electrical gremlin

Suzzy-Q

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Used to have to install “hot start” switches on turbos for the reason of when ppl are ripping around the engine and whatnot is all hot obviously, then when you shut down and don’t move you can actually gain engine temp due to no more circulation also the heat can soak into the intake as well, so with air and coolant temps reading so high it screws up the fuel table and isn’t giving proper fuel for starting. Hot start switch was installed in series on one of the coolant sensor lines so when you turn the switch off your coolant sensor reads failed and adds fuel
 

kidwoo

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Did it again this weekend.

I'm convinced it's a heat soak/vapor lock thing with the fuel line. If I put a few CC's of gas in a cylinder AND use the hot start switch I've got on the coolant line, it fires up and runs. Otherwise it just burbles and bit and dies, then won't start at all. I think Frostbite is correct.

I got a new fuel line I'm going to install, heat taped and probably rerouted underneath the exhaust instead of over the top of it. If that doesn't fix it, I'll probably get my pipe and y-pipe ceramic coated.

I'll report back after another weekend with the fuel line shored up. If it's happening in the rail, I really don't know what to do other than tape it. I've already got my heat shield taped.
 

kidwoo

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Already tried. Not enough to keep it running.
 

89sandman

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Have you checked to see if the wiring to the injectors is "strobing" when it won't start? If the ecm grounds the injectors to cause them to fire like a car, could be a capacitor in the ecm is shorting out. I see this often in cars, a capacitor starts to leak and corrodes the legs that connect it to the board causing the injectors not to pulse intermittently.
 
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kidwoo

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Have you checked to see if the wiring to the injectors is "strobing" when it won't start? If the ecm grounds the injectors to cause them to fire like a car, could be a capacitor in the ecm is shorting out. I see this often in cars, a capacitor starts to leak and corrodes the legs that connect it to the board causing the injectors not to pulse intermittently.
Now that I haven't checked. I was running a hillclimb/race programmed ecu for a while and still had the same problem. Cat had mine in hand to reflash it in an attempt to fix the problem. I'd like to think they'd have noticed something like that.

Would that be evident looking at the bottom of the ecm? I know you can see a capacitor or two on them.
 

89sandman

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Just open up the ecu and bend the capacitors over slightly, if they have leaked it is usually easy to see. The legs will be black and the board might be discolored in that area.
 

kidwoo

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Didn't see anything weird with the capacitors. Although it's tough to recognize 'black' against that soft polymer stuff that's well.....black


I just wrapped the fuel line and rail with a velcro heat blanket made for fuel lines.

I'll have it out this weekend and see how it goes.
 

kidwoo

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They make what they call "noid" lights available at most auto part stores. You can usually rent them for a few bucks they will plug right into your harness at the injectors. Plug one in and pull the rope if it flashes you're good to go, simple and quick.

https://www.youtube.com/watch?v=6uj0X5sWRUc
It's not an continuous problem. My sled starts and runs fine. It's only after it's been run hard and sits for a while, heat soaking. I guess I could take those lights with me but if it were the harness it wouldn't start ever I'd think.

We'll see how the fuel like wrap goes. Thanks for all the ideas. Much appreciated.
 

89sandman

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Yes you'd take them and use them when it won't start. A lot of things expand and contract with heat, electrical connections can be lost and gained when this happens. I would be most interested in seeing if your injectors are strobing when your no start occurs. You obviously have a fuel problem because adding fuel to the cylinders makes it fire. Injectors would be the first place I'd start the trouble shooting process. The shotgun method of trying to find a problem has never made sense to me.
 

kidwoo

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Yes you'd take them and use them when it won't start. A lot of things expand and contract with heat, electrical connections can be lost and gained when this happens. I would be most interested in seeing if your injectors are strobing when your no start occurs. You obviously have a fuel problem because adding fuel to the cylinders makes it fire. Injectors would be the first place I'd start the trouble shooting process. The shotgun method of trying to find a problem has never made sense to me.
Well to be fair, I've been buying only one expensive part at a time.

