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Dolly_Dagger
Samba Member
Joined: July 22, 2015
Posts: 57
Location: Bay Area
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 Posted: Wed Jul 29, 2015 12:33 pm Post subject: confused about FI vs carburetor |
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Hi All!
I'm looking at a 1970 Fastback. Yesterday I went to test drive it and noticed that while stopped, it starts to idle roughly and seems close to stalling out. The owners have had the engine and trans rebuilt pretty recently so I was wondering if maybe despite this, the trans could be having an issue or if perhaps its the FI.
I called a couple reputable shops around here and neither will touch fuel injection. They both said they feel like the idle issue is most likely due to the FI system and both recommend a conversion to carb.
I'm confused. I've been trying to do my research and so many Samba folks say to stick with FI but these two known mechanics are both saying to convert.
What's up with that?
I don't know a lot about these cars. I had a 71 bus a long time ago and loved it but it ran well and I didn't do much to it.
I mean, if no one around will work on an FI and I have an FI, without knowledge how am I going to keep her running well while I learn some of the ropes? I was hoping to start out doing some of the work myself and going to a mechanic for the other things (while I learn).
Unless I misinterpreted the conversion and it's not a bad thing?
If you have any advice to give, I'd appreciate it! 
*also, the owners had previously taken it to another mechanic (different than the two above) for FI issues because he will work on it but apparently he's not so great. They don't want to return to him and he has less than stellar reviews. (he's also the one the rebuilt the engine and transmission) |
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Tram
Samba Socialist
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Location: Still Feelin' the Bern- Once you've felt it you can't un- feel it.
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| Posted: Wed Jul 29, 2015 1:04 pm Post subject: |
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Is this a stick shift or an automatic?
The reason your mechanics are trying to convert you to carbs is that they don't want to work on FI- e.g., they don't know how.
Always go through the ignition system before just assuming all issues on a FI car are caused by the FI. The others here will chime in to tell you how many times a "fuel injection" issue winds up being a basic settings problem- point gap, timing, idle speed, valve adjustment...
The hell of it is that if it's NOT a fuel system issue, you'll pay for a carb conversion and have the same issue- only now you have a hacked car on top of it.
How mechanically inclined are you?
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Donnie strickland
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Joined: December 21, 2009
Posts: 2403
Location: Moody, AL
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| Posted: Wed Jul 29, 2015 1:09 pm Post subject: |
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Sigh...
They recommend the conversion because they don't know how to work on the FI. Notice that both of them, without even laying eyes on the car, immediately blamed the FI. It may or may not be at fault, but they can't tell.
There's plenty of info here. The best way to learn is to give a detailed description of the problem, with specific symptoms, and ask for advice. There's lots of FI info in the sticky above, but it can be overwhelming for a first timer. Don't be afraid to ask!
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sjbartnik
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Joined: September 01, 2011
Posts: 5998
Location: Brooklyn
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| Posted: Wed Jul 29, 2015 1:13 pm Post subject: Re: confused about FI vs carburetor |
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| Dolly_Dagger wrote: |
Hi All!
I'm looking at a 1970 Fastback. Yesterday I went to test drive it and noticed that while stopped, it starts to idle roughly and seems close to stalling out. The owners have had the engine and trans rebuilt pretty recently so I was wondering if maybe despite this, the trans could be having an issue or if perhaps its the FI. |
Stop right there. FI is never the first thing to suspect. Check out ignition system first, make sure dwell and timing are correct, make sure spark plugs are gapped properly, make sure plug wires, cap, and rotor are in good shape, make sure valves are adjusted correctly, make sure there are no vacuum leaks.
| Quote: |
I called a couple reputable shops around here and neither will touch fuel injection. They both said they feel like the idle issue is most likely due to the FI system and both recommend a conversion to carb. |
Stay away from those shops. I can't believe that any shop that would recommend such a move could be called reputable. If they are not competent to understand and diagnose the FI system then they are not competent to work on your car, period. Find a better shop. It's not a complicated system. Without even looking at it and checking out the basics there is no way they could assess over the phone that the issue is related to the FI and most likely it's not.
| Quote: |
I'm confused. I've been trying to do my research and so many Samba folks say to stick with FI but these two known mechanics are both saying to convert. |
Don't be confused. They're just wrong.
| Quote: |
I mean, if no one around will work on an FI and I have an FI, without knowledge how am I going to keep her running well while I learn some of the ropes? I was hoping to start out doing some of the work myself and going to a mechanic for the other things (while I learn).
