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busdaddy
Samba Member
Joined: February 12, 2004
Posts: 51156
Location: Surrey B.C. Canada, but thinking of Ukraine
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 Posted: Tue May 17, 2022 12:29 pm Post subject: Re: Official Fuel injection questions thread |
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Disconnect all 4 injectors, then probe for power at each plug while the key is on, take the green wire off the coil to save the points during all this key on but not running stuff, don't forget to put it back when done.
The test must be done with all the injectors unplugged, if you don't power backfeeds through the other ones coils and all will show power.
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cfroderman
Samba Member
Joined: November 23, 2021
Posts: 29
Location: Avon, IN
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| Posted: Tue May 17, 2022 3:23 pm Post subject: Re: Official Fuel injection questions thread |
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| busdaddy wrote: |
Disconnect all 4 injectors, then probe for power at each plug while the key is on, take the green wire off the coil to save the points during all this key on but not running stuff, don't forget to put it back when done.
The test must be done with all the injectors unplugged, if you don't power backfeeds through the other ones coils and all will show power. |
Thanks to all. Problem fixed and you all contributed greatly. 1 cylinder had a broken wire at the series resistance block. The other cylinder had the FI plug wires pulled away from the connector. Once everything got corrected it runs like a dream. 😎 |
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Maltboy!
Samba Member
Joined: June 17, 2006
Posts: 137
Location: Santa Fe, Texas
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| Posted: Tue May 17, 2022 3:25 pm Post subject: Re: Official Fuel injection questions thread |
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| cfroderman wrote: |
| busdaddy wrote: |
Disconnect all 4 injectors, then probe for power at each plug while the key is on, take the green wire off the coil to save the points during all this key on but not running stuff, don't forget to put it back when done.
The test must be done with all the injectors unplugged, if you don't power backfeeds through the other ones coils and all will show power. |
Thanks to all. Problem fixed and you all contributed greatly. 1 cylinder had a broken wire at the series resistance block. The other cylinder had the FI plug wires pulled away from the connector. Once everything got corrected it runs like a dream. 😎 |
WOOHOO! I love it when that happens. Busdaddy is the expert on these systems. I just chime in because I can't help myself. 
_________________
76 Super Beetle convertible, Ford Chrome Yellow - body-off restoration, 100% of work done by me
59 Beetle convertible, future project - 25,000 actual miles, original interior |
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busdaddy
Samba Member
Joined: February 12, 2004
Posts: 51156
Location: Surrey B.C. Canada, but thinking of Ukraine
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| Posted: Tue May 17, 2022 3:57 pm Post subject: Re: Official Fuel injection questions thread |
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| Maltboy! wrote: |
| cfroderman wrote: |
| busdaddy wrote: |
Disconnect all 4 injectors, then probe for power at each plug while the key is on, take the green wire off the coil to save the points during all this key on but not running stuff, don't forget to put it back when done.
The test must be done with all the injectors unplugged, if you don't power backfeeds through the other ones coils and all will show power. |
Thanks to all. Problem fixed and you all contributed greatly. 1 cylinder had a broken wire at the series resistance block. The other cylinder had the FI plug wires pulled away from the connector. Once everything got corrected it runs like a dream. 😎 |
WOOHOO! I love it when that happens. Busdaddy is the expert on these systems. I just chime in because I can't help myself. |
Hey now!, it's a community thing here, nobody knows it all, everyone encounters new issues now and then and it all adds to the knowledge base. I'm gifted with a good memory on things like this, I've dealt with alot hands on, but much of it also comes from observing others while we work through issues, every one (including you) contribute greatly to solving what was once regarded as witchcraft.
Bet Cfroderman's car is amazing now that it's got 50% more power! 
_________________
Rust NEVER sleeps and stock never goes out of style.
Please don't PM technical questions, ask your problem in public so everyone can play along. If you think it's too stupid post it here
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Maltboy!
