vapor lock?
Thread Starter
Instructor
Joined: Jun 2005
Posts: 193
Likes: 0
From: woodinville washington
vapor lock?
1991 A4 L98,
my car ran great for 2 years without problems, 2K miles per year, then it was idling in the driveway for about 5 minutes and died, would not restart. would turn over and on the first try it caught and then immediately died, then it would turn over with no start or even a sign of starting. had it towed home and i replaced distributor cap and coil as they were in bad shape.
the car then ran better than ever for 45 miles and then as i was pulling into a parking spot it died, it DID restart and i made it 100 yards and then died. now if i let it sit for a half hour or so it will catch as i start it, rev to about 3 thousand RPMs and then die, it will then only turn over with not sign of starting unless it sits for an hour.
had it towed and would not restart at home, opened the gas cap last night and a lot of vapors seemed to be released as i heard a large sucking noise, this morning it started and has been idling now for about a half hour just fine.
i hear the fuel pump prime when i try to start it, and the filter is brand new
question... could this have been a vapor lock in the gas tank?
thanks
YD
my car ran great for 2 years without problems, 2K miles per year, then it was idling in the driveway for about 5 minutes and died, would not restart. would turn over and on the first try it caught and then immediately died, then it would turn over with no start or even a sign of starting. had it towed home and i replaced distributor cap and coil as they were in bad shape.
the car then ran better than ever for 45 miles and then as i was pulling into a parking spot it died, it DID restart and i made it 100 yards and then died. now if i let it sit for a half hour or so it will catch as i start it, rev to about 3 thousand RPMs and then die, it will then only turn over with not sign of starting unless it sits for an hour.
had it towed and would not restart at home, opened the gas cap last night and a lot of vapors seemed to be released as i heard a large sucking noise, this morning it started and has been idling now for about a half hour just fine.
i hear the fuel pump prime when i try to start it, and the filter is brand new
question... could this have been a vapor lock in the gas tank?
thanks
YD
Thread Starter
Instructor
Joined: Jun 2005
Posts: 193
Likes: 0
From: woodinville washington
checked the vent, its clear and tested the cap, it is still sealing perfectly, so now im thinking its a much larger problem, since its intemitent i cant tell if what i do actually fixes the problem, any ideas?
Supporting Vendor
Joined: Mar 2008
Posts: 1,762
Likes: 14
From: Cumming Ga
there is no such thing as vapor lock in a fuelie. However since you have multec injectors, you probably have a shorted one causing the ECU to shut down the driver,, The test is free and easy.. Take an ohm meter and check the injectors 1 by 1. if any of the readings are 10 ohms or less unhook that injector and see if it starts. If you have several around 10. Its time for injectors. Its preferable if you can get the car to start to check the injectors hot. At least this way you won't be throwing alot of parts and money in the car when the cause is a common thing today.
Safety Car
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From: :45 minutes from everywhere / E-I-E-I-O
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Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
Sounds more like a dead ignition module. You check fuel with a pressure gage - MAP (air) signal with a scanner or DVM on the signal line (and you can wriggle the harness around to make sure there isn't an intermittent) - and then spark by removing a plug and grounding the electrode while someone cranks it or pickup a tester that you can simply touch to a wire to see if any juice is flowing.
Supporting Vendor
Joined: Mar 2008
Posts: 1,762
Likes: 14
From: Cumming Ga
We have a video on this. But, an injector with a dead short will feed the 12 volts back to the driver in the ECU through the ground circuit (not chassis ground) back into the ecu. To make it real simple. There is always 12 volts at the injectors on 1 side. the other side is hooked up to a wire that goes into the ecu. When the ecu calls for a pulse the driver which is basically a switch, connects that wire to ground and the injectors fire. It the injector has a dead short the full 12 volts goes through the injector into the driver. The ECU will not operate if this occurs. By disconnecting that short the car should start. In the 30 years doing this injectors never shorted (or very rarely) so this diagnoses is not common. Untill the multecs started to fail. Upon taking apart bad injectors we noticed that the coils were wet and corroded. Further research revealed that the epoxy seal inside the injector was disolved by alcohol or other additives causing fuel to penetrate the coil housing and causing the short. Thats why eventually all multecs will self destruct. (89-93) Delco even said back in the late 90's advising dealers not to clean injectors with any alcohol based solvents. Of course no one really paid attention.
