Why are injectors gushing? [Archive] - Team Camaro Tech

: Why are injectors gushing?


paperpro
Oct 4th, 05, 08:40 AM
I have a stock '92 RS 5 litre and occassionally for no appearant reason the injectors just start dumping fuel to the point that it actually floods the throttle body and consequently the engine.

Has anybody else had this problem. What is the problem.

Everything is stock so I don't know what to look at. :clonk:

BonzoHansen
Oct 4th, 05, 12:42 PM
Is it setting any codes?

a67
Oct 4th, 05, 04:10 PM
If the Coolant Temperature Sensor (CTS) reports cold the ECM will add a LOT of fuel. This is a failure mode that happens quite often. Problem is the engine needs to be running for a while before it'll set a CTS code. And with the amount of fuel being dumped in, the engine won't always run long enough.

Best bet is a scan tool on the ALDL port with key-on engine-off. What does the CTS report for an engine coolant temperature?

Bob.

sick67
Oct 5th, 05, 04:08 PM
my girlfriends car did that and the fuel ran out the intake. It turned out to be the fuel pressure regulator.

Joekool1234567
Oct 6th, 05, 03:53 PM
Fuel pressure regulator is common, just pull the vacuum line and check for fuel in it. One or more fuel injectors can be stuck open, easiest way to find those is to unplug then one at a time and see if the flooding stops or slows. Lastly is the cold start injector can be stuck open or if the coolant temp sensor is bad like what was stated before it can cause the cold start injector to stay on. Ive seen the wires for the coolant temp sensor get damged easily on TPI engines and when that happens they can interminently short together.

a67
Oct 6th, 05, 04:38 PM
A stock '92 RS with a 5.0L is a TBI fuel injection setup. Two injectors, no vacuum line on the FP regulator, no cold start injector. If the regulator failed there would be fuel pouring out of it, around the top of the TB, and then down the throats. Unplugging a leaking injector will not cause it to stop leaking, it will continue to leak. As reported by Paperpro he can see that the injectors add too much fuel and flood out the engine.

As I previously mentioned the CTS is a prime culprit.

Bob.

BonzoHansen
Oct 6th, 05, 05:10 PM
I agree with CTS (check for codes!). He didn't say leaking, he said gushing. Wouldn't a vaccum or bad map sensor cause it to dump fuel?

Joekool1234567
Oct 6th, 05, 10:13 PM
Your right about a leaking fuel injector leaking even when unplugged (my bad, long day I wasnt thinking straight) but a good way to find which ones are leaking is to unplug each injectotr one at a time, if the engine runs the same with the injector unplugged then you found one of the bad ones, if it runs worse the injector is doing its job. Since he never said if it was a TPI or TBI in the first place I assumed he had a TPI. He still might have a TPI for all we know, if he does have a TBI then finding the cause for the flodding should be alittle bit easier since taking off the aircleaner lets you see the fuel injectors and throttle body in action. Much easier to spot a fuel flooding/leaking problem when 90% of the fuel system is is in plain view.

ZZMike
Oct 7th, 05, 06:33 AM
I would agree that a CTS would be a prime suspect (along with the MAP) if he did not say that the throttle body was filling with fuel. If the throttle body is filling with fuel, the injectors are going to full "on" (static) with the throttle plates closed. This is common with late 80's and early 90's TPI cars, where the QDM holds one bank of injectors wide open by giving them a hard ground for no apparent reason. This would be only the second time I would have seen it on a TBI, but I am willing to postulate that the injectors are getting a ground and being held wide open by a faulty QDM. It is the only plausible explanation for filling a throttle body with fuel, a CTS and a MAP won't do that. Both a CTS and a MAP may cause it to be so rich it won't start, but not fill the throttle body with fuel.

Ultimately codes need to be pulled (easy enough on a '92), but the PCM is where my money is.

Everett#2390
Oct 7th, 05, 08:40 AM
I hope he has a TBI, if he has a TPI and flooding, Step back, Jack!!! But, I agree with Mike, faulty QDM will flood, faulty CTS & MAP will richen, but not flood.

a67
Oct 9th, 05, 08:38 AM
A bad CTS will most certainly cause the engine to flood out. The common failure mode is for the sensor or connector to go open. This tells the ECM that the engine is at -40C. Now, two things happen: 1, the commanded AFR is very rich; 2, the inverse temperature term is very high. With these two terms used in the PW calculation the end result is an injector PW that is large, very large. Easily enough to flood the engine while filling the TB with fuel.

As for a bad quad driver (QDM), sorry, they are not used to fire the injectors. Also, the ECMs in the late 80's and early 90's TPI cars only have ONE injector driver. They are batch fired. If that one driver shorts (it is a MOSFET) all 8 injectors will be full on.

