Technical Question
 

when I remove the gas hoze that puts gas into the carburator and try and turn the enine over, no gas comes out. If I pump the gas pedal the gas will pour out then but that is the only way I can get gas to come out. Does this mean I need a new fuel pump? accelerator pump? carb rebuild?

Thanks in advanced


Josh

you need to explain your self better. if you are talking about the fuel hose that attaches to the carb then you need a fuel pump. when you step on the gas pedal you should see a stream of fuel coming out of the jets above the rings in the venturies.

I pulled off the black hose the is hoocked onto the side of the carburator, and extends into the firewall I beleive. I placed the end of the hose into a measureing cup and tried to turn the car over. Nothing would come outa the hose until I pretty much floored it and then a little gas gushed out...

Please Help?

Not sure what fuel line you're pulling to check but pumping the gas should not affect the fuel supply hose to the carb. If you have the correct line in a glass jar or other approved container ;) with the key on you will have a rush of gas if nothing is wrong or blocked up back at the fuel pump and tank. Otherwise, you will have no gas, or very little, if it is blocked, a bad pump, or a year that doesn't turn the fuel pump on until the key is in the start position.

Here is a picture of the fuel lines leading into the carb. The one with the metal cylinder in it is the return line. Which hose are you pulling to check for fuel? What year do you have? Some years didn't start the fuel pump until the car was actually trying to start.

don't forget to tell hime fuel dosen't pump with key in ON position unless the car is running, you have to have the key turned to the start position to pump fuel.

early models may be an exception. can't remember.

I pulled the one on the right hand side(in your picture alien) and when I turned the key to on. i.e. the engine was turning over no gas would come out into my measureing cup... The only way I could get gas to come outa the tube was to pump the accelerator petal up and down real hard. then a small amount gushed out. I have a 1985 GS. Thx alot so far guys ^_^ I hope to have my rx7 running tomarrow if I can get an idea to run with =)

Thx again, Josh

Hmmm.....thats really wierd because the accelerator pedal is in no way connected to the pump or tank or filter or anything besides the carb........like alien said.....you either have a bad pump or pluged line somewhere....mabye the filter. Does the pump make a humming sound when u turn the car over? That might be a good place to start if it does then either the voltage is not high enough at the pump, the pump is broken, or u have a plugged line. Just a little input from someone with not too much experience:p:

If the line is plugged the pump will only run for so long (overheat shutoff safety feature). Youve deffinately got an issue. Check for clogged lines, filter, the easy stuff before the pump. Turn the key and go listen at the back right of the car for the pump, you should be able to hear it. Remove the left line at the carb and see if you can blow in it (fuel return line) then start methodically searching. Good luck. Keep us updated.

Yup, should be the 1984 and 1985 models that had this. My '82 and '83 both turned the fuel pump on as soon as I turn the key forward.

If you have an extra battery, try hooking it up directly to the fuel pump to see if it starts the pump pumping. The connector for the fuel pump is directly beneath the storage bin behind the driver's seat.

Guys, if he's getting a little bit of fuel could it just be that the fuel filter is clogged up? I'd check that first. I mean, you could just take the line off of the filter and have some one try and crank the motor to see if any fuel comes out of the line that way. You would know right away if the pump was bad or not that way.

I live in San Diego. Where can I get inexpensive Mazda auto parts?

your local automotive store ( I have auto zone and o'reily's)

I just replaced the fuel filter a week or 2 ago so that isnt the problem... a friend of mine that works at autozone has a friend with like 5 rx7s in his back yard so he is going to pull off a pump from one of his part cars and sell it to me for 20 bucks today. so hopefully this will fix the problem. Thx so much for the help so far! Im hopeing Iam close to fixing the problem. The other day when I lifeted my car i.e. the factory jack, kinda scray to get under with only that, I noticed that the undercarriage that was protecting the fuel pump was quite loose so Iam guessing this mite be a problem too. *shrugs* Iam off to try and remove the pump itself I'll update soon.

good call, you can also take out your storage bin on drivers side disconnect the pump then run some cheap little wires from your battery and test pump that way.