Samba Member
Joined: June 17, 2006
Posts: 137
Location: Santa Fe, Texas
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| Posted: Tue May 17, 2022 4:10 pm Post subject: Re: Official Fuel injection questions thread |
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| busdaddy wrote: |
Hey now!, it's a community thing here, nobody knows it all, everyone encounters new issues now and then and it all adds to the knowledge base. I'm gifted with a good memory on things like this, I've dealt with alot hands on, but much of it also comes from observing others while we work through issues, every one (including you) contribute greatly to solving what was once regarded as witchcraft.
Bet Cfroderman's car is amazing now that it's got 50% more power! |
Thanks, but this really is your sandbox. Your time and your dedication are commendable.
Thanks to you another FI beetle has been saved. It's a great system that got a lot of undeserved "shade" because people didn't know how to work on them. It's people like you on this forum who have changed that. Now his car can go 0-60 in under a minute just like it's supposed to! 
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76 Super Beetle convertible, Ford Chrome Yellow - body-off restoration, 100% of work done by me
59 Beetle convertible, future project - 25,000 actual miles, original interior |
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PuddleRainbow
Samba Member
Joined: April 13, 2018
Posts: 288
Location: The Dirtiest Of Jersey
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| Posted: Wed May 18, 2022 11:34 am Post subject: Re: Official Fuel injection questions thread |
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| nice! |
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Maltboy!
Samba Member
Joined: June 17, 2006
Posts: 137
Location: Santa Fe, Texas
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| Posted: Wed May 18, 2022 1:57 pm Post subject: Re: Official Fuel injection questions thread |
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| busdaddy wrote: |
If the harness is bendy enough try swapping the injector plugs and see if the dead cylinders move with the plugs. It's batch fire so, mixing them doesn't matter. |
I always wondered why Bosch designed it that way. It seems odd to have each injector cycle 4 times per combustion cycle. And why not have just one return to the ECU if they all fire at once anyway? It must have something to do with current surges from the solenoids or something like that.
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76 Super Beetle convertible, Ford Chrome Yellow - body-off restoration, 100% of work done by me
59 Beetle convertible, future project - 25,000 actual miles, original interior |
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busdaddy
Samba Member
Joined: February 12, 2004
Posts: 51156
Location: Surrey B.C. Canada, but thinking of Ukraine
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| Posted: Wed May 18, 2022 2:52 pm Post subject: Re: Official Fuel injection questions thread |
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| Maltboy! wrote: |
| busdaddy wrote: |
If the harness is bendy enough try swapping the injector plugs and see if the dead cylinders move with the plugs. It's batch fire so, mixing them doesn't matter. |
I always wondered why Bosch designed it that way. It seems odd to have each injector cycle 4 times per combustion cycle. And why not have just one return to the ECU if they all fire at once anyway? It must have something to do with current surges from the solenoids or something like that. |
Theory is there's a small puddle of gas sitting on the back of the hot intake valve all ready to leap into the cylinder when the valve opens. As for wiring?, don't know, I'm sure it made plenty of sense to schmartypants German engineers at the time, maybe leaving it open to possible future upgrades?.
_________________
Rust NEVER sleeps and stock never goes out of style.
Please don't PM technical questions, ask your problem in public so everyone can play along. If you think it's too stupid post it here
Stop dead photo links! Post your photos to The Samba Gallery!
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Maltboy!
Samba Member
Joined: June 17, 2006
Posts: 137
Location: Santa Fe, Texas
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| Posted: Wed May 18, 2022 3:43 pm Post subject: Re: Official Fuel injection questions thread |
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| busdaddy wrote: |
| Maltboy! wrote: |
| busdaddy wrote: |
If the harness is bendy enough try swapping the injector plugs and see if the dead cylinders move with the plugs. It's batch fire so, mixing them doesn't matter. |
I always wondered why Bosch designed it that way. It seems odd to have each injector cycle 4 times per combustion cycle. And why not have just one return to the ECU if they all fire at once anyway? It must have something to do with current surges from the solenoids or something like that. |
Theory is there's a small puddle of gas sitting on the back of the hot intake valve all ready to leap into the cylinder when the valve opens. As for wiring?, don't know, I'm sure it made plenty of sense to schmartypants German engineers at the time, maybe leaving it open to possible future upgrades?. |
Maybe it had to do with reliability. If it only had one return, then all four cylinders are dead if it quits working due to a bad wire or ECU failure. With separate returns, you can limp home on 3 cylinders. It makes me wonder if it would be possible to tap into another injector circuit if one goes bad.
