Ziggy682

Here's the deal. My 86 N/A has been acting really strange since I bought it a month ago. When I have a full tank of gas, the car runs just fine. When I have less than half a tank, things start to get weird.

After I start the car, it will run fine for the first few minutes. After that the car starts bogging down if I give it more than 1/4 throttle. This seems to mainly happen after the secondaries have kicked in, but it will sometimes happen under 3800 rpm. It's like one or both of the secondaries are not getting fuel. Here's another weird part. If I kill the car for about 30 seconds, it will run fine for a few minutes, then start acting up again.

This had me boggled for a long time, because it seemed to randomly happen. Then I realized that the problem goes away after I kill the car, or fill up with gas.

My hypothesis(even though I might sound like an idiot):

There's some kind of gunk in the gas tank. When the tank is full, the car runs fine. As it gets low, something is partially clogging the in tank fuel filter. When I kill the car for a few seconds, the gunk floats away from the filter. Once I start it up again, and after a few minutes, it gets sucked back to the filter.

Does this seem possible to anyone? I've tried everything else I can think of. Does anyone else have any ideas? If not, I will be draining the gas tank in a few days. Also, what is a good technique for cleaning out a tank?

Thanks

Ranzo

Why don't you pull the pump and look at it? could it be that the pump is not mounted properly and does not sit low enough in the tank. Without turning some bolts you will never know.

seveninphilly

iTrader: (7)

Check the fuel filter

My mechanic said some of the (cheep) aftermarket ones fall apart and cause the same prob

Location; left side frame rail, near the engine

TRURX7

I had this problem. Here is how to fix it.
First of all this problem is common and its electrical. It is caused by not enough current flowing through critical engine management components.
Here are somethings that will help if not rid the problem completely.
1. Run a capacitor (commonly used in high power stereo systems) I ran one that was rated at one farad. You can find these on ebay for like $50. Make sure you wire it properly because you can cause a fire if you dont. I can help you in the install.

2. If you dont have that much money, Go to autozone or a local parts place and get some 4gauge or 2gauge wire. the smaller the number the better. Run some extra grounds from the battery to the chassis. Run some grounds to the engine itself. Make sure the connections are secure and tight.

3. Clean all electrical contacts, while you are at autozone, have your electrical charging system and battery checked for free. Make sure everything is working properly.

4. After doing all this, reset your battery, disconnect the (-) battery terminal and push on the brake pedal for about 5 seconds. Then reconnect the negative and you should notice a great improvement.

Let me know if you have any more questions, I had this problem before and have gone through all the trial and error parts of it and finally ridded the car of the problem. You must first realize the problem is caused by lack of current.

Thanks for asking
Horacio
reyrey68@hotmail.com
AIM: TRUDSL
Yahoo Messenger: horacio_lacayo

RETed

Peek into the gas tank - you might have a rusted tank with perforated baffles.


-Ted

Icemark

Huh???? I am hoping you don't mean a 1 farad cap on the wire supplying power to the fuel pump.

That would keep the fuel pump running for about 2 minutes after the power was shut off unless you shunted the cap with a relay and resister.

The problem he describes is very common if the fuel pump intake is dirty.

Before spending any money (like on a $50 cap) he should be checking to see if the fuel tank and pump assembly is clean.

HAILERS

It could be several things, but mine was a clogged inlet filter at the pump. The gas tank itself was free of foreign objects like rust, and looking at the filter on the pump you could not see anything obstructing the mesh filter, but when the pump was removed from the tank, I could not help but notice that the fuel trapped inside the filter was not flowing out except in dribblets. The filter was half or more full and barely dribbling out. Soooooo I soaked it in a varnish remover overnite and rinsed it off. The it would not hold fuel as described previously. After installation the engine did not cut out under hard left cornering anymore. Your problem could be something totally different. EDIT: P.S I pulled a pump out at a wreck yard once, and phewy! That car had been sitting up for years and the gas had turned to tupentine, varnish, dark brown gook. Whoof! What a smell. I passed on that pump.

