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Vapor Lock?; Car won't start after sitting
Topic Started: Aug 25 2009, 08:54 PM (3,575 Views)
geosedan
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I have a '96 Metro Lsi 1.3L manual sedan. On hot days after I park the car for about a half hour or 45 minutes it will crank and crank but not start. If I let the car sit about an hour and 10 minutes it will start. If I only park the car for 10 minutes or so it will start. This seems like vapor lock to me but I thought you couldn't get vapor lock with fuel injection. I saw that the fuel lines pass so close to the intake manifold that they almost touch so I raised them about 3/8 of an inch with shims and a modified bracket but it still happens. This happened last summer and this summer. When the weather cools off the problem ends. I do notice that the engine fan does not run after the car is shut off like on my Accord. Is it supposed to on a Metro? Any ideas on what could be causing this?

Thanks
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Johnny Mullet
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Fear the Mullet

I would suspect you are either losing a crank signal or the distributor is malfunctioning. Was there any previous work done to the car? Has the oil pan been dropped? If an oil pan gasket was used instead of RTV, the crank sensor gap is too far and when the engine is hot, the expansion is enough to make it not start.
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geosedan
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Well Johnny Mullet you are amazing. I would have NEVER thought of an oil pan gasket being the cause. Yes my car has an oil pan gasket! When I first got the car it was leaking oil from the drain plug. It had looked like the surface the oil drain bolt mates against had been hit with a hammer and the washer could not seal. I dropped the pan to file it flat so I could clean the filings out of the pan after filing the surface flat (I must have taken 3/16 of an inch off of that surface) anyway, I put the pan back on with a cork gasket. I'm not sure where the crank sensor is but I guess the cure is to drop the pan, clean it, and use nothing to reseal it all the way around but blue RTV silicone sealant right?
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Johnny Mullet
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Fear the Mullet

You are correct sir. Git R Done :deal

And don't call me amazing until it's fixed :)
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geosedan
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Welllllll,

I pulled the oil pan scraped and wire brushed the cork gasket off and put the pan back on with blue RTV silicone and it still won't start after I leave it for awhile when it is hot. It will start if I spray starting fluid down the air cleaner wingnut hole so at least I guess I know it's fuel. It still starts right up after sitting for a few hours though. Anybody have any ideas?
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Bad Bent
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Facetious Educated Donkey

Was there a plastic sensor thingy on the oil pan? It could still be malfunctioning.

If the thinking is still "vapor" I'd check the Evaporative Canister plumbing and the gas cap hisses when opened. So what would heat up, expand, or over heat and keep the car from running - only in the summer? :dunno

Now "When the weather cools off the problem ends." Sounds like A/C 'When it cools off I no longer use my A/C' and is there something related to the A/C or an unused A/C circuit? :dunno
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BillP
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Sure sounds like vapor lock. I had a 260z that vapor locked bad in hot weather. The fix was insulating the fuel lines in the engine compartment. Even wrapping with aluminum foil might give enough shielding to help.
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mwebb
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FOG

it is not vapor locking ,
to prove that , crack the pressure line when the problem is occurring , if liquid fuel spills out and it will , there is no vapor lock .

or remove return line ,operate starter , does liquid fuel spill out ? if yes there is no vapor lock ,

if no
your fuel pump is not functioning as designed or your fuel filter is stuffed with doo-doo or the fuel has frozen water in the line
..............................................................................
coolant temp sensor ground or coolant temp sensor

do you have ability to get scan data ?
when hot and not starting look at coolant temp in scan data , compare to actual measured cylinder head temperature at coolant temp sensor , use infared temp gun if available , if coolant temp in scan data is significantly less than actual measured coolant temp ...

you will need to voltage drop coolant temp sensor ground from battery negative WHILE operating the starter
must be less than 50mv or .050 volts .

or
the injector is failing hot
i posted a very detailed method to prove that using a test light . in another thread, if you get this far , i can post it again
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mwebb
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FOG

if coolant temp sensor ground is bad , all grounds are bad .
which may be the problem .

but it may start
if you go to "clear flood" by holding throttle to the floor and cranking the starter , this shuts off fuel.

