prjct87rx7

iTrader: (7)

k heres the deal... my car wont start/or even pushstart...after cranking the car for a couple min...in intervals of course of 15 sec.. i pulled the fuel line that goes from the main filter to the primary fueal rail,and maybe 1/8 cup of fuel came out...by this time it should have tons of pressure,and should squirt out....could this be the regulator? considering i replaced the main filter,and it has a walbro with only about 2,000 miles of use... when i jump the fuel pump under the hood it turns on so i dont think the pump is bad....what do you guys think? ive never had a regulator go out so i dont know if it would allow enough fuel to start??? thanks jr

prjct87rx7

iTrader: (7)

bump

prjct87rx7

iTrader: (7)

well, in the chilton it says if your fuel pressure is below spec,check these in this order

check for leaks/ i have none...

check fuel pump/ replaced it today

check fuel filter?put a new one in...

the last but no least it says to replace the fuel pressure regulator,wich i didnt think was a big deal since it works of vaccum,wich wont occur till the engine is started,but if the manual says if your fuel pressure is low replace it,and thus tomarrows/saturday project is to find one,and replace the regulator/i guess the secondary rail..hopefully this works if not i am running out of options....

HAILERS

If you turn the fuel pump on and leave the fuel feed line off at the engine, does fuel come out? Can the pump be heard to run?

NOT bad fuel pump regulator.

Wankel7

I made this fuel pressure tester cheap ...

All hardware store stuff...

https://www.rx7club.com/showthread.p...=fuel+pressure

prjct87rx7

iTrader: (7)

yes fuel comes out but not very much at all...and it should be near 40 psi? correct? and i mean the fuel pressure regulator on my rail

HAILERS

Put a gauge on the outlet line of the pump and see how much pressure its making. It should be in the 70-90psi range (coming from the pump, gauge in the pump outlet line at the engine. See the fsm.

prjct87rx7

iTrader: (7)

i did read the fsm that is why i have reason to believe its the regulator cause i replaced everything else....is there some kind of fuel pump relay? if so would thats lessen my pressure if it was going bad?

HAILERS

Whether the fuel pump see 9vdc or 12vdc, the output of the pump will be in the 70psi range and the fuel pressure regulator will regulate it to approx 37psi or 28psi in the rail, if the engine is idling.

A gauge on the outlet of the fuel pump will show if the pump is putting out or not or tee'ing into the outlet at the fuel filter outlet line will show if the fpr is regulating to approx 37psi.

From my experience, a zero psi fuel rail will pressurize to 40psi in less than 2 seconds of holding the key to Start.

prjct87rx7

iTrader: (7)

could this be caused by the fuel resistor relay???

imdrax

iTrader: (1)

sorry to raise the dead but i have a quick question. i just recently did a fuel pressur test and when i did the test for the pump i got 60 psi both times i did it and if i turned the ignition off or unplugged the jumper it would bleed down to like 20. in my manual it say it should be 71-96 and the hold should be like 45 or something(dont have book near me) just wondering if this is a definate pointer that my pump is dying? also when i checked the pump voltage reference i read 9v is that correct with KOEO?

buttsjim

The rapid bleed down indicates leakage, probably from the injectors (assuming you're not smelling gas).

The low pump output could be due to a clogged filter, fuel line restriction, bad pump, or poor electrical connection. I believe, but I'm not sure, that you should see 9 volts at the pump, except for a 50 second period immediately after starting, and at wide-open throttle with the secondaries on line. (I may be wrong--I don't clearly remember).

Did you check your voltage on the pump side of the electrical connector mounted on the rear strut tower?

HAILERS

************************************************** ***************
Can you clear something up? Where do you have the gauge? Deadending the line out of the fuel pump? Or tee'd into the line out of the fuel pump?

If deadending the line out of the fuel pump you should read apprxo 71-96psi and if you then turn the key to OFF, the pressure should be more than 57psi AFTER 5 minutes have passed.

If you have the gauge tee'd into the fuel line and turn the key to ON (jumper in also), the pressure should read approx 37-39psi and if you then turn the key to OFF and wait 5 minutes the pressure should be more than18psi.

So you can see that it matters which configuration you are in.

Frankly I can't remember what the voltage should be at the pump with the engine off and the yellow connector jumpered with the key ON. I think it should be battery voltage. I KNOW upon starting the engine it is battery voltage and once the engine starts the voltage drops to 9vdc because a ground signal out of the ECU to the Fuel PUmp REsistor/Relay pulls the relay to the low voltage position.

