 79 VW Bug fuel injection(NPC), Need Help with VW bug fuel injection |
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| BIGKAT_83 |
 Oct 2 2015, 12:54 PM
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#1
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Senior Member  Group: Members Posts: 1,798 Joined: 25-January 03 From: Way down south Bogart,GA Member No.: 194 Region Association: South East States 
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I've got a 25k mile 1979 VW Bug convertible. It starts up fine and runs for just a couple of seconds and then quits.
It does not matter if its hot or cold. Any ideas on where to start? Thanks in advance Bob |
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| Jeffs9146 |
Oct 2 2015, 01:13 PM
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#2
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Ski Bum Group: Members Posts: 4,062 Joined: 10-January 03 From: Discovery Bay, Ca Member No.: 128 |
QUOTE(BIGKAT_83 @ Oct 2 2015, 11:54 AM)  I've got a 25k mile 1979 VW Bug convertible. It starts up fine and runs for just a couple of seconds and then quits. It does not matter if its hot or cold. Any ideas on where to start? Thanks in advance Bob Vacuum leaks. Your cold start injector is firing a squirt to start and the MFI doesn't have enough vacuum to open the injectors. (IMG:style_emoticons/default/idea.gif) |
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| Tom |
Oct 2 2015, 01:14 PM
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#3
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Advanced Member Group: Members Posts: 2,139 Joined: 21-August 05 From: Port Orchard, WA 98367 Member No.: 4,626 Region Association: None |
Put a fuel pressure gage on it and monitor. I bet the fuel pump run after start circuit is not working properly. I believe the old VW's had something close to L-jet injection, so some of the troubleshooting methods would be the same.
Tom |
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| hcdmueller |
Oct 2 2015, 01:49 PM
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#4
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????????????? Group: Members Posts: 542 Joined: 4-February 06 From: UK Member No.: 5,527 Region Association: England
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Definitely L-jet. I retrofitted the same setup onto a Euro Baywindow bus I used to have. Your double relay might be bad or the wiring to the air flow sensor. You can check the fuel pump by pushing the air flow flap on the intake. If the key is on the pump should run. The pump only runs on the double relay while starting. Obviously check for vacuum leaks. The entire alternator stand is part of the intake. You may have some leaks there if the rubber parts of your intake are good.
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| Mark Henry |
Oct 2 2015, 03:30 PM
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#5
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that's what I do! Group: Members Posts: 20,065 Joined: 27-December 02 From: Port Hope, Ontario Member No.: 26 Region Association: Canada |
All of the above, plus Bug FI is famous for cooking the wire harness, it's why so many backyard wrenches would rip off the FI and stick a carb on. Check the condition of the wires and connectors.
Also in your hunt replace the injector seals, while the injector is out take a pin and press on the pintle, you should hear/feel a slight click. |
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| Jake Raby |
Oct 2 2015, 05:07 PM
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#6
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Engine Surgeon Group: Members Posts: 9,394 Joined: 31-August 03 From: Lost Member No.: 1,095 Region Association: South East States |
Could be a dozen things. Verify fuel pressure, and pull an injector to check the spray pattern for starters.
Hook up with the Athens VW Club guys, they are awesome, and have tech days all the time. Sometimes they hang out at my garage. |
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| aircooledtechguy |
Oct 2 2015, 06:21 PM
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#7
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The Aircooledtech Guy Group: Members Posts: 1,966 Joined: 8-November 08 From: Anacortes, WA Member No.: 9,730 Region Association: Pacific Northwest |
I've seen more than just a couple of these where one of the hoses coming off the large rubber elbow between the MAF and the TB popped loose. It will do the very thing you describe.
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| rgalla9146 |
Oct 2 2015, 06:39 PM
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#8
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Advanced Member Group: Members Posts: 4,544 Joined: 23-November 05 From: Paramus NJ Member No.: 5,176 Region Association: None
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The big hose on top is not just a connector to the air filter.
It must be clamped and vacuum leak proof from flapper box to throttle and beyond. |
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| rgalla9146 |
Oct 2 2015, 06:40 PM
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#9
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Advanced Member Group: Members Posts: 4,544 Joined: 23-November 05 From: Paramus NJ Member No.: 5,176 Region Association: None
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The big hose on top is not just a connector to the air filter.
It must be clamped and vacuum leak proof from flapper box to throttle and beyond. |
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| Jake Raby |
Oct 2 2015, 08:01 PM
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#10
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Engine Surgeon Group: Members Posts: 9,394 Joined: 31-August 03 From: Lost Member No.: 1,095 Region Association: South East States |
That hose will bite you!
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| JeffBowlsby |
Oct 2 2015, 09:42 PM
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#11
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914 Wiring Harnesses Group: Members Posts: 8,470 Joined: 7-January 03 From: San Ramon CA Member No.: 104 Region Association: None
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| BIGKAT_83 |
Oct 8 2015, 08:25 AM
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#12
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Senior Member Group: Members Posts: 1,798 Joined: 25-January 03 From: Way down south Bogart,GA Member No.: 194 Region Association: South East States
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Thanks everyone got a chance to work on it today. You guys nailed it a vacuum leak. (IMG:style_emoticons/default/first.gif)
Bob |
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| Chris H. |
Oct 8 2015, 10:14 AM
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#13
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Senior Member Group: Members Posts: 4,027 Joined: 2-January 03 From: Chicago 'burbs Member No.: 73 Region Association: Upper MidWest
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So you bought a Beetle or what (IMG:style_emoticons/default/biggrin.gif) ???
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| Jeffs9146 |
Oct 8 2015, 09:21 PM
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#14
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Ski Bum Group: Members Posts: 4,062 Joined: 10-January 03 From: Discovery Bay, Ca Member No.: 128 |
(IMG:style_emoticons/default/piratenanner.gif) (IMG:style_emoticons/default/piratenanner.gif)
I had the same problem on my 3.0L FI six when I first fired it up so it just made sense! (IMG:style_emoticons/default/beerchug.gif) |
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