1996 GTS Will Not Run Off Main Tank Setting, Needs To Be On Reserve

[JDusza]

Got the 1996 GTS running pretty well.
When running with the fuel selector switch on the main, it will only give me about 1/2 mile at high speed before it stalls out for lack of fuel. Switch to reserve, fire up and enjoy the ride.
So, why would the fuel system die on main setting and run on reserve? Could the selector thing be bad?
The machine runs great on reserve so the fuel lines, filter, fuel pump and crank puffer must all be working,
Bad pick-up in the tank?
What are the fuel source selection failure modes?
Thanks,
J

 

[burtshaver2021]

Can you drive at WOT on Reaerve with no issue at all? If yes, then replace the fuel selector valve, if not, rebuild the carbs and pressure test the fuel system.

 

[JDusza]

Yes. WOT on Reserve all day long.
Thank you,
J

 

[2strokeboy]

Fuel selector is clogged ot the sending unit is clogged, check fuel selector first. If its clogged replace it.

 

[BrianMoore]

I have never understood the replace the whole valve valve thing. The stock one has a set screw retaining the rotary valve. If you can remove the screw, the valve comes apart and you can clean out the passages and replace the o-rings if needed because they are leaking. Use nitrile seals.

 

[burtshaver2021]

I have never understood the replace the whole valve valve thing. The stock one has a set screw retaining the rotary valve. If you can remove the screw, the valve comes apart and you can clean out the passages and replace the o-rings if needed because they are leaking. Use nitrile seals.

I’m all for that, do you have any part numbers for the o-rings? Has this worked well for you?

 

[BrianMoore]

I am amazed what falls out of my mouth before thinking.

When I replaced all the gray lines, I went blindly into it by reading this forum. I bought the lines and clamps and a new selector valve before I started. After I got the old valve replaced, then I started looking at the old valve. So no I never ran the old valve. But I did take apart the old valve and now wish I hadn't bought a new one since the old valve was serviceable. Tricky part of cleaning the old one would have been a clogged right angle passage in the body. A bit of wire and some compressed air would have been necessary to clean those.

I am American and worked in America so I am pretty ignorant when it comes to metric stuff. The o-ring if definitely Metric. ISO 3601-1, 8.75mm ID 1.80mm cross section. In the Parker O-ring Handbook, this size shows in Series A and also in Series G. I have no idea what the difference is between series and which is the correct one for this application. Series A has a bit more tolerance so it could be for static applications (me talking out my butt here). I live in a metro area so I would drive to Omni Seal, put it on the counter, and they would get me a bag of the correct o-rings. A couple bucks will get you more than a lifetime supply.

Then again the o-ring from 1997 wasn't leaking so I would not have replaced it. Just grease it up and put the valve back together.

 

[burtshaver2021]

I am amazed what falls out of my mouth before thinking.

When I replaced all the gray lines, I went blindly into it by reading this forum. I bought the lines and clamps and a new selector valve before I started. After I got the old valve replaced, then I started looking at the old valve. So no I never ran the old valve. But I did take apart the old valve and now wish I hadn't bought a new one since the old valve was serviceable. Tricky part of cleaning the old one would have been a clogged right angle passage in the body. A bit of wire and some compressed air would have been necessary to clean those.

I am American and worked in America so I am pretty ignorant when it comes to metric stuff. The o-ring if definitely Metric. ISO 3601-1, 8.75mm ID 1.80mm cross section. In the Parker O-ring Handbook, this size shows in Series A and also in Series G. I have no idea what the difference is between series and which is the correct one for this application. Series A has a bit more tolerance so it could be for static applications (me talking out my butt here). I live in a metro area so I would drive to Omni Seal, put it on the counter, and they would get me a bag of the correct o-rings. A couple bucks will get you more than a lifetime supply.

Then again the o-ring from 1997 wasn't leaking so I would not have replaced it. Just grease it up and put the valve back together.

View attachment 65568

I’ve done the same, replaced 2 of them and there may not have been anything wrong with them, can’t quite remember now, but I do still have the old ones and I will have 2 more to change or repair in my 98 Challenger I’m working on now. Definitely something I would like to look into further

 

[mikidymac]

It has been years since I took one apart...
Isn't there an internal seal also to prevent the mixing of the ON/OFF/RES?
Also the o-ring isn't easy for the average Joe to source so it is just easier to suggest replacing the valve. Keep in mind that was when the OEM ones were $35 and would last another 20 years.

 

[BrianMoore]

There's like a bushing deep in the skinny end. Original post was about a plug on the RUN side. A little time to remove the valve, a phillips screwdriver and luck getting the screw out, and they might get it unplugged and be back running for zero dollars and not waiting for a part in the mail. O-rings are a black art. They take a compression set over time. Engineering hat on, always recommended to replace them every time since they are so cheap. Regular Joe hat on, I replace them if I have to. I have