1974 1.8L FI Vacuum hoses? Options

[JeffBowlsby]

This is what it should look like if the second vacuum line is not on the TB.

A short three inch piece of tubing going no where connected to the advance port of the distributer. do not cap the port. This is the way they came from the factory.

Hey Pete...thats exactly the same diagram that initiated this thread because of the conflict I noticed between it and the diagram in the first post. I am told the diagram in the first post is correct, please read post in this thread. I deleted the diagram you posted because of the comments by people here who know more about it than I, to avoid future confusion.

[zonedoubt]

A short three inch piece of tubing going no where connected to the advance port of the distributer. do not cap the port. This is the way they came from the factory.

Are you sure? I think the vacuum from the TB should pull on the advance port of the dizzy can. I'm confused. (IMG:style_emoticons/default/confused24.gif)

[Cap'n Krusty]

There are some disturbing errors throughout this thread, and they need to be addressed.

MY 1974 and MY 1975 1.8 equipped 914s sold in the US were all equipped with L-jet electronic fuel injection. There were NO 1973 MY 1.8s, nor were there any 1976s. None were equipped with D-jet EFI. All 1.8 L-jet engines were equipped with dual vacuum controlled distributors, and with dual vacuum port throttle bodies. None were equipped with vented cylinder heads. As the vacuum retard function of the distributor is required for both ignition timing and control of the idle speed, none were vented to the atmosphere, and all used the vacuum advance function, as well. Because starting and running in an L-jet engine depends on ALL the intake tract air passing through the air flow meter (AKA "air mass meter" or "air box"), the system is sealed. Common leaks, which will prevent the engine from starting, are loose, cracked, or disconnected hoses and fittings, missing or damaged oil filler gaskets and o-rings, and loose or damaged valve cover gaskets. The 2.0L 912E induction system shares all the characteristics of the L-jet equipped 1.8L cars. L-jet equipped 914s are unique in that they're the only 914s to require the timing to be set at idle, and there's a specific procedure for doing so.

The Cap'n

[zonedoubt]

I have seen several Ljet equipped engines with the single vacuum throttle bodies, including the one I own. I have read that sticky throttle valves were common. So perhaps replacement was often done with the more readily available single vac TB. I only say that because I found it more difficult to source a good used dual vac TB compared the relatively common single vac type.

[pete000]

This seems to be a controversial topic ! (IMG:style_emoticons/default/chowtime.gif)

There are a lot of threads on this over on the Pelican Parts site too.

Here are just a few: (IMG:style_emoticons/default/popcorn[1].gif)

http://forums.pelicanparts.com/porsche-914...-necessary.html

http://forums.pelicanparts.com/porsche-914...1976-2-0-a.html

http://forums.pelicanparts.com/porsche-914...-hose-help.html

[pete000]

There are some disturbing errors throughout this thread, and they need to be addressed.

MY 1974 and MY 1975 1.8 equipped 914s sold in the US were all equipped with L-jet electronic fuel injection. There were NO 1973 MY 1.8s, nor were there any 1976s. None were equipped with D-jet EFI. All 1.8 L-jet engines were equipped with dual vacuum controlled distributors, and with dual vacuum port throttle bodies. None were equipped with vented cylinder heads. As the vacuum retard function of the distributor is required for both ignition timing and control of the idle speed, none were vented to the atmosphere, and all used the vacuum advance function, as well. Because starting and running in an L-jet engine depends on ALL the intake tract air passing through the air flow meter (AKA "air mass meter" or "air box"), the system is sealed. Common leaks, which will prevent the engine from starting, are loose, cracked, or disconnected hoses and fittings, missing or damaged oil filler gaskets and o-rings, and loose or damaged valve cover gaskets. The 2.0L 912E induction system shares all the characteristics of the L-jet equipped 1.8L cars. L-jet equipped 914s are unique in that they're the only 914s to require the timing to be set at idle, and there's a specific procedure for doing so.

The Cap'n

If this is the case why do so many 1.8 L-Jet engines only have one port on the TB? Were they swapped out for some reason? how do you get vacuum to both sides of the distributer with only one vacuum port on the TB?? (IMG:style_emoticons/default/popcorn[1].gif)

This is interesting....

