Deceleration Valve Options

[Ian Stott]

This is a very difficult to get item to get! Many have said soaking the existing one in kerosene for a few days will do the trick, have not done that yet as I am still trying to track down a new one. Wondering what the success rate has been with soaking it in kerosene, also wondering would WD 40 do the same thing. Would hate to ruin the one I have, which is original to the car!

Ian Stott
Moncton
Canada

[bdstone914]

@Ian Stott

For L jet or D jet ?
Can you post the number on yours?
Bruce

[Ian Stott]

@Ian Stott

For L jet or D jet ?
Can you post the number on yours?
Bruce

Bosch 022 133551

[Ian Stott]

I thought I would bring this back to the top, as I have not had any response to the soaking the valve in kerosene or WD 40 suggestions. Maybe my title was misleading in that many saw it as looking for a deceleration valve, of course I am looking for one but just as important is the question has anyone does this and what were the results?

Thanks!

Ian Stott
Moncton
Canada

[timothy_nd28]

I was alittle confused reading what you were doing with the decel valve. I haven't heard of people soaking a decel valve before, maybe soaking a aux air valve. I wouldn't think there's much inside a decel valve other than a large rubber diaphragm.

[Highland]

Have you tried turning the adjustment screw to loosen things up then readjusting the decel valve to open at the vacuum setting you want? Maybe blow some air in there to clean out any debris.

[dr914@autoatlanta.com]

we try the wd40 first then buy a used one

[914werke]

[Ian Stott]

we try the wd40 first then buy a used one

Do you have one I could purchase?

Ian Stott
Moncton
Canada

[cary]

I have 2 soaking in kerosene right now. I'll drain, dry and let you know the outcome.

[rjames]

(IMG:style_emoticons/default/popcorn[1].gif)
I’ll be interested in your results.
I’ve got one that leaks but only after driving the car for 15-20 minutes or so. I’d like to keep mine connected as I’ve read they help reduce strain on the MPS but mine is disconnected for now.

[Ian Stott]

I have 2 soaking in kerosene right now. I'll drain, dry and let you know the outcome.

Thanks, I will wait to hear from you!

Ian Stott
Moncton
Canada

[Rand]

I'm curios if you understand why you need it? Why do you think you do?

[Ian Stott]

I'm curios if you understand why you need it? Why do you think you do?

According to the mechanic working on my car it controls the vacuum, so when not working you can have backfiring on deceleration, which I have. Also it is not possible to set the idle correctly with it being plugged. I am sure more knowledgeable people can explain the need for it better than me! I am also pretty confident it is there for a reason or Porsche would have not put it in the car.
My mechanic is an ASE from Belgium, has worked on these cars before emigrating to Canada; until I found him I was on the verge of switching to aftermarket fuel injection.

Ian Stott
Moncton
Canada

[GregAmy]

It doesn't "control the vacuum" (if I understand you correctly); it uses manifold vacuum to open itself, to add un-throttled air to the intake to lean it the mixture on decel to reduce backfire (and excessive emissions) due to a rich mixture.

Modern EFI simply backs off the injector pulse (or shuts off the injectors entirely) when the throttle is closed (as indicated by the TPS) and on engine over-run to lean out the mixture. For whatever reason, D-Jet was not able to do that back then (or maybe they didn't think of it?)

Testing the decel valve is fairly straightforward. With no vacuum on the port, the valve should be closed and you can't blow through it. Adding a vacuum via a Mity-Vac and the valve should open and you can blow through it. As I recall the desired setting for that cutover is 17mmHg?

If you can blow through it when it's off the car, and/or cannot blow through it with vacuum on it, then it's bad and/or out of adjustment. I wouln'dt be surprised if a prior owner danked around with the adjustment...

If it works fine but the cutover vacuum is either too high or too low, then it can be adjusted via that locknut and screw to ~17mmHg.

What are your current symptoms when testing in this manner?

