bornagainyank

Hi all. I'm really stuck with a problem on my 1990 305 TBI Camaro. it will only fire if I use starter spray and will only run, although a little roughly, if I keep pumping the throttle. As soon as I stop pumping the engine dies. I tried pouring a bit of petrol directly into the top of the throttle body and it will start but again quickly die.( presumably when that petrol is used up)
So far I have replaced the following: fuel pump,fuel filter,O2 sensor,map sensor, cold start sensor,all the spark plugs,high torque starter motor,fitted new heavy duty battery.Removed the egr valve and checked that was working as per info on the internet. I have checked all the vaccuum lines for damage or loose connections but this seems ok.I have cleaned the terminals inside the distributor and cleaned the outside contact edge of the rotor.It did look a little rusty inside but nothing major. I have also tried another ecm(numbers matched).I have also replaced the belt tension pulley although I know this has nothing to do with the starting issue.
If I check the diagnostics, after the code 12 it is flashing a 53. I checked the output from the alternator and I was getting a max of about 14V whilst pumping the throttle to keep the engine going.
Is there anything that I am missing? I'm not a mechanic so only know the basics. Can anyone help please.Its turning my hair grey!

Drew Morgan

Check the IAC. It may need to be cleaned or replaced.

bornagainyank

ok thanks,what is the best way to check them for correct operation? Would just a small thing cause all the issues I have?

Drew Morgan

Yeah it could. Especially if you've done as much as you have already. Just unscrew it out of the passenger side of the TB, spray it with carb cleaner, scrub with a little brush. If its still gives you problems, buy a new one.

henryd3

iTrader: (128)

Here's an article from the HOW-Tos section. Lots of good stuff in there. You may want to do this
https://www.thirdgen.org/tpimod2/

bornagainyank

Thanks for all the info guys.I have taken the IAC off and realy cleaned it,refitted and no difference.. I am a bit reluctant to change straight away as they about £60-70 over here. If I have to then obviously i will. Is there anything else that I could look at in the meantime. I can't check theidle speed or anything as the car won't run. I am beginning to think weather I am even looking in the right ball park.
Cranks-starts-runs smooth for 2-3 secs max if i dont touch the gas pedal,runs longer if I pump the pedal like mad-stop touching pedal then dies straight away.
it might be like this a few times then it will only crank unless I put starter spray in or pour some fuel straight into the top. Then repeat as before. I am defo getting fuel up to the TBI as i get it coming out if i loosen the solid fuel line connection going into it.
As a footnote, my rev counter only shows max revs during all of this,although I suspect this might be a entirely different issue altogether.

bornagainyank

Sorry I forgot add that when I pump the pedal it runs like a dogs dinner.

Drew Morgan

You may end up having to replace the IAC. Before you do, check the voltage from the IAC with the key on/engine off. ICR what the voltage is supposed to be, but I know it's on here and a video on YouTube. While you're checking voltage, check it on the TPS just for good measure. If you replace the IAC and it still gives you grief, check the fuel pressure just be sure you didn't get a bad part. You've already replace so much, there's not a whole lot left. You could try to rebuild the TB. It's pretty easy and they're even a video on YouTube as well. Keep me posted on what you find out! As for your tach, it's a very common problem with third gens. Mine was the same way uuntil I sent it off to be fixed ($50). That is because the chip in the back of the gauge is messed up somehow. IDK bc I'm the furthest thing from a electrician!! Hope it works out and, like I said, keep me posted!

Drew

bornagainyank

ok I will look up what voltage and give it a go. I read somewhere that even though the oil pressure gauge is showing decent pressure the sender can still be naff and shut down the fuel pump.If this is true and it could possibly be another angle for me to check.I will definately keep you posted as it might help someone else with the same problem before they end up looking for a room in the funny farm like I am. Thanks for your help;

antares57

iTrader: (8)

Have you rebuilt your throttle body assembly and replaced your injector filters? Sounds like your FPR diaphragm may be ruptured.

bornagainyank

no i havent done that. i was looking at the TBI rebuild kit but I can only find them on your side of the pond and the delivery date is end of september. To be fair ,you're the first to mention the FDR diaphram. so i will defo check that. Are my symptons a sure sign of this then?

bornagainyank

sorry fat fingers.. that should of said FPR ....Doh!!!!!

antares57

iTrader: (8)

Take the air cleaner assembly off and observe the injectors with the car on. Should be spraying an even conical pattern of fuel. If they are dripping or not spraying, may be faulty injectors or bad diaphragm. Rule out your your injectors by ohming them - should be in the 1.3 range.

RBob

iTrader: (1)

On the TBI f-bodys code 53 is a VATs error. Apparently the VATs input to the ECM has been lost. It will act exactly as you are seeing. Needs added fuel to start and requires pumping the gas to keep it running (runs on AE).

RBob.

bornagainyank

Thanks for the info. I will also check this out.I thought that if the VATS was defective then the engine wouldn't crank at all

RBob

iTrader: (1)

Most of the time a VATs failure is due to the module not being able to read the key.

If the module fails to send the ECM the signal, what you are seeing occurs. There can be other reasons the VATs signal to the ECM gets lost. Such as a connector failure.

RBob.

bornagainyank

would the resister bypass trick work with this? I have measured my key and have purchased the correct resistor value (4,7k ohms)

Tuned Performance

iTrader: (92)

You can disconnect the key reader pigtail and install the resistor .
http://www.austinthirdgen.org/index.php?pid=41

RBob

iTrader: (1)

Probably not, is the security light on all of the time? If not then the resistor trick isn't the fix.

RBob.

bornagainyank

RBob you are a living god!!!!!! bought a 18 pence 4.7k ohm resister,fitted it and bingo.... car now starts and and at the moment stays running. Thanks to everyone who gave info. I am still going to to a TB rebuild as I have the kit on order.