[pete000]

After Jan 1 1974 the vacuum advance was discontinued so there was no port at the back top of the throttle body but one remained sticking up on the advance. The assembly line workers just stuck a small piece (about 2.5 inches) of 3.5 line on the port and left it breathing to the wind.

"After Jan 1 1974 the vacuum advance was discontinued "

Does this mean the advance side of the distributer should be vented to the wind or the retard side of the distributer on single port TB cars? I think that is the big question here. (IMG:style_emoticons/default/popcorn[1].gif)

[JeffBowlsby]

We need a 'dog-chasing-his-tail' smiley because thats how I feel right now. (IMG:style_emoticons/default/biggrin.gif)

The question is how to plumb distributor advance/retard for the 1.8 L-jet cars? Lets sort this out, I don't have a 1.8L car so I have nothing to refer to - counting on the 914world braintrust to figure it out. "Jim Hoyland...Clay Perrine...Come to the white courtesy phone please"

We apparently have two different throttle bodies, one with only one port (#1 on non-pressure side of throttle plate) and another with two nipples (#1 on non-pressure side, #2 on the pressure side of the throtle plate).

The distributor vacuum can always has two ports: a 4mm OD advance port (away from dizz) and 5mm OD retard port (towards dizz).

I searched the tech sources I have for answers - 2 different Bosch L-jet manuals, the 1974 and 1975 914 Service and Training manuals, the factory 914 repair manual, Harold T. Glenns manual and a privately authored 912E manual (L-Jet) I found on the internet.

Only the 912E manual has a vacuum hose diagram (below). Note how the vacuum retard port on the vacuum can is shown connected to the single port throttle body in the diagram. Dr. 914 also suggests that the vacuum retard function is the hose that is connected to the throttle body. Another point of reference is the 1974 and later D-Jet cars with only a single port throttle body (which is a 5mm OD port) - the hose is connected to the retard side of the vacuum can for these cars (also a 5mm OD port).

The preponderence of evidence suggests: The vacuum hose on 1.8L single port throttle body (5mm OD) gets connected to the vacuum can retard port (5mm OD)? If so, the second diagram Pete posted would seem to be correct after all.

Can someone with a single port 1.8L throttle body verify the port OD size? Is it 5mm OD?

Does anyone have a 2 port 1.8L 914 throttle body they can check the port OD sizes?

When it is verified, I'll be sure the correct diagram is posted in this thread and on my website for future reference.

(IMG:style_emoticons/default/thumb3d.gif)

[pete000]

Here is a photo of my TB on my 74 1.8 L-Jet I am changing out to a Terry throttle cable at the moment and snapped a picture.

Only has the rearward port and it is 5mm.

Currently I am running the vacuum line to the retard port. I did notice when I purchased this car it would not idle very well when it was cold and it tended to ping a bit. The hose was to the advance port when I got the car and the retard port went to the manifold which I know was wrong. I replaced all the vacuum lines and AAR valve and it seems happier.

Hopes this helps solve this mystery. (IMG:style_emoticons/default/popcorn[1].gif)

[zonedoubt]

Single port on throttle body to distributor vacuum advance. Vacuum retard has hose with open end stuffed out of sight. This is like schematics #1 at the start of this thread.

(If the hose is swapped to the vacuum retard, the engine runs like crap, lurches and sputters under load.)

Note the tee off to the EGR valve.

Throttle body is p/n 022 133 067C.

[zonedoubt]

This is a two-vacuum-port throttle body (p/n 022 133 067A) that I was thinking of trying out to see how things go with the retard vacuum connection. This was pulled from a 1975 1.8L L-jet engine.

[zonedoubt]

This is probably due to some confusion with 2.0L vacuum hose diagram. The throttle body is in a different orientation than a 1.8L engine (vertical vs. horizontal).

This seems to be a controversial topic ! (IMG:style_emoticons/default/chowtime.gif)

There are a lot of threads on this over on the Pelican Parts site too.

Here are just a few: (IMG:style_emoticons/default/popcorn[1].gif)

http://forums.pelicanparts.com/porsche-914...-necessary.html

http://forums.pelicanparts.com/porsche-914...1976-2-0-a.html

http://forums.pelicanparts.com/porsche-914...-hose-help.html

[zonedoubt]

...there's a specific procedure for doing so.

