86 fj wants to start then dies

[kirkh213a]

I just got a 86fj1200 that had been sitting around for a while. cleaned up the carbs, changed the fluids, so far so good. the bike has a fuel pump on it but I had it hooked up and it pumped fuel out the overflow tubes so I unhooked it and went back to gravity feed. the bike will crank and run for 10 seconds then stops. i can then crank and start immediately same results. the petcock has a vacuum tube that is 4 inches long. after reading other post it needs to run somewhere? to the carburetors? the problem is that none of my carbs has anything it can hook up to. did the PO modify for the fuel pump and replace a carb? if so what keeps the fuel pump from continuously pumping? any help would be appreciated.

[movenon]

I just got a 86fj1200 that had been sitting around for a while. cleaned up the carbs, changed the fluids, so far so good. the bike has a fuel pump on it but I had it hooked up and it pumped fuel out the overflow tubes so I unhooked it and went back to gravity feed. the bike will crank and run for 10 seconds then stops. i can then crank and start immediately same results. the petcock has a vacuum tube that is 4 inches long. after reading other post it needs to run somewhere? to the carburetors? the problem is that none of my carbs has anything it can hook up to. did the PO modify for the fuel pump and replace a carb? if so what keeps the fuel pump from continuously pumping? any help would be appreciated.

1986 did not have a fuel pump on it stock.  Someone has added it onto the bike.  Probably without fully exploring the concerns. In the newer FJ's the fuel pump will shut off after around 5 second if you don't start it. Controlled by the CDI box.  Also if they converted it there are different needle and seats in the carbs. The gravity feed ones have larger inlet diameters than the fuel pump models.

Now when you unhooked the pump and went back to gravity feed we go back to what that vacuum hose is suppose to do. It is a vacuum controlled petcock.
With no vacuum it will not open to feed fuel to your carbs.  I don't have an 86 so I am shooting in the dark here but that line should hook up to one of the vacuum ports on top of your intake manifolds.

Now for the reason the PO possably converted to a fuel pump.  Take that 4 inch hose and suck on it... If it holds a vacuum then it is good if it doesn't hold a vacuum then it needs to be replaced if you are going back to a gravity feed system. Also as a note if you go to the gravity feed system make sure there is no fuel filter in the line if the PO installed one. Not much head pressure with gravity feed systems.

I am all for converting the older FJ to a fuel pump BUT there are some issues that need to be addressed in doing a safe conversion.  At this point lets not get into that.  For quick and dirty fix I would suggest going back to a gravity feed system.  In the gravity feed models with the power off fuel flow has to be stopped at the petcock and the second safety is at the needle and seat valves. When you crank and start  the engine the vacuum controlled petcock will open to let fuel flow.  Hope some of this helps out.

And welcome to the group ! I don't know if you have posted an introduction but if you haven't then you might want to do that and let us know where you are located.  You might have help in the local area.  
George

[movenon]

Also the gravity feed model had a funky fuel line routing.. It had to be routed correctly other wise it would pinch off some of the fuel flow.
Is there an electrical connector also attached to the petcock ?
George

[kirkh213a]

thanks for the help. I am not a mechanic. I am not finding a vacuum port on top of my intake manifold to run the vacuum hose to. that is why I think the po replaced the carburetor that had the port on it? the petcock has the electrical connector, fuel and vacuum ports. I will do the petcock test today, and make sure the fuel line is routed correctly, but I guess I am stuck if I cant find the port on the manifold.thanks

[movenon]

thanks for the help. I am not a mechanic. I am not finding a vacuum port on top of my intake manifold to run the vacuum hose to. that is why I think the po replaced the carburetor that had the port on it? the petcock has the electrical connector, fuel and vacuum ports. I will do the petcock test today, and make sure the fuel line is routed correctly, but I guess I am stuck if I cant find the port on the manifold.thanks

Do the vacuum test. You have 4 vacuum ports, one for each carb. They are on your intake manifolds, right on top. Look between the heat shield and the engine head, there they are. Those ports are also what you use to sync the carbs. One port should have a rubber vacuum line going to your CDI/TDI box the other 3 have rubber caps on them with spring clip to provide tension.  If the hose holds vacuum then hook that line to one of those ports.

I highly doubt that the PO changed a carb or carbs.  Look for a connector that hooks to that petcock connector. 

Sorry for all the confusion, just trying to help with what little I know.
George

[Mike 86 in San Dimas]

Bet once you get the fuel set up back to stock you will be ok. Riders have tried to improve or fix issues with fuel pumps only to create new trouble. Get a repair manual, the pictures alone  help us non gearheads a lot. The petcocks are crucial and not really repairable; if fuel doesn't flow once engine turns over (creating vacuum). Get a new OEM petcock.  Fuel line routing is critical. The bike should have a diagram of line routing displayed once tank/seat is removed, if not it will be in the manual. My experience is engine running problems with the FJ are almost always fuel related.
No "in line" filters allowed, if it there take it out.

[FJmonkey]

If fuel is flowing with the vacuum line disconnected then the vacuum function has been disabled. That means the current fuel pump is the check valve for fuel. If the suck test fails then don't connect the hose to your intake manifold, you will induce a vacuum leak and that cylinder will not run properly. As George mentioned, converting back to gravity feed requires some external changes and internal changes. Gravity feed (GF) uses 10MM hose, Fuel Pump (FP) uses 6MM (measure at the inner diameter for hose). FP carbs have a single 6MM barb connection in the center, between carb 2 & 3. GF have two 10MM barb connections, one between carbs 1 & 2 and another between 3 & 4. This means the hose routs differently for GF vs FP. Here is an example of the GF routing



This example shows a common mistake, the hose needs to go under both of the splitter lines to connect at the petcock.

The GF carbs use a larger diameter needle seat to assist with proper fuel flow as the pressure reduces caused by less fuel in the tank pushing down. GF is 2.3MM and FP is 1.5MM. If your seats are GF the pressure from the fuel pump may over power the floats and flood the carbs. Crap in the gas can also prevent the seats from sealing and cause the same problem but normally only one carb, rarely all 4 at once.

I think you need to take the carbs off and do a proper clean and verification of what is inside.

Answer the following questions:
1. Do the carbs have one or two fuel line connections?
2. What size are these connections, 6MM or 10MM hose?
3. What petcock do you have? This might help http://www.rpmracingca.com/products.asp?cat=39&filter=petcock
4. Is a fuel filter installed?
5. Did the bike ever run properly for you?

This is just a start, we will help you get this sorted out.

[kirkh213a]

Thanks all I feel stupid for not locating the vac hookup I found it.tried the suck test - big fail.so I will order new petcock.I already got the oring kit from rpm and installed.maybee need jet kit next but everything seems good.gas cap makes such sound should I worry about that yet? Oh ya bike sounds real good when it does briefly run - can't wait to ride.not my first bike but even though getting it running has been frustrating, I can't wait.again thanks to all.

[FJmonkey]

The gas cap sings as it vents, it needs to do that. Sing to me....

[JOMPPA10]

The gas cap sings as it vents, it needs to do that. Sing to me....

yes it also sings to me hours to become, almost love... hope i get my baby run..

[andyb]

The tank venting gives you the meowing sound that you stop getting once you've shot the cat with the clutch pushrod and it's scared to go into the garage again.

(I removed the shit, the only kind of singing I want the bike to do is through the pipe.)