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Question 1.8 L Jet care and feeding assistance

I love to drive my 1.8L car, she's soo tight ooh...but, detailed L jet tuning information seems hard to find. I hope I did not overlook an already established thread about 1.8L. Does anyone have any good info about tuning a 1.8 L Jet, specifically the CO% on the air flow meter? Most books I have don't say much about it. Where should the screw be as a good starting point? It seems to run well no matter where I put that screw. What is a common setting point for the idle air bypass in the throttle body? all vac hoses are new and installed ALMOST per the Pete Klager diagram on the Pelican site. My throttle body only has one vacuum port, not 2 as pete shows it. PKs Diagram shows the distributor adv/ret vacuum lines both going to the 2 ports on the throttle body. WOW, I just read this. I gues what I meant to say was, Help?
Old 04-23-2003, 03:41 PM
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If your TB only has the one fitting, hook that one to the appropriate port on the distributor dashpot. Don't hook up the other port on the dashpot to anything. You can hook a hose to it, but run the hose to nowhere. (That's what the factory or the dealers did to stop people from complaining.) Don't just cap it, the air actually does need to go in and out there when the vacuum retard functions.

The idle bypass on the throttle body should be set to wherever it is that makes your car idle at 900 RPM.

CO spec, as I recall, was 1.5% or 2%. The only real way to set the bypass screw in the air flow meter is to use a CO meter or other good mixture meter.

Some good L-jet info can be found on http://www.type2.com , as the later Buses used L-jet EFI.

--DD
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Old 04-23-2003, 03:49 PM
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1% CO is too lean and will eventually cause heat-related valve problems.
3% CO will only unnecessarily wash the cylinder walls.

Dave is right on with his recommendations.
Old 04-23-2003, 04:11 PM
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thanks guys! Dave, just to be sure my pee brain has got this...the distr vac advance line (points out) goes to the TB. The distrib vac retard line(points to distr center) goes nowhere, unplugged. Si Senor?
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Old 04-23-2003, 05:02 PM
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I always remember it based on the type of vacuum:

Ported = This is vacuum that doesn't exist at idle. It appears when you open
the throttle. It is used for the vacuum advance.

Manifold = This is vacuum at idle. It is used for vacuum retard, decel
valves, and pressure regulators.

VW Folks, have the Factory Service Manual from Bentley Publishers that goes into excellent detail wrt diagnosing L-Jetronic FI. Is there a 914 manual for this type of FI?
Old 04-23-2003, 06:38 PM
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Ratwell, you've got the vacuum right. There's also "ambient", which is taken from the rubber pipe that runs from the air flow meter to the throttle pipe. (Oh, and there is "unmetered" air, which is air that comes direcly into the intake without going through the air flow meter.)

Haynes has some info on 914 L-jet, but not the kind of detail I'm used to seeing in Bentley books. I haven't paid that much attention to the Bus manuals, though... They may be worth a look.

Sean, I think you have it backwards actually. The advance is the line that doesn't get hooked up; the retard still does. Make sure that your throttle body fitting is manifold vacuum and not ported vacuum. In the 914, the ported vacuum shows up only at very small throttle settings--but not at idle.

--DD
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Old 04-23-2003, 08:14 PM
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Ratwell, I apreciated the way you explained the types of vac. I never thought to look up L Jet in the Bently manual. I did not know that the VWs went to L Jet. I only remembered about the D Jet on my 68 Squareback. the vacuum fitting on the TB is "ported" . It is very faint at idle but as soon as I open the throttle, it gets strong vacuum. On the distrib, which is adv and which is retard?
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Old 04-23-2003, 08:32 PM
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Interesting! Usually the single fitting is manifold vacuum...

The adance fitting, the one that should be hooked to ported vacuum, is the one that points away from the distributor body. So it looks like you were right in your earlier note, and I was wrong for "correcting" you!