Ziggy682

Thanks for your input guys. I'm going to pull the fuel pump tomorrow, and maybe drain my tank if it looks dirty.

TRURX7

With my experience with this problem (which I once had) it took me about 4 weeks worth of troubleshooting the fuel system to determine it was working properly. I did a lot of research on the topic and tried most everything. Obviously the cheapest solution is the one you want to try first. After realizing that my car ran a whole lot better (but still had the problem but not as occasionally) when I added some heavy gauge wire grounds to the block and frame, I was convinced it was an electrical problem. Engine electrical problems can be very tricky, especially when the problem is right under your nose. The grounds allow a charging system to do its job more adequately especially in the case of our RX-7s.

The capacitor I described above does not wire directly to the fuel pump or does it allow any component to stay running after you shut the car off. All this does is to keep a constant voltage to critical engine management components under heavy strain (ie above 3000rpm). What exactly is lacking the current? I dont know.
All I know is that somewhere the engine management system (ie sensors, ecu) or ignition (coils etc.) arent getting the power they need to operate properly.

The 1 Farad Capacitor in my car is wired through my stereo system, and believe it or not, it does the job well of keeping the car sounding good and running healthy.

My first suggestion as I mentioned above is to run some extra grounds and reset the ecu. However checking the fuel system never hurt anyone either.

Hope all you guys that have this problem find a cheap solution to it.
Good luck
Horacio

TRURX7

By the way,
quote
When I have a full tank of gas, the car runs just fine. When I have less than half a tank, things start to get weird.
quote
I had the same EXACT problem with mine.
quote
After I start the car, it will run fine for the first few minutes. After that the car starts bogging down if I give it more than 1/4 throttle. This seems to mainly happen after the secondaries have kicked in, but it will sometimes happen under 3800 rpm. It's like one or both of the secondaries are not getting fuel. Here's another weird part. If I kill the car for about 30 seconds, it will run fine for a few minutes, then start acting up again.
quote
Let me guess it gets worse as your fuel level goes down. It gets worse as the car warms up.
I cannot describe the problem I had with any other words.

Ziggy682

Well here's what I did today. I pulled the fuel pump out, and the strainer was brown with rust. It held fuel in there, and slowly leaked out like some of you described. I bought a new fuel pump strainer($11.99...Yes!!), and the car seems to be running just fine now(Cross my fingers). There was lots of rust all over the fuel pump assembly and the inside of the tank. I imagine my problem will come back as the new strainer gets clogged with small rust particles.

Does anyone know of a fuel additive that will eat away at rust? I looked at Wal-Mart(only thing open late) and they didn't have anything. Also, how much does it cost to get my fuel tank proffesionally cleaned to remove all that rust?

By the way, TruRX7, thanks for all your advice, but I don't think this is an electrical problem. I did think it was until I diagnosed everthing under the sun, and nothing fixed it. Thanks for the thoughts anyway.

TRURX7

Normally you would have to remove the fuel tank to get it cleaned professionally. I have heard it cost from $50-75 because I considered it.

RETed

If you have THAT much rust in your tank, your sump baffles are probably gone (see previous post).&nbsp Look inside your gas tank, the fuel pump (assembly) sits in a 4-walled section in the middle which is the "sump."&nbsp This sump keeps gas from sloshing around too much when you corner.&nbsp Corroded gas tanks tend to perforate the sump walls and cause all kinds of bog problems due to fuel sloshing away from the fuel pump.&nbsp The sump walls need to be INTACT!



-Ted

Ziggy682

I think that sump wall is intact, because the level of gas inside it was higher than the level outside of it. The tank didn't really seem to have rust floating around in it, there was just some on the sides and on the fuel pump. Anyway, the car seems to be running great now, so I'll just deal with getting the tank cleaned if it starts acting up now.