I removed the solenoid rack/vacuum lines (metal assy) from my 87 TII, I have the twin scroll solenoid hooked up like stock, that was easy but I'm wondering why the fuel pressure regulator line was also connected to the one of the solenoids, is this necessary? Someone has been working on this before because some of the vacuum lines aren't stock, I'm wondering if they had it hooked up wrong. It seems like it could be just hooked up to one of the nipples on the intake manifold near the throttle body.

Anything else I need to keep in mind? ACV, EGR, subzero solenoid, charcoal system are all removed. I kept the BAC, oil metering system and double throttle control (to lazy to remove it).

Thanks for any help, I want to put this motor in tonight, please respond ASAP if you actually have done any of this work.

Thanks,
Jeff
87 TII
93 R1

 

I just hook mine up to a nipple sticking out of the lower intake manifold, under the secondary fuel rail.

 

OK, I thought that would work just fine. Any idea on why it would go to a solenoid?

I don't have a manual, that is why I'm asking this stupid question. There are 5 solenoids, 4 on the rack and near the oil filler neck, do I need any of them besides the twin scroll solenoid?

Thanks,
Jeff

 

The pressure regulator solenoid valve is part of the hot start assist system. Normally, fuel pressure is controlled by the presence or absence of vacuum (27psi with vacuum, 38 without). Mazda has decided, for some reason, that when you start a hot engine, it needs full fuel pressure, vacuum or not. So, for 90 seconds after starting a hot engine, the vacuum is cut off from the pressure regulator, forcing 38psi fuel pressure. After that, operation is normal. My suggestion would be, if you have trouble starting/running a hot engine for the first 90 seconds, try it with the solenoid. Otherwise, don't worry about it, just connect the pressure regulator directly to a vacuum source.

Irv, Keith's dad

 

From my understanding of the system, Irv is correct in that the FPR solenoid is used with the hot start system.. when cranking a hot motor, the solenoid is activated and the FPR sees vacume and fuel pressure is reduced.. This most likely is to help with potential flooding problems from injecting too much fuel.. however once the motor is started, the solenoid is deactivated and you then get full fuel pressure to your injectors..
Many people have said that it is possible to just connect the FPR vac line to a nipple.. however in my opinion I would suggest against that method.. I have had situations where the diaphram in the FPR had torn and fuel was drawn straight through the vac line.. this can cause certain quirks such as poor idle and running rich.. and also provides quite a fire hazzard.. In my opinion I would keep the solenoid in place...

On a side note, you removed all your solenoids.. I am curious as to what you have done with the twin scroll solenoid. Did you wire the twin scroll actuator open all the time, or remove the flapper door in the manifold all together? If you didn't and no longer have the solenoid, then your flapper door will remain shut at all times.. this leads to very quick spoolup times, but also very bad overboost situations.. you are also robbed of alot of power.. the flaper door remains shut, spooling the turbo quicker, you build greater boost, but you are restricting flow.. without flow you are just wasteing the boost..

 

Cris Ng, you might be interested in this post https://www.rx7club.com/vforums/show...threadid=15340 The bottom line is that the solenoid valve is energized all the time(with the exception of hot start). Energized means the valve is open giving a vaccum to the pressure regulator every single moment that you are driving down the road. A vaccum means the regulator is on the low schedule, 28psi all the time until you slam your foot to the floor. When that happens there is no vaccum available which results in the higher schedule for the pressure regulator, about 40psi. You only have the high schedule, 40psi, when there is a high demand. When the engineer got through designing the logicon he took time to design the pressure regulator system, which due to the gene pool he came from, gave us this silly system as described above.

 

Thanks for the great posts!

I kept the twin scroll solenoid and plumbed in like stock, so I should be OK there. This car will be used for auto-x and drags. I know that for dragging I could wire open the twin scroll (or cut it out permanently) but for auto-x I need all the throttle response I can get.

So I'll just run the FPR line to the intake manifold, that should be just fine. As for the fuel leaking into the line from a torn diaphragm wouldn't you have the same problem with the stock system? The fuel would run the path through the solenoid and back into the intake right?

There are vacuum nipples in several places on the upper and lower intake, are the all the same? They look the same and all seem to feed into the primary runners. The ones I'm wondering about are on the lower intake manifold, one between the primary oil metering nozzles and the other is near where the subzero solenoid used to fit.

I would like to use a vacuum nipple on the lower intake to plumb into the FPR to make it easier to remove the upper intake (not forget to reconnect the FPR hose to the upper intake).

Thanks,
Jeff
87 TII
93 R1

 

when the solenoid is energized, vacume comes from the intake manifold, however when it's not energized, it vents through the little round airfilter on the solenoid and doesn't have a path back into the manifold..

 

I should have enough sense to leave this post alone, but..... in my last post I stated things just **** backwards. When the solenoid is de-energized there IS a vacuum supplied to the regulator causing it to go to its 28psi schedule. Under hot start conditions only, the valve is energized causing the vacuum to the regulator to shut off and that causes the regulator to go to the 40psi schedule, for 50 or 90 seconds depending what car you have.. Under everyday driving the vacuum is at the regulator making it go to the 28psi schedule. When you step on the gas the vacuum is no more because you opened the butterflys wide open, therefore the regulator goes to the 40psi schedule until you let off the gas pedal. There is no switching of the solenoid during this procedure. The on/off of the vacuum is singularly the result of the throttle plates opening, not the solenoid opening and closing. Dime get you a dollar that by next week I'll have it backwards again. Anyway turbojeff got it right when he says he's going to just find a vac nipple and hook of. Rid yourself of that useless solenoid. Some days I can't leave well enough alone.

