Help - Engine Cuts out mid driving (91 Firebird)

[Anil]

Hi everyone,

I could really use some help here as I don’t even know where to begin with the problem I am having. I have been searching thirdgen and other forums and can’t seem to find the answer anywhere.

I have a 91 Firebird, 305 V8 TBI. It is a Knight Rider replica, so I don’t have the instrument cluster but all the lights etc (such as the check engine light) are wired up to an appropriate LED.

My car runs fine most of the time, but recently the engine cut out while driving and would not restart immediately. When turning the key a few moments after it cuts out, nothing happens i.e. you can’t hear the starter motor engaging (which ordinarily would mean a lack of power). Turning the key literally does nothing except power on the dash. This has happened twice now and on both occasions I have been stuck in traffic, or waiting for someone for a lengthy period of time (10+ mins) i.e. the car has been idling or driving very slowly, which may have allowed it to get it hot. On the first occasion, I parked the car up, disconnected the battery, left it for 20-30 mins, reconnected and it started up absolutely fine. I did a few journeys post that and all was fine. On the second occasion, I left it 5 mins (after disconnecting and reconnecting the battery), and the starter motor engaged but the engine could not quite start. It sounded like it was nearly there, but then stalled. Once again, left it a little longer and the car started absolutely fine.

I always keep an eye on the temperature gauge as once upon a time the radiator fan did not come on (as it was faulty). On both occasions that it cut out it was around the 180-190 mark (so not hot) and I am fairly sure the fan did come on. Furthermore, when I opened the bonnet on I didn’t notice or hear any bubbling from the overflow tank.

I didn’t check the engine light on both occasions (I wish I had now).

After the first incident I took the car to my mechanic and he said he read the ECM/ECU and saw no faults. When I disconnected the battery would this have wiped any error code?

I am looking for any help /advice/direction on this matter as I don’t even know where to begin or what to advise my mechanic to look over.

Thanks so much guys.
Anil

[SUPERCHARGEDGTA]

if you disconnect the battery it will clear any stored codes
the reason for not starting till it cooled could be starter overheated (had this on my 2nd gen, stop with a hot engine, then try to restart and nothing. let it cool 10 minutes and starts ok)
the starter is between exhaust manifold and engine so dose get hot. if you are not driving at reasonable speed there is no airflow so it gets hot faster.

as for cutting out, several things it could be, over heating sensors, fuel system/pump or injector
next time don't disconnect battery, just let it cool

[jonbullnose]

AS john said your restarting issue could well be that the exhuast is cooking the starter you need to look into this as it will do your starter motor in if it keeps getting cooked
you need a heat sheild or wrap the starter or both

cutting out could be so many things like john said get back to us with more info and we will try to help

[Anil]

Hey Guys - Thanks so much for the info. I agree on the starter idea - ill get on that.

I guess why it cut out is probably something to do with the heat. John you mentioned over heating sensors? would they likely cut the engine out? Where do they take their reading (water temp?)

Cheers,
Anil

[SUPERCHARGEDGTA]

water temp is one, could be any one of several causes,

[jonbullnose]

after rereading your syptoms im going towards a possible fuel vaporization isssue due to heat in the engine bay do you have unwrapped headers? i think the starter motor could be a seperate issue or the other problem could be is your starter motor is starting to fail they can draw a huge amount of current out of the battery and kill your ignition system when you try to restart as it will not spark with less than say around 10.5 volts
but the list is long as to what it could be but under bonnet temp could well be the issue as if you have a full conversion i beleive the grill air intake is reduced to what it had from factory

[Anil]

Hi John & Jon,

I have had a think about this and I am confident that the heat, given I was idling for a long time during both occasions. I read a few other articles that state when the starter is very hot (i.e. at the point straight after cutting out) it will feel like it has no power as the wire can't carry current due to the resistance. This matches my fault. If it was a power issue, then it wouldn't restart a little later.

As for it cutting out, I suspect it is like you both say, some sensor failing/giving a high temp reading under the pressure.

One thing I failed to mention was that the standard thermostat that activates the fan when it is too hot is not working. I actually have an after market one fitted that has a sensor that reads the temperature of the radiator. There is a dial to calibrate the level at which it comes on. I adjust once a quarter and recently did so it comes on between 190-200, which I suspect might be a little high.

Just out of curiosity, and just to be sure, there is only one cooling fan in the car? The one right by the radiator?

So my thoughts are drop the temperature required to activate the fan and buy a heat shield for the starter. What do you guys think? Any recommendations on which heat shield to buy.

I really do appreciate all your advice!