Alright just got done doin what Steve suggested, I took off the fuel return lign and blew air into it, via my mouth, and it would not go. so I dug deeper and removed the silver cylinder about 6 incheches from the carb along the fuel return lign and this appears to be where the clog is. Iam postin pictures.

return fuel line( & valve )
 

This is the return fuel line and the 1 way check valve, the valve seems to be clogged up a little bit but air will still flow through it under high pressure( i.e. me blowing realy hard into it )

Carb-Return Fuel line
 

after I removed the 1 way fuel valve in the return line, and blew through the remainder of the hose it had no clogs and I could tell that it was bubbleing air all the way through the hose and into the fuel tank.

Re: return fuel line( & valve )
 

Not sure if that would be a problem or not but easy enough to change, just grab one off one of those parts cars when you get the fuel pump. Mine seemed like it was kind of hard to get it open just blowing into it but everything works fine. Oh, and make sure that the arrow is pointing in the right direction when you install it. I believe it must point towards the tank, away from the carb.

Update - I removed the fuel pump, a friend brough over a 3.5 ton jack and we threw my rx7 up on some rims, and took it into the autozone which is in the ajoining parking lot to my house ;-) They tested the pump for me and said it was working fine. So my next step was to see if the pump was getting power from the wires it was hooked to. There was no amp/ohm/power what ever it is. Anyone got any advice on where exactly the wires go to? another lil bit of a question, the pump has a psi rating of 2.5-4.0 psi on it and it was made in mexico, it was jimmy rigged into the wire system too. lots of black electrical tape. anyone know if this pump is acualy suitable for use in my 1.1 liter carburated 1985 mazda rx7 gs? any help would be great

Thanks alot, Josh

Did you have the key in the "ON" position when measuring voltage at the wires? Have your friend try and start the engine also while you measure voltage at the wires. You should have at minimum a steady 12V there.

If you don't already have one, by a Haynes manual for the 7. I don't have mine hand right now but as long as you have at least 3.8psi on a stock nikki and the correct flowrate you should be set. I don't recall the flowrate off hand and that is the most important number for the gas supply. You could have the correct pressure and not flow enough gas to the carb which you've already proven you're not getting any up there any way. Like a couple of us have suggested, run some wires from the battery to the pump and see if that will pump some gas up to the carb. If so, then it is in the wiring somewhere. The hookup for the pump is beneath the driver's side storage bin.

Oh, and check your fuses too!

quick question, where's the fuse for the fuel pump.

quick question, where's the fuse for the fuel pump.

He's got the '85 GS, so he will def have the fuel kill relay...PM V8kilr for the bypass trick on that one...the other fuse, besides the fusibles, to consider is the one in the inside fuse box marked engine. Replace it even if it looks good. Of course, this only applies if you've lost all spark and fuel up front....just some more info for you to digest...:cool:

Update
 

I just got in from tinkering under my rx7 for about 2 hours... most the time was spent trying to make the fuel pump cover go back on... lol... So here is the info, Iam getting 12 volts outa the wires where I attach my fuel pump. My pump is good according to autozone, its makes a pitter patter sound when its wired up at the store. The pump has a PSI of 2.5 - 4.0 will this be suitable for driving, not performance... after reinstalling the pump and doin all the hook ups I went up to the front of the car and got under the hood. I pulled the fuel line off the carb and put it into a measureing cup. I got in and turned the engine over for a good 30-50 seconds and nothing would come out. So I further investigated by plugging the end of the fuel hose with my finger and then reached into the car with my other had and turned it on. I got pressure but no gas. I have half a tank of gas in the car rite now. If this has happened to anyone else or anyone has some input it would be greatly appreciated!

Thanks in advanced, Josh

Sounds like there is a blockage somewhere. If you're feeling pressure against your finger while you're doing that I would doubt it is on the outlet of the fuel pump but you can do a couple of things to check it.