Back to the '92 RS with the TBI setup. Don't know if paperpro is still reading the replies, but if you are there are a couple of approaches. With a DVM on the ohms scale measure the CTS sensor value. It is located on the front of the intake manifold with a two wire connector. At room temperature (22C/72F) it should read about 3300 (3.3K) ohms. If it reads infinity (open) replace it.

Another way to trouble shoot this is with a scan tool. Plug it into the ALDL port, key-on, engine-off. Check what value the CTS reads and the intake air temperature (IAT) reads. On a cold engine they should read within a few degrees of each other. And, read at the ambient temperature.

A free scan tool is WinALDL by Joby. Runs on a PC/laptop and requires an inexpensive or easy to build, one-transister interface cable.

http://w1.601.telia.com/~u60113744/software/winaldl/winaldl.htm

As for a shorted injector driver, the 1228746 ECM ('92 RS w/TBI) has two drivers. One for each injector. If one shorted out, only one injector would fill the bore. And, it would do it without even starting the engine.

Bob.

ZZMike
Oct 9th, 05, 12:43 PM
A bad CTS will most certainly cause the engine to flood out. The common failure mode is for the sensor or connector to go open. This tells the ECM that the engine is at -40C. Now, two things happen: 1, the commanded AFR is very rich; 2, the inverse temperature term is very high. With these two terms used in the PW calculation the end result is an injector PW that is large, very large. Easily enough to flood the engine while filling the TB with fuel.

As for a bad quad driver (QDM), sorry, they are not used to fire the injectors. Also, the ECMs in the late 80's and early 90's TPI cars only have ONE injector driver. They are batch fired. If that one driver shorts (it is a MOSFET) all 8 injectors will be full on.

Back to the '92 RS with the TBI setup. Don't know if paperpro is still reading the replies, but if you are there are a couple of approaches. With a DVM on the ohms scale measure the CTS sensor value. It is located on the front of the intake manifold with a two wire connector. At room temperature (22C/72F) it should read about 3300 (3.3K) ohms. If it reads infinity (open) replace it.

Another way to trouble shoot this is with a scan tool. Plug it into the ALDL port, key-on, engine-off. Check what value the CTS reads and the intake air temperature (IAT) reads. On a cold engine they should read within a few degrees of each other. And, read at the ambient temperature.

A free scan tool is WinALDL by Joby. Runs on a PC/laptop and requires an inexpensive or easy to build, one-transister interface cable.

http://w1.601.telia.com/~u60113744/software/winaldl/winaldl.htm

As for a shorted injector driver, the 1228746 ECM ('92 RS w/TBI) has two drivers. One for each injector. If one shorted out, only one injector would fill the bore. And, it would do it without even starting the engine.

Bob.


In the late 80's and early 90's injectors could be batch fired or bank fired, I don't care what your AutoZone education has taught you. They are controlled by a power transistor (or "injector driver" since you enjoy splitting hairs)that I referred to generally as a QDM, based simply on fact that if it goes, the PCM requires replacement, regardless.


You are correct that the CTS can cause a rich condition, BUT BECAUSE THE INJECTOR WILL STILL BE PULSED IT ABSOLUTELY WILL NOT CAUSE THE THROTTLE BODY TO FILL WITH FUEL!!

Sorry, your CTS argument is baseless and not capable of creating the situation he is describing. :thumbsup:

a67
Oct 10th, 05, 02:38 AM
To check the facts about the ECMs in the late 80's and early 90's TPI cars find yourself a 1227165 ('80s MAF) ECM and a 1227730 ('90s SD ECM) and measure the resistance between the two injector driver output pins. You will find basically 0 ohms. Inside of the ECM the pins are connected together. One injector driver, a MOSFET, not a transistor, for all 8 injectors, batch fire only.

Ever look at TBI injectors during idle? A lot more fuel then one would think. As for being pulsed, sure they are pulsed, and with a bad (open) CTS, will be pulsed on long enough to fill the TB. Check the gap between the butterfly and TB throat. Not much room at all. Add to that an engine that is making very little vacuum as it struggles to run with the IAC fully retracted, and the fuel just sits there.

Maybe you need some educating. Go find a TBI car, truck, whatever, disconnect the CTS, start it up and see how it runs.

Bob.

ZZMike
Oct 10th, 05, 10:21 AM
I took your advice, I am certainly up to experimentation

It certainly did not want to run, the 5 gas had the A/F ratio at about 5:1 at the times when it did sputter to life. But the throttle body did not fill with fuel.

And honk my hooter, you're certainly right about the bank fire thing, man I gotta hand it to you, There is continuity between the two PCM pins. Thanks for that.


I like you man, you're smart, but for the record

MOSFET=

Metal
Oxide
Semiconductor
Field
Effect



wait for it,......




wait for it.........



Transistor, ahh there it is :clonk:

P.S. I know, I know.....
Source, Gate, Drain instead of Emitter, Base, Collector bulk electron travel over a medium instead of through it, blah blah blah