Topic: Infrequent warm engine no start in 1997 Monte Carlo Z34 -- help!!!

[jbbadboy]

Hey guys,

I've been lurking this site for a while and have gotten a lot of great information. With that in mind, I thought I'd try my hand at asking a question.

I have a 1997 Monte Carlo Z34 with the 3.4DOHC motor. Recently, I would be driving my car with no problems. If I stop (to go to a store, friend's house), I have had about 4 instances where the car starts but diesels and stalls out, whereby the car would not start for at least another hour. The trouble is, when I try it again (be it overnight or in an hour) she runs like a dream!

My mechanic couldn't find anything wrong, the fuel pressure is fine, the coilpacks, plugs and wires are new from January and the fuel relay has been changed.

Can anyone help me out? Your responses are greatly appreciated!

Thanks in advance!

[ovr50]

Barrie or Articsteve are the guys you need for this one - but this new system may slow them down (Artic's already on).

Hang in there for help - it will come. 

[articsteve]

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I have a 1997 Monte Carlo Z34 with the 3.4DOHC motor. Recently, I would be driving my car with no problems. If I stop (to go to a store, friend's house), I have had about 4 instances where the car starts but diesels and stalls out, whereby the car would not start for at least another hour. The trouble is, when I try it again (be it overnight or in an hour) she runs like a dream!

Thanks in advance!

Traditionally,vapour locks in the fuel rail or fuel line near the motor will cause this when they get to hot.  I don't have any experience with your motor.

If I were you I'd get a used crank position sensor and replace that.

Are you showing any codes.  I assume you would have mentioned it.

[jbbadboy]

No, the mechanic scanned it and there are no codes. The fuel pressure is fine too, which is good because replacing the fuel pump would be expensive.

I ran across a link about vapor lock but I thought it was impossible in newer engines, isn't it? Is there any way to test for this or to relieve the temperarature?

[articsteve]

I ran across a link about vapor lock but I thought it was impossible in newer engines, isn't it? Is there any way to test for this or to relieve the temperarature?

Well vapour lock is usually a design fault so I doubt that is the problem.  I still think a crank position sensor is worth a shot.  Other than that I am out of ideas.

[barrie1]

If this is happening when the car is shut off only for a short time then the heat is building up in your engine while parked and creating the problem. I would strongly suspect one of the sensors is not liking the heat and is breaking down.

[jbbadboy]

I've been thinking about this for two weeks now. I wonder, if this is a heat issue, would changing the coolant help? I've owned the car for 3 years, bought at 64000km and now sits at 159000km's and I haven't changed the coolant.

Could this be the reason? What do you think?

Thanks again for your help!

[Railton]

It's certainly time to change the coolant so it can't hurt but I doubt it will fix your current problem. In mechanical FI systems on Aircraft you see this vapor lock issue alot. The cure is to purge the fuel lines prior to start up by opening up the throtle(s) a touch and turning on the fuel pump to presurize the lines to about 30 psi then turning the ley to engage the starter. This won't help you I know but one other thing you could try before replacing sensors is to wrap the fuel lines with insulation backed aluminum tape to keep the heat away from them.
Good luck.
Railton

[barrie1]

Railton has a very good suggestion on wrapping the fuel lines with the silver cooling tape. Check with your local Hotrod shop who will know where to buy it or maybe even stock it as well. Do a Rad Flush and change your thermostat out to a new 195* stat as well. It will help a little.  When was the last time you ran Fuel Injector Cleaner thru this engine? This may help as well. 

[articsteve]

If your problem continues in this relatively cool weather then I say again, Crank Poistion Sensor.  Go to a GM dealer and see if your CPS fits all 97 3.4s or if it is specific to your model only.  Then go and get a used one and replace.  Ask the dealer where located.  Probably near the main pulley but it could be on the bellhousing.

[barrie1]

Its very possible that Steve is correct as I also believe its a sensor that causing your problem.   

[jbbadboy]

Just a quick update:

The car finally conked out and wouldn't start at all, warm or cold. I towed the car to my mechanic last night and he confirmed first thing this morning that the fuel pump is gone.

I just wanted to say thanks to everyone for all your help! You guys are great!