--DD
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Old 04-24-2003, 07:51 AM
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The trigger to this whole thing was 4 years ago. I built the car from 2 dead cars, a 74 and a 75 fire victim. The original distrib was rusted solid as a rock (fire victim+rain+years of sitting) so I had a 009 sitting around. I put the 009 in and drove it 4 hard 914 years. Besides being dogged on power, it ran great, 25-30 mpg, topped out around 115 mph. I had a vac leak 2 months ago so I figured 4 years was reason enough to pull the motor and freshen it up with seals ect...Went to D&G swap, scored an original 74 1.8L jet distrib, installed it. The car is MUCH quicker at lower RPM but idle adj, timing adv, ret seem a bit quirky, and the parts I have dont match the books. This is why I sought help on this fine BBS. I apreciate yous guys pointing me in the right direction. I looked in my car library last night, I guess I will be buying a Bently manual covering the L Jet years. Does Pelican sell one?
Dave, I had several concusions as a child, hit in the head with a train....do I leave the retard hose hanging? the idle races when I disconect this (while plugging vac source)
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Old 04-24-2003, 08:24 AM
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I just want to get it right. I fear messing this up and burning up my fresh mojo.
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Old 04-24-2003, 08:26 AM
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Look here. You'll find some good FI info.

http://www.914club.com/downloads
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Old 04-24-2003, 12:55 PM
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Quote:
Originally posted by sean_V8_914
I looked in my car library last night, I guess I will be buying a Bently manual covering the L Jet years. Does Pelican sell one?
There is a blue book by Probst that Bentley publishers but it will only contain general descriptions of the system.

Get the green 68-79 Type 2 manual from Bentley. The last section has detailed procedures for testing a L-Jet system using only a VOM and fuel pressure tester. L-Jet is very easy to diagnose.

You can cross reference the Bosch part numbers against the bus FI system. When you get matches you can assume the values will be the same.

Here are links for a how it works manual on the web and VW's workshop diagnostic manual to get you started. You may get enough out of them to avoid buying the mostly bus related Bentley.

Quote:
do I leave the retard hose hanging? the idle races when I disconect this (while plugging vac source)
I'm not an expert on that setup, but it sounds like the idle went up because manifold vacuum isn't present to retard the timing on that particular distributor or worse, you've created a vacuum leak after the AFM (unmetered air).

I've never taken a vacuum can apart but I imagine a single diaphragm inside. If there are two nipples on the dizzy, one has to connect to manifold vacuum. The nipple pointing away from the shaft is the advance as it pulls the plate CCW advancing the cam lobe relative to the points. The other nipple is retard.

Of course this is only if you have a DVDA distributor but mention you've had put in a 009. Which is it?

First the throttle body. Only one nipple means it's advance and you proved this. If you have a DVDA dizzy then you've got to hook up the retard nipple to manifold vacuum somewhere. You need to tee into the pink 5mm hose in Pete's diagram. Either use a 4-way tee or cut the hose and put in another 3-way.

If you still have the 009 then you need to plug the port on the throttle body because there's no vacuum can. That is unless you have the EGR system connected still and/or have a style of air cleaner with an EEC valve. The air cleaner needs ported vacuum to open to allow fumes from the charcoal canister to purge into the intake system when not at idle. The EGR valve is closed at idle so it needs ported vacuum as well.

I don't have a picture of your particular engine configuration so I thought I'd give you all the options.

Last edited by ratwell; 04-24-2003 at 05:47 PM..
Old 04-24-2003, 05:12 PM
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very good link mr woodman. They have the Porsche shop manual up there. GRP.1 engine pdf page 42 gives exact detail about twin vacuum distributor
Ratwell, I have removed the 009 as it performed less favorably at lower engine speeds. My car is a bastard, per Porsche shop manual. It should have a single vacuum distrib. I found a vacuum "T" in my stash and will "T" off of the manifold vacuum for the retard and use the ported TB vacuum for the advance.
thanks to Ya'll, this thread has almost any info a 1.8 L jet owner needs to correctly tune their system .
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Old 04-24-2003, 10:50 PM
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...or a 2.0 VW type II enthusiast
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Old 04-24-2003, 10:53 PM
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Cool. I just received my Mallory Unilite w/vaccum advance distributor and CDI. I'm salivating at the thought of putting in in my engine once I get it put back together.

I think that just about every manual or book related to FI or these cars is available online.
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Old 04-25-2003, 06:59 AM
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I have an L-Jet troubleshooting guide on my web-site http://persweb.direct.ca/aschwenk/earlyefi.htm .

Alfred
Old 04-25-2003, 08:21 AM
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