Thanks,
Anil

[SUPERCHARGEDGTA]

there are several on the market, try ebay for cheapest
summit sell them, or use header wrap

bringing fan in earlier would be good

if non AC then one fan only

cant you replace the correct temp. sensor? (is it the sensor or the relay?) as the rad temperature is not always directly related to engine temperature
also the sensor tells the ECU the engine temperature and this affects how it runs the engine (if it thinks the engine is cold when its hot it will run rich among other things which could cause it to stall or cut out)
is the thermostat opening at correct temperature and is it opening fully?

[Anil]

Hi John/Jon,

So over this weekend I took the car out to see if the issues continued to occur (which they did) before taking it to a mechanic and/or buying parts.

Before I started the car up on Saturday I wanted to see what the engine check light was doing. When the ignition is on, but car is not running, the light is on. When I start the car, the light disappears and does not come on while driving. So I start my journey (and this is before I have adjusted the temperature the fan comes on as in order to calibrate it the car needs to be at the temperature you want the fan to activate at), car starts fine and I drive on mostly A-roads about 7ish miles. I park up, leave the car for 10 mins, car won't start. Starter motor is doing something as you hear it trying to turnover, but fails to get the car going. I don't recall seeing the temperature gauge getting that high, I let it cool to 120F and give it a go and it starts fine. I go somewhere else, maybe 10 miles a-roads again with the no problems. As the car is warm I calibrate the fan. A couple of hours later I head home, about 12 miles once again mostly a-road with no issues. When I got the car home and let the car idle a bit to ensure the fan was coming on where I set it (180F). I switch the engine off at 170F and then after a minute try and restart the car and it does so with no issues.

I thought this might be the end of the issue, but most definitely not. I took the car out today to see if this adjustment was the root cause. I was driving in the city, so between 20-30 mph most of the time, and slower on occasions. The temperature never went above 176F. Whilst driving at about 20 mph the car cuts off, and the engine check light is on. Luckily it wasn't in an awkward spot so I pulled over, tried to start the car up and had the same problem as Saturday. Turning over but not starting the engine. The temp gauge was reading 180F. I left it for 20-30 mins, an the car started fine at 135F. The check engine light was not on while driving.

As before, given these symptoms I think some sensor and the starter motor are getting to hot/faulty.

I am planning on taking the car to the garage next week. Couple of questions I hope you can help with before I do so:

1. Is the correct temperature for the fan to come 180F? Or should it be lower?
2. Is it normal for the engine check light to be on when the ignition is on but the car is not running?
3. As I have not disconnected the battery I assume the ECM will still have the error code on it, even though the engine check light was not on while I was driving last? If so how do I get the error code from it? Any pointers would be great.

In responses to your points John B:

1. What do you think of this: http://www.ebay.co.uk/itm/Thermotec-Sta ... 4d17e1ffe1
2. The thermostat that sits inside the engine to turn the fan on as a siezed bolt that may snap and then I am in a world of trouble. However, I think given what is happening Ill see what my mechanic says. The aftermarket one was fitted on my car when I bought it as the previous owner was also scared.

I really do appreciate all your help and taking the time to read and reply to this.

Thanks - Anil

[Anil]

I found this....

http://www.troublecodes.net/gm/

[SUPERCHARGEDGTA]

check engine light should be on with ign. on and engine not running
this is how you read the codes (socket is under dash just to the right of steering column

viewtopic.php?f=42&t=1563

[Anil]

Thanks mate - ill try and fine the plug tomorrow.

[Anil]

Hey guys,

So see pics for where I shorted the two pins in order to get the code. Its where all the fuses are on the left hand side of the driver side, just under the cover.





I get codes 12-12-12-54-54-54 and then it repeats. Video here:



Any thoughts on what usually causes the fuel pump or relay to have low voltage?

Cheers,
Anil

[banker]

Fault code list can be found here http://www.iroczone.com/2009/10/1982-19 ... -firebird/

[SUPERCHARGEDGTA]

wiring to fuel pump poor connection maybe, or relay fault
is oil pressure ok when hot? there is a pressure switch near the oil filter, if oil pressure drops too low it cuts the fuel pump.
faulty water temperature sensor in engine will make the ecu think there is no water in the engine and it will cut fuel
(had cars with blown headgasket that wont restart if turned of as there is air in system. when cooled they go to open loop and start ok)

[Anil]

Guys thank so much for all your help.

It turns out the the fuel pump relay connection pins weren't great. When the area was getting warm the pins/connectors were pushing away in the wrong direction and then cutting the power to the fuel pump. Seems to be all good now I have had all the connections renewed (touch wood).

I have a few more issues now, will post in a separate topic!

Once again - thanks so much for all your help