Here it is, courtesy of the Cap'n.

[Cap'n Krusty]

I've worked on the 1.8s since BEFORE they were on the market (prepped some at the school, and replaced a head on one before we sold it) and there have been a couple here at the shop in the past month or 2. Both had dual vacuum, and one is a '75. I don't recall any without it. Later bus engines didn't have dual vacuum, but the timing procedure is different, too.

The Cap'n

[pete000]

After Jan 1 1974 the vacuum advance was discontinued so there was no port at the back top of the throttle body but one remained sticking up on the advance. The assembly line workers just stuck a small piece (about 2.5 inches) of 3.5 line on the port and left it breathing to the wind. There is absolutely NO REASON to plug it as it connects to nothing and does not influence the vacuum system.

What about this statement (see above quote) from Auto Atlanta? (IMG:style_emoticons/default/popcorn[1].gif)

BTW: My engine seems to run just fine with no vacuum advance hooked up???? (IMG:style_emoticons/default/huh.gif)

Here is another quote from Rennlist: (IMG:style_emoticons/default/popcorn[1].gif)

[zonedoubt]

Probably referring to the 2.0L engine. No 1.8L in '76.

What about this statement (see above quote) from Auto Atlanta? (IMG:style_emoticons/default/popcorn[1].gif)

BTW: My engine seems to run just fine with no vacuum advance hooked up???? (IMG:style_emoticons/default/huh.gif)

Here is another quote from Rennlist: (IMG:style_emoticons/default/popcorn[1].gif)

[Dave_Darling]

Check the position of the vacuum fittings on the throttle body. The retard fitting would be "downstream" of the closed position of the throttle body. The advance fitting would be just barely "upstream" of the closed position of the throttle body.

The advance fitting on the distributor is the one that points away from the distributor body; the retard fitting is the one that points back toward the distributor body.

Hook up the advance fitting on the TB to the advance fitting on the distributor, and the retard fitting on the TB to the retard fitting on the distributor. If your TB is missing one of those fittings, leave the corresponding fitting on the distributor open to the air. Or do what the factory did, which is hook up a short piece of hose and run it to nowhere.

--DD

[jim_hoyland]

My '75 1.8 L-Jet has the 2 port throttle body; last year, I installed the Mallory Unilite distributer I got from Tangerine Racing. The unilte does not have a vac can; and, I put rubber boots over the throttle body nipples.

[pete000]

Check the position of the vacuum fittings on the throttle body. The retard fitting would be "downstream" of the closed position of the throttle body. The advance fitting would be just barely "upstream" of the closed position of the throttle body.

The advance fitting on the distributor is the one that points away from the distributor body; the retard fitting is the one that points back toward the distributor body.

Hook up the advance fitting on the TB to the advance fitting on the distributor, and the retard fitting on the TB to the retard fitting on the distributor. If your TB is missing one of those fittings, leave the corresponding fitting on the distributor open to the air. Or do what the factory did, which is hook up a short piece of hose and run it to nowhere.

--DD

Ok let me get this right, if the car came with only one fitting to the TB that would make it the retard fitting. Then the advance fitting on the distributer would then get vented to the air with a short peice of tubing. (No vacuum advance on these cars!)

That would make my diagram correct. (IMG:style_emoticons/default/cheer.gif)

[zonedoubt]

Ok let me get this right, if the car came with only one fitting to the TB that would make it the retard fitting. Then the advance fitting on the distributer would then get vented to the air with a short peice of tubing. (No vacuum advance on these cars!)

That would make my diagram correct. (IMG:style_emoticons/default/cheer.gif)

I think this could only be proven by looking at the position of single vacuum nipple on the TB (i.e. upstream or downstream of the throttle disc).

I kinda think the rear facing nipple is for the advance on the 1.8L. That's how I have mine set up and it runs like poo if I switch it to the retard port on the dizzy diaphragm. So mine basically follows the PP diagram: http://www.pelicanparts.com/914/technical_...4_18FI_diag.htm

I think there is some confusion with the other FI types. If you look at the 2.0L D-jet diagram http://www.pelicanparts.com/914/technical_...4_20FI_diag.htm, the rear-facing vac port on the TB is the retard.