but
if ground on TPS is bad too
Mr PCM sees "clear flood" all the time on your car because bad ground will elevate TPS signal and MR PCM will think you want to "clear flood" so Mr PCM shuts off the fuel .
no start

get out your DVOM ...
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blkpwr
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mwebb
Sep 16 2009, 10:18 PM
it is not vapor locking ,
to prove that , crack the pressure line when the problem is occurring , if liquid fuel spills out and it will , there is no vapor lock .

or remove return line ,operate starter , does liquid fuel spill out ? if yes there is no vapor lock ,

if no
your fuel pump is not functioning as designed or your fuel filter is stuffed with doo-doo or the fuel has frozen water in the line
..............................................................................
coolant temp sensor ground or coolant temp sensor

do you have ability to get scan data ?
when hot and not starting look at coolant temp in scan data , compare to actual measured cylinder head temperature at coolant temp sensor , use infared temp gun if available , if coolant temp in scan data is significantly less than actual measured coolant temp ...

you will need to voltage drop coolant temp sensor ground from battery negative WHILE operating the starter
must be less than 50mv or .050 volts .

or
the injector is failing hot
i posted a very detailed method to prove that using a test light . in another thread, if you get this far , i can post it again
please post very detailed method to prove hot injector using a test light. I am having same problems as above on my 97 auto metro. I left it with a mechanic friend this week who told me today he got a chance to look at it. He said it wasn't vapor lock, that the fuel pump was working getting the gas to the throttle body but the TB injector wasn't working. He didn't know if it was faulty or if it was getting a bad signal. Also when he hooked up my sct scanner to the obdii port it read data error. I'm commuting 160 miles a day now in a mustang gt and really appreciate any help especially timely
Edited by blkpwr, Jun 18 2011, 09:30 PM.
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geosedan
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I fixed the problem but I'm afraid the way I did it will not be much help to those with a similar problem. I rebuilt the engine and when I did I replaced the intake manifold with one I got from the junkyard (along with everything that came attached to it). I was going to replace the fuel pump but when I lowered the tank a lot of the steel lines were very rusted and pitted so I replaced all ot that along with the fuel pump. The bottom line is the problem is solved but I can't say what fixed it because I did all this at once during the rebuild.
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nerys
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Grr

that last part right their is what I think did you in. (rusted fuel lines)

you had a small fuel leak and it had trouble "drawing" gas from the tank sometimes (when hot leak was larger??)

what makes me think this is you said when you used starter fluid it started up fine.

this implies "lack of fuel" but once engine was running (starter fluid) it was able to do enough of whatever it had to do to restore fuel flow.
Edited by nerys, Apr 29 2012, 09:36 AM.
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mwebb
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FOG

nerys
Apr 29 2012, 09:36 AM
that last part right their is what I think did you in. (rusted fuel lines)

you had a small fuel leak and it had trouble "drawing" gas from the tank sometimes (when hot leak was larger??)

what makes me think this is you said when you used starter fluid it started up fine.

this implies "lack of fuel" but once engine was running (starter fluid) it was able to do enough of whatever it had to do to restore fuel flow.
while rusty particles in the fuel system will not do anything positive for the injector
remember the system is designed to wash particles back to the fuel tank , what ever fuel does not get used by the injector gets routed via the return line back to the fuel tank

this essentially continuously washes the inlet to the injector with filtered fuel

it is more likely that the injector coil was opening up when hot.
the old injector was "bad"

you can measure voltage drop across the injector resistor , if there is no current flow , injector circuit is open
key on engine off . the fuel system runs about 5 seconds
you can look for 12 volts positive at both injector pins (use Tpins) when injector is in the circuit , if only one pin has positive
and the other has nothing , the injector itself is open .
nothing means nothing - nothing does not mean ground or negative or zero

Posted Image
T pins

Posted Image
exotic T pin in MAP sensor , using MAP sensor to provide waveform to view vacuum pulse per cylinder
pulse damper / orifice on the air filter , no polarity to the pulse damper
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nerys
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Grr

I meant that rusty fuel lines allowed fuel to seep back to the tank.

on crank it had trouble building enough "pressure" to get fuel to the injector. when he sprayed to start the engine "RAN" long enough at "speed" to build the needed pressure.

when "cooled" the hole was smaller and it could build pressure?

just a guess :-)
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