Fuel pressure

wingman · Posted: Mon Sep 01, 2014 8:03 pm Post subject:

Hi Ray,

Sounds like a long way to go but I will try to tackle them one by one.

The device I thought was the deceleration valve only have 2 ports on it. One is connected to a 3 way plastic connectors that has 2 fuel hoses connect to it. The other one is connected to a (vacuum?) hose that has the same size as dizzy vacuum hose. It also has 2 electrical terminals on it. Do you know what's the function of this device? I cannot find the deceleration valve if this is not the one.

Thanks,
Michael

raygreenwood · Posted: Mon Sep 01, 2014 8:38 pm Post subject:

That is the decel valve. It has an in port and and out port. It has a positive and a negative electrical connection. It should go to a 3 way (Y shaped fitting) on the right side of the center manifold. There may also be a 25mm small canister connected in or near it on the left side of the engine. That may have a small bore vacuum line. That is an advance cut off unit. Its purpose is to limit vacuum advance during certain periods like warm up. There may also be a silver control relay nearby and connected to it.

It is odd that you would find this combination outside of certain emmision controlled areas. What is your geographic location? Dont worry....you will get it fixed.....you just have ro work methodically. Ray

wingman · Posted: Mon Sep 01, 2014 10:08 pm Post subject:

I am in bay area, California.

My understanding is that the decel valve should have 3 ports which are connected to fresh air and vacuum sources. Mine only has 2 ports and one of them is connected to the fuel lines.

Thanks,
Michael

raygreenwood · Posted: Mon Sep 01, 2014 10:14 pm Post subject:

Ah!....california.....that explains it. This is a CA vehicle. The electric decel valve itself has only two ports. In emissions control areas like CA there is another wystem that controls advance vacuum to lower NOX emmisions. This combination only comes on late type r in CA with automatic. Can you post a picture even if its to my pm? Its a pain in the backside system but the advance cut off portion is adjustable. Ray

wingman · Posted: Tue Sep 02, 2014 12:09 am Post subject:

I will try to get some picture but it may be hard since it is under the car. Is there a proper way to adjust it? I just screwed the control port all the way in when I connected it. I found an article to adjust the traditional 3 port one:
http://members.rennlist.com/pbanders/djetparts.htm
but since mine is so different I am not sure whether it is the right way to do.

Thanks,
Michael

raygreenwood · Posted: Tue Sep 02, 2014 6:18 am Post subject:

Technically the adjusting point is the same. By that I mean that both the electric and vacuum powered valves should bleed air into the intake at the same volume and at the same time in the engine operation cycle.
However the electric pressure switch that triggers the valve may cause a slightly different effect or delay.

For the moment though.....the main thing is to make sure the decel valve is not leaking or operating at idle or during normal running. The only time the valve should open is when the engine is above 28-3200 rpm and you close the throttle all the way.
Also since we are looking at what may be affecting idle and looking at vacuum leaks.....it is worthwhile to get an o-ring from a 1.8 bus engine (its the only one available and works well) and replace your tb o ring. It commonly leaks and you should check and adjust the TVS (throttle valve switch) if its poorly adjusted it can cause an idle problem.
I will check to see what I can find about the electric decel valve adjustment. Ray

bradself · Posted: Wed Sep 03, 2014 12:07 pm Post subject:

Hijack warning! Ray, I hate to make you repeat yourself but I'd like to ask, what's the reco for a second pump and where would you locate it, in the typical plumbing scheme.

I'm going to flip my DJet pump, which is good, for an LJet pump and filter, but as I recall it needs a stand alone check valve on the return line, is that so??

I just bypassed a leaky cold start injector myself, world of difference in the idle, and hopefully the economy.

Thanks man!

raygreenwood · Posted: Wed Sep 03, 2014 1:15 pm Post subject:

bradself · Posted: Wed Sep 03, 2014 11:01 pm Post subject:

Cool, thank you! To circle back one step, for the sake of speculation, with the DJet pumps the Walbro would go between the tank and the Bosch, correct? And would likely need to be relayed like the Bosch, to kick on briefly at the same time as the Bosch?

raygreenwood · Posted: Thu Sep 04, 2014 5:34 am Post subject:

Yes.
There are lots of other pumps that can work as well and may be cheaper and smaller than that rotary pump. Let me look. It really doesnt take much except that the feeder pump simply needs to be able to supply enough volume that the main pump does not out draw it and make a restriction out of it. Any small amount of positive pressure is plenty. Ray


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