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76 Super Beetle convertible, Ford Chrome Yellow - body-off restoration, 100% of work done by me
59 Beetle convertible, future project - 25,000 actual miles, original interior |
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busdaddy
Samba Member
Joined: February 12, 2004
Posts: 51156
Location: Surrey B.C. Canada, but thinking of Ukraine
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| Posted: Wed May 18, 2022 4:10 pm Post subject: Re: Official Fuel injection questions thread |
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| Maltboy! wrote: |
| busdaddy wrote: |
| Maltboy! wrote: |
| busdaddy wrote: |
If the harness is bendy enough try swapping the injector plugs and see if the dead cylinders move with the plugs. It's batch fire so, mixing them doesn't matter. |
I always wondered why Bosch designed it that way. It seems odd to have each injector cycle 4 times per combustion cycle. And why not have just one return to the ECU if they all fire at once anyway? It must have something to do with current surges from the solenoids or something like that. |
Theory is there's a small puddle of gas sitting on the back of the hot intake valve all ready to leap into the cylinder when the valve opens. As for wiring?, don't know, I'm sure it made plenty of sense to schmartypants German engineers at the time, maybe leaving it open to possible future upgrades?. |
Maybe it had to do with reliability. If it only had one return, then all four cylinders are dead if it quits working due to a bad wire or ECU failure. With separate returns, you can limp home on 3 cylinders. It makes me wonder if it would be possible to tap into another injector circuit if one goes bad. |
I'm not sure the resistors could handle it, or the transistors in the ECU, hopefully no body has to find out.
Here's some thoughts on limping home just FYI: https://ratwell.com/technical/LimpingHome.html
_________________
Rust NEVER sleeps and stock never goes out of style.
Please don't PM technical questions, ask your problem in public so everyone can play along. If you think it's too stupid post it here
Stop dead photo links! Post your photos to The Samba Gallery!
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VW_Jimbo 
Samba Member
Joined: May 22, 2016
Posts: 9971
Location: Huntington Beach, CA
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| Posted: Wed May 18, 2022 10:30 pm Post subject: Re: Official Fuel injection questions thread |
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The resistors will handle 2 injectors for a short period.
The transistors do not fair so good.
The system is one of the toughest ever designed! I have worked on all of GM 80 & 90s systems, all of Fords 80 -90s systems, all of Chrysler, Mitsubishi, Nissan, Toyota, Renault, BMW, Mercedes, etc, etc. Not one of those other systems was as resilient as VW L jet. The only other system that is, maybe as good, was VW CIS even when they went to CISE. Bullet proof systems!
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Jimbo
There is never enough time to do it right the first time, but all the time necessary the second time!
| TDCTDI wrote: |
| Basically, a whole bunch of fuckery to achieve a look. |
| 67rustavenger wrote: |
GFY's Xevin and VW_Jimbo!  |
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Lost69Convertible
Samba Member
Joined: July 29, 2020
Posts: 447
Location: Rhode Island
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| Posted: Thu May 19, 2022 6:30 am Post subject: Re: Official Fuel injection questions thread |
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| Maltboy! wrote: |
| And why not have just one return to the ECU if they all fire at once anyway? It must have something to do with current surges from the solenoids or something like that. |
I've done my share of voice-coil and solenoid actuator design over the years. Here's my guess. Four parallel circuits/cables, one per injector, reduces the Inductance of each circuit. The precise control of on/off injector timing improves as the Inductance goes down.
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1956 Beetle Ragtop: My Father's car
1969 Beetle Convertible: My first car. I loved it, I lost it, and I never got over it.
1979 Super Beetle Convertible |
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waller
Samba Member
Joined: March 20, 2006
Posts: 332
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| Posted: Sat Jul 02, 2022 1:25 pm Post subject: Re: Official Fuel injection questions thread |
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Hi all,
I'm replacing the fuel filter on my 78 FI Beetle (fuel pump up front). The new filter from Cali Imports has a 7mm connection on the left, but larger on the right. My current right fuel line is also 7mm so I guess I need to change it?