Therefore drawing out the process as long as possible. :face-icon-small-hap


The noid lights test your harness and electrical system, not the injectors. I've been through two of everything leading up to the injectors at this point. I can hear the injectors click so I have to assume they work. IE: I don't think the problem is with the harness/ECU causing strobing. Like I said, I even tried a different ECU.
 

summ8rmk

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Well to be fair, I've been buying only one expensive part at a time.



Therefore drawing out the process as long as possible. :face-icon-small-hap





The noid lights test your harness and electrical system, not the injectors. I've been through two of everything leading up to the injectors at this point. I can hear the injectors click so I have to assume they work. IE: I don't think the problem is with the harness/ECU causing strobing. Like I said, I even tried a different ECU.
Before shutting off sled, how long do u let it idle?


Legends ZX2 SR
 

kidwoo

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Before shutting off sled, how long do u let it idle?
Plenty long enough. Trust me it's none of the 'normal' things

1: TSS disconneced since day one
2: always idle down, actually removed a tether I had to prevent hot stops
3: Started with carbed sleds, always work the throttle when pulling the rope


It's vapor locking. It has to be. It's gotten worse since riding in warmer temps. And fuel in the cylinder plus the hot start switch on the coolant temp sensor forces fuel. There's a bubble in there.
 

summ8rmk

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With an in tank fuel pump at 40+psi, how many pulls should it take to purge the air from 2ft of fuel line?
I believe it could be vaporized fuel but the fuel pump should be able to expel the air in the line. It may take 7pulls or 70pulls, that i do not know......

Legends ZX2 SR
 

kidwoo

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It may take 7pulls or 70pulls, that i do not know......

I've covered that whole range. :face-icon-small-hap


The fuel pump isn't getting full juice from the stator/regulator, and not for very long either.

Usually it will start, run for about 2-3 seconds but will then just gurgle and die. Then begins the dead pulls.

That tells me there's enough fuel in the cylinders/rail to at least start the thing, then the bubble gets pushed in and there's not accessible fuel for the plugs to fire anything.

What's funny is that since it's warmed up this spring, if I park the sled overnight, it will do it in the morning too. Which if you think about it is the same scenario......running and then sitting for long enough that the phenomenon occurs again. It wasn't doing this when it was cold outside.
 

summ8rmk

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I've covered that whole range. :face-icon-small-hap





The fuel pump isn't getting full juice from the stator/regulator, and not for very long either.



Usually it will start, run for about 2-3 seconds but will then just gurgle and die. Then begins the dead pulls.



That tells me there's enough fuel in the cylinders/rail to at least start the thing, then the bubble gets pushed in and there's not accessible fuel for the plugs to fire anything.



What's funny is that since it's warmed up this spring, if I park the sled overnight, it will do it in the morning too. Which if you think about it is the same scenario......running and then sitting for long enough that the phenomenon occurs again. It wasn't doing this when it was cold outside.
Have u tried using a 9v battery to purge the fuel line? Maybe 5seconds?

Legends ZX2 SR
 

kidwoo

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Have u tried using a 9v battery to purge the fuel line? Maybe 5seconds?
I haven't.

And honestly that doesn't fix the problem. I'd rather just figure out how to make it stop. I'm not going to carry around a battery with me and disconnect the fuel pump. It takes the same amount of time to drop fuel in the cylinder.

I'm sure it would work.
 

summ8rmk

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Just me thinking.....
There must be a bad valve or seal.
This is not a carbed engine with 8si.
40 lbs of pressure in a sealed line.... fuel cannot just disappear.
It is either go backwards through the pump or forward, through the injectors into the engine (causing flooding) or through the return line back in to the tank (causing an empty line).

What keeps the fuel in the line?
Seals/valve on the pump.
What about the fuel rail and return line?
Is it a pressurized valve that opens at a set point?

Legends ZX2 SR
 

kidwoo

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I've been thinking the same thing.

I don't smell any vapors under the hood, and my tank is never pressurized (so it's either not going backwards or the tank vent is working well)


If I had to guess I'd think it's pushing it through the injectors. It would explain the initial start, and then burble/die. Fuel in the throttle bodies/cylinders, but then a blank spot.

The 40psi is only happening when it's running. So it's going somewhere when the sled is off. Going back through the pump seems unlikely. I've got another pump since I replaced mine, I might just see if I can blow through it backwards.
 
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