Intriguing hiccup 76 Fuel injection

[Xevin]

So about 3 months ago Xatie’s 76 fuel injection bus developed an intermittent hiccup. Kinda spooked her. She couldn’t explain it and I couldn’t replicate it after she got home when I drove it. A couple weeks later I drove it 15 miles to a buddy’s house. The hiccup emerged 5 miles into the trip at 4000 rpm. Happened 3 times. At my friends house we checked for good connections plugs, grounds, and etc.
On the way home all was good until a mile from my house when it hiccuped at 3700rpm in 3rd gear as I came off the freeway ramp. WTF. I called Stuartzickfoose about this new issue.
https://www.thesamba.com/vw/forum/profile.php?mode...c788aa3c7c

He thought it was maybe due to the Flamethrower (Pointless) Electronic distributor (PO installed) messing with the ECU signal or something like that. I’ve read about this happening so I was hip to what he was saying.

Side note; I know the PO as do many of you and he had about 20k miles on this engine with the Pertronix.

Oddly my friend Alex daily drives a Champagne FI bus with one of these crappy distributors and has never had an issue like I was having. Although the module did crap out after 30k miles. Stuart suggested I drive the Bus to see if I can replicate the hiccup. So the next day I drive it 30 miles. Sure as shit, It happens again 10 miles in and I feel I can indeed replicate the issue. I got the bus to hiccup twice trying and one time it just did on its own. The next day on the way back home the hiccup became more frequent and for no rhyme or reason. Without me trying. Would happen between 3700-4000 rpm maybe once in a mile.

Side note; It never happened under load pulling a hill regardless of RPM. Nor did it ever happen driving around town. Only on a freeway or long stretch of flat road.

Stuart suggested we go back to points. He’s had a few Clients with similar issues. Sounded good to me. I emailed wcfvw69,
aka Bill to see if swapping points into a Flamethrower body was doable.
https://www.thesamba.com/vw/forum/profile.php?mode...c788aa3c7c

He berated me for running that Chinese POS distributor and sold me an OEM distributor. What a shyster. Kidding of course. Bill rebuilds beautiful OEM distributors with all the nice fixins.

Knowing the Pertronix might not be the cause . I bought the new old distributor to eliminate it from being the issue or issues in the future. Bill sent me this beauty to me.

So finally last Thursday I had some time to dork around with the bus. First I cleaned up the TS2 connection on the mating surface on the case. Wanted to eliminate that from being the issue as Stu has had that be a problem with a few clients. Drove to my friends house 30 miles away. The bus ran great for 10 miles. Then it started to hiccup again. About the same spot as before. The hiccups appeared at about the same spots as before.

Once at my buddy’s house we installed the OEM distributor from Bill. On the way home the bus drove great. I could push it and not get the bus to hiccup as I could in the past. The next day I took the bus to work (30miles round trip) Again the bus ran fantastic, better then ever. It pulled a hill much better then it ever has. So I now have 60 miles on the bus and it’s running terrific. I can’t remember the timing last set with the old Flamethrower but it was inline with spec about 200 miles ago before the hiccup issue. The timing on this new distributor is 28* BTDC and 7.5 BTDC at idle hoses off and plugged. Hoses connected 37* BTDC total and sits back down at 5*BTDC at idle. More miles needed to confirm this was the fix. Will update later. I plan on taking her bus to work more often to see what happens. I will update when I get another 60 miles or so.

Edit: TDC.
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Keep on Busin'

[dstimm]

Bill does good work!
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1979 Sage Green California Westy.

[Abscate]

It's great having the guys in the business reworking real parts as opposed to buying pot metal crap.
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.ssS!

[alman72]

that is some sexy distributor porn. Bill indeed does some nice work.

[SGKent]

you mean 28 BTDC don't you?
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“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin

[Xevin]

[aeromech]

Bills just a girly boy
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[wcfvw69]

[AlmostHeavenWV_VW]

"I love it when a plan comes together"

Strong work, my friend! Gotta keep Xatie happy till Mullet is ready
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1973 Standard Beetle
1600DP AK case
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[Xevin]

Update. I have put 140 miles on the bus since distributor swap. The “Hiccup”
has not returned. Big thanks to Stuart and Bill helping me out with this. Thanks to aeromech for sorting out my dancing tachometer issue after the swap.

Getting ready for a road trip to British Columbia next week. Katie is looking forward to driving her bus

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Keep on Busin'

[mikedjames]

I once put an oscilloscope on the coil power feed of a bus that was hiccuping like that. It would do it even if you opened the throttle when the bus was in neutral.

There was a pulsing, the voltage was dipping about half a volt periodically.
This was due to an electric fuel pump drawing current in pulses, causing the drop.

It had a Pertronix Ignitor in it and this was being upset.

At certain speeds, the beat of the fuel pump speeds up and increases the chance of the supply dipping just at the point the Pertronix triggers.

This wobbles the timing as the adaptive dwell is modulated by the fuel pump current.

Moving the fuel pump positive supply away from the coil positive terminal cured it.

So would using points, but the average British bus owner's idea of maintenance would result in their bus stopping some time later because they and their garage guy know nothing of points these days.
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