[Ian Stott]

It doesn't "control the vacuum" (if I understand you correctly); it uses manifold vacuum to open itself, to add un-throttled air to the intake to lean it the mixture on decel to reduce backfire (and excessive emissions) due to a rich mixture.

Modern EFI simply backs off the injector pulse (or shuts off the injectors entirely) when the throttle is closed (as indicated by the TPS) and on engine over-run to lean out the mixture. For whatever reason, D-Jet was not able to do that back then (or maybe they didn't think of it?)

Testing the decel valve is fairly straightforward. With no vacuum on the port, the valve should be closed and you can't blow through it. Adding a vacuum via a Mity-Vac and the valve should open and you can blow through it. As I recall the desired setting for that cutover is 17mmHg?

If you can blow through it when it's off the car, and/or cannot blow through it with vacuum on it, then it's bad and/or out of adjustment. I wouln'dt be surprised if a prior owner danked around with the adjustment...

If it works fine but the cutover vacuum is either too high or too low, then it can be adjusted via that locknut and screw to ~17mmHg.

What are your current symptoms when testing in this manner?

Will talk to the mechanic about what you have posted, thanks so much for the info, will keep you posted!

Ian Stott

[Mark Henry]

@Ian Stott

For L jet or D jet ?
Can you post the number on yours?
Bruce

Ljet on a 2056 engine with a #73 WEB cam.

Ian did you get your starting issue sorted out?

[Ian Stott]

@Ian Stott

For L jet or D jet ?
Can you post the number on yours?
Bruce

Ljet on a 2056 engine with a #73 WEB cam.

Ian did you get your starting issue sorted out?

Yes we did Mark, now I can start the car and I let it warm up as it stumbles until I get close to operating temp, then it works nice, pulls strong and smooth. Idle is good if I have been just around town, if I have run it at {hwy speeds plus} the idle is too low and can stall til engine cools a bit. I have never even got close to the m on the temp gauge just so you know I am not abusing it!Thanks to the new heads I think, supposed to run cooler with those.

Ian

[bdstone914]

@Ian Stott

For L jet or D jet ?
Can you post the number on yours?
Bruce

Ljet on a 2056 engine with a #73 WEB cam.

Ian did you get your starting issue sorted out?

Yes we did Mark, now I can start the car and I let it warm up as it stumbles until I get close to operating temp, then it works nice, pulls strong and smooth. Idle is good if I have been just around town, if I have run it at {hwy speeds plus} the idle is too low and can stall til engine cools a bit. I have never even got close to the m on the temp gauge just so you know I am not abusing it!Thanks to the new heads I think, supposed to run cooler with those.

Ian

I checked but did not find that I have any decel valves.
Found this on Brad Anders site

Porsche number 022 133 551 Bosch 0 280 160 102 1.7L 1972 - 1973

1970 -1971 1.7L 914's didn't have a decel valve, because their ECU cut off the fuel flow on overrun.

Bruce

[Ian Stott]

@Ian Stott

For L jet or D jet ?
Can you post the number on yours?
Bruce

Ljet on a 2056 engine with a #73 WEB cam.

Ian did you get your starting issue sorted out?

Yes we did Mark, now I can start the car and I let it warm up as it stumbles until I get close to operating temp, then it works nice, pulls strong and smooth. Idle is good if I have been just around town, if I have run it at {hwy speeds plus} the idle is too low and can stall til engine cools a bit. I have never even got close to the m on the temp gauge just so you know I am not abusing it!Thanks to the new heads I think, supposed to run cooler with those.

Ian

I checked but did not find that I have any decel valves.
Found this on Brad Anders site

Porsche number 022 133 551 Bosch 0 280 160 102 1.7L 1972 - 1973

1970 -1971 1.7L 914's didn't have a decel valve, because their ECU cut off the fuel flow on overrun.

Bruce

Thanks for checking!

Ian