linuslove

Since checking for codes is easy and I did it before I just did it again. Tell me if I have done it right. I ran a wire from the small single green connector next to the front leading coil to the negative of my battery. I went in the car and turned the key to "on" and watched the lights like the check engine light and NOTHING AT ALL HAPPENED! Eventually the check engine light just went off like it normally does. This is what happened last time. Does that indicate no codes as I thought I got last time or have a done something incorrectly? If I did this correctly and there was a problem with gas pressure, would take give some sort of code? I would imagine not and I need to preform the gas pressure test with a gauge as you indicated yesterday.

RotaryEvolution

iTrader: (30)

if it just turns off then there is no codes. fuel pressure out of spec won't throw a code. the ECU only monitors the electrical sensors and that's about it.

linuslove

Thanks so so much. Now we have ruled out a lot and left are 1)fuel pressure and 2)fuel injectors. I am going to need help with checking these fuel pressure values and after I get the guage early nect week can you answer in the meantime: I know the line that goes from the fuel filter to the engine that is hard lined. When I remove the hose from the engine, don't I have to clamp it to make sure gas does not leak out before I connect it to the gauge? And, do I also need another piece of hose to hook from the other side of the gauge to the engine and then measure the pressure with engine not running and then with engine running? Or does this guage just have an inlet? I assume it has an inlet and outlet? ALSO, I need to know where the return hose is? And when you say "clamp the return hose" do you mean leave the gauge where it was previously and in addition clamp the return hose so that it is in effect clamped closed and read the gauge at that first location at the hard lined hose?

RotaryEvolution

iTrader: (30)

depends on the gauge if you will need another piece of hose, some come with standard size hoses and others just have a generic fitting to slip hoses onto.

remove the gas cap and you can pinch the line to reduce the amount of fuel coming out when you remove the line, there will still be some so put some rags under the line when you disconnect it. most gauges have a relief port to pour into a cup to relieve pressure before you disconnect it.

leave the gauge on as you would when checking the system and clamp the other hose that goes to the firewall and down at the flex hose from the engine.

linuslove

Hi. Thanks so much. I am a novice at this so although you explained what to do, I do not understand because I am a little confused. All I know is there is a hose coming from my fuel filter going as a main line into the engine. I assume I am supposed to pinch it as hard as I can to prevent any fuel from dripping and pull it off the engine and put it into one side of a fuel pressure gauge that I rent or borrow. Now does the other side of the gauge then get connected via another line back into the engine? Is that the way the gauge gets configured so that I can measure pressure with the car off and with the car idling in an attempt to get the 2 values of 40 and 32 psi respectively?

satch

iTrader: (1)

The gauge has two ends to it so it obviously requires two hoses. You already have one hose running from the filter to the engine so this is but one hose and not two. If it is one hose and it is one hose then you need a second hose. So if the fuel filter connection is point A and the connection to the engine at the other end of the hose is point B then it works as follows. If you disconnect the hose at point A and connect it to the gauge then the gauge needs a hose running from the gauge to the filter. In doing so there is a hose running from the engine to the gauge and another hose running from the filter to the gauge so the gauge finds itself in the middle of the engine and the filter. Now if you remove the hose connected to the engine at point B and connect it to the gauge then you need a hose running from the gauge to the engine. Understand? Just do the simple thing of drawing a diagram where you have a hose already in place running from the filter to the engine and what it would take to place a fuel pressure gauge in the middle of the filter and the engine. You have two choices.

linuslove

Now I have it! It was like pressure reading for dummies, but very well explained and understood! Thanks! Now as far as checking the pressure with car off and with car running. When the car is not running I read the pressure with no key in the car at all correct? Then I try to start it and read the pressure as close to trying to get the rpms to around maybe 500-750 without it stalling correct? Are those my 2 readings?

satch

iTrader: (1)

Engine not running: You need the key to on to power the pump or there will be no pressure and you need to jumper the fuel check connector so when the key is to on the pump will pump.