I'm betting it should be battery voltage with the key ON and engine OFF with the jjumper in the Yellow Fuel PUmp Check Connector. Anyway, back to the top.

HAILERS

If you only got 60psi with the gauge deadending the line out of the fuel pump....that is low and I'd start thinking about the low voltage at the pump. I can't help but believe the pump voltage should have been in the 12vdc plus range when doing that test. Sorry, I don't have a 87fsm handy to look at right now nor a car to fiddle with.

EDIT: I just looked at the online series five fsm and can assure you that if you have the jumper in the Fuel Pump Check Connector and the key to ON (engine off) you should have 12vdc at the pump. I'm positive about that.

imdrax

iTrader: (1)

well first off, yes i had the gauge hooked straight up to the line coming form the filter. i also did the test with it teed in and got within spec. i cant remember if when i checked the voltage at the fuel pump connector if i had the little yellow check con. jumpered or not. after i get my car all back together im going to go ahead and run all the tests again and make sure. i figure im going to replace the filter also and see if it makes a difference. just to clarify with KOEOff & connector jumped=12v , and with KOER= 9v, and WOT=12v correct? and to buttsjim since i had isolated the fuel from the injector and regulator path the bleeding off of my fuel pressure has nothing to do with the injectors as they werent in the circuit. i read somewhere about the fuel pump bleed/check valve by the pump that lets excess fuel return when engine is off. could this cause the hold pressure to drop so drastically? i looked under the car as the pressure bled off and saw no fuel and did not smell any either. before i put everything back together this weekend though im going to go ahead and test the injectors for leakage. should bailing wire be used to hold the injectors in? am i just supposed to hook all the fuel lines up, pressurize the system, then de-presurize the system and watch the pintles for leakage?

buttsjim

Good point. (I knew that)

Now, to further embarrass myself, let me opine that I thought that the check valve was part of the evaporative system to control the pressure in the tank, rather than in the fuel lines. Mazdatrix sells a part that balances the pressures between the supply and return lines, but that's an aftermarket part.

HAILERS

*********just to clarify with KOEOff & connector jumped=12v , and with KOER= 9v, and WOT=12v *********

Yes to the above.

This is just from memory: I had a fuel gauge on one of my cars once and drove it hanging on the wipers. From what I remember, if the engine was idling the pressure was around 30-32psi. If I turned the engine off, the pressure actually rose up to approx 37psi after a half minute or so passed. That makes sense since the vacuum was not on th FPR anymore and it was now seeing atmospheric pressure.

Now if I remember right, the pressure took quite sometime to drop down below 20psi. I'm talking over fifteen minutes or so. I think you might try this and see what happens on your engine. Just tee in the fuel line and idle the engine, then turn the engine off and see how long it takes the pressure to drop from the upper 30psi range to below 20psi. In my opinion if it takes over fifteen minutes you have nothing wrong.

I notice the series five fsm fuel pump checkout is different than the series four. I see nowhere in my 87fsm where they put the gauge in the output of the filer line .....turn the pump on......note the pressure and then see if it drops below 57psi after five minutes. They do that in the series five fsm. They suggest replacing the fuel pump if it drops below that figure. That's in the series five fsm, not the series four. I've never done that myself.

HAILERS

Here's something to watch out for. If you have the fuel pressure gauge on the outlet of the filter and do the pressure test, don't be surprised if your fuel pump voltage isn't what you expect.

With the key to on and the fuel pump check connector jumpered, there will be a fairly large voltage drop on the wire feeding the fuel pump. I'll bet your voltage will show around 11 volts give or take rather than 12vdc plus. And the longer the pump runs and the key is to ON, the lower the voltage will get because your alternator isn't putting out anything to replace the loss. You might consider jumper cables from another car to keep the battery up.

I did this on my car a hour ago and the pressure was around 75. With the key to off, the pressure held there for thirty minutes til I called it a day.

EDIT: In the post before this one I wrote ***output of the filer line **** I meant FILTER LINE.

imdrax

iTrader: (1)

so your pump held at 75 psi for 30 min"? thats way off from mine i could visually watch my pressure just DROP so i think ill go ahead and take off the inspection cover and check some things out. the whole upper portion of my motor is torn apart right now because im waiting for all new injector grommets and rings and such as well as doing to vac rack delete. so i think before i put it all back together im going to check the injectors for leakage and remove the filter also and check what pressure i get before the filter and how much,if any, it varies from my previous reading. one more thing to note is that im using a standard water pressure gauge with brass barbed fittings and teflon tape, could this cause an abnormal reading? but without any leaking at the gauge it couldnt cause the rapid bleed down could it?

