puma

iTrader: (2)

i just finished my hose job and i found out that i have this solenoid missing. It is the one closest to the firewall on the solenoid rack.

Now i asked this before and someone told me that he don't have it either but i wonder what happens with the two hoses. On my car, the hose goes from the pressure regulator to the engine, is this good? should i put back the solenoid?

thanks a lot for any info

puma

spyfish007

It is the fuel pressure solenoid ..... it is an orange connector? I'll ship it to if you like? I can also tell you how to hook up the lines without it. It is for hot starts mainly.

puma

iTrader: (2)

it is for hot start?

well i don't have that kind of problem, my problem is big hesitation at wot.

StellarZ

I just noticed on my 93 that the previous owner actually bypassed the solenoid that you are talking about. Don't know of the benefits but it is the case on my car and have had no problems. I say leave it off unless someone says ohterwise.

spyfish007

Well what did you do with the vacuum lines attaching to the solenoid?

StellarZ

the vacuum lines are just cut on both sides of the solenoid completely bypassing it. In other words, he apparently started at point A (Pressure regulator) and skipped over point B (Solenoid) and took the vacuum line directly to point C (Somewhere below the upper plenum). I took my upper plenum off and noticed this... so I took everything in the way off just to realize what he had done.

spyfish007

I was asking puma where his were connected .... I guess he should know now where they should be connected!

puma

iTrader: (2)

it is the same thing as him

FD Racer

Is there an Up and/or Down side to bypassing the solenoid?

neevosh

What exactly does it do?

FD Racer

Bump.

Anyone?


Carson,

I know you know the answer to the last two questions

spyfish007

Ok, I'll give more detail ......

From the Mazda manual:
Description:
"This system cancels the vacuum applied to the pressure regulator and increases the fuel pressure during hot engine start-up and for a period immediately following engine start-up. This improves hot starting as well as providing smooth idle." F-111
Operation:
"To prevent vapor-lock during hot restart idle"

*Note: lasts for about 90 seconds after start

Ok, basically it gives more fuel to the engine when hot to prevent vapor lock. Here is general info on vapor lock I swiped off the net:

"At idle, less fuel is being consumed, which means that the ready fuel supply in the fuel rail is exposed to heat for a longer period before it is injected into the engine. Somewhere in the fuel system, probably in the fuel rail and injectors, temperatures are climbing high enough to boil the fuel. And when the fuel begins to boil, vapor bubbles are generated, which cause a loss of fuel pressure. It is this loss of fuel pressure that creates the driveability problems.

Once fuel begins to percolate, the only answer is to wait until enough underhood heat is dissipated and the fuel stops boiling, then try restarting the engine until the bubbles have been bled out, fuel pressure returns, and the engine runs cleanly.

In trying to restart a vapor-locked engine, holding the throttle about three-quarters open may help bleed out the bubbles, pump cooler fuel into the fuel rail faster, and restore fuel pressure. Spraying water from a pump bottle onto hot fuel system components may help cool things down faster, and expedite a restart.

How can you prevent vapor lock in the first place? Lower underhood temperatures by servicing the cooling system and improve airflow by cleaning the condenser and radiator. If you have the option, use non-oxygenated fuel.

And if you must stop for more than five minutes or so with the engine running and A/C on, open the hood to allow hot air to escape."

No big deal if you live up north ... have found ways to dramatically lower the heat under the engine .... have aftermarket ECU that you can tune!! (Haltech is setup to help fight this problem.)

spooledUP7

The fuel pressure solenoid turns the manifold vacuum source off and on to the fuel pressure regulator. In the off position, the regulator is wide open and non-regulating fuel pressure to the injectors. By bypassing the solenoid you are basically eliminating the function or the ability to produce maximum fuel pressure during a non boosting situation. Such as at idle or when any vacuum is present.

By bypassing the solenoid you are controlling the fuel pressure by the condition of the manifold pressure. This is totally the way the pressure regulator works in the first place, and it should not cause any major problems.

I am guessing that mazda wanted to insure that the chance of detonation during hot startups was minimal by turning off the regulator when the thermosensor read above a set value. Pretty smart actually.

FD Racer

Thanks guys, I think i'll decide to disconect it or not after i install my fuel pressure gauge since I should be able to see when the solenoid indeed turns off the signal to the regulator and how it effects my idle and stuff.