Engine running: You don't really need to worry about the idle speed when measuring the pressure w/the engine running, just state what the rpm is along w/the pressure reading.

linuslove

Ok, I understand everything except HOW EXACTLY DO I JUMPER THE FUEL CHECK CONNECTOR AND WHERE EXACTLY IS IT?

satch

iTrader: (1)

Post #3 far right pic.

https://www.rx7club.com/2nd-generati...erence-671004/

Take a short piece of wire bare at both ends shaped in a form of the letter U
and each bare end is stuck into the terminal in the plug. The plug is Yellow and covered in a Black boot just like in the pic, found between the engine and passenger fender in the Emission Harness, which feeds the Pressure Sensor that is bolted to the passenger fender. And do not ask what the Pressure Sensor is (post #2 pic #4, yeah the rectangular thing).

linuslove

Amazing! You must have been a teacher of star excellence in another life! I wish I knew what all the sensors were so I could quiz you! I really find your knowledge astonishing! Thanks again. I hope to do this sometime this week; getting the pressure gauge will prove now to be the hardest part! Have a great weekend!

linuslove

My old mechanic had no such gauge and neither did napa nor another place I visited! Amazing! My mechanic showed me how all cars should have a fuel pressure value you can hook up a machine to such that it has a Schrader value and it reads a pressure! I even went on line and saw a few videos of guys hooking up their cars via a single port to a single hose to a gauge and getting a reading. I guess my car has no such place to check fuel pressure. CORRECT? I thought I saw a utube video of a gues with an RX7 that has such a value but it can ot be my year! So I spent the day putting together a gauge and it looks something like this with the difference that I had to buy the guage and fittings separately and assemble it:FUEL PRESSURE GAUGE & ADAPTOR TEST KIT NEW INJECTION | eBay
I jumpered that fuel pump connector that is yellow and turned the key on and got out of the car and watched some fuel spurt because everything was no sealed correctly so I retightened all the connections and did it again and I got around 30-32 psi at rest engine off. I assumed NOT GOOD! Now the gauge and fittings are not leak proof either and the metal tube the gas runs through felt cold and a little wet so I do not know if what I am doing is measuring accurately. Are we 100% sure there is not an easier way to do this OR a guage that I can get to do this more simply? I am a little frustrated as you may guess.

RotaryEvolution

iTrader: (30)

nope, most '95 and newer cars have a single schraeder valve on the fuel system for simple fuel system testing. no RX7 has ever had a test port that the newer cars do. you will need a "tee" for the fuel line, some will have a schraeder port to hook the gauge up to.

linuslove

Understood. So should I try again and get all connections real snug and tight so there are no leaks and test again? If I was getting 30-32 psi when the fuel pump connector was jumpered and the engine on "on" does it look bad already? The guage I bought was bought from the plumbing department at Home Depot and the plumber said regardless of wether it is water or gas it should measure an accurate psi. Is he correct?

RotaryEvolution

iTrader: (30)

should be close enough to give you an idea, if the numbers drop dramatically before the engine stalls/struggles you should get an idea if the fuel system is having issues delivering enough fuel for the engine to run properly.

that PSI isn't dramatically low but i would like to see where it stands with the engine running.

i know some auto parts stores carry a universal tester, i believe i got mine from Kragen/Oriellys/Schucks many years ago and it worked well enough that i didn't replace it.

linuslove

Ok. Sounds good. I am going to work on this again over the next few days and Wednesday I should have more information. Thanks again and we shall chat Wednesday! David

linuslove

I have a question about the fuel pressure test when the car is not running. Since the pump is pumping gas continuously as i can hear it on with the fuel pump connector jumpered is it filling the engine with gas or is something stopping it after it gets to the main line after my fuel guage before it enters the engine so it doesn't get filled with gas and flooded during this test??

satch

iTrader: (1)

If the injectors are closed then it should be able to hold back the fuel.

linuslove

Here is an update. I managed to get my fuel pressure gauge to be fully operable with no leaks....I needed to use plumber's Teflon tape around the screw joints and now there are no leaks and it reads pressure accurately. Again, I did it with the engine off and key to ON with fuel connector jumpered so the fuel pup was pumping and for the same exact 30 psi. You said this value is not bothering you too much even tough you mentioned it should be 40 psi; is that correct? Today I will try to get the car started and let you know what I get when keeping it idle at maybe 1000 rpms or so with something on the pedal. Now one last question. I assume when I do the last test and cut off the return gas hose I am of course doing this with the car off and key to ON like the first test and you say I should get around 90 psi. Is that all correct? Thanks!

