Amur_

It's more of a question than an idea.


Does anyone have any ideas on a way to get the FPR to open up (if only for a few moments) after the car is shut off, allowing the fuel rails to depressurize and thereby avoiding flooding?


Practical or not, all suggestions would be appreciated.

RotaryResurrection

iTrader: (8)

Use a vacuum chamber from an FD and a solenoid that will then supply this stored vacuum to the FPR upon shutdown. You'd need an electrical trigger to indicate shutdown condition to the solenoid, though.

OR, just apply throttle on startup or use a fuel cut switch, it's vastly cheaper and simpler.

Amur_

I've been using a fuel cut switch with mixed results. I want to try a different way of taking the bull by the horns, as it were.


I'll try to find a vac chamber. Other than that, I can use one of the solenoids on my emissions rack (now disabled) and adding a switch to the cabin is no big deal...

Given that spare FD parts aren't what I'd call common finds, what else could I use as a vac chamber? What other, more common cars use them?

Aaron Cake

iTrader: (1)

How are you using the cutoff switch? If you allow the car to idle, then actually shut it off with the switch, it works much better then using the switch to unflood the car on the next startup.

Or, you could solve the actual problem. Half the time, it's the injectors. The other half, low compression.

RotaryEvolution

iTrader: (30)

most chevys use a vacuum chamber, my s-10 has one mounted on the RF fender but i don't know if you want something like that cluttering your engine compartment. you could always just make one yourself, all it is is a sturdy canister fully sealed with a fitting on it, you can find a clamp nipple fitting at almost any hardware store, the can could be anything from a large tin soup can(older cars used to use this style for vacuum reservoirs) to a plastic ball.

or if you want to go a little fancier and go for looks and race proven you can buy one at summit or Jegs, american race cars with heavy duration cams like my elcamino had low vacuum so a vacuum canister helps at idle, having brakes is nice sometimes... these stores sell them for race applications.

example:
http://www.jegs.com/cgi-bin/ncommerc...73&prmenbr=361

Amur_

I'm using it to control the power windows.


How do you think I'm using it?



No, it doesn't.

https://www.rx7club.com/showpost.php...4&postcount=16




Neither injectors nor compression is the problem.

https://www.rx7club.com/2nd-generation-specific-1986-1992-17/fuel-sys-wont-depressurize-sec-rail-prob-260464/


Thanks, Karak! (hope the JB Weld holds up for you )


Okay, so for this vac can... after it has discharged, the next time the car is running it will be recharged? Or will an extra action be needed (ie me doing something under the hood) the next time the car is running?

WAYNE88N/A

Considering it takes 40-ish psi of fuel pushing against the spring/poppet to even crack it open, how the heck are you going to fully open it with vac???

RotaryResurrection

iTrader: (8)

Vacuum opens a FPR at idle and light throttle, for lower fuel pressure and delivery. At higher throttle positions and/or boost, it clamps down more and more to increase pressure for more delivery. By showing it vacuum, you force it to open and bypass more fuel.

WAYNE88N/A

I don't think you're following me here, Kevin...The fuel pressures initially crack the FPR open, and are responsible for the primary forces against the spring during operation. Heck, even without the vac connected you're only going to run, what, about 7-10 psi above normal at idle (akin to the hot start assist system). During normal operation the vac (manifold) pressures are used as a reference, a "tweak" on the spring pressures, if you will, not an actuation pressure.

Now, if you look at the OEM FPR (on my car, at least), the vac source feeds the top chamber of the unit. The fuel rail meets at the center of the unit or so, and the return line meets at the bottom. This tells me that the fuel comes from the rail, pushes DOWN on the spring-loaded poppet to exit via the return line, and the poppet is mechanically connected to the vac chamber for the "tweaking" discussed earlier. In other words, applying more vac to the upper chamber would actually CLOSE the FPR, not open it, by "pulling" up on the poppet against its seat.

So, you would actually need about 40 psi of air pressure in that upper chamber (which I wouldn't recommend, lol), to apply the same amount of force that the fuel pressures apply, to crack it open and kill the rail pressures.

My theory

RotaryEvolution

iTrader: (30)

thinking about this the only way it would work effectively is if it starves the engine prior to shut down which would have to be done manually. this is effectively the same as using a fuel cut switch, as said, how are you using the switch?

i have a fuel cut switch installed in my FC and it worked wonders for starting my overhaul. i would flip the switch on for about 2 seconds with the key in the on position then i would turn it off, crank the engine until it fires then after it runs for about 3 seconds flip the switch to the on position and it should work perfect. it works much better if you have a fuel pressure guage installed so you can monitor how the engine is reacting to various fuel pressures.