Unless I misinterpreted the conversion and it's not a bad thing? |
The knowledge is here on the Samba. We have lots of people here who know a lot about the FI system, most notably perhaps is Tram who will no doubt be chiming in here.
| Quote: |
*also, the owners had previously taken it to another mechanic (different than the two above) for FI issues because he will work on it but apparently he's not so great. They don't want to return to him and he has less than stellar reviews. (he's also the one the rebuilt the engine and transmission) |
Hmmmm....so the guy who's not so great is the one that built the engine and transmission. But the problem must be in the FI??? Hmmmm....also that would make me wary of the quality of the build of the engine and transmission.
I'm not saying that the FI systems never have problems. There are some known issues, but again it's not the first place you look when trying to troubleshoot an issue.
I will say that if you are going to own an air-cooled VW and pay someone else to do your work/maintenance, I hope you are independently wealthy. Learning to do the stuff on your own is the right move and I'm glad to see you working toward that goal. Lots of people here to help along the way.
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Dolly_Dagger
Samba Member
Joined: July 22, 2015
Posts: 57
Location: Bay Area
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| Posted: Wed Jul 29, 2015 1:19 pm Post subject: |
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You guys are awesome! Thank you so much for responding!
Tram, it's an automatic.
How mechanically inclined am I? That's a tough one. Let's put it this way, with some instruction, I can usually figure it out. But at this point it isn't intuitive at all for me. I get overwhelmed by all the "could be's" and can't figure out where to start.
Donnie, that's so true. I am just surprised that these well known shops would immediately recommend the conversion.
The problem right now is pretty simple. Car is great but when I get to a red light and am stopped, the idle sounds off. It starts to slow and you can hear that and it sputters a little. It shakes a little like it's about to stall but then corrects itself again. When it corrects itself, it's not loud. It does this repeatedly until I push the gas pedal at the green light. It did this even after it was warmed up.
If the car was a person, it'd be an elderly guy with a phlemgy cough trying not to hack loudly in church. (gross, sorry but that's just what came to mind) |
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Erik G
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Joined: October 16, 2002
Posts: 13281
Location: Tejas!
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| Posted: Wed Jul 29, 2015 1:26 pm Post subject: |
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if the car is cheap, and otherwise everything else checked out good, buy it
then follow Tram step by step to the T
then you don't have to worry about "what if's and could be's"
thats what I'd do if I came across a nice 68 auto FI sunroof squareback at a "gotta buy it" price
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Tram
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Location: Still Feelin' the Bern- Once you've felt it you can't un- feel it.
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| Posted: Wed Jul 29, 2015 1:27 pm Post subject: |
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| Dolly_Dagger wrote: |
You guys are awesome! Thank you so much for responding!
Tram, it's an automatic.
How mechanically inclined am I? That's a tough one. Let's put it this way, with some instruction, I can usually figure it out. But at this point it isn't intuitive at all for me. I get overwhelmed by all the "could be's" and can't figure out where to start.
Donnie, that's so true. I am just surprised that these well known shops would immediately recommend the conversion.
The problem right now is pretty simple. Car is great but when I get to a red light and am stopped, the idle sounds off. It starts to slow and you can hear that and it sputters a little. It shakes a little like it's about to stall but then corrects itself again. When it corrects itself, it's not loud. It does this repeatedly until I push the gas pedal at the green light. It did this even after it was warmed up.
If the car was a person, it'd be an elderly guy with a phlemgy cough trying not to hack loudly in church. (gross, sorry but that's just what came to mind) |
Then you're perfect for a FI car. Seriously.
As soon as you start "thinking about things" you're doomed. The FI system is actually so simple most people think it's just got to be way more complicated than it is.
If the car is an automatic, the issue might just be as simple as whoever set it up is unaware that an Automatic has a higher base idle speed than a manual.
I'd get the ignition system checked out first- point gap, timing, and correct idle speed for an Auto- 950 RPM plus or minus 50 at full operating temperature.
Checking and adjusting the valves also can't hurt.
Only after you do the above and also make sure the charging system is putting out 14.1 to 14.5 volts at 2000 plus RPM and you are still having the issue should you follow this chart:
This procedure will help pinpoint your FI problems- unless they're not really FI problems.
Notice how the second to the bottom symptom on the last page, which most closely describes your issue, points you directly to the ignition system....
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Dolly_Dagger
Samba Member
Joined: July 22, 2015
Posts: 57
Location: Bay Area
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| Posted: Wed Jul 29, 2015 1:48 pm Post subject: |
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I wish I was independently wealthy! 
Erik, it's not cheap. The asking price is $4500.
Tram - you are awesome. I'm going to go over this and study and apply all that I can to this instance and see what I come up with.
So, regarding the ignition system...yesterday when I test drove the car they handed me a new looking key and I was totally confused and trying to start it with another older key on their keychain. That's when they told me that the ignition switch is also pretty newly replaced. (it's on the steering column)
Could that play a role in the ignition system? |
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Tram
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| Posted: Wed Jul 29, 2015 2:29 pm Post subject: |
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| Dolly_Dagger wrote: |
I wish I was independently wealthy!
