Fuel delivery issues on stock 12a
 

hi all,

first off some quick background info. For all intents & purposes the car is a stock 80 RX7 with carbed 12a (duh). I've had it since Feb, shortly after i got it i did a full tune-up (plugs, wires, cap & rotor, fuel filters, oil, water, etc). Runs like a champ.

Now the prob, car has run perfectly since feb until about a month ago. Started to notice that sometimes when under acceleration through the gears, after maybe 7-10 secs it would start to bog and sputter. Like hitting a fuel cut on an EFI car. Only does this after several seconds of heavy acceleration. Goes away if i step on the clutch and just coast for a few seconds.
Did a little poking and proding, and noticed that the gas was just kinda dribbling into the fuel filter by the carb. Before this i had noticed that the filter was always at least half full of gas. So i assumed bad fuel pump, ordered a stock replacement from MazdaTrix. Installed it and problem immediately went away, and filter was half full again.

That was about two weeks ago. The last couple days it started bogging again. And again gas is just dribbling into the filter. WTF?? Is has been rather cool here (AZ) this past week, would that cause something like this?

Did i get a bad pump? Is there some common prob like this? Any advice on where to start would be appreciated.

Oh yeah, i know on some EFI setups the ECU adjust voltage to the pump which regulates the flow a small %. Anything of this nature on the RX.

Sorry for the long post, i'm just stumped here.
Thanks guys.
Jesse

Although unlikely, I think you may have got a bad pump. Best place to start is to check vollume and pressure of your new pump. It certainly sounds like you are running short of fuel.
Iam guessing you have already checked for some sort of blockage elsewhere in the fuel system.
Cheers Sue

Do you only have the one filter by the Carb? or one under the car also? Replace the one under the car if it is there and then retest.

Yes there are two filters. Both were replaced when i did the previously mentioned tune-up.

I did not specifically test for a blockage, because when i replaced the pump and turned in on for the initial leakage test, i could see the gas flowing freely into the filter.

I plan on blowing through the lines with some compressed air (low pressure of course) this weekend/turkey day.

How would i test the volume and pressure from the pump?

Replacing the first filter is most likely what fixed your problem not the pump.


to test volume just turn the pump on for one minute and guage the amount of fluid it flows by catching it.

Im almost positive on the -SE there isnt, but on the 2nd gens there is a thing that adjusts the voltage to the fuel pump under certain circumstances, just FYI I guess, lol.

I would definatly be looking at your pump as the problem. Either its not picking up fuel (clogged pickup from debris in the tank maybe?), or its not pumping fuel, which would be a bad pump or possibly a clog somewhere, but I have yet to see that be the problem on here.

~T.J.

thanks for the help guys.

guess i will go pickup another filter, and throw that in and check for clogs. Then if that doesn't work email Mazdatrix for another pump.

Whatever happens, let me know because I have THE EXACT SAME PROBLEM on the EXACT SAME CAR. I even bought a new fuel pump and filters and the SAME THING HAPPENED! So let me know.

Really?
who did you buy your pump through?

no more work til monday for me, so sometime in the next 4 days , i 'm gonna examine everything i can think of that my be an issue.

im having this prob 2 i put a new pump in and it stoped for a few days then came back i checked plugs so i know its not miss firing let me know

ALWAYS suspect the main line filter to the fuel pump!!!! probably at least 9 out ot 10 times that is it, then there is a sock filter on the outlet line inside the tank. To get to this you have to drop the tank, drain and flush it well. The clear plastic filter in line is best because you can see through it and see the crap .

thanks bob
great, now i can look forward to dropping the tank, wooohoooo that'll be tons of stinky fun :rolleyes:
happy turkey day gentlemen :bigthumb:

alright more BS.
so over the long weekend, i got sidetracked and only got around to swapping in a new filter (in the back by the tank). This seemed to have an immediate, although, slight positive effect on the gas flow. And based on the amount of crap in the filter that was only a few months old, my tank definitely NEEDS to be dropped and cleaned.

Anyway this morning, start the car, check to make sure gas is flowing while it warms. All good, head to work, runs great, give it a few heavy pulls through 2nd-3rd-into 4th. No probs....goto lunch, go to start after lunch, and no start. WTF? Sure enough no gas flowing into upper filter, lean down by the pump and hear nothing, no humm, no whine, nothing.

Got the car towed home after work :( Figured i'd start with the electrical. At the terminal where the pump harness joins the main harness, i am only getting 1.xx volts!! This can't be right, can it? If i hardwire the pump to 12volts it works, great flow, kinda loud humm.

So what the hell is causing me to lose 11 volts, is there some sort of relay or controller circuit??

I don't know about a stock relay, but to solve the problem without really understanding why you have 1xx volt at the pump leads, use a relay to power the pump with the signal wire in it being hooked up to 12v accessory power. Anything that gets 12v when you turn the key will serve as a signal for the relay to power the pump. Then, you can know for certain the pump gets 12v all the time because it is hardwired to the battery with the relay acting as a switch. Of course the relay is switched on with that accessory 12v.

i think i got it this time.
studied the FSM for a few minutes and learned that there is no relay or controller, so i figured i must have a short or something. So i went and started looking at things. Decided that i should check the fuses again ( for the third time today) this time i took them out one by one for a closer look, and sure as shit, the engie fuse was blown, a very clean, very slight break that i apparently missed the first two times.

so yeah i am a damn retard, and on top of that its Monday!! :p:
still doesn't make sense why i was getting 1 volt thru a blown fuse :confused:
whatever, pump is pumpin strong, we'll see how she runs tomorrow.

I'm glad yours is going again. I just went through everything you did and mine runs like crap. I had to soak and clean all of my jets in the carb and I'm second guessing that I may have accidentally swapped my primary slow air bleed and my secondary slow air bleed. Does anyone have any idea what effect this would have? I'd rather not pull the air horn again, but if I must...

im having the same problem...it must be a first gen thing.

Start a new thread with your specific problems and someone will help. (this thread is 4 years old)

If you follow these guidelines you'll get what you need more quickly. https://www.rx7club.com/1st-generation-specific-1979-1985-18/how-use-forum-request-help-diagnostic-problems-376511/


The air bleeds and emulsion tubes will not fit in the wrong places (different size and threads). The main jets will fit in either position. http://intertron.com/ron/images/carb/c17.jpg