DallasFC1

iTrader: (2)

OK. I am trying to get my lil 7 back to life.
Problem: Fuel is NOT reaching the carb from the tank.

Symptoms: Dry Fuel Filter

Known GOOD PARTS: Fuel pump (new and bench tested for flow before install), Gas Tank, Clean and un-obstructed, Fuel sock (inspected when tank was dropped yesterday) perfectly clean clear and gas flows thru it beautifully, ALL NEW rubber fuel lines.

UNKNOWN: Fuel lines (hard lines) seem to be un-obstructed but can't say for sure.

I have currently a little over 1/4 tank of gas in the tank (premix with TCW-3) 1oz per gallon.


I cannot seem to get the fuel pump to prime and pump fuel to the carb. From my understanding the pump should run with the key in the "ON" position. However it does not. It only runs when the car is being cranked with the starter, and runs for 4 seconds AFTER the car shuts down. I cannot understand what the HELL the problem is.

FUEL GURU's PLEASE RESCUE ME!!!

I just dont understand. I blew air thru the pickup tube etc. All I can say is: THIS FRIGGIN BLOWS ***!!!


Please share any and ALL ideas!

DivinDriver

iTrader: (15)

Simplest guess would be that a rubber line got crimped or pinched when reinstalling the tank... try hooking a hand vacuum pump with a reservoir (like a brake bleeder) to the end of the line that feeds the pump, and see if you can suction fuel out of the tank easily. You can also try blowing into it with low-pressure air from a compressor (like, no more than 15 lbs or so!) and seeing if you make bubbling noises

Second simplest explanation is that the rubber lines got crossed up on installation, and you're trying to pump fuel out of the vent line or some such.

Kentetsu

Any chance that the pump is running backwards?








.

Rx-7Doctor

iTrader: (13)

Had to look for a thread that told what year your car was!

84-85 fuel pumps only come on when you start to crank the engine. Earlier models came on when you turned the key to the on position.

DallasFC1

iTrader: (2)

I was just in a hurry to figure this out before daylight crapped out on me. Its an 84 S model. 5sp.

Yes I have blown into the tank good bubbles there. I have manually pumped gas from the hardline connection at the pump to the carb and received fuel.

Pump is pumping the correct direction.

I must have the vent and feed line confused.... I will drop the pump and look at it again.

Thanks for the responses!

DallasFC1

iTrader: (2)

OK.. Please look at the picture yes I know im not an artist. Critique that later. I am running under the assumption that the BIGGER LINE is the FUEL INTO PUMP, and the smaller line from the tank is the VENT LINE...

Do I have this mixed up or am I correct?? I cannot seem to find any diagram under the sun showing those hoses correctly routed...

I am almost positive this is my problem...

DallasFC1

iTrader: (2)

Picture should be here now...
Sowwy

whistlepig87

iTrader: (2)

Pump discharge is the larger line. It is the hard line that is above the smaller hard line at the firewall. If you work backwards, you should be able to determine which one it is at the rear of the car.

You can jumper out the fuel relay(connect the large blue and black wire at the harness), which is under your dash by the steering wheel so that the pump will run when you turn the key to on.

When I did my line I blew out all the hard lines with compressed air just to make sure they weren't clogged. You can do this to determine which line is which too. I then hooked everything up and after a few seconds, the pump was operating just fine. Just try to be systematic about it and do one thing at a time to try to deduce the problem.

Erik Paez

power the fuel pump direct to get the car started first

DallasFC1

iTrader: (2)

I know what all the lines from the pump to the firewall go and do...

I am fuzzy on the lines from the tank to the pump...

Is the BIGGER line from the tank going to the pump inlet or is the SMALLER line supposed to run to the pump...


THAT is what i need to know

Any help is appreciated!

Thanks!

Twilightoptics

iTrader: (1)

Big line is always fuel feed. Both sides of the pump. Then make sure the return line is hooked up properly.

Use shop air and a rag, hold the rag over the fill tube and blow into the tank to pressurize it a bit. It will force fuel out the feed line.

I know it gets a little convoluted down there at the pump, make sure the filter is installed in the correct orientation and lines also.

Does the pump indeed run?

25yrfan

I had a problem after I replaced the fuel pump. Got an OEM from Mazdatrix. I hooked up the pump, had it hanging down from the car to check for leaks etc. Everthing seemed ok, was getting plenty of fuel under the hood. So I bolted that puppy up to the frame, and car no starty. I had already been through replacing rubber and filters cleaning the tank etc. Really puzzling. So I was looking at the pump while bolted up and noticed it was cocked a little sideways and was pinching the fuel line, can't remember if it was gozinta or gozouta, but the result was the same.

So even though the pump was new and had a brand new mounting bracket, the rubber grommets (original) in the plate that bolts the assembly to the car, were so worn out that they wouldn't hold the pump straight when it was bolted up. So the car runs with the pump hanging down from the car (not good eats), when installed, the hose was pinched so no fuel. I had a rubber sleeve from a GP fuel pump kit that I didn't use (another long story), so I cut it up to help stiffen up the mounts. Now the pump sits staight, no bend in the hose and I gots lots of fuel now with the pump mounted.

DallasFC1

iTrader: (2)

I am about to get mad and re-plumb the damned car the way its supposed to be.
Is it possible that the rollover cut off valve is jammed and preventing fuel?

any more ideas?!

DivinDriver

iTrader: (15)

Not likely, if you were able to freely blow air through it.

Don't get frustrated - - it will cause you to stop seeing things clearly.

Sometimes you gotta back off, spend a few minutes clearing your head, and then re-approach the problem as if you've checked nothing. We see what we think we see, sometimes, not what is right in front of our eyes.