Erik, it's not cheap. The asking price is $4500.
Tram - you are awesome. I'm going to go over this and study and apply all that I can to this instance and see what I come up with.
So, regarding the ignition system...yesterday when I test drove the car they handed me a new looking key and I was totally confused and trying to start it with another older key on their keychain. That's when they told me that the ignition switch is also pretty newly replaced. (it's on the steering column)
Could that play a role in the ignition system? |
By ignition system I mean the system which runs the engine. The switch is either good or bad, pretty much.
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sjbartnik
Samba Member
Joined: September 01, 2011
Posts: 5998
Location: Brooklyn
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| Posted: Wed Jul 29, 2015 4:09 pm Post subject: |
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| Dolly_Dagger wrote: |
So, regarding the ignition system...yesterday when I test drove the car they handed me a new looking key and I was totally confused and trying to start it with another older key on their keychain. That's when they told me that the ignition switch is also pretty newly replaced. (it's on the steering column)
Could that play a role in the ignition system? |
If the electrics turn on when you turn the key and the starter turns on when you turn the key to start, the ignition switch is pretty much good.
When we are talking about the ignition system we are talking about the system that boosts the 12V that the car's electrical system runs on to the 20,000V or so necessary to make a spark jump a gap and thus create a spark capable of igniting the fuel/air mixture in the cylinders, hence ignition system.
If it runs you obviously have spark BUT there are some key parts of the ignition system that need to be adjusted and maintained on a regular basis. First of those is the breaker points which are located inside the distributor. These need to be adjusted every so often to a gap of .016". Then after that's done, the ignition timing needs to be checked and adjusted. These are very basic maintenance operations that you will need to learn to carry out if you are to keep an old VW running. Usually needs to be done every 3000-6000 miles or so. If the points are not adjusted correctly you could get weak spark and the driveability issues that come with that such as stalling, stumbling, misfiring, etc. Also the same can happen if the timing is not adjusted correctly.
It's also important to know that changing the gap of the breaker points changes the ignition timing. So you must check and adjust the ignition timing after any adjustment you make to the points.
Also in the ignition system you have the distributor cap and rotor, both of which could have worn or corroded contacts. You also have the wires that carry the spark to the cylinders which could be in bad condition. You have the ignition coil which is the transformer that steps the 12V up to high voltage. That can also go bad though it's relatively rare compared to the other stuff. Then you have the spark plugs themselves; it's important that the gap between the center electrode and the ground electrode meets specification. Any/all of these things could cause the symptoms you're seeing so you kind of have to go through and make sure everything is in spec.
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Bobnotch
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Location: Kimball, Mi
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| Posted: Wed Jul 29, 2015 7:21 pm Post subject: |
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Yup, check the idle speed. With AT, it should be 850 rpm +- 50 rpm IN GEAR. Everybody seems to miss that part when dealing with idle speed AND Automatic Transmissions (I guess everyone else has a MT car). 
Also, double check the system voltage (at the battery at medium rpms). What you're looking for is 14.1 to 14.5 volts. Anything less than 13.8 replace the Voltage regulator. The FI is looking for a stable voltage above 14 volts to operate correctly. When you start getting below 13.8, the system WILL run rich. 
But I do agree with Donnie, follow Trams instructions to the letter, and that car will run the best it ever has.
The biggest problem with finding a good FI mechanic, is that there aren't any around anymore. Most have retired, or simply don't work on VW's anymore (they do work on Porsches though, as that's where the money is ). This sucks, as the system is pretty damn good, and there are people making parts to keep it around.
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71 Notch ...aka Krunchy; build pics here;
http://www.thesamba.com/vw/forum/viewtopic.php?t=249390 -been busy working
64 T-34 Ghia...aka Wolfie, under construction... http://www.thesamba.com/vw/forum/viewtopic.php?t=412120
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Tram
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| Posted: Wed Jul 29, 2015 8:50 pm Post subject: |
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| Bobnotch wrote: |
Yup, check the idle speed. With AT, it should be 850 rpm +- 50 rpm IN GEAR. Everybody seems to miss that part when dealing with idle speed AND Automatic Transmissions (I guess everyone else has a MT car).
Also, double check the system voltage (at the battery at medium rpms). What you're looking for is 14.1 to 14.5 volts. Anything less than 13.8 replace the Voltage regulator. The FI is looking for a stable voltage above 14 volts to operate correctly. When you start getting below 13.8, the system WILL run rich.
But I do agree with Donnie, follow Trams instructions to the letter, and that car will run the best it ever has.
