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1994 3.4 dies immediately after it starts


Mstg007
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i have a 1994 supreme convertible 3.4. i was out shopping and then went to leave started the car and the engine just died. i finally was able to start it and rev the engine up and it finally after awhile was ok. so i went to another store. again when i started the car to leave. it did the exact same thing. so i am home now..... Fun!

this has never happend that to me with this car. any ideas? thanks guys.

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You can rent a fuel pressure gauge at most auto part stores for free meaning you get the rental deposit back. Just connect the line to the shrader valve(usually protected by a black cap and is not unlike the air valve on a tire in appearance) at the end of the fuel rail and turn the key to ON without starting the engine. What is the PSI and is it steady?

 

Congrats you have just successfully tested your fuel pressure! Open beer, throw confetti or however you prefer to celebrate.

 

Testing for spark can be done a few ways, easiest is to get an inline sparkplug tester and connect it between the cable and plug and the crank the engine, if it lights up then guess what? Or you can pull the plug out of the block connected to the cable and try and start the car to see if the spark archs.

 

Also I would not be beyond suspecting the Passkey anti-theft system, this sounds identical to a situation with a 03 Grand AM GT a few months ago. Did the rpms just surge as it started/died at the same time. Like it fired up for a split second but then something killed the engine? I cleaned the ignition cylinder and key but it just started for me after testing the ICM and reconnecting it to the car. During that ordeal diagnosing the crankshaft position sensor came up as well. :thumbsup:

 

Check this page out http://easyautodiagnostics.com/gm/3.1L-3.4L/testing-the-ignition-module-and-crank-sensor-1

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You can rent a fuel pressure gauge at most auto part stores for free meaning you get the rental deposit back. Just connect the line to the shrader valve(usually protected by a black cap and is not unlike the air valve on a tire in appearance) at the end of the fuel rail and turn the key to ON without starting the engine. What is the PSI and is it steady?

 

Congrats you have just successfully tested your fuel pressure! Open beer, throw confetti or however you prefer to celebrate.

That's a fine test of static fuel pressure. I'd also want to know how much pressure it has when the engine is running at WFO and maximum RPM. This requires some creativity so that you can see the gauge while driving at highway speed. A weak fuel pump may have adequate pressure during low-fuel-demand situations like idle or low speed, but can't keep up when the fuel demanded by the injectors goes up.

 

 

Testing for spark can be done a few ways, easiest is to get an inline sparkplug tester and connect it between the cable and plug and the crank the engine, if it lights up then guess what? Or you can pull the plug out of the block connected to the cable and try and start the car to see if the spark archs.

Also a reasonable test of a single coil-pack. Need to do this test for each coil pack. I prefer the spark-testers that look like a spark plug with no side electrode, that have an alligator clip welded to the side. There are other kinds, and other people may prefer them. I'll stick with this:

 

Left side: HEI tester. Right side: points or low-energy electronic tester.

image010.jpg

 

 

Left side: HEI tester with recessed center electrode for longer spark gap. Right side: Points or low-energy electronic ignition with standard spark gap.

image012.jpg

 

Either kind would be about $15 or less. Any 1975-newer GM will use the HEI style spark tester. You'd want to ground the alligator clip to the engine rather than the battery.

Edited by Schurkey
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Ive never seen spark testers like that, they would probably be more helpful than a light or visual confirmation because then you could see the actual voltage at the plug vs just seeing a light.

 

That tool on the right, the non HEI tester, is that for older engines with the distributor cap and rotor setup? I`m not sure how often I`d use them but I wouldn't mind snagging at least the HEI tester, did you make them yourself?

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Ive never seen spark testers like that, they would probably be more helpful than a light or visual confirmation because then you could see the actual voltage at the plug vs just seeing a light.

 

That tool on the right, the non HEI tester, is that for older engines with the distributor cap and rotor setup? I`m not sure how often I`d use them but I wouldn't mind snagging at least the HEI tester, did you make them yourself?

The two spark testers are calibrated for low-energy (ballast resistor) and high-energy (no ballast resistor) coil systems. Points and some electronic ignitions including some distributorless ignitions use a ballast resistor in the coil wiring, so they'd use the low-energy spark tester. GM's HEI and various other systems--distributor and distributorless--which don't use a ballast resistor would use the HEI tester, and it's larger spark gap.

 

No, I didn't make these. They used to be popular, but some idiot lawyer decided someone could get an owwie from the open spark gap and sue, so they're getting phased-out. Buy 'em now while you still can.

 

Another style I own but haven't bothered to use yet:

http://www.amazon.com/Thexton-THE404-Spark-Tester/dp/B0002STSBM/ref=sr_1_1?ie=UTF8&qid=1429488387&sr=8-1&keywords=Thexton+spark+tester

31zKrGoCurL.jpg

Note that the version I have doesn't have a plastic tube over the spark gap. Mine has the electrodes out in the open, like God intended. I'm sure I could be killed using it.

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I am also having the same issue, my vert (3.4) starts up cold every time without a hitch. It is when I have driven it for a while and turn it off and restart it after a few minutes it just doesn't want to start up. If I catch it on the first turn I can usually coach it and eventually (a couple of minutes) the engine calms down (miss firing) and I can drive away. If I don't, then it just turns over and I can't get it to start. ERG valve?

 

Thanks for the help, this car has been a load of fun to drive over the last couple of years but the 3.4 engine is gonna make me shoot the car at some point.

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I am also having the same issue, my vert (3.4) starts up cold every time without a hitch. It is when I have driven it for a while and turn it off and restart it after a few minutes it just doesn't want to start up. If I catch it on the first turn I can usually coach it and eventually (a couple of minutes) the engine calms down (miss firing) and I can drive away. If I don't, then it just turns over and I can't get it to start. ERG valve?

 

Thanks for the help, this car has been a load of fun to drive over the last couple of years but the 3.4 engine is gonna make me shoot the car at some point.

Connect a scan tool, see what the data stream says.

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I am also having the same issue, my vert (3.4) starts up cold every time without a hitch. It is when I have driven it for a while and turn it off and restart it after a few minutes it just doesn't want to start up. If I catch it on the first turn I can usually coach it and eventually (a couple of minutes) the engine calms down (miss firing) and I can drive away. If I don't, then it just turns over and I can't get it to start. ERG valve?

 

Thanks for the help, this car has been a load of fun to drive over the last couple of years but the 3.4 engine is gonna make me shoot the car at some point.

 

 

Any idea what you found out was the problem with your convertible?

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Sounds like you are reading a service manual for something else... but here's my input: I had a car behave like this. It was due to low fuel pressure, and therefore vapor lock after shut down and attempted restart when warm. Venting the vapor from the fuel test schrader valve would be a short term fix... final fix was fuel pump replacement.

 

Get a pressure test tool, you can get a lone-a-tool at autozone for proper diagnosis.

 

Also check/clean/replace fuel pump relay if in doubt. Cheapest to try switching it for an identical relay to see if any change occurs.

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