91 only runs on 1 and 4 cylinders

[jono]

Ive just  done my valve shims and remounted the carbs on my 91 3xw when I got the bike the wiring was a mess the PO removed the abs system and added a starter button because the original starter switch was broken so while I was waiting for my shims to arrive  during this covid thing I tidied up the wiring loom and fitted a new  starter switch  now when i start the bike it will only run on 1 and  4 cylinders ive swapped coils ,checked all the connections every thing looks good al 4 pugs have spark and the 2 middle plugs are wet but it wont run on 2 and 3 ,the only indication of something wrong was a couple of times the plugs have sparked when I was touching them like something is shorted out and I wasn't touching the starter button also when I put a test light on the power wires to both coils the red/white ones the test light goes on when grounded .I am sure its not the carbs they ran mint before I started working on the bike .
I wonder if somehow Ive shorted the ignition black box or is there a condenser somewhere in the wiring system
jono

[ajacstern]

Compression? The inner two would go first from overheating I think. I think you would still get them firing though. Are you saying the spark plugs were firing even when not touching ground of the bike? I would try replacing the plugs because that sounds like insulator failure. You can also try starter fluid because if there is spark and compression and you add starter fluid you will hear something in my experience. If spark is at the wrong time though that could be dangerous.

[Pat Conlon]

Switch coils.
Take the left coil (#1/4) off and move it over over on the right side. Put the right coil (#2/3) over on the left side.

Now see if cylinders 2/3 fire off and 1/4 go dark....see if the problem follows the coil.

If the #2/3 problem remains, then you know it's not the coil.

[jono]

it's not the compression it's good ,the shim clearences are good ,carbs are good .Ive swapped the coils Pat and same problem .I'm pretty sure its a wiring problem the 2 main things that I'm wondering about,
is the reserve switch malfunctioning I read some where that when the fuel level drops to reserve status the ignition cuts to 2 cylinders
or maybe ive shorted out and damaged the ignition sender unit ?
the wiring has been changed significantly when they removed the ABS and it fire's on 1 and 4 with the reserve switch unplugged and the speedo unit wires unplugged and the wire from the clutch lever unplugged as well
will it fire on 2 cylinders if the ignition box is damaged or would there be no spark at all ?
I'm going to buy a multi meter in the weekend and see if there is a wire shorting out
Jono

[Pat Conlon]

Yes, you need more than a continuity test, the multimeter will ohm test the circuits and connectors.

Isolate out the reserve switch (bypass) the reserve function which we know affects the fuel delivery.
Does the reserve switch also interrupt power to 2/3 coil? Jury's out, but I know it affects the fuel pump.

Make up some temporary jumper wires (both + power and ground) and run them directly from the battery to your #2/3 coil. See it that wakes up #2/3

If it does, then you have a power delivery problem to that coil.

If not, then I would suspect an internal signal problem from your ignition box

I don't think your crank signal is at fault. With your DCI system you have a single pick up for the crank signal to your ignition box, so if that works for 1 coil (1/4) it should also work for 2/3 coil.

Hang in there. These problems can be infuriating.  Study the single line diagram. Try to understand the logic on the different circuits. If the logic is unclear to you, ask for help.
CutterBill put together an excellent current flow diagram for your '91.
http://www.fjowners.com/index.php?topic=18991.0
^^^ This helps me understand the circuit logic. Be methodical. Step by step.
Follow the start/no start flow chart in the GYFSM. Murphy's law dictates that whatever step you bypassed in the flow chart, holds the answer to the problem.
Avoid the temptation of buying parts until you know for sure. (don't ask me how I know this)

As a general rule: If the bike was running before storage or before your service work, and now it's not running, rarely is it caused by an electrical component failure.

Let us know how you are doing..... cheers.

[Old Rider]

Mayby its getting way to much fuel on 2 and 3 what are the mixturescrews set at?

[jono]

No  I'm pretty sure it's not fuel related, the carbs were good before I started work on the bike and I fitted new o rings and sealed every thing up pretty good but didn't touch them I left the cables as they were, I didn't even disconnect them .I got my new automotive multi meter today and I've printed out the wiring  diagram Cutterbill has put together so hopefully tomorrow I'll find the problem. Once the motor goes the fun starts ive accumulated all the parts I need and i can start building a decent bike

jono

[jono]

well I've finally got it going ,I rechecked all the wiring, installed a new set of plugs and swapped out the original 3xw speedo unit for one out of my 1TX donor bike
and it started  then I swapped back to the original speedo unit and it now starts and idles strongly and thats with out a airbox or any mufflers
now I can get rebuilding it

jono   

[jono]

now that the motor is running Ive got a problem with the fuel supply I don't know how it shuts off. While ive been assembling the bike and sorting the wiring carbs etc ive had the tank sitting beside the bike to start it and Ive been turning the petcock off with a pair of pliers when not in use but last night I left the petcock open and this morning the garage smells of petrol and the is gas on the floor it looks like its coming from one of the four  pipes that attach to the carbs it hasn't emptied the tank or anything but it is seeping maybe there is crap in the bowls ill check that later, my question is how do I turn the fuel off? the only way I can see is with the set of pliers on the small square drive on the valve of the petcock which is hidden under the side cover .Has anyone fitted a second fuel tap that is accessible for daily riding ?

this is how its looking now all that's left to do is fit the refurbished brakes ,mount the fairing properly and wire in the tail light and indicators then off to the painters for a good paint job

Jono

[ribbert]

... how do I turn the fuel off? the only way I can see is with the set of pliers on the small square drive on the valve of the petcock which is hidden under the side cover .Has anyone fitted a second fuel tap that is accessible for daily riding ?