RotaryResurrection

iTrader: (8)

Oh, you're right, and I know what you're trying to say. I didn't tell him it would *work*, just told him the only way to *try* to make it work

Amur_

Ya bum.






I've been using the switch for both shutdown and startup. But I don't do the 3k+ shutdown at home b/c I don't want to disturb my neighbours.

I wouldn't be asking about this except that the flooding problem makes using my remote starter first thing in the morning a game of chance.


So I'm outta luck on that idea, then?

WAYNE88N/A

Well, you could always experiment, then get back with us, lol...

Let us know how much pressure (or vac) it takes to blow the FPR diaphragm, that kind of thing

RotaryEvolution

iTrader: (30)

not unless you could program a timer for a fuel cut switch, i don't know how well the FPR bypass would work. once the fuel pump is pressurized it can still easily flood out your engine just during cranking alone. once you turn your key on your fuel system is as it was before you shut the engine off. now a question i have, has anyone ever proven that revving your engine to 3k prior to shutdown even helps with flooding on a restart? personally it sounds good but i don't put any stock into it after doing my own tests with the fuel system.

Amur_

Actually I do have a fuel-cutoff device thingy that I got as a gift. But he didn't remember how the wires are supposed to go and he couldn't find the manual.

And I keep forgetting to start a thread about it.

He did say that the device was made in New Zealand/Australia. It's a small blcok box with a red, white and black wire coming out of it and small hole with an inset yellow dial that you turn with a very small Philips screwdriver. The device is supposed to interrupt fuel flow for the first few seconds of cranking.

When I remember I'm going to take pics of it and post a thread. Unless this description rings a bell with one of you...

Amur_

Doesn't this answer that?

RotaryEvolution

iTrader: (30)

didn't notice that, all i have read is people stating that they revv their engine then cut it off, to me that does nothing but if you have fuel cut then revv it then that makes some sense, at least if you still have the fuel rail depressurized while cranking on startup.

Aaron Cake

iTrader: (1)

Lots of people use it to unflood the car after it floods. It's generally best to use it to try and prevent the car from flooding.

I didn't say that it depressurizes the entire fuel system. I just said that it works better then using the switch to unlfood the car.

Based on that information, it looks like whoever cleaned your injectors screwed up. Maybe they damaged the pintle, nicked the seat, etc. Or they may have been damaged upon install. Perhaps dirt got in at some point, as is now wedged between the pintle and the seat?

If compression is good, process of elimination says injectors. Have you tried swapping with a known good set?

HAILERS

If you have a fule cut switch, and kill the engine at idle with it, the RAIL PRESSURE WILL STILL BE AROUND 30PSI for the next fifteen to twenty minutes.

IF you kill the eninge with a fuel cut switch, but rev the engine to say 2-3 grand and go to OFF with it at that rpm and hold your foot to the floor at the same time.......once the engine dies you will see pressure, but it will be in the range of five to ten psi (menory there).

I've done the above with a fuel pressure gauge inline, so don't give me no hassle over it.

It makes sense that if you shut the switch off at high rpm that the FPR will be seeing a pretty large vacuum as it spools down.

Tiers

I've read all the threads regarding this...and I wonder if it is still just the injectors...
I have also read quite a few threads where having injectors cleaned caused more probs. Could it not just be that they are still faulty, I mean in most cases they are 17+ or - year old units with one hell of a run of clicks...There are electronics involved in there workings as well as internal seals etc. I went through a cleaning this summer and 2 of the 6(had extras ) injectors that were "cleaned" actually have a mechanical failure internally tho they flow correctly sometimes. Perhaps depending on who actually does the job, that their scrutiny of the injectors end performance is not as important as collecting the moeny for the job or simply incompetence. You never know. Obviosly new injectors are pricey, so most of us never consider a replaement when a cleaning sounds like a better plan. I have faith in the cleaning process but as I said I had 6 of them done and found myself that 2 were still not up to snuff.


Aaron:
"Based on that information, it looks like whoever cleaned your injectors screwed up. Maybe they damaged the pintle, nicked the seat, etc. Or they may have been damaged upon install. Perhaps dirt got in at some point, as is now wedged between the pintle and the seat?