HAILERS

We're not communicating.

The gauge was put in the end of the line that comes off the fuel filter. The fuel only went to the gauge.

That was a test of the output pressure of the fuel pump and to see if the pump was leaking back into the tank thru the pump itself after the pump was turned off.

The fuel was NOT going anywhere else. It couldn't.

I have done the test where you TEE into the fuel filter output line before. When you do that your looking at the pressure in the fuel rail of the pressure side of the FPR.

When I do that with the engine running, I see approx 28- 31psi.

If I turn the engine off the pressure will initiall go UP to 37-39 psi because I've lost the vacuum signal to the FPR and it will now regulate higher as the motor winds down and stops pulling vacuum on the FPR. I found it interesting the pressure would go UP after I turned the key off.

It will hold that 37-39 psi for some time. I did not do that test today. I have done it in the past and the pressure will, if memory serves, stay over 20psi after a half hour. That's from memory. I'll redo that test tomorrow. The one on the fuel rail pressure.

imdrax

iTrader: (1)

yes we are communicating. i fully understand what all the tests involve and what the readings should be . i realize with the gauge TEED in at the line from the filter to the rail i will see ~30 psi and i did. i also realize that when i hook my gauge straight up to the filter that i should have a reading of 72-91 or something and i DIDNT see that. so in my previous post i was saying that if i hook the gauge directly to the line FEEDING INTO THE FILTER i can tell if my filter is clogged and is the culprit of my low pressure reading. For an example if i were to get a reading of 75psi with the gauge hooked directly to the fuel line going into the bottom of the filter, it would indicate to me a clogged filter. the only thing i dont understand is what could cause my FUEL PUMP PRESSURE to drop from 60 psi to ~25 psi in less than 5 min. i completely understand all other aspects of how fuel pressure is regulated. and when i was reffering to your post about your FUEL PUMP PRESSURE test where your pump showed an output of 70 psi and held it there for 30 min in comparison to my FUEL PUMP PRESSURE reading of 60 psi and dropping off drastically in a matter of seconds/minutes, i was expressing dismay due to the fact my pump and or system is having serious problems. and just out of curiosity the haynes man. states that after de-powering the fuel pump your pressure should drop and HOLD and they give a specification for that which is i believe somewhere in the 50's, so why would your pressure stay constant at 70psi for 30 minutes with the fuel pump diabled?

imdrax

iTrader: (1)

Ok today i got to test pressure before the filter. i got a reading of 65 psi. this was with the battery hooked to my other car while it was running because the 7's battery was dead. while i had the pump on i tested for voltage at the harness by the strut tower and got a reading of 10.65 volts. My battery voltage was at 14v. Hailers can you confirm that with Key On Engine Off and connector jumped i should be reading 12v and not 9v? also when i turned the key to the off position my pressure dropped to 5 psi in 90 seconds. is it possible that the previous owner could have installed one of those pressure relief T's that mazda trix sells? i know there is not one in the engine bay but maybe he installed it near the pump? ill have to check it out. but if i could get your opinion on these readings hailers i would really apreciate it because i think im going to buy an FD pump.

buttsjim

Do you have a stethoscope? Maybe you could listen to your pump after you turn the key back off, to see if you can hear fuel backflowing through it. You could listen at the pump, or maybe even at the pump outlet line near the fuel tank.

imdrax

iTrader: (1)

what im thinking of doing is maybe disconnecting the fuel return line from the pump and then powering the pump up and shutting it down. and with my gauge hooked directly to the outlet there should be no fuel returning through the return line. if there is fuel flowing back towards the pump when i shut the pump off then i will know that there is one of those return tees installed. if not the problem may be the pump itself. unless there is some sort of check valve installed at the outlet of the pump from the factory that could be leaking but so far ive only seen one person on this forum make a reference towards this check valve so im not certain if it exists or not.

buttsjim

I'm going to look for a cutaway drawing of a fuel pump when I get home, to see what might cause one to leak internally.

A thought just ocurred to me though. There's a short length of fuel line (about 2") inside the tank that connects the pump body to the outlet tube. I don't know what would cause that to fail, but it could be split, or leaking at the clamp connections. Such a failure would allow the pump to build up pressure, but then bleed down quickly, and you wouldn't see or smell any gas leakage.