 

I'm afraid you still have it backwards Hailers..
page 4B-84 of the FSM..

The solenoid is NOT energized for 50 seconds after the motor is started... after 50 seconds the solenoid IS energized (I confirmed this on my car as well)

When the solenoid is NOT energized (During the first 50 seconds) air can pass through ports A and B on the solenoid.. since port B is connected to a source of vacume and port A is connected to the FPR, then the FPR is getting vacume and fuel pressure is lowered (Easier to start car when it's hot cause it's dumping less fuel)

When the solenoid IS engergized, air flow through port A is redirected through the tiny air filter on the solenoid.. port B is shut at this point in time..When this occures there is no vacume at the FPR allowing fuel pressures to increase to normal levels

I have confirmed that all of this happens on my 10AE.. so hear lies the problem.. A car that has it's FPR connected to it's solenoid might end up runnign a tad richer at idle due to the increased fuel pressure... however that shouldn't affect things too badley..
Now in a car with the FPR connected straight to a vacume source, her eyou're going to run into some problems..
#1 you are putting alot more stress on the FPR itself causing earlier failure (Torn diaphram).. the FPR is not ment to be seeing upwards of 28inches of vacume, which can be seen at high speed deceleration, nor is it ment to continually cycle from vac/no vac situations during normal driving..
#2 a torn diaphram leads to fuel being drawn into the vacume line and into the motor.. at the very least this will cause rich running problems.. at the very worse this could lead to a fire..

I realize that many people go ahead and install the FPR to a vacume source.. and while some might be lucky and never run into some problems, others have.. Basically your car will run no matter how you hook up the FPR.. it won't leave you stranded on the road (except if it causes a fire) and chances are you won't even notice and diffrence in driveability with it connected or not..

I just thought I would present the other side of the coin

 

Chris NG,

Sorry, but HAILERS is correct. Page 4A-80 of the 1988 FSM for N/A engines states, the solenoid will be energized for 90 seconds when starting a hot engine. This particular solenoid will vent to the little air filter when it is energized. This means that there is no vacuum on the fuel pressure regulator. Page 4A-67 states that when the vacuum line is pulled (a no vacuum state), the pressure is 39 psi. After 90 seconds, the solenoid is de-energized, and vacuum is applied to the pressure regulator solenoid at idle. This causes the pressure to drop to 28 psi. This solenoid will remain de-energized until the car is started again when it is hot. As you state, you need less pressure at idle, more under acceleration. When you accelerate, the vacuum through the still de-energized solenoid will disappear, and you will have high pressure. That is to say, the pressure regulator normally will be subjected to vacuum coming and going 99.99% of the time! This has been verified on my 87 TII, HAILERS TII and NA, and the guy that started the thread referred to in HAILERS earlier post.

So why is this valve even there, you ask? It seems that Mazda engineers determined that the heat of the engine will vaporize fuel in the fuel rails when it is hot. So, they use a 90-second shot of high pressure at idle (I know, it seems backwards) to condense the fuel back out of the fuel rails.

Oh yes, I have port injection in my Pontiac Grand Am, my Oldsmobile Ciera, and my Nissan Maxima. Guess what? They all have a vacuum line going to their fuel pressure regulators, and fuel pressure follows engine vacuum inversely (in my Olds, pressure at idle (22 inches vacuum) is 28 psi, pressure at WOT (no vacuum) is 42 psi. Verified with a pressure guage. As you can see, a pressure regulator on any modern port injection system must be connected to a vacuum port to properly handle fuel delivery, it seems.

Just my 2 cents worth, HAILERS is my bud!!!!

Irv, Keith's dad

 

Shoulda left well enough alone I suppose. But anyway, after writing my earlier post where I realized that I had things backwards just to confirm yet again how it works, I started the engine and pulled the orange plug off the solenoid. Then pulled the vac hose off the pressure regulator. The vaccum was there like it should be, put the plug back on and still a vaccum.. It might be worth stating that several weeks ago I patched a six foot long piece of vac hose between the solenoid and the regulator to the front seat of the car. Went for a ride with the hose in my mouth. Continuous vaccum all the time unless I put the pedal to the metal. Then the vac dissapeared until I let up on the pedal. Did the same with the turbo except that one changed from vaccum to back pressure as I stepped on the pedal. There was no real need to do this since I have a volt meter hooked to the output of the solenoid to the ECU and I could see that there is no change in the output from the ECU except during times of startup, 50 seconds on one car and 90 on the other. At least I've learned from Irv, the father of Keith, the reason for the high pressure on startup. This whole exercise also satisfied my curiosity about a quirk on trying to tune the turbo after a rebuild. I'd start the thing and all would be where i wanted it but then mysteriously the idle would drop a hundred. It was the on/off of the fpr solenoid. creating a minor vac leak for 50 seconds thru the solenoid being energized.

 

will not having the FPR hooked up to any vaccum contribute to bad mileage? Mine is just capped and im debating wether or not to hook it up to the intake.

 

Yeah. Connect it to a source of vacuum. If capped off its regulating in the 37-40psi range all the time. If it goes to a source of vacuum then it will regulate at about 28psi when under vacuum.

 

Hell yes! Any time you're not at WOT you'll be bucketing in far more fuel than is required, lowering milage and ruining part-throttle power and response.
Whoever did that should not be allowed to work on cars. If it was a turbo it could have easily blown the engine. Get a line onto it now.

And next time please start a new thread instead of digging up one from three years ago.

 

lol my bad

but anyway, mine isnt a turbo... and i capped it myself when i removed the emissions... i wasnt aware of its required function at the time :p

all things considered, i swapped this '87 13b into my '83 GSL, and it runs, so i think i did a pretty good job