RotaryEvolution

iTrader: (30)

yes, you can also crimp the line just after the fuel pressure gauge so as to not possibly create a leak on the engine due to the rather extreme pressure. do the last test with the engine off. for now the next step is to see what pressure the pump is putting out with the engine running and/or cranking.

linuslove

High RotaryEvolution. The verdict is in, but I want to go through the details because some of these symptoms MAY clue your keen understanding of this engine and its operation into a full diagnosis at this point. Yesterday after the part I of the test with car not running gave the value of 30 psi as you know. But, I did not proceed because it would not start; INTESTINGLY enough it starts when the fuel gauge is up a little from the empty bar when I put another 2 gallons in, BUT it refuses to start but cranks beautifully when the bar is just on empty and WE ALL KNOW THAT THE CAR HAS PLENTY OF GAS TO RUN WHEN ON THE LAST BAR IN RESERVES AND I HAVE DRIVE THIS TO WAY BELOW THAT EMPTY LOWEST BAR WITH THE FULE LIGHT ON FOR LOW GAS! Maybe this is a clue for you also to a problem with the fuel pump itself? I do not know, I am just asking you. Now, it started today and boy did a lot of white smoke come out for the first 5 minutes as I kept it up near 2500 rpms....then the white smoke dissipated and I kept it at 2000 rpms for a while and it rattled and rocked a little but not as much as last week. Then finally I brought it down to around 1000 and even as low as 750 with foot on pedal with out it stalling. I put something strategically on the pedal to keep it between 800 and 1000 rpms and got out of the car and looked at my perfectly functioning gauge and it only read 20 psi!! And vacillated a small amount between 19-22 psi!! Now, what has happened to this fuel pump? They slowly die? I thought the either operate or die and do not pump!! Shows how much I know about cars! Can we assume enough power is going to the fuel pump or is it just simply a case of a dying fuel pump? If so, do you suggest I do anything else before saying this IS for sure the problem? Any other things to check, inspect, test before I buy a new one and install it? And I will try test #3 NOW BUT I assume it would not matter given that low test #2 value. Correct? Where do I get that exact stock Denso pump because I assume use nothing but original correct? Also, the area of the bumper around the exhaust got stained again with some black soot and i cleaned it; does that indicate something bad to you? Awaiting your reply and thanking you for all you did for me.

RotaryEvolution

iTrader: (30)

at this point i would remove the pump from the tank and inspect everything, it may be a dirty fuel sock on the pump but unlikely. inspect the inside of the tank and pump itself for rust and corrosion indicating the pump has been sucking up a bunch of debris and is probably weak in volume.

if everything looks ok inside the tank then reassemble it and check the voltage at the black/white wire to the top of the tank with the engine running and pressure output low. it should be near or above 10v if the electrical system is in decent working order.

if that all checks out ok, move your pressure tester line to before the fuel filter and recheck your pressures. if it comes up more than a few PSI then replace the fuel filter.

you will need at least 3 gallons in a bone dry tank to get it to start and run reliably. if the lines go dry and fuel level low enough the fuel pump will cavitate and will not be able to run as low as it would after the engine is already running and pulling up fuel. the lower the fuel is the more a dirty sock will present itself with low volume and pressure to the fuel rails.

as far as the white smoke, could be a number of things.. old fuel, oil seepage internally in the engine from a flooding condition or from the engine sitting for weeks without being run, or lastly and hopefully not the case- bad coolant seals allowing coolant to pool up inside the engine.

wvumtnbkr

Can you please use some spaces in your posts? It makes it tough to read.

I would check voltage at the pump. If that proves good, check your sock filter (on the bottom of the fuel pump) and your main filter (on the drivers side of the engine compartment a little up from the starter).

After replacing the filters, I would then redo the tests with the pressure guage.

Hope this helps,

Rob R.


Edit: He beat me to it.

linuslove

Hi Rob, sock was checked and is like new.....I replaced the fuel filter even tough I probably did not have to so at this point the fuel system running to the engine is like new accept the fuel pump. Thanks for the input so my values I have for pressure are POST new clean sock and new fuel filter.

linuslove

I may have to check voltage at the pump, but I am unsure exactly how to so I was Awaiting RotaryEvolution to instruct me if that is necessary before just installing a new Denso fuel pump which I found many of on the net:
90 1990 Mazda RX-7 Fuel Pump - Fuel Delivery | Drivewire.com

951-0011 Denso - Fuel Pump (New) At StylinTrucks.com


Fuel Pump Installation Kits for 1990 Mazda RX-7 Convertible | StreetPerformance.com

1990 Mazda Rx 7 Fuel Pump And Strainer Set - Bosch, Carter, Denso - TheAutoPartsShop