because the o2 is stuck in open loop.

Another fuel thing to check is the lines themselfs.
Turn the key 3 or so times then get under the truck and run your hand along the fuel line. A majority of the time these leak at the cross over(drivers side to passenger
side) or at the top of the tank as there is steel lines in both spots that eventually fail.

There are a few things off the top of my head to start with.
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Old 09-15-2019, 03:56 PM
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Quote:
Originally Posted by deadlywolf72 View Post
I just got a GMC 3500 with a 454, TBI. It runs fine when cold and floods out when it warms up. You can smell the fuel as it keeps flooding out. Any suggestions.

Those TBI's are kind of funny. You know they're essentially the hermaphrodite of fuel delivery. It's the awkward crossover between a carburetor and full-blown fuel injection.

Man, you know, I wish I could offer you more advice on this but my knowledge is limited on those late model 454's they made in the 80s and 90s. Your problem is obviously an over-delivery of fuel; so perhaps the replacement injectors in there are bigger than what was originally called for, or, alternatively, you may have an oversized fuel pump; which probably seemed appropriate to the applier since that truck I can almost guarantee has duel gas tanks. I'd call the fellow up you bought it from and see what some of the last things he changed on it were. That'll give you a good idea of where to start. Hope this helps
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Old 09-15-2019, 04:50 PM
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I had a TBI car that did something similar. Mine had a bad coolant temperature sensor. It failed, and defaulted to something like 42 below zero, and was dumping fuel. If you don't already have one, some of the smaller "pocket" code reader type scanners can read live data.
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Old 09-16-2019, 10:27 PM
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Quote:
Originally Posted by deadlywolf72 View Post
I just got a GMC 3500 with a 454, TBI. It runs fine when cold and floods out when it warms up. You can smell the fuel as it keeps flooding out. Any suggestions.
Does it flood out as in not running or is it rich and fuel hungry but running.

Some of the first places to look if it's overly rich but running are the temp sensor that feeds the computer with coolant temp. This is designed to switch off the cold start mixture (choke) at about 175 degrees, if it fails that signal may not be sent then the computer stays in cold start enrichment.

Another common source of running rich is a failed O2 sensor, air leak into the exhaust system ahead of the O2 sensor, exhaust gasket leaks being common.

If this uses a vacuum control on the EGR and the diaphram of the valve leaks this will admit excess air into the intake for which the O2 sensor similar to an air leak into the exhaust will read as a lean mixture and it will throw prodigious amounts of fuel in to correct the problem which of course it can't. Add to this a significant leak will alter manifold vacuum downward which will be read by the Manifold Absolute Pressure sensor as more throttle opening to which the computer will command even more fuel.

These are some things that operate with the coolant temp sensor commanding closed loopoperation when the engie warms up which could show why you see a ifference between cold start and warmed operation. There's plenty of other candidates but they tend to be all the time problems.

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Old 09-17-2019, 06:22 PM
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all the fuel lines have been replaced. same with the brake system. will check the erg
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Old 09-17-2019, 06:23 PM
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it floods out as in stop running.
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Old 09-21-2019, 02:02 AM
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Quote:
Originally Posted by deadlywolf72 View Post
it floods out as in stop running.

That's a lot of fuel to drown out the fire. I would like to say that it's a regulator failure but one would expect that all the time not just as the engine warms up.


Unless something is totally insane this doesn't sound like an air leak messing up the closed loop. That at least in those I've experienced don't flood out the fire with so much fuel the spark plugs can't light it off.


Certainly a fuel leak around the injectors would probably put enough fuel in to wash out the fire but that would be an all the time thing.



That much fuel coming in when the engine hits operating temperature has got me scratching the sack my brains are in. Gotta cogitate on that a bit.


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Old 09-22-2019, 02:08 PM
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all the temp sensors have been replaced. one guy told me to replace the distributor cause it isn't retarding the firing like it should. I'm trying to figure out how the firing rate would have anything to do with it. the cap and rotor have been replaced as with all plugs and wires.
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Old 09-26-2019, 12:44 PM
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engine code

Got a code 22 throttle position sensor error (signal low). any idea on how this is fixed. get paid on the first and going to replace the egr valve.
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Old 09-26-2019, 01:20 PM
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Quote:
Originally Posted by deadlywolf72 View Post
Got a code 22 throttle position sensor error (signal low). any idea on how this is fixed. get paid on the first and going to replace the egr valve.

If the code pointed to the throttle position sensor, why don't you replace that instead of the egr valve? Did it give an egr valve code also?
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Old 09-26-2019, 09:25 PM
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If TPS sensor is wacko this could be the issue. It is a significant part of the injector duty cycle calculation.


It's job is to inform the computer as to how open or closed the throttle is. If it is erroring by sending a signal that throttle is more open than it is then the computer will richen the mixture by holding the injector 'on' time longer.


This will also lead to some confusion within the computer as throttle angle is also resolved with manifold pressure (sensed by the Manifold Absolute Pressure ((MAP)) sensor), a tach signal for engine RPM, and trimming with the O2 sensor. Since the integration of all these data sources as well as coolant temperature the integrator is now calculating a "false" fueling and timing address who knows how or what that is leading to but it can't be good!


As I said before is you have to look at this in a systems context. That's to say the error code can derive from someplace else but the computer may select something in the data stream that is out of context with what it thinks is the integrated product. That means the code given my reflect the actual problem or result in that problem source for a problem elsewhere in the data stream. That said, the most likely possibility is the error code! If that doesn't correct the problem then you have to go hunting in the data stream that in the end effects fueling.


And people wonder why I like carburetors, go figure?



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Old 10-07-2019, 05:53 PM
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the TPS sensor had already been replaced.
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