Conversion back to EFI, from single carb Options

[billd]

I am considering converting my 73 2.0L back to D-Jetronic EFI. The PO converted it to a single 2-barrel progressive carburetor. I have a few questions.

Fuel lines. Currently there is no return fuel line and the PO has run the supply line with 3/8 copper tubing down the right (passenger) side of the car (not through the tunnel). The fuel hose on either end appears to be clamped directly to the copper tubing - no AN fittings.

My thought was to run a second 3/8 copper tube along the same path as the supply tube for the fuel return (sharing grommets). Is this routing reasonable? or should I relocate both tubes back to the tunnel? Is copper a reasonable material for this or should I use SS line? Is it OK to clamp the hose directly to the tube in a high-pressure EFI system? (This doesn't seem like a great idea to me since there doesn't appear to be anything keeping the hose from getting pushed off the end of the tube by fuel pressure). If not, what type of fittings do you recommend? I was thinking of flaring the tube ends and using AN fittings.

Component Locations. I have all of the pieces from the D-Jetronic that was removed: fuel pump, pressure regulator, rails, injectors, throttle body, MP sensor, control module. However, its not clear where they are supposed to be mounted. Can anyone point me to a picture that shows the original locations of these components on a 73. (Its pretty clear where the injectors, rails, and throttle body go, but the other components could be bolted almost anywhere).

Unit testing. While I'm hopeful that everything works, being realistic one or more of these 33 year old components is probably out of spec. For the fuel pump, regulator, and injectors the unit test is pretty simple, but what about the MP sensor, temp sensor, and control unit? Does anyone have an easy way to unit test them?

Thanks much for the help.

[Mueller]

this site has everything needed to learn about the D-Jet related to 914's

D-Jet guru


you'll want to run 2 new lines in the original location, you can buy steel or stainless steel fuel line for only $25 at Summit Racing....you get hit on the side with fuel lines in the current location and you could turn into a BBQ real quick

[lapuwali]

There's a tech article on this site (see the 914 Info tab at the top) about running stainless lines down the tunnel. The only thing I'd comment on from that article is that you don't need to run them nearly as far as Clay did. My car has them stop just as they exit the tunnel at each end, and run longer rubber hoses. You can also flare the ends of the lines to retain hose-clamp'd lines rather than threading them or just roughing them up. All three work, but I prefer flaring.

You can get the braided rubber hose from various places. It will be in metric, not standard, but the 7 and 8mm sizes are pretty close to the usual inch sizes (3/8 and 5/16). If you don't use the braided stuff, be sure to use high-pressure FI hose. D-Jet pressure isn't all that high (25-30psi), but it's more than a carb sees (3-5psi), and blown hoses are not only a fire hazard, they're a messy pain in the ass to replace when they're full of fuel.

[billd]

Thanks for the link to the D-jet Guru site. It has lots of info. I guess you're right about the location of the lines. Its a lot easier to route them down the side, but they are a far less protected. Why SS rather than copper?

[BMartin914]

I would be certain (110%) that the MPS you have is GOOD before you convert back to the D-Jet. Just because you have it doesn't mean it's good - far from it. I have 3 and none hold a decent vacuum and I am trying to figure out what to do to make it run properly. Right now (with a so-so 1.7) it runs too lean and too hot.

These things are a big issue when it comes to these 30-year-old systems.

Just my $0.02

[JoeSharp]

Bill: Check my blog. Ho! And you might find some interseting stuff in the others blogs.
:PERMAGRIN: Joe

[Mueller]

QUOTE (billd @ Jul 14 2005, 05:35 PM)

Thanks for the link to the D-jet Guru site. It has lots of info. I guess you're right about the location of the lines. Its a lot easier to route them down the side, but they are a far less protected. Why SS rather than copper?

ditto on the MPS recommendations....it could become costly and frustrating.

Luckly for you, you are surrounded by a bunch of aftermarket FI "nut'z" so we can help steer you in the wrong direction with ease (IMG:http://www.914world.com/bbs2/html/emoticons/biggrin.gif) (IMG:http://www.914world.com/bbs2/html/emoticons/wacko.gif)

as for fuel lines...a few, (very few) people use copper lines, it can and does work, however there are better materials to use.....sometimes I base what to use by what you see sold for that particular application...I have not seen "copper" lines sold for fuel use by any automotive supply house, plenty of steel (copper coated ironicly), stainless steel and even aluminum.