If compression is good, process of elimination says injectors. Have you tried swapping with a known good set?"



Just a thought, if all other things check out, how about finding another set of known good babys and testing them out?

Amur_

Here's the thing about the injector cleaning, and this didn't get into the original thread.


Once upon a time I decided to get my injectors cleaned. Not b/c there was a problem -> far from it. The engine had NEVER had a flooding problem. In fact, contrary to what almost seems to be rotary law the engine could be started while cold, shut off a minute later, then restarted at any time without a hitch. Every time. I could use the remote starter without a second thought whenever I wanted to.

But I decided to get the injectors cleaned. It seemed like a 'good maintenance' thing to do, plus I was hoping it would finally nix the 3600 stumble that had never quite gone away (and still hasn't completely.)

My mechanic tells me he's about to send off a batch to be done locally. Perfect. I give him mine, and he gives me his spare set (which I was told were fine) so I can continue to drive my car.

His set goes in. And THAT'S when the flooding began.

I decided not to worry about. I'll put my own set back in, that'll be the end of the flooding, back to business as usual is me...

The set comes back, I pay the bill, I put them in, the flooding continues...



I talk to my mechanic, I get a shrug (a surprised shrug,) I give him mine to return and borrow his again.

The flooding continues...

I get mine back with the comment that they were found to be leaking "a little bit" and that they had been redone. I put them in. From that moment to this, the flooding has continued.

The reason I left out that part of the story (the engine flooding on the borrowed injectors) when I posted it was b/c I felt it was important to keep it short and simple. Looking back now ->

There's a shop out in the prairies that's run by a forum member and they do injector cleaning. I'm seriously considering taking one last stab at this and firing my set off to him.

http://www.agt.net/public/nowback/rx7club/injectors/ (56k warning - some big pics on this page)

If there's a problem with the injectors, I'm confident that he'll find it.


Back to the story. The only thing that makes sense to me is that my mechanic's set was leaky, and the shop that cleaned my set either damaged them or just did a lousy job on them. Nothing else comes to mind to account for the flooding problem 'carrying forward' from the instalation of the borrowed set.


The situation now: I shut off the engine, hot, using the FCS. If I try to start the motor again within a few hours with the remote starter (meaning that the car is sitting with the FCS in the ON position) odds are she will flood. If she sits overnight, she'll fire right up the next morning (again using the remote starter.)
For a successful start-up with the motor still hot, I have to use the switch to deny fuel for the first two to three seconds of cranking. Flick the switch on and VROOOM!


Who said anything about depressurizing the entire system? That link describes, and what I've learned myself is that shutting the car off from idle doesn't significantly deter flooding.


None have been available to try. Add to that the assurance that the borrowed injectors were fine and... confusion and annoyance ensures.

In lieu of using a 'known good set,' I think I'd rather send them off to our friend in Alberta for some extra TLC. If there's something wrong, maybe they'll sniff it out.




Yup. I've seen this firsthand. If I go to take the TB off within about a half hour of shutting the motor off, there's a blast of gas when disconnecting the feed from the secondary rail. Last weekend I disconnected the same line after the engine had been off for about 3 hours and there was nothing other than a few drops from the rail...

RotaryResurrection

iTrader: (8)

Amur, is your car low impedance or high impedance? I have a suggest you for you, depending on your answer...

Parastie

My car did the same thing until i got a new battery with slightly higher cranking power.

HAILERS

Sorry to tell you this, but the fuel rail will pressurize to 30plus psi in a heart beat....literally. Just the act of holding your key to START makes the fuel pump come on. It WILL pressurize the rail to thirty plus psi in less than a second. Try it sometime. Put a fuel pressure gauge on your fuel line. Completly depressurize it. Then go to START. I will guarantee you the rail pressure will be thirty psi or better in one second. If there's and doubters out there......get off your bottom and try it for yourself.

And its occured to me why RotaryPerformance recommends to rev the engine to about three grand and turn the key to off. While the engine spools down its causing a vacuum at the FPR. A vacuum at the FPR will cause it to release fuel pressure from the assumed pressure of about 30psi down to 10psi??????15psi??? If someone had a leaking injecotr it seems less fuel would enter the combustion chamber at 10-15psi than 30psi.

Amur_

No idea. She's an s4 NA, if that helps...


How do I find out?