1975 1.8 (L-Jet?) Help!, Vacuum Hoses and Wiring Harness/Components |
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1975 1.8 (L-Jet?) Help!, Vacuum Hoses and Wiring Harness/Components |
Nor.Cal.914 |
Nov 13 2013, 10:37 PM
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#1
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1975 914 3.0SC Group: Members Posts: 1,050 Joined: 28-January 05 From: Weatherford, TX Member No.: 3,523 Region Association: None |
So I've grown tired of the poor and stinky driveability of my carbs and have decided to return to fuel injection. I have a 1975 1.8L, but I purchased another engine for it that was said to be a '75 1.8L as well, but I'm not entirely sure (hence the question mark next to L-Jet in my title). Based off of what I am finding online, it looks to be that it is indeed an L-Jet system. I am new to this system as I got rid of it immediately when I bought the car and haven't seen or touched it since, which was over 7 years ago. I understand how it all works, but I'm having trouble with the connectors, where some things go, and vacuum hoses.
I found a .pdf of a 912 with L-Jet for the vacuum diagram, but it has some smog equipment on it such as an EGR valve and EVAP Charcoal Canister, which I do not have. In this .pdf it also contains a component list of all the things that are used in this system and I think I have all of them. I just dug the whole setup out today so I will have to check on exactly what I have tomorrow, but I'm specifically wondering about where a few things go/are such as the cold start valve (I assume this is attached to the TB or the intake plenum?), thermo time switch (I know I have this but I don't know where it goes), auxiliary air valve (I also know I have this but don't know where it goes), the "temperature sensor II (I have no idea where this is and whether or not my engine has it), and the dual relay which has its own harness (I'm pretty sure the relay I have is junk--the cover is missing and things look tweaked). Next thing I am looking to find is a vacuum diagram for this engine/fuel injection. I have lots of pieces of vacuum line, lots of nipples, and no idea what goes where. I did search on here to find some already posted, but I could only find one for the 1.7/2.0L D-Jet system. Also, is there a simple way to figure out which connectors go where? More specifically, the male and female spade connectors... I can pretty much figure out where most of the connectors go based off of the number of pins and color/shape. I also found a wiring diagram in that 912 .pdf but I am not sure if the wire colors will match to my engine so that's another concern of mine. I greatly appreciate the help and thanks in advance for all information! -Chris |
Cap'n Krusty |
Nov 15 2013, 06:49 PM
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#2
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Cap'n Krusty Group: Members Posts: 10,794 Joined: 24-June 04 From: Santa Maria, CA Member No.: 2,246 Region Association: Central California |
The car will NOT run without thew MAF sensor, AKA the airbox. Cone filters aren't good enough to qualify as junk. Temperature sensor 2 is inboard of the 3/4 intake manifold, beneath the tin. There's a hole in the tin for the wire, and the sensor can be accessed through that hole. The car will NOT run without it, and it has to be properly installed to ensure a good ground. There are used resistor packs available. I have a couple. The most common failure is broken wires. It is worth noting that L-jet as installed on a 914 will NOT run with vacuum leaks. There are 2 very specific rubber gaskets in the oil filler cap that must be there and intact, as well as the cork gasket under the filler assembly and the valve cover gaskets. The rubber intake boot must be free of cracks, too. Timing is set in a manner different from all other Porsches. I probably wrote that up in the classic threads.
Good luck! The Cap'n |
Nor.Cal.914 |
Nov 15 2013, 07:09 PM
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#3
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1975 914 3.0SC Group: Members Posts: 1,050 Joined: 28-January 05 From: Weatherford, TX Member No.: 3,523 Region Association: None |
The car will NOT run without thew MAF sensor, AKA the airbox. Cone filters aren't good enough to qualify as junk. Temperature sensor 2 is inboard of the 3/4 intake manifold, beneath the tin. There's a hole in the tin for the wire, and the sensor can be accessed through that hole. The car will NOT run without it, and it has to be properly installed to ensure a good ground. There are used resistor packs available. I have a couple. The most common failure is broken wires. It is worth noting that L-jet as installed on a 914 will NOT run with vacuum leaks. There are 2 very specific rubber gaskets in the oil filler cap that must be there and intact, as well as the cork gasket under the filler assembly and the valve cover gaskets. The rubber intake boot must be free of cracks, too. Timing is set in a manner different from all other Porsches. I probably wrote that up in the classic threads. Good luck! The Cap'n I know that disabling the MAF will stall an engine so my mistake, what I should've said was is there a way to relocate the MAF or use a MAF from a different car that is something like a 3" housing with a MAF, for example? Are there any cars that use a MAF that will work with these systems? I have other plans for the future that will require removing the air box, if it is possible. I'm pretty sure the temp sensor II is broken then because I was looking through the hole in the tin and could not see/feel anything in there. Is timing set differently than it is with carbs? Please let me know. Thanks! -Chris |
ClayPerrine |
Nov 18 2013, 07:51 PM
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#4
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Life's been good to me so far..... Group: Admin Posts: 15,519 Joined: 11-September 03 From: Hurst, TX. Member No.: 1,143 Region Association: NineFourteenerVille |
I know that disabling the MAF will stall an engine so my mistake, what I should've said was is there a way to relocate the MAF or use a MAF from a different car that is something like a 3" housing with a MAF, for example? Are there any cars that use a MAF that will work with these systems? I have other plans for the future that will require removing the air box, if it is possible. I'm pretty sure the temp sensor II is broken then because I was looking through the hole in the tin and could not see/feel anything in there. Is timing set differently than it is with carbs? Please let me know. Thanks! -Chris Chris, It is not really a MAF (Mass Airflow Sensor), it is a VAM (Vane Air Meter), but that is just me being picky about the nomenclature. (IMG:style_emoticons/default/blink.gif) You have to understand that the L-Jet fuel injection is very primitive in comparison with a current FI system. This even applies to the Motronic on a 911, which is the direct decedent of the L-Jet system. Modern FI you can reprogram the computer for the replacement MAF, and it will work. There is no way to reprogram an L-Jet ECU to accept a different Air Flow Meter. The innards are just discrete transistors, and everything is done with hardware. You would have to know what resistors and capacitors to replace, and then you would have to experiment with the values until you found the one that gave you the correct mixture. My suggestion is to use the Vane Air Meter that came with the L-Jet. It is correctly calibrated for the engine already, and it is very reliable. My wife's 74 914 1.8L has 350,000 miles on it, and she drives it to work every day. It starts and runs in any weather, and other than the old age of the parts causing failure, I don't worry about it. Oh, and don't put one of the crappy K&N rock stopper cone filters on it. They let too much crud into the engine for what you get. Hope that helps. |
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