SJ410 fuel problem after tank replacement

[bramlauwers]

I've got a Suzuki SJ410 1986-model (std carburetor, 997 cc engine), which used to run just fine. But, the old fuel tank was rusty and leaking when filled more than half, so I replaced it with a second hand one which seemed ok, at least it does not leak. Now since I installed the "new" fuel tank, the car runs fine the first 5 kilometers or so, but then it suddenly looses power just as if there's no more fuel coming. This only happens while rolling the wheels. When I let the car rest for about 10 minutes, it goes fine again, some kilometers, and then the same behaviour comes back.

While warm, I've tried running it in neutral at a couple thousand revs for some minutes and then it runs fine too. But one I start rolling, after a short while it just dies again. I've tried emptying all fuel from the tank and refilled with fresh fuel, this didn't help. The fuel filter is quite new, replaced it about a month before I replaced the tank. Have not yet cleaned the carb because I reckoned it should be ok considering the engine runs fine when standing still in neutral.

This problem really puzzles me. Any suggestions?

[ack]

since you have gone throught the fuel system pretty thoroughly, i have only two guesses for you:

There is something big in the tank that is getting sucked into place over the fuel pickup while the engine/fuel pump is running. after a few minutes of sitting, the blocking item floats away allowing fuel to flow again for a while.

You have a loose ground in the ignition system that is causing the ignition to cut off from road vibrations.

just a couple of educated guesses, there...

there is an '86/'87 410 factory service manual in pdf format at Ack's FAQ (see link in signature). Do a search for fsm. It's the first link in the resulting search list.

I hope that this helps!

[captron]

Check the fuel cap.

[Baratacus]

I have a samurai so I don't know a lot about your fuel tank or how similar or different it is from mine. I do know that a lot of people don't hook up their vapor return line properly or it gets plugged by debris. When this happens, a vacuum forms in the tank as the engine draws fuel out of it. If air can not enter the tank through the vent on the vapor return line the vacuum pressure overcomes the pumps ability to draw fuel. When you shut the engine down, the tank will equalize pressure since the engine is no longer sucking fuel out of it. Try taking your gas cap off and see if it still has the problem. If removing the gas cap works, then you need to find out where in the venting system it's plugged.

[captron]

Very well said. Take the advise to the bank. Hope it's something simple like a plugged vent line or new fuel tank cap

[bramlauwers]

Hi! Many thanks for tha replies so far. I did not write that I tried loosing the fuel cap while this behaviour occurs, to check if the tank is drawing vacuum, but even while riding without the cap on, it still occurs. I don't think it's a vacuum problem but still I could suspect the fuel feed lines. Originally, there is a metal pipe from the fuel tank to the fuel filter, but the owner of the second hand tank that I bought has cut that one about an inch from the tank outlet so I had to replace it with a quite thick rubber fuel line. Could it be that this rubber feed line from the tank to the fuel filter is wrong dimension? It's quite a lot thicker than the original metal pipe. I've got ok clammers on it and checked so it's fitted properly but still.... could this be an issue that the pump cannot draw enough pressure because of the non-standard setup here?

[Baratacus]

well that seems to eliminate the vacuum theory... The larger diameter fuel line shouldn't be causing a problem, It may need a few extra cranks to get it running when cold starting, but it shouldnt cause it to choke after it's been running a while. Even if you damaged the hard line when clamping it, it shouldn't cause an intermittant failure. I would have to go with either of Ack's first 2 assesments. Something floating over the fuel pickup or a loose ground on the ignition. If this problem didn't start untill after you changed the fuel tank, its probably NOT going to be the ground wire issue, but don't rule it out.

[bramlauwers]

Thanks again. It's hard to diagnose the tank on the inside, but I'm going to try first putting in a brand new fuel filter, and if it still occurs after that I'm thinking of replacing the fuel tank - again, but this time with a new one. Maybe the second hand tank was faulty... I'm going to keep you updated on the outcome when I know more.

[murphysj410]

Sorry about butting in but i got this problem to with my sj410 i have replaced all things on mine due to that i restored it about a year, its had a head new gasket set, new metal and rubber fuel line, fuel filter, ht leads, disruptor cap, posh spark plugs, contact points, coil, even a extra earth wire (the whole thing) now its has been cutting off when i drive it, only once and a while this happens or some times for the whole day, and it is hard to start on the choke this has been doing this for about 4 months now and iv been talking to my friend who is an x mechanic he says that there may be crap in the carburettor so get a air line take the carb apart and clean it and give it a blow out so don’t bother with red ex, funny that which is the only thing i have not checked yet lol so i may give that a go this Saturday. Hope this helps (And i all so put a little hole in the fuel cap so it’s not an air lock)

[Baratacus]

Keep in mind that with Bram the problem didn't start untill he replaced the tank. Logic dictates that the problem would be related to the tank. Since Samurais are anything but logical, it could be anything.