What size is the right line supposed to be?
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busdaddy
Samba Member
Joined: February 12, 2004
Posts: 51156
Location: Surrey B.C. Canada, but thinking of Ukraine
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| Posted: Sat Jul 02, 2022 1:44 pm Post subject: Re: Official Fuel injection questions thread |
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| waller wrote: |
| What size is the right line supposed to be?] |
10mm, 7/16" works in a pinch.
The bigger question is what sort of fuel pump is in there now?, the correct Bosch ones have a 10mm inlet.
_________________
Rust NEVER sleeps and stock never goes out of style.
Please don't PM technical questions, ask your problem in public so everyone can play along. If you think it's too stupid post it here
Stop dead photo links! Post your photos to The Samba Gallery!
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Maltboy!
Samba Member
Joined: June 17, 2006
Posts: 137
Location: Santa Fe, Texas
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| Posted: Sat Jul 02, 2022 3:44 pm Post subject: Re: Official Fuel injection questions thread |
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It looks like the flow arrow is pointing toward the big side. Am I seeing that right? Flow should go from the big side to the small side.
_________________
76 Super Beetle convertible, Ford Chrome Yellow - body-off restoration, 100% of work done by me
59 Beetle convertible, future project - 25,000 actual miles, original interior |
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waller
Samba Member
Joined: March 20, 2006
Posts: 332
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| Posted: Sat Jul 02, 2022 3:50 pm Post subject: Re: Official Fuel injection questions thread |
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| Maltboy! wrote: |
| It looks like the flow arrow is pointing toward the big side. Am I seeing that right? Flow should go from the big side to the small side. |
Im no genius, but I think my filter was on backwards. |
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Maltboy!
Samba Member
Joined: June 17, 2006
Posts: 137
Location: Santa Fe, Texas
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| Posted: Sat Jul 02, 2022 3:52 pm Post subject: Re: Official Fuel injection questions thread |
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| waller wrote: |
| Maltboy! wrote: |
| It looks like the flow arrow is pointing toward the big side. Am I seeing that right? Flow should go from the big side to the small side. |
Im no genius, but I think my filter was on backwards. |
Wait. I'm wrong. It goes the opposite way. Small to big.
_________________
76 Super Beetle convertible, Ford Chrome Yellow - body-off restoration, 100% of work done by me
59 Beetle convertible, future project - 25,000 actual miles, original interior |
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busdaddy
Samba Member
Joined: February 12, 2004
Posts: 51156
Location: Surrey B.C. Canada, but thinking of Ukraine
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| Posted: Sat Jul 02, 2022 4:41 pm Post subject: Re: Official Fuel injection questions thread |
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| Maltboy! wrote: |
| waller wrote: |
| Maltboy! wrote: |
| It looks like the flow arrow is pointing toward the big side. Am I seeing that right? Flow should go from the big side to the small side. |
Im no genius, but I think my filter was on backwards. |
Wait. I'm wrong. It goes the opposite way. Small to big. |
Yes, small side to tank, big side to pump.
_________________
Rust NEVER sleeps and stock never goes out of style.
Please don't PM technical questions, ask your problem in public so everyone can play along. If you think it's too stupid post it here
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waller
Samba Member
Joined: March 20, 2006
Posts: 332
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| Posted: Sun Jul 03, 2022 5:42 am Post subject: Re: Official Fuel injection questions thread |
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| busdaddy wrote: |
| Yes, small side to tank, big side to pump. |
Got it figured out, thanks! |
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plextor
Samba Member
Joined: April 15, 2021
Posts: 104
Location: Texas
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| Posted: Mon Jul 18, 2022 3:42 pm Post subject: Re: Official Fuel injection questions thread |
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OK! New FI tank and hoses etc. from a few months ago. I noticed a gas smell at the latest fill up and found the main vent hose sliced here. The angle it's coming out of the tank definitely means it's going to rub on the bodywork here.
Tank is flush and seated properly, so I'm assuming the angle of that vent nipple is a bit off. Would y'all try and bend it down some, or have another suggestion?
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