Jono

Yes, an electronic one. Fit and forget for $27!

The theory is, if the needles & seats, floats and the fuel pump are in good order this shouldn't happen. That's all good and well, but it does. The interval between these episodes of incontinence can range from several times a day to once every 20 years and I would venture to say, most members have had it happen at some point. At worst, it can dump the contents of the fuel tank into the crankcase.

Anytime is an inconvenience, but on a trip it can be a major disruption or even a ride ending event. I recommend a fuel cut-off solenoid, it only allows fuel to flow when the ignition is turned on.





The default position is closed, so if it fails it stays shut, and if that should occur it has a manual override for opening and closing it. It simply mounts inline anywhere between the tank and the pump (or carbys if you don't have a pump). Installation is simple, It only requires power from a switched source of which there are plenty around the bike.

It cost less than $30 and has done more miles reliably on my bike than most FJ's will ever see. One thing I don't have to worry about is my FJ quietly sabotaging the next days ride while I sleep, let alone the cost of the oil, fuel and filter.

The wonderful thing about solenoids is their simplicity, which equates to reliability and low cost.

Noel

[jono]

Thanks for that Noel ill check one out ,I was thinking inline tap but a solenoid is far better I can just fit it and forget it

jono

[T Legg]

I have the original style petcock with a prime position (always flowing gas ) and an on position which should only flow gas when vacume is present. A few weeks ago I took a midnight ride up the mountain road by my house. About 11 miles up my bike began to sputter and die. I thought the vacume hose might of fallen off so  I   turned the petcock to prime. It didn't help the bike still sputtered and died. Before I lost all momentum I turned the bike around and was able to coast back down eleven miles to a gas station at the bottom of the hill ( by the very dim light my head light produced on battery only). When I checked my tank it was empty. I rolled up to the pump and started filling the tank. After putting four and a half gallons in my foot began to slip. I looked down and gas was pouring like rain from my carb overflows. I remembered switching the petcock to prime so I turned it back to the normal position but the gas kept pouring out. I pushed my bike away from the gas pumps and pulled my tank off the bike and propped the fuel hose up above the gas level in the tank to stop the flow. In that short amount of time my bike dumped a couple gallons of gas. while this happened a guy on a Harley had pulled up and walked over to see what was going on . The store clerk came out with a bag of kitty litter and then I heard her say to the Harley rider you have to be kidding. When I looked over he had an unlit cigarette in one hand and a wooden stick match in his other hand as he was standing next to the stream of gas leading to my bike. A close call.  My son drove out and we loaded the tank in his truck and I rode the bike home without a tank by stopping and filling my float bowls twice with gas from the tank in the back of the truck. After getting it home I fixed the petcock by polishing the face of the selector switch and replacing the o-ring on the vacume shut off. Oddly after putting the tank back on none of the carbs leaked gas when in the prime position. I've never had gas leak so fast from a carb before. The moral of the story, the redundancy of a shut off like Noel's would have been nice.

[Pat Conlon]

You should not need to add an aftermarket solenoid.
If your fuel pump dribbles gas when the pump is off, that's the problem, fix that.

[jono]

the pump works correctly Pat it starts with ignition on and when what I presume the bowls are full it shuts off like its meant to ,Ive run it into a container and when power is off it doesn't leak,
after reading you guys reply's I'm thinking maybe the bowls are over filling then dumping fuel (dirty seats maybe ? I stripped the carbs of my old 1tx donor bike last night to familiarize myself with them "I know there slightly different to the 3xw" and those rubber valves could get dirt stuck to them and leak ,ive had the carbs of recently to fit new o rings and i did tip them up and move them around quite roughly so may ive stirred up something in one of the bowls) I started the bike today with the tank in place and when it was idling it started dripping fuel from one of the pipes
so I gave the carbs a bit of a tap and revved the motor up and it stopped so hopefully the fuel on the floor last week was just from one or more of the bowl's does that make sense ?

having said that I grew up building 650 750 parallel twins with amal carbs and I just cant rest easy knowing I haven't shut my fuel of when the bike's parked up so I'm going to fit a fuel solenoid like Noel suggested  if only for piece of mind ,

jono

[ribbert]

You should not need to add an aftermarket solenoid.
If your fuel pump dribbles gas when the pump is off, that's the problem, fix that.

Well Noel, you need to know what you're talking about, and in this case, because you don't have a gravity fed FJ, you don't know what you are talking about. You have a fuel pump FJ.

Well Pat, if that's true, I guess the converse must also be true.......
(Humour alert)


Pumps failing to hold the fuel back are an anomaly and not necessarily related to wear or age. I have observed this many times on pumps with very little use and even on my own FJ and cars. The last overnight fuel flood I had was over 230,000km ago, not long after I bought it, at low mileage, and at which point it was dribbling a bit of fuel even then (the seats keep that in check) .....however, that very same pump remains in service to this day, that is, my bike still has the original pump fitted with the original points (they get a file occasionally).

So Pat, knowing the pump alone is not fail safe, how would you set about making sure it didn't happen to you?

Noel



Pat, while we're on the subject, to clarify a safety concern you had earlier (below)...

"With the vacuum petcock the fuel flow stops when the engine stops.
With the electric solenoid the fuel flow stops when you turn your key off.
In an accident with the engine stalled, you may not be able to get to the key to turn it off."

The solenoid is "in-line" it doesn't override any of the original plumbing, it is additional to the standard set up. For all intents and purposes, it has no more control over the fuel flow when it's open than the 2" piece of hose it replaced.
It does not present any sort of risk because you can't turn the ignition off.