viper1_20012004

All right this is getting really old, My car idels fine but will spudder and die when cruising.

Some times it will run fine, but ever since I've had it it starts spudering when I get to 90 or so, Now its geting realy bad I can't even go into town
I'll be crusing along and it will start stalling so I push the clutch and it will Idel then when I push the gas it will stall, so then I let out the clutch it will start and run fine for a while then stall again (some time pump ing the gas will help it start)

Ive drained the fuel tank, changed the fuel filter, blew out the fuel and return line's, and cleaned out the carb.
still no change, I'm thinking maybe fuel pump but I took the fuel line off and tuned it over, and quite a volume of fuel came out so I don't think thats it, so now I'm starting to think maybe there is a short in the wires or conectors for the fuel pump

ALSO IT THE FUEL PUMP IN THE TANK

oh ya, its a 85 gs with a 12a

Kornyfan

Sound exactly like what happens to mine. It starts at 40-45 mph and will even out after 60mph, but will sputter and jerk. If you find something out, let me know.

viper1_20012004

mine doesnt even out it still does it thrn the motor wont even fire like its out of gas

Feds

https://www.rx7club.com/forum/showthread.php?t=420409

The pump is external. More or less behind the driver's seat, outside of the car, of course...

cdrad51

do a volume and pressure test as per the manual. If not within specs, replace fuel pump.

viper1_20012004

Ok found the fuel pump volume and pressure are good, I even installed a fuel pressure gauge, and a indicator light to tell me when my fuel pump is on.

so this is what its down to, when the spuddering started ocuring today I hopped out and checked the fuel pres. it wasnt even 1/2 psi, and it stays there until I restart the car, due to the light now I know that the pump is on so I can rule that out, but I'm still lost

another thing what is the thing the fuel line goes to in line after the pump before it goes to the metal line and heads to the carb. its about the size of the oem fuel filter but a little smaller (maybe a check valve) and what does it do

Kentetsu

Sounds like the check and cut valve. This is there to relieve vacuum/pressure buildup in the tank and cuts the fuel flow in case of rollover. If you want to eliminate it as a possible cause, just replace it with a fuel filter (temporarily, of course).

Kentetsu

Does it make a difference how much gas is in the tank when this happens? Just curious if maybe you've developed a hole in your pickup tube, or maybe some type of floating clogging material in your tank...

cdrad51

Your fuel pump is dying, IMO. Replace.

SimRX-7

having been through it all...(as someone posted the link to my thread)
replace the pump!!!
the stock holder is capable of holding most aftermarket FI external inline pumps.
napa has a really decent pump and i am sure autozone as well. just check your manual and see what pressure outputs should be and match the new pump to those specs. and the instal is very simple...no worries there!
GOOD LUCK!!!

tracer

Bottom Line: I had a long drawn out problem of your exact description and a new stock fuel pump fixed it for good.

Story: Same problem as yours. Fuel Lock? I had no idea.
• Drove around without a gas cap on. Worked for a couple days.
• Put in a cheapo fuel pump, and that fixed it temporarily.
• Problem came back. Rebuilt the carb, and it went away for a little while. (It was time for a rebuild anyway)
• Problem came back. New stock fuel pump. Life has been good since. For several months. It's daily driven. All the other little things just made the original pump's life harder. And the cheapo Pep Boys special was designed around "planned obselescence". Or so I believe.

That was the only "demon" I've experienced with the car, and it's nice to have sent it back to hell... I feel for ya.

viper1_20012004

thats was I thoght at first because it would only do it if the tank was a 1/8 or lower now it does it no matter what full or emety still does it

my dad also said it was the fuel pump, but I'm still looking for a other posible answer because it flows good vol. and pressure when I tested it unless it only works some of the time

I'm going to see if I can find a e-fuelpump somewhere in our shop to try it

lovintha7

Sounds like the pump is going to me. It will work fine under certain conditions, but dies later. I'd try replacing the pump. Summit has a fairly cheap Carter pump as well as FPR's.

viper1_20012004

I repaced the pump that wasnt it
This is really getting on my nerves

But I did find out if I block off the return line it does it as much (like 75% less)
So i've narrowed it down quite a bit but still I'm lost

cdrad51

Which pump are you running?

viper1_20012004

I don't know who makes it, but it runs about 5.5 psi

viper1_20012004

now there is no check valves or whatever they are; fuel goes from the tank to the pump to the carb, and it still does it, so I am pulling the tank out tomarrow if thats not it I think I am going to light it on fire and push off a bluff, If I didnt have to spend all my money on this thing, I would have my 72 chevy pickup done, althogh I might just trade my ford for $800 and a 2nd gen that needs a rebuild

Rogue_Wulff

This may sound stupid, but just might help. Have you tried leaving the fuel cap loose? If the tank is not venting correctly, it could be causing the pump to starve for fuel after running for a while. Ever hear a "Whoosh" when you remove the fuel cap? If so, the vent system is plugged.

viper1_20012004

yeah I tried that, it made is worse

viper1_20012004

ok after putting about 50 man hours in to it trying to fix it I found the problem, I feel real stupid now

ya see I put a brass reusable fuel filter in her and it doesnt flow enough, because I pulled it out and it runs perfect

Kentetsu

Hey man, at least you found the problem. Congrats! Now go burn some rubber and see what breaks next!

cdrad51

Oh you dork!

j/k, glad you found the cause of the problem. So it drives perfect now?