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Bosch CIS injection system: Swapping for B-18 manifold and SU carburetors

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  • Bosch CIS injection system: Swapping for B-18 manifold and SU carburetors

    I recently accepted custody of a pristine, low mileage '74 145 wagon with the original Bosch CIS injection system. From the prior mechanic's notes, the cold weather module was not working, and until colder weather set in here in NW Illinois, it all seemed fine, if suffering from a little hesitation on launch. Now, with weather regularly below freezing, the misfire on one cylinder, and stumble at lower speed. It's driveability is affected now. Other findings: the plug insulators are all running silver-gray white, fuel economy is running 15 mpg in around town driving (on unblended premium), and, perhaps related, the B & W automatic is hanging in low unless I drop the gas pedal to drop revs and raise vacuum. Should I be looking for a vacuum leak? By the way, my notion of solving this is to remove all the CIS equipment and replace it with earlier B-18 manifold and SU carburetors.... Anyone with related issues or insight on where to look? Thanks, Tim

  • #2
    I've got time to kill, so I'll give you a long, way too involved answer.

    I'm a teacher, so I have summers off to play around and try different things on my car. I often go back and forth between the D-Jet and SU's on my 1973 145. Here's a little bit about my experience.

    The Bosch D-Jet

    You're right to suspect vacuum leaks any time you have drivability issues because the D-jet is very sensitive to manifold vacuum, but there's more to it than that. Rather than risk sounding like an idiot offering too much advice for a problem I have not seen in person, here's a link to the D-jet fault tracing and repair handbook: http://volvo1800pictures.com/documen...lt_tracing.pdf. Take a look because the cartoon drawings and short explanations make It the Holy Grail for this sort of thing. It's how I figured out the D-jet on my car. You probably already know about this one, but here's a link to https://jetronic.org/en/d-jetronic, which has helped me solve a few problems over the years. For what it's worth, I bet you can get the D-jet on your car working in no time. I say this because it's a lot simpler than it at first seems. When I first got my 145 I felt like the whole engine bay was just wires and hoses all over the place. I was going to give up and just replace all of it with a Weber. Now I can rip the entire thing out and throw it on the garage floor to clean because it's more comfortable to do it that way, and I know where every single wire and hose goes when I put it back together. In other words, if I can figure it out, anyone can. Fixing your D-jet will probably cost you a few bucks: $100 for random hoses, just replace them! $100 for txl wire, some flexbraid, and connectors. Less than $100 for the one part that needs replacing, but it's probably just a broken wire on your 5th injector - I'm being a little funny here because most problems really are cheap and simple but tedious. So you might spend $300 to fix it.

    The SU carbs

    The SU's are beautiful little carbs, as in they look great! They did not come on our 145's, but any engine looks classically beautiful with a pair of these sitting on top with their neat little tilt. The turds will give you a hard time for wanting to do this swap, but if you like the carbs, go for it. Here are a couple things to keep in mind if you try to snag a set. 1) your exhaust manifold will not match your intake, so you'll need to get the carb manifold too or fab up some special washers. This link will show it a lot better than I can explain it: https://www.sw-em.com/manifolding_no...anifold_washer. 2) the SU's you get will probably have loose butterfly shafts, which will prove to be the bane of your life. This is just something that happens over time, and it leads to all kinds of drivability issues, so people give up on them and sell them on ebay. You'll have to get someone to ream out the old shafts, and that's no fun after you just paid $150 on ebay. I snagged a set off ebay with the manifold and linkage. I drove them for a semester, but then I had to pull them off because the car would not idle. I rigged them over the summer and had to pull them off again mid-year because of reliability. Now they are in a box while I decide if it's worth paying someone to ream out the shafts or I figure out how to do it right myself. Expect the cost to go something like this: $150 for the cabs, intake, and a few parts in a bundle on ebay. $125 for the rebuild kit. $200 for stupid little things you didn't know you needed. $200 for someone to ream out the shafts. This would put you at $675.

    The Weber

    You didn't ask about the Weber conversion, but I thought I'd put it out there. I'm talking about the entry-level 2bbl, not the big DCOE, but the cheap 2bbl is a pretty practical solution because it will cost you about the same as a set of SU's after you rebuild them. I'm totally down with this option, and I even came really close to buying one of these kits to replace my D-jet, but it just didn't feel right. For one thing, I can't get over how clunky the square manifold and carb look. More importantly, I couldn't bring myself to dish out $600+ all at once. It doesn't hurt as bad when the parts bleed you dry little-by-little, but those big purchases are hard to stomach. With all that said, if you just want to have the thing running so you can cruise worry-free, the Weber is probably the best choice. If you go with the Weber, you can take your time and learn about the D-jet when it's convenient.

    Comment


    • #3
      Originally posted by Jrv6a View Post
      I've got time to kill, so I'll give you a long, way too involved answer.

      I'm a teacher, so I have summers off to play around and try different things on my car. I often go back and forth between the D-Jet and SU's on my 1973 145. Here's a little bit about my experience.