Take the line off at the fuel pump that runs to the front of the car. Blow through it or shoot some compressed air through and see if you or a partner can feel it at the other end.

Next, take the line off at the inlet to the fuel filter. See if you can blow air back into the tank from that point.

Also, make sure all the hoses are connected up correctly to the different valves and to the tank itself. If you can fuel pressure, that pump is pulling air from somewhere then.

In the Haynes manual (finally grabbed it off the bookshelf, you need to grab one from Autozone or somewhere) it states the two conditions the pump has to meet. First, measure pressure and the results must (for stock) be between 3.7 and 4.7 psi. If you're within that range, you need to next measure flow which needs to be a minimum of 1.16 US quarts after 1 minute of time running the fuel pump.

Summarizing, check for blockages all the way back to the tank and also check for air leaks. Try taking the gas cap off while you crank the engine and see if any gas comes out the fuel supply line then.

I just had this problem the other day and I thought I had a blocked fuel line. I'm not that good with carbs because I've never worked on one before but my next door neighbor has been working on cars his whole life this is what he did to make the fuel flow again. we pulled the fuel inlet line off of the carb and left the return line on. Then we put the fuel line in a jar so that we can see when we have fuel. Then he had a little bottle with some some fuel in it and pour it down the intake while I turned sat there and cranked the engine. after about a minute or so of doing this off and on as to not burn up my starter, we started seeing fuel coming out of the line so then we plugged it back in to the carb and I sat there and cranked it some more and after a while I could see the little fuel bowl window filling up like it was suppose to. Until I did that I could not any fuel into the carb for some reason and I changed out my fuel filter and I was damn near ready to change out my fuel pump. My neighbor said it had something to do with the pressure in the return line or something but I didn't really grasp it. I was just happy that I was getting fuel again. Now I'm just telling you what we did a couple of days ago that worked for me. I don't know if everything we did was neccessary or not but you can try or if someone else here is real knowledgable about how incoming fuel and fuel pressure works they can explain it. Hope it helps. Oh, and by the way I just did this 2 days ago.

Sorry, I know that this doesn't help with your immediate question, but I have to note that there is a REASON why it's scary to get under your car with just the factory jack. It's scary because it's DANGEROUS. Seriously, don't do this. You should get the Haynes manual (or similar) but if money's tight, then a set of jack-stands MUST be your first priority if you're gonna be wriggling around under the car.

Even if you're using your buddy's 3-ton jack, you should always use jack stands any time you're under the car. A 3-ton hydraulic jack is very unlikely to fail in a dangerous way (unlike the factory tire-change jack, which can just fall over), but it's still a risk with no possible reward. :P

Play safe,

When you unhooked the fuel pump initially, did a whole bunch of fuel spill out from the line coming from the tank? You didn't unhhok the small white canister that was imline with that and then hook it up wrong later, did you?

A section of the fuel pickup tube inside the tank runs horizontally and is prone to getting clogged, especially if the tank itself is rusting, or if the car has been sitting awhile. You can check it easily by blowing through the hose that supplies the fuel filter. Sometimes that will actually unclog them for the time being, but they tend to plug up again in a fairly short time. I ended up having to use an old bass guitar string with a little hook bent on the end chucked into my hand drill as a sort of roto-rooter. Just another possibility you may want to check out.
Good luck with it, the fuel system on these old cars is their Achilles' heel.

What a huge thread for a fuel pump problem. Damn.


Hey Alien....

The fuel volume works even if you use an unapporaved container!!

Cheers!

Again, PM V8kilr and ask about the infamous gas tank episode....I think the car fell as they were getting out or some such disaster....but he will have the answers you need...seriously...;)

Yeah, that was suppose to be a joke :p: on the approved container bit. Just like the whole cellphone at gas station thing. Your cellphone just isn't going to ignite that gas.

Also, don't use a styrofoam fountain drink cup for the test......don't ask how I know that. :D

Cheers

that's Chemistry 101 for those that paid attention...;)