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Discussion Starter #1 (Edited)
Won't idle with more than 1/3rd tank of gas.<Solved>

I've had cars that would not idle when near empty, or just after filling up, due to trash or rust in the tank, but mine won't idle until it is near empty.

At first I thought it was trash getting stirred up, but I ran it near empty and put a couple of gallons in, and it would still idle.

It idles great when the level drops below 1/3rd tank, but won't idle at all when full.

The carb was rebuilt and set up by an experienced Samurai guy. I asked him about it and he says he has never heard of such a thing. I can't bring it back to him because he is in Nevada and I'm in California. It started doing this, to some extent, from the first time I filled it up after buying it. Of course, it was under 1/3rd tank when I bought it.

It got worse and worse over several tanks, until it stopped idling altogether when over 1/2 a tank.

It also idles fine upon cold start, but as soon as the engine starts to warm up, it dies if over 1/3rd tank.

I've checked the vacuum lines and they look good. The only thing is that the vapor canister return line is not hooked up and is plugged. The carb vent line and tank line are hooked up though.

Edit problem solved;

So the saga of the intermittently idling Samurai began on the first tank I put in it after purchasing it.

For a while, it would surprise me by suddenly running more smoothly and at higher RPM, whereupon I could turn the idle down to 1k. Generally, later that day, or the next, It would not idle and I would turn the idle back up to 1500.

The previous owner told me that it had sat with the same fuel in the tank for a year, so I figured it was trash in the carb. I ran many cleaners through, and sprayed cleaners through the ports. Early on, it seemed like it would fix it some times, for a while. I really did not want to pull the carb off of it, and so I lived with it.

So a couple of weeks ago, I broke down and bought a reman carb, even though the one I have was a fresh rebuild(a year ago) from someone who knows what they are doing. I just did not feel like pulling it apart and wind up having the Samurai sit in the driveway for a month after I lose some hard-to-find part or screw up in some other way.

So I slap the reman in and it STILL DOES NOT IDLE!!!! You can imagine my frustration.

Back when this first started, I ran all the checks on the carb, replaced vacuum lines, made sure everything was hooked up right, all that stuff..., and came up empty.

Won't idle,(on a freshly rebuilt engine that runs GREAT otherwise) it's gotta' be the carb right? No, of course not.

So I get back to basic troubleshooting. It's the idle circuit. What would keep a good carb from idling? The fuel cut solenoid. Thing is, I check that way back when. I pulled a connector while the igintion was on and heard clicking from the carb. I was not sure which solenoid was clicking, so I pulled the fuel cut solenoid out and had my girl turn the key on, and felt it pulse in my hand. Musta' been a good day... Grrrr...

Today, I pulled a connecter and put it back in, while the ignition was on. There was no clicking form the carb. NONE!

So, I checked for voltage at the connector. There was about 8 volts between the two connectors. I figured, well, guess there is something pulling the voltage down. I checked for the voltage from hot to battery ground and it was 12 volts. Hmmm...

I tried grounding the negative side of the solenoid to battery with the positive side fed from the ECM, and "CLICK" Sumbirch...

So, It's gotta be the ECM ground, but whats up with that? It still runs GREAT, except for the idle.

So I dig in the FSM, and find out where the two ECM grounds are. One is near the thermostat and it is fine. The other is on the firewall near the negative terminal of the battery. I give it a tug. It's loose...

So, I give it 4 or 5 turns with the screwdriver, and it bottoms.

I start it up, and turn the idle down to 1k.

The idle is alive, IT'S ALIVE.

Time for a frosty beverage...
 

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What you are describing sounds like a negative pressure vent not a positive pressure vent. The vent line to the canister is just for expelling vapor from the tank. It can draw vapor back into the tank but not enough to equalize pressure by itself. Try removing the fuel cap and seeing if it idles ok. The fuel cap is for relieving the vacuum draw on the tank as the fuel level lowers.
 

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Discussion Starter #3
I tried removing the cap and nothing changed. Even tried driving around for a bit with it off and saw no change. Grrrr...
 

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Discussion Starter #4
Still don't know why it would idle at low fuel level, but I figured out the problem.

The PCV valve was bad. While troubleshooting, I tried plugging it, and the idle at low fuel level got a lot smoother. I replaced the valve, filled it up, and it still idled.
 

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wow you lucked out! Never in a million years would I have guessed that the PCV valve is affected by the level of gass in the tank.
 

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Discussion Starter #6
There is no connection between PCV and fuel level. The only thing I can figure is that the excess vacuum leak caused by the bad PCV(PVC causes a calibrated vacuum leak when working properly) put the carb right on the edge of what it could compensate for. Fuel level must have some effect on the carb's metering ability. That is the only thing that even comes close to making sense.

I'm just happy that it idles now. Sure wish I lived somewhere where I could switch to 4 Mikunis.
 

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sigh.. i had to give up my mikunies, such a hassle swapping them out every few years and I was really putting some wear on my rig with my heavy foot.

my brother in law has them now in colorado and he hasn't installed them yet as far as I know... breaks my heart.

Your summation of what's goin on with the idle is better than anything than I can come up with. I would have been chasing my tail on that one for weeks.
 

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Discussion Starter #9
Well, spoke too soon. It idled great for a while, and has now taken to randomly idling and not idling. I never know when it will idle one minute to the next.

I am SO glad I got past Smog before this started...