      The Bosch D-Jet

      You're right to suspect vacuum leaks any time you have drivability issues because the D-jet is very sensitive to manifold vacuum, but there's more to it than that. Rather than risk sounding like an idiot offering too much advice for a problem I have not seen in person, here's a link to the D-jet fault tracing and repair handbook: http://volvo1800pictures.com/documen...lt_tracing.pdf. Take a look because the cartoon drawings and short explanations make It the Holy Grail for this sort of thing. It's how I figured out the D-jet on my car. You probably already know about this one, but here's a link to https://jetronic.org/en/d-jetronic, which has helped me solve a few problems over the years. For what it's worth, I bet you can get the D-jet on your car working in no time. I say this because it's a lot simpler than it at first seems. When I first got my 145 I felt like the whole engine bay was just wires and hoses all over the place. I was going to give up and just replace all of it with a Weber. Now I can rip the entire thing out and throw it on the garage floor to clean because it's more comfortable to do it that way, and I know where every single wire and hose goes when I put it back together. In other words, if I can figure it out, anyone can. Fixing your D-jet will probably cost you a few bucks: $100 for random hoses, just replace them! $100 for txl wire, some flexbraid, and connectors. Less than $100 for the one part that needs replacing, but it's probably just a broken wire on your 5th injector - I'm being a little funny here because most problems really are cheap and simple but tedious. So you might spend $300 to fix it.

      The SU carbs

      The SU's are beautiful little carbs, as in they look great! They did not come on our 145's, but any engine looks classically beautiful with a pair of these sitting on top with their neat little tilt. The turds will give you a hard time for wanting to do this swap, but if you like the carbs, go for it. Here are a couple things to keep in mind if you try to snag a set. 1) your exhaust manifold will not match your intake, so you'll need to get the carb manifold too or fab up some special washers. This link will show it a lot better than I can explain it: https://www.sw-em.com/manifolding_no...anifold_washer. 2) the SU's you get will probably have loose butterfly shafts, which will prove to be the bane of your life. This is just something that happens over time, and it leads to all kinds of drivability issues, so people give up on them and sell them on ebay. You'll have to get someone to ream out the old shafts, and that's no fun after you just paid $150 on ebay. I snagged a set off ebay with the manifold and linkage. I drove them for a semester, but then I had to pull them off because the car would not idle. I rigged them over the summer and had to pull them off again mid-year because of reliability. Now they are in a box while I decide if it's worth paying someone to ream out the shafts or I figure out how to do it right myself. Expect the cost to go something like this: $150 for the cabs, intake, and a few parts in a bundle on ebay. $125 for the rebuild kit. $200 for stupid little things you didn't know you needed. $200 for someone to ream out the shafts. This would put you at $675.

      The Weber

      You didn't ask about the Weber conversion, but I thought I'd put it out there. I'm talking about the entry-level 2bbl, not the big DCOE, but the cheap 2bbl is a pretty practical solution because it will cost you about the same as a set of SU's after you rebuild them. I'm totally down with this option, and I even came really close to buying one of these kits to replace my D-jet, but it just didn't feel right. For one thing, I can't get over how clunky the square manifold and carb look. More importantly, I couldn't bring myself to dish out $600+ all at once. It doesn't hurt as bad when the parts bleed you dry little-by-little, but those big purchases are hard to stomach. With all that said, if you just want to have the thing running so you can cruise worry-free, the Weber is probably the best choice. If you go with the Weber, you can take your time and learn about the D-jet when it's convenient.
      This is the kind of content I love to see.
      Customer Service guy | [email protected] | 800-444-6473 ext. 181

      Comment


      • #4
        Good afternoon, JRV6a! Thanks very much for the substantive reply! Sorry for the very delayed acknowledgement - we had a really miserable snowfall, Karen had a cataract removed, and there's all the reading from Christmas books to catch up on.

        In my earlier life, like waaaay earlier, I lusted after DCOE's for my mildly tuned Fiat twin-cam, in part because they looked like they'd sound really awesome with the engine up on the curve, and because there was nothing more tune-able.. Time, money and lack of opportunity precluded such an exotic "fix" for a car that's probably long since been turned into nails and re-bar. I didn't really consider such a thing for my workaday 145 for maybe more than a minute, and the IPD replacement downdraft Weber for maybe two minutes. I didn't do as well as you did on eBay, but came upon a set of SU's that are in better condition than I deserve, for a price that was a shade over $300, and a decent manifold for $80. I'm going to have to do some head-scratching on the cable to linkage throttle conversion.

        I'd read through the Bosch manual enough to see that I could probably put the injection system (more) right than it is, but I'm an old guy that's lately taken a skeptical view of modernity, at least of the automotive kind post-1970, which is also when I graduated high school, for background. Come to think of it, as much as I appreciate e-mail and eBay, I'm having second thoughts about those improvements, too...

        But, be all that as it may be, I'm enamored of the SU solution, am well aware of how all the little bits add up in such a conversion; yet, in pursuit of mechanical simplicity, will pursue the install of the SU's. They're tagged as AUD 252 R and E, and have new jets and fuel tubes and float valves. They'll need different needles, as the ones they have don't seem to have the same taper, and aren't the ones in the spec sheet, but, the throttle shafts are snug with just enough play to operate, they're clean and all the other replaceable bits have been replaced. I will be mindful of shaft play going forward, but I'm only driving the car (my only car) some 10,000 miles a year, tops (my other motor vehicle is a workmanlike '72 Bonneville 650 twin, which should validate my earlier self-observation re modern machinery), so I expect they'll last as long as I care.

        I also appreciate your point about making sure the mounting plane between intake and exhaust manifolds on the studs is parallel. Also, some 20-ish years ago, my daily driver was a '67 122 sedan with the SU's, and I was able to keep them sync'ed and tuned, just like dealing with dual carburetors on a variety of Japanese motorcycles. I used to enjoy the satisfaction of tinkering such things into just right-ness. We'll see if I still do a couple of weeks hence....

        It's time to walk the dog, but I'll be getting back to the nitty gritty of organizing this over the weekend.

        Thanks, again, very much!
        Tim

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