The biggest problem with finding a good FI mechanic, is that there aren't any around anymore. Most have retired, or simply don't work on VW's anymore (they do work on Porsches though, as that's where the money is ). This sucks, as the system is pretty damn good, and there are people making parts to keep it around. |
Ummmm... all my info says 950 RPM + - 50 for AT...
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Tram
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Location: Still Feelin' the Bern- Once you've felt it you can't un- feel it.
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| Posted: Wed Jul 29, 2015 8:57 pm Post subject: |
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| Bobnotch wrote: |
Yup, check the idle speed. With AT, it should be 850 rpm +- 50 rpm IN GEAR. Everybody seems to miss that part when dealing with idle speed AND Automatic Transmissions (I guess everyone else has a MT car).
Also, double check the system voltage (at the battery at medium rpms). What you're looking for is 14.1 to 14.5 volts. Anything less than 13.8 replace the Voltage regulator. The FI is looking for a stable voltage above 14 volts to operate correctly. When you start getting below 13.8, the system WILL run rich.
But I do agree with Donnie, follow Trams instructions to the letter, and that car will run the best it ever has.
The biggest problem with finding a good FI mechanic, is that there aren't any around anymore. Most have retired, or simply don't work on VW's anymore (they do work on Porsches though, as that's where the money is ). This sucks, as the system is pretty damn good, and there are people making parts to keep it around. |
Yeah, there are. If you can find a mechanic or specialist that deals in Mercedes 3.5 Coupes and Cabriolets, or, better yet a Volvo guy that does P1800S cars a lot... these cars have the exact same injection system (only the Mercedes has twice as much of it! ). If you don't want to do the work yourself, maybe check with someone like this to see if they would be willing to work on your car just for the injection system. Their injector tester machines will work on your car, too. 
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Bobnotch
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Joined: July 06, 2003
Posts: 22431
Location: Kimball, Mi
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| Posted: Thu Jul 30, 2015 9:14 am Post subject: |
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| Tram wrote: |
| Bobnotch wrote: |
| Yup, check the idle speed. With AT, it should be 850 rpm +- 50 rpm IN GEAR. Everybody seems to miss that part when dealing with idle speed AND Automatic Transmissions (I guess everyone else has a MT car). |
Ummmm... all my info says 950 RPM + - 50 for AT... |
Sorry about that, but I was going off my memory (and we know how bad that can be). I do remember wanting about 900 rpms though (that falls on the low end of your numbers, and the high end of mine). 
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Bob 65 Notch S with Sunroof
71 Notch ...aka Krunchy; build pics here;
http://www.thesamba.com/vw/forum/viewtopic.php?t=249390 -been busy working
64 T-34 Ghia...aka Wolfie, under construction... http://www.thesamba.com/vw/forum/viewtopic.php?t=412120
| Tram wrote: |
| "Friends are God's way of apologizing for relatives." |
| Tram wrote: |
| People keep confusing "restored" and "restroyed". |
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Dolly_Dagger
Samba Member
Joined: July 22, 2015
Posts: 57
Location: Bay Area
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| Posted: Thu Jul 30, 2015 12:22 pm Post subject: |
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Thank you all so much. The info here is priceless!
I can actually read and understand what your saying or at least dissect it and work on it in pieces.
There's a lot for me to take in and a lot to learn but my desire to figure it out doesn't detour me. I definitely want to figure out the FI system. I mean, how can I make any decisions about converting it if I have no idea what I'm dealing with?
So again, THANK YOU! |
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Mike Fisher
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| Posted: Thu Jul 30, 2015 12:30 pm Post subject: |
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Tram keeps my FI/AT square running/shifting 'perfect'. 
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sjbartnik
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Location: Brooklyn
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| Posted: Thu Jul 30, 2015 12:39 pm Post subject: |
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| Dolly_Dagger wrote: |
Thank you all so much. The info here is priceless!
I can actually read and understand what your saying or at least dissect it and work on it in pieces.
There's a lot for me to take in and a lot to learn but my desire to figure it out doesn't detour me. I definitely want to figure out the FI system. I mean, how can I make any decisions about converting it if I have no idea what I'm dealing with?
So again, THANK YOU! |
Here's a great basic primer on the fuel injection system.
http://w107.pbworks.com/f/DJetronic.pdf
The FI system used on these cars is manufactured by Bosch and is called D-Jetronic. D stands for Druck which means pressure. Because in this system, pressure in the intake manifold is used as one of the main factors to decide how much fuel to inject. I think if you read through this PDF you will have a much better understanding of the components and how it works.
Also, as you can see from the first page, it was used in several other European cars of the era so as Tram said, mechanics who can work on those cars should be able to work on your FI system too if needed.[/url]
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Bobnotch
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