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Fuel Injected Rabbit Slow Start When Hot
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KoMbI19
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PostPosted: Fri Sep 21, 2018 6:13 am    Post subject: Fuel Injected Rabbit Slow Start When Hot Reply with quote

Hey All,

Just bought my first antique FI VW last month, and its been a blast. 1982 Rabbit convertible with 38k on it, nearly mint condition. Runs like a top on the road with a little bit of a rough/low idle that jumps up and down from 800 to 600 RPM every few seconds. Never stalls out, just fluctuates.

Though lately after sitting after a drive anything over an hour I've noticed it cranking longer and longer before catching and firing. Last night it cranked for at least a minute (on and off), foot fully off or fully on the gas, no start, hardly any firing. New cap, rotor, plugs, and leads. I also swapped out the nasty oil soaked air filter and ran fuel system cleaner through it. I'm about to swap out the ignition coil for a higher rated one, and then the fuel filter. That's my next step. Any tips for diagnosing the FI system to rule that out or make adjustments?


Thanks!

-jd
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TDCTDI
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PostPosted: Fri Sep 21, 2018 6:49 am    Post subject: Re: Fuel Injected Rabbit Slow Start When Hot Reply with quote

Probably a vacuum leak. Check intake boots at fuel distributor & throttle body, then for any of the small hoses, listen for hissing sounds. If none can easily be found, you might want to have a smoke test done to see where they're at.
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Butcher
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PostPosted: Fri Sep 21, 2018 7:24 am    Post subject: Re: Fuel Injected Rabbit Slow Start When Hot Reply with quote

I too recommend a smoke test. You'll probably have to pay for that test. I would ask the mechanic to be present when it is done. That way you can see for yourself what needs to be fixed.

Fuel pressure tests should be done too. If you do not know how CIS works, you might as well start reading up.
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KoMbI19
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PostPosted: Fri Sep 21, 2018 7:35 am    Post subject: Re: Fuel Injected Rabbit Slow Start When Hot Reply with quote

My old shop has a smoke test machine, I'll hook it up this weekend and test it. Hadn't considered that.
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ps2375
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PostPosted: Fri Sep 21, 2018 11:01 am    Post subject: Re: Fuel Injected Rabbit Slow Start When Hot Reply with quote

Sounds like the WUR is getting old. It is that thing mounted to the front of the block next to the oil filter flange. They do have remans available (or they used to be, but very expensive). That item was the main reason I converted my last Rabbit to MegaSquirt. Never had a hot start issue again.
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racer23
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PostPosted: Thu Jan 16, 2020 10:13 pm    Post subject: Re: Fuel Injected Rabbit Slow Start When Hot Reply with quote

injectors are leaking when the car sets. look on ebay for a CIS Hot start book.
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volksworld
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PostPosted: Fri Jan 17, 2020 8:02 am    Post subject: Re: Fuel Injected Rabbit Slow Start When Hot Reply with quote

i agree on the warmup regulator...but you need the proper pressure gauge setup to test it...injector seals dry out on these engines and cause vacuum leaks...you can pull the injectors (little puller hook shouldnt be expensive) and raise the plate on the air cleaner housing under the big rubber boot (pump relay jumped) to check your spray pattern and see if they drip when closed( disclaimer...dont set yourself on fire)...the tolerances on CIS stuff is very precise and dirty fuel can really screw things up... iirc there was also a check valve on the nose of the fuel pump that held pressure in the system on shutdown so the fuel wouldnt boil off in the lines and make starting hard...you basically need the same gauge as i mentioned before for the wur....a varying idle speed is usually a lazy oxygen sensor taking too long to react so the idle goes up and down as it makes the mixture too rich, too lean....get a bently book as it has the FI troubleshooting procedures...compression test wouldnt hurt either....iirc thats still a solid lifter engine and since adjustment required a couple special tools and a shim kit it didnt get done by an average owner...you also need a duty cycle meter (some old dwell meters will work) to adjust the idle mixture properly....but if everythings working properly you can pretty much adjust the CO by ear with the 02 sensor disconnected...fixed a ton of these cars but my major problem was that bosch discontinued virtually everything you needed to fix them during the recession and i never found a reliable source for rebuilt stuff
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Butcher
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PostPosted: Fri Jan 17, 2020 8:11 am    Post subject: Re: Fuel Injected Rabbit Slow Start When Hot Reply with quote

Looking at the OP original post, he's probably got it resolved or sold by now.
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volksworld
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PostPosted: Fri Jan 17, 2020 7:00 pm    Post subject: Re: Fuel Injected Rabbit Slow Start When Hot Reply with quote

damn...cant believe some other fool answered a year and a half later and i never noticed the date....i really hate when that happens
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