[Joe Bob]

Solid copper lines will not flex and can crack. s/s lines will flex with the car and not cause a leak. You can also use high pressure rubber with cloth cover German fuel line....

[goose2]

copper for fuel line...bad mojo! copper hardens and gets more brittle every time it flexes even a tiny bit

[billd]

Joe Sharp's blog is very helpful to see where everything goes. A few more questions.

Any easy way to check out an MPS to see if its any good? What is the typical failure mode? Leaky diaphram?

In Joe's blog is the pressure regulator just hanging on the hoses or is it bolted down somehow?

[bd1308]

buy a vaccuum pump, and put a 20PSI vac on the MPS....if it leaks down any its gettign bad....if it drops 1PSI per 10minutes...its bad.

should hold vac preetty well.

[JoeSharp]

Bill: Sorry about some of the pics, I'm praticing to take pics like Andy. The picture of the fuel regulator looks like its floating. Try this one.
:PERMAGRIN: Joe

[Bleyseng]

This is what the Djet set up should look like on a engine.

[scotty914]

you pull a vacumn and about 3 to 5 inches of water is plenty to test with, it should hold it for at least 10 mins

[brant]

my guess is that the previous owner removed the fuel injection and installed the carbs because the injection was malfunctioning.

The prime reason for going over to carbs is because people either can't figure out why, or don't want to spend the money to repair the fuel injection...

so I'm 99.999999% sure one of your F.I. components is bad.

the brad anders site listed above has all of the tests for every single component.

before you put your car up onto the proverbial jack stands, I would test all of the components and get all of necessary parts/pieces you will need.

you don't want to go through all of this only to find that it doesn't run at all when your done. Plus diagnosing problems is tough enough on a job like this when you don't even know if the problem might be a component or a wiring harness, or a relay board or whatever.

brant

[Jakester]

QUOTE (bd1308 @ Jul 14 2005, 08:58 PM)

and put a 20PSI vac on the MPS

20 lbs of vacuum? What planet are you on? (IMG:http://www.914world.com/bbs2/html/emoticons/confused24.gif)

[bd1308]

i said low vac on another thread and i got my ass kicked.


just ignore everything i say, seems to work out better.

[Jakester]

QUOTE (bd1308 @ Jul 15 2005, 09:12 AM)

i said low vac on another thread and i got my ass kicked. just ignore everything i say, seems to work out better.

No butt kicking here - just wanted to clarify that on Earth, atmospheric pressure is nominally 14.69 psi (at sea level). Therefore, a perfect vacuum would equal -14.69 psi or ZERO absolute.

No such thing as 20 psi vacuum on this planet...thus the question about your planet of inhabitance.

(IMG:http://www.914world.com/bbs2/html/emoticons/aktion035.gif)

P.S. I make it a habit of getting corrected around here, too. It's good for the soul to know that I don't know it all.

[Mark Henry]

QUOTE (Mueller @ Jul 14 2005, 10:24 PM)

QUOTE (billd @ Jul 14 2005, 05:35 PM)   ...Why SS rather than copper? ...I have not seen "copper" lines sold for fuel use by any automotive supply house, plenty of steel (copper coated ironicly), stainless steel and even aluminum.

Papco (sp?)...One of the larger hardware suppliers does carry copper fuel line. Even says fuel line in the catalogue.

I use good old steel...cheap, easy to bend (SS can be a bitch to bend) and any FLAPS has it.

Copper has a bad rep, but it's more likely do to poor installation than breakage. If it goes through steel it should have a grommet and make sure to secure it proper. Any material "rubbing" against a sharp or moving part will fail.

[Dave_Darling]

Do you have any records for the car? In particular, was an engine rebuild done sometime around when they went to the carb setup? If so--you may have a camshaft that will not work with the stock EFI system. It's an engine rebuild to change it back to stock, so it's usually not worth it just to go back to stock EFI. (IMG:http://www.914world.com/bbs2/html/emoticons/sad.gif)

--DD