Car doesn't start - sometimes.

klankymen

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OK, I've been having some weird problems with my car, maybe you guys can diagnose it - seem to be some pretty knowledgeable people here.

It's a 2000 Mk4 Golf, with a 1.6litre petrol engine, I bought it used last year.

Anyway, here's the weird thing, some times it won't start. Usually after taking a very short drive (5 minutes or less - such as stopping by the bank on my way out of town) if I turn the engine off, do something for like 10 minutes, and then try to start again, the engine won't start. I hear the starter motor chug-chugging away, but the engine won't get running.

If I wait like 5-10 minutes, and do nothing in the meantime, then it will start again. If I take a longer drive, and then leave the car for 5 minutes - no problems.

One exception: I drove a 1 hour drive, parked the car in the middle of the glaring sun, at midday for like 2 hours, (must have been like 50C in the car when I got back....) and then it also didn't start. waited half an hour, then it started.

My mum took it to the mechanic last week (I've been too busy with work lately) he said he diagnosed something, and changed some part (plastic tube my mum said, not sure what), but my mum was using the car on the weekend, and she encountered the same problem - short drive, no start, wait.

I was at the VW dealer previously about this, to have the error memory read out, and there were several errors in the alpha probe (oxygen sensor) - both of them actually. But my mechanic said that wouldn't cause the engine to not start.

Any clues?
 
I believe Joe Namath knows a little something about Vapor Lock..



My car started intermittently a few years ago. Turned out to be the ECU after trying a million different other things.
 
Next time it does it, give it some (read: lots) of gas when you start it. If it will start then Kajun is probably right and it`s vapour lock.
 
I'll try that today... if it is vapour lock - is there anything I can do to fix it?
 
Yeah this sounds like a common problem. If it's similar then it might be solved by tweaking the throttle before cutting the engine. It keeps fuel in the carbs apparently. helps my SIII start on the first crank anyway.
 
I'll try that today... if it is vapour lock - is there anything I can do to fix it?

A small puff of starting fluid into the air cleaner. It should help the engine fire, and after that, you should be golden.
 
I'm going a different direction. I'm going to say something in the ignition is not allowing to start. The only thing is I'm not familiar with the VW ignition system, so I don't know where to tell you to start.

Other than, take it for a drive, come back home shut it off, pull a plug wire and plug, ground the plug against the block and have someone crank it over. If there is spark it's not it, if there isn't there's your problem.
 
Could be fuel pump, ECU or crank position sensor.

My moms new 08 or 09 Nissan Versa had intimitant starting issues. I diagnosed it as a fuel pump. She took it to the dealership and there was a recall on the fuel pumps. Only they never told anyone about it.

Also if the capictors in your ECU start leaking, then it can cause all kinds of wierd problems. I deal with this alot in Mitsubishi's.

And finally, my friends Jeep Grand Cherokee also had intimitant starting problems. The crank sensor was done and did not know where the pistons were in relation to the firing order, so it would do nothing or just random fire them.
 
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Yeah this sounds like a common problem. If it's similar then it might be solved by tweaking the throttle before cutting the engine. It keeps fuel in the carbs apparently. helps my SIII start on the first crank anyway.

That would be interesting on his car, since he doesn't *have* carbs.
 
That would be interesting on his car, since he doesn't *have* carbs.

yeah, so that rules out vapour lock.

that leaves:
-ECU
-crank sensor
-fuel pump
-ignition

My mechanic did the following:
-replace two corroded tubes/hoses from somewhere in the fuel line in the engine
-toy around with the ignition system trying to replicate the problem
-replace the ignition coils

So far no help, it's still doing the same thing.

AND: New problem
as of a few weeks ago, the engine will just shut off while driving.
After driving a short period (like 100meters), the engine just dies, usually while the car is slowing down, or braking. It won't start again, but waiting a few minutes makes it start.
Except, once of the 4 times it has happened, I restartet it while still rolling, and it jumped right back on again (we're talking lightning reflexes here, like 1 second between it going off and me turning the key off and back on again. I can't remember if I clutched while doing this, or maybe used the cars movement to get the engine going again)


Any extra symptoms (should) help, so guys (and girls), any ideas what that might mean?
 
My mom has a 2000 golf as well and had similar issues. The step-dad replaced a bunch of parts, so I can't remember which one did the trick. I do believe the following were replaced:

-Crank position sensor
-MAF sensor
-Coolant temp sensor
 
Sounds ignition related to me. Does that car have a distributor or coil packs? Could be fault in that department. Also, it could be as simple as vacuum leaks. Take a can of carb cleaner (or something similar) and spray around the engine compartment when its running. If the idle raises, you may have a vacuum leak.
 
My guess would be the battery.
 
I've had similar problems with my Jeep when the Crank Position Sensor decided to take a shit.
 
yeah, so that rules out vapour lock.

Actually, it doesn't, it just rules out fuel boiling out of the carburetors that you don't have. :p EFI can still get vapor locked if there's enough heat or not enough insulation, or if someone screws up the fuel plumbing design.

All three of which have happened to recent vehicles and forced recalls, BTW.

AND: New problem
as of a few weeks ago, the engine will just shut off while driving.
After driving a short period (like 100meters), the engine just dies, usually while the car is slowing down, or braking. It won't start again, but waiting a few minutes makes it start.
Except, once of the 4 times it has happened, I restartet it while still rolling, and it jumped right back on again (we're talking lightning reflexes here, like 1 second between it going off and me turning the key off and back on again. I can't remember if I clutched while doing this, or maybe used the cars movement to get the engine going again)


Any extra symptoms (should) help, so guys (and girls), any ideas what that might mean?

Sounds like a crank position sensor or wiring fault.
 
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