Huskyfox

About a month ago, one day the engine suddenly didn't seem to be getting enough fuel. I was taking it onto the high-way and as I accelerated quickly it had sputters and power loss, if I kept on the throttle, or especially if I increased the throttle it would just get far worse and even lose all power. If I back off the throttle long enough it builds up some fuel pressure again and I can increase speed, and so long as I keep my speed/demand below the supply then it is fine. But this generally has me limited to driving from 55-70Mph (it seems to vary, sometimes I can even get up to 90, it has moments where it flies, then others where I can hardly maintain 50) I had put a used fuel tank about 5 months ago in it that I got from Mazda Recycling. My old one was so badly rusted that it leaked. The new tank was mint looking in and out, I checked everything, it was completely rust free inside, amazingly clean, and the nylon filter looked perfect. I replaced the rubber hoses and fuel filter as well of course. So the only thing I could figure was the fuel pump, which I replaced 3 weeks ago with a NOS original.. the problem seemed to improve, though not go away, after replacing the pump it was a challenge to re-create the problem, and I could easily get up to 95 on the highway. However the next day when I went for a 2 hour trip the problem started up again half-way there, and now it's back to exactly as it was. I did a volume test from the line that inputs fuel to the carb and only got 16oz (1-pint) in 1 min:14 sec Which I hear is really bad. It's confusing that a new pump helped but didn't cure it and then stopped helping at all. I also notice that I can't give it abrupt-throttle from idle or else it just bogs down and sometimes dies.. there is always a hesitation when I first apply throttle from idle when driving, such as after shifting to a new gear.. That may be completely seperate though, because it used to do that somewhat before this fuel problem, the hesitation just seems worse now. It seems like you need to be light on the throttle from idle as to build up vacuum and then it sucks fuel through just fine (till you try to accellorate to much to fast for to long or go above 70 then it runs out of fuel, heh heh) What should I be looking at next? Thanks in advance for any help.

trochoid

iTrader: (6)

Did you use your old fuel pick-up? I've had them plugged with rust to the point the engine would idle, but die as soon as I gave it any throttle. When is the last time you changed the fuel filter?

Kentetsu

Sounds like its doing exactly what mine was when I had the main jets clogged up with gunk. Remove the carb, take of the sight windows front and back, then you can pull out the jets. Loosen them with a screwdriver, then slip a wooden toothpick into the jet to remove it the rest of the way. Chances are they are gunked up. Otherwise you may be looking at a carb rebuild or bad fuelpump. Good luck.

Huskyfox

I wouldn't put my old rusty fuel pickup into a perfectly good mint tank, this one I got had everything, even the sending unit.. like I said the nylon screen on the fuel pickup inside of it looked mint, I assume thats the part you mean..? I don't know what you could mean other than whats built into the tank, I didnt' even know you could swap out those parts in there.

Well it's in the 20's here so it's to cold for me to be removing the carb, plus i've never done that before and i'm a little weary. For the heck of it i'm going to do a volume test at the fuel pump output for comparison. Also, even though you may be right about the jets/floats, doesn't the fact that I only got 16oz of fuel in 1min:14sec seem really bad? Thanks.

trochoid

iTrader: (6)

Sorry, not paying enough attention. The S3 tanks have the removeable pickups, I don't think the earlier ones do. Did you clean out the hard lines under the body? If you are going to do a flow test, do one at the pump and another just before the carb. If the flow is the same, it's either the pump or the carb.

Huskyfox

Yeah thats how it seems, would suck if the new old stock fuel pump I put in it 3 weeks ago is a lemon, but even worse for me if I have to do carb work.

Can anyone tell me how much fuel I should have been getting in 1min?

christaylor

It sounds to me like it's a pump. Where in the line is your filter? It's for this very reason that I run a filter before the bump and a filter before the carb (though the filter in front of the carb also acts as a surge tank...).

Your best bet in diagnosing it is to find out what the flow looks like directly after the pump. It can be unpleasant rolling around under there dealing with gas in the cold, but once the gas starts burning your skin you don't notice the freezing cold as much.

Huskyfox

*chuckles* Yeah, I will be getting to it soon. The fuel pump I got is completely new and shiny! heh, what a shame if it's a dud.. I'm not thinking that that debris damaged the new one since the filter is also new and lays right before the fuel pump, besides the tank was sparkly! That’s what really gets me is that my old tank never gave me any fuel issues like this, and it was rusty junk, now a new one is in with a new pump and filter and 3 months later I have problems. Heh. I will for the hell of it replace the filter again and then do a volume check directly from the fuel pumps output. I will post the results here and hopefully someone can say if it's normal or too slow.

Huskyfox

I want to thank you all for the help and admit now that I was an idiot for not doing the obvious steps. I skipped replacing the fuel filter because it was already so new, and so was the tank... and yet that ended up being the problem. Thanks again.

trochoid

iTrader: (6)

Don't feel bad at all. I put a clean looking, renewed SE tank on my former GS, along with a new fuel pump and all new fuel lines, including new 3/8" aluminum supply and return lines. The only parts of the fuel system that was the same was the carb and I had gone through that. Somedays, I couldn't go more than 6 blocks and the engine would die from lack of fuel.

Turned out that the fuel filter I installed was plugging from the sand still in the tank from the sandblasting. Problem was, when I shut the car off the debris in the filter fell back into the tank,( high dollar barrel type filter). I finally put a stock type fuel filter back in and it captured the debris. Went through a couple of them the first week and now keep a spare in the glove box, right next to the spare spark plugs.

Kentetsu

A great many people have made the assumption that it "just couldn't be the fuel filter". Join the club...

aussiesmg

iTrader: (1)

Ditto, I suggest you keep a spar in the car at all times, after all these are 20+ year old cars and a filter cost $3.