First, make sure the pump actually pumps - not just runs, but moves fuel at pressure. You might want to test it's ability to pump fuel when removed from the car, using a couple lengths of hose and test cables (be careful not to do any sparking around fuel vapors). Because of the internal design of the pump, it is possible for it to fail in such a way that it hums like mad but does not move fuel.

Once you're sure the pump can pump, start with the line coming from the tank, and test that you can draw fuel from it, then go junction by junction.

You WILL find the problem. You just gotta be methodical, and not trick yourself into thinking "I already checked that." If the first pass through doesn't find it, that only means you've missed something.

The engineer's version of hell is where everything checks out , but nothing works. You're not there yet.

Isolate, inspect, eliminate. You'll get it.

DallasFC1

iTrader: (2)

I am a damned mechanical Engineer...
ugh.

I have checked, double checked, re-checked and started over about 4 times now.

There is no reason barring the pump now for my issue. If it is the pump (I have already bench tested it for both FLOW and PRESSURE (gpm not lpm but same test.) max pumping pressure was right at 4.02psi. (12V DC with a 2amp draw).

I have manually pumped with a hand pump gas thru every damned line on the car. I have even drawn gas from the tank with the pump via BOTH the vent and the Supply soft lines from the tank. (I did blow the gas back into the tank thru the vent line to make sure it was not obstructed and causing a vapor lock type situation....)

Honestly, this has 6 years of my life coming up as a worthless failure on paper lol. Degree!? WHAT DEGREE?!

Also, I went ahead and removed the rollover safety valve just to eliminate any more stops and cut down on the rubber line. I have no kinks in any rubber line, they are all secure and not leaking. (Pulled 20"Hg with a vac pump on the system and waited for bleed off). I got less than 1"Hg bleed in 50 minutes. Safe to say it will hold fuel pressure just fine.

There is an avenue that I have not explored YET. ELECTRICAL FAILURE. Since the 84 - 85 pumps do not kick on until the engine cranks, I need to jumper the system to turn the pump ON when the key reaches the ON position.

I have manually primed the system then tried to crank and NOTHING happens. So either the pump i have tried to run 3 times is now fried and just humming and not functional. (Which would make me want to go cram it up some idiot Quality Control personnel's **** at the factory...)

OK. SO. Lets get back to basics.

HARD LINES: CLEAR FUNCTIONAL AND NOT OBSTRUCTED
RUBBER LINES: CLEAR FUNCTIONAL AND NOT KINKED OR OBSTRUCTED
FUEL FILER: CLEAR AND GAS VISIBLE IN THE FILTER (can be easily pulled thru)
GAS TANK: NO CORROSION, FRESH TANK COATING, ALL SEALS HAVE INTEGRITY
FUEL PICKUP TUBE AND FUEL SOCK: CLEAN CLEAR AND NOT OBSTRUCTED
FUEL LEVEL SENDER: FUNCTIONAL AND PROPERLY FUNCTIONING
FUEL PUMP: BENCH TESTED AND FUNCTIONAL

GARAGE SANITY TOOL: Fender Strat with a beat up neck and good strings, totally functional.

OK. Let's try electrical. Is there a simple way to jumper the pump or do I have to dig out my wiring diagrams and soldering iron and toil endlessly until I have a suitable solution...

Thanks for the help all, DivinDriver I was so impressed by your car even tho I just don't like the rear end of the 79-81 cars That's one sexy ride you got there brotha!

- DallasFC1 (considering I ditched my FC cars for my baby FB I guess I should change my handle???)

whistlepig87

iTrader: (2)

I sent you a reply for instructions for jumpering the fuel relay under your dash....I had an interesting situation when I got my car....

When the trailing ignitor was bad, I didn't have a working tach, which made sense. I was able to trace it back to the ignitor. However, when my ignitor was hooked back up, my fuel pump would run when the ignition was set to run, but it would cut off when cranking and when the engine was running. It was like it was working *** backwards. I had to jumper out the fuel pump and find the problem, which of course was related to some poor wiring by the previous owner. A lot of people jumper their pump out and even put a switch on it for fixing flooding issues.

If you have a factory manual, the fuel relay is shown in one of the adds pages in the back of the manual. This is where I looked to learn about what wire goes where and how to fix problems.

If your fuel relay went bad, you wouldn't be able to pull that coil in to close the switch to get power to your fuel pump. There are also a series of other electrical issues to check....but its a start.

j9fd3s

iTrader: (3)

jump the relay, and the pump will get power with the key on. if everything else works, then the car should just run.

the relay works thus. trailing ignitor -> tach signal -> emissions control unit -> f/p relay. if you have a bad ignitor or bad emissions control unit, then it won't turn on the relay and then you won't have a fuel pump.

the pre 84 cars are wired with the pump right to the ignition switch, so i think if you bypass or have the relay on with the key, its fine. i think they mostly did it because some of the 84-85's are efi.

85TIIDEVIL

iTrader: (2)

Did you check to make sure the wiring at the pump is not backwards...?? The pump will then just blow bubbles back into the tank instead of sucking fuel foward. Checking all this stuff is sooooo much easier with help from another person. A length of hose, a clear bottle and a little gas can easily tell which way you're pumping being you can't actually see into the tank. Who knows, sometimes it can actually be that simple. Ooops, I see that was already covered at the begining of the thread.

DallasFC1

iTrader: (2)

After all of this, apparently, the pump I had bought and bench tested. Failed after my bench test.

Returned it for another one and low and behold. I mounted it up and tried it... POOF I got fuel flow!

Thank you all. Turned out it was a faulty fuel pump. Must have been a factory defect of some kind.

Ugh, yeah, Quality Control needs to step it up a notch.

DivinDriver

iTrader: (15)

(Those are Congarats, for you)

And +1 for persistence!