It always idles fine when cold. It is once the engine warms up that the idle issues start.

Also, when I took it for a long ride Sunday, it started a very high idle, like 2,500 RPM or more, and the hot idle screw would not change that. It did that for almost an hour, and then stopped idling altogether, before getting back to the random idle / not idle. I did not try pulling the idle up hose or TWSV connector as I had not run into this problem before. If it happens again, I will try that.

I can also tell that, when the idle is working, the engine feels and the exhaust sounds smoother at low rpms.(I keep the engine reved up most of the time if not accelerating) This is my biggest cue as to when it is going to idle and not idle.

I also noticed that the fuel level in the float bowl is slightly high. It sits just over the top of the ball that the manual says the level should be inside of.
 

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Discussion Starter #10
Thanks to one of Baratacus's previous posts, I found that the solenoid valves for the secondary actuator and the idle up actuator's electrical connectors were crossed. Fixing them has done nothing for the idle, but it made for a nice power boost, now that the secondary side of the carb is working properly.

The idle situation seems to be getting worse. Guess I'll pull the carb, set the float and see if there is any trash to be found in it.
 

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well that should allow the high idle to function at the right time as well... but it won't solve the "not idling at all" problem. If your fuel line is good, your return line is good, your vent is good, your vacuum lines are all good... there's not much left to check other than the guts of the carburettor.
 

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Discussion Starter #12
I removed the idle mixture needle jet screw and blew carb cleaner into the jet. This restored my idle so I figured there must have been some trash in the carb.

The next morning, the idle was not working, so that evening I pulled the drain plugs and sight-glass. I sprayed carb cleaner into the jets visible through the drain plugs, as well as the pilot jet. I pulled the fuel inlet line and fitting. When I removed the fitting, I saw fine black particles, which I assumed were pieces of hose.

The lines look and feel good, but I figured some of the inside of the lines must have been scraped off when they were reinstalled after the rebuild. I have heard of this happening with old lines. I flushed out the fuel inlet port and put the carb back together.

Still no idle... At this point, I figured that the next step was to disassemble the carb, but it was getting dark, and I had a trip planned for the next day.

For the trip, I packed the tools I would need to remove the drain plugs and a can of carb cleaner. Thankfully, I did not have to do that, as the Samurai ran great, except for no idle(actually, I had a very high idle set, and it would die when braking or going down-hill if I did not give it extra gas.)

Sometime during the trip, about halfway through the 500 mile trip, I noticed that I was not having to give it gas when braking, so I dropped the idle back down, and it held. It held through filling the tank up, and has continued to hold through 2 mornings. Yesterday, I set the idle down to 800 RPM and it still ran. I put it back up to 900 where it idles more smoothly and will leave it there until next time I have to smog it.

I did install a new fuel line between the pump and carb, with a clear inline filter, just to make sure that the old lines don't cause problems. I also bought new lines to replace all of the rubber fuel lines, but did not have time to do that yesterday.
 

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Discussion Starter #13
So the saga of the intermittently idling Samurai began on the first tank I put in it after purchasing it.

For a while, it would surprise me by suddenly running more smoothly and at higher RPM, whereupon I could turn the idle down to 1k. Generally, later that day, or the next, It would not idle and I would turn the idle back up to 1500.

The previous owner told me that it had sat with the same fuel in the tank for a year, so I figured it was trash in the carb. I ran many cleaners through, and sprayed cleaners through the ports. Early on, it seemed like it would fix it some times, for a while. I really did not want to pull the carb off of it, and so I lived with it.

So a couple of weeks ago, I broke down and bought a reman carb, even though the one I have was a fresh rebuild(a year ago) from someone who knows what they are doing. I just did not feel like pulling it apart and wind up having the Samurai sit in the driveway for a month after I lose some hard-to-find part or screw up in some other way.

So I slap the reman in and it STILL DOES NOT IDLE!!!! You can imagine my frustration.

Back when this first started, I ran all the checks on the carb, replaced vacuum lines, made sure everything was hooked up right, all that stuff..., and came up empty.

Won't idle,(on a freshly rebuilt engine that runs GREAT otherwise) it's gotta' be the carb right? No, of course not.

So I get back to basic troubleshooting. It's the idle circuit. What would keep a good carb from idling? The fuel cut solenoid. Thing is, I check that way back when. I pulled a connector while the igintion was on and heard clicking from the carb. I was not sure which solenoid was clicking, so I pulled the fuel cut solenoid out and had my girl turn the key on, and felt it pulse in my hand. Musta' been a good day... Grrrr...

Today, I pulled a connecter and put it back in, while the ignition was on. There was no clicking form the carb. NONE!

So, I checked for voltage at the connector. There was about 8 volts between the two connectors. I figured, well, guess there is something pulling the voltage down. I checked for the voltage from hot to battery ground and it was 12 volts. Hmmm...

I tried grounding the negative side of the solenoid to battery with the positive side fed from the ECM, and "CLICK" Sumbirch...

So, It's gotta be the ECM ground, but whats up with that? It still runs GREAT, except for the idle.

So I dig in the FSM, and find out where the two ECM grounds are. One is near the thermostat and it is fine. The other is on the firewall near the negative terminal of the battery. I give it a tug. It's loose...

So, I give it 4 or 5 turns with the screwdriver, and it bottoms.

I start it up, and turn the idle down to 1k.

The idle is alive, IT'S ALIVE.

Time for a frosty beverage...
 
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