niterydr

Greetings round motor gods! I've had a dilema with my winter car ('85 gsl-se) since i bought it last month. Once it reaches operating temperature and has run for more than 5 minutes at that it begins to 'buck' at high rpm (above 4500) and gradually the bucking and the 'fuel cut' or so it feels, gets worse and worse, and eventually the car will reduce the rpm until it can't idle. The only solution I have found to this problem is to shut it off for approx. 10 seconds and restart the car. This makes the problem go away for another 5-10 minutes. I've checked my tps, thats fine, it looks like its getting good spark (all resistances check out), and judging from my tuning experience with turbo'd cars (granted this is n/a), it almost feels like a fuel cut. We noticed that the fuel pump becomes quieter when this situation occurs.
So to remedy this we hardwired the pump with 10 gauge wire straight from battery (obvously using a 30amp relay in the circuit, im not a moron).
I have a new fuel filter sitting in the back of the rx7 that will be installed this weekend. Here are a few of my theories.
1) tank has rust in it and clogs the pickup, and when i shut the car off it floats down due to lack of suction, and eventually reclogs the orfice.
2) something electrical that I don't know to check
3) faulty fuel pump? injectors? etc..
any suggestions o knowledgable ones?

Wankelguy

It could be a blockage in the fuel pick-up tube in the tank. You can check by disconnecting the fuel supply line at the carb and observing the flow of fuel into a can when you have the key in the ON position. Or it could be a dirty fuel filter, as you already mentioned. The little fuel inlet screens on the carb are frequently overlooked as a source of potential problems as well. I doubt it is an electrical problem, as it does sound like your float bowls are running dry. I would continue to check the fuel pump and lines. The tank was completely blocked in the '80 I was given. It had sat for 10 years, and the pickup tube was so blocked, I could not blow through it.
I ended up getting an old bass guitar string, bending a little hook in the end, and chucking the other end in my hand drill like a little roto-rooter. I fed it in while turning it with the drill and it cleaned it right out. Then I squirted some carb cleaner in the pick-up tube and rinsed out the tank. The problem is the pick-up tube has 3 90-degree bends in it, with a horizontal section inside the tank which sort of sags down in the middle. That's where the crud had accumulated in my tank. HTH. -WG

1985 gs

i had the same problem with my gs, found the fuel filter was badly clogged and tank dirty. replaced the filter and had the tank steamed cleaned and sealed. Its been all good ever since.

RacerX7fb

A way to check the fuel in an SE is to get down and look under the back of the car, theres a bolt that you can remove CAREFULLY and drain some into a bottle.

niterydr

umm this car is fuel injected, not carburated mr. wankelguy, but thanx for the input.
Im going to attempt to replace the fuel filter (once i locate it on the car)tommorrow, hopefully I won't destroy any lines in the process. If that doesn't do it, i guess its time to drop the tank this weekend and clean it out.
I'll keep everyone posted, wish me luck.

Wankelguy

Whoops! I missed the "SE".
I'll give you another helpful tip though. When you pull the tank, take the sending unit out and take the tank into a dark environment, like in a garage with the door closed. Then when you shine a flashlight in the sending unit hole you can see inside the tank much better. It's like the whole inside of the tank lights up. -Mike

speckamp

the fuel filter on the -SE's are on the rear of the car, up behind the fuel tank, once you get up under there, it's kinda a "duh".

Filter / crud in the tank is a possibility, also check your cats (if they're still on the car ) to see if they're all clogged up. The cats on my -SE went and it started to run bad, made no power, ect.. if the fuel system cleaning job doesn't fix it, just drop the cats off the car and look into them to see if the catalyst matrix is discolored, or worse broken up and clogged into the cat behind it.

good luck
--matt

niterydr

'dropping the cat' doesn't work well in minnesota, i'll just wip out the sawsill and put in a straight pipe , but thats the last resort (lol).

ZeroBanger

I don't usually answer questions in this forum, but I have some similar experience. My answer warrants you having to read my long drawn out story. long before I bought my FD, infact back in 1989 I saw a 1982 RX7 and bought it (not knowing anything about engines). Anyway being a kid with a fast car I got crazy and crashed it going around a heavy turn, the car fishtailed and my rx7's rear smashed into a huge tree.

It was in the garage being repaired and the owner of the garage said he could save me money by getting a used gas tank from the junkyard and he will put on the insurance claim that its a new gas tank. he did that with all the parts I needed and he gave me money back.

Ok, so after a few weeks (car was painted too). I drove the car and after about 500 miles it would cut out on me. It would stop working. Gosh I am really babbling, huh?

Anyway over the next two months I would get my car back and from a few hours to a few days my car would stop running. I mean...I would be driving and it would stop. Kinda the say you described it. They took my car to a specialist, flushed the entire fuel system and it ran for about 1500 miles and then stopped again.

Guess what the problem was? The gas tank had sludge in it from the junk yard, which damaged the fuel pump. Now Its been like 13 years, but if I recall they said the RX7 had an Electro-magnetic fuel pump. All that junk caused it to malfunction. They replaced the gas tank and fuel pump and then it worked.

Now, did I have to tell you that long drawn out story? Probably not, but what else do I have to do?

niterydr

nice reply, well changing the fuel filter did fix the problem, but now its doing the cutout again...argg...about ready to wrap this car into a tree (gotta re-instate full coverage) and start over!!!!

ZeroBanger

Did you check the fuel pump? Here is why. when they fixed my car way back in '89...they would change the fuel filter and it would run for like 200 to 1000 miles. Then the fuel pump would clog the filter and fuel lines again. It did not stop until I got the fuel pump and gas tank changed. You should check your filter and see if its clogged again. I'm not saying 100 pct that it is your issue, but its an idea.

niterydr

it could be the filter, but for ***** and giggles i unplugged my tps on the way home..and it didn't affect anything...maybe it is because my throttle body doesn't close all the way..grr..now i have to tear about my tb, afm, and probably mess with the fuel again! Also, fixing my radiator leak would be fun as well, sounds like im going to have a busy day off.. (finally got rid of the checker 'autolite' wires and got some ngk's on their, $26!!!).
wish me luck, thanx for the imput.

MustGoFaster

*well, cleaned the throttle body/afm and it started right up and i went inside to let the smoke screen do its thing..well it was already low on gas, and apparently it ran out when it was trying to idle (very lumpy), so i went and got gas, now the car won't fire...just floods out the sparkplugs (fuel actually coming out of the holes!!), and thats it..i assume i have everything adjusted correctly, this is really pissing me off, i was 1/2 hr late to work yesterday, and since i just started my job, if im late 1 more time, i get my 'starting' pay pushed back another 90 days before i can get a raise for a punishment!!
wtf should I do? how do i fix it?.

*damm this post was by niterydr...apparently my friend ryan is signed on this computer as well..

niterydr

well it runs now, and idles at 2k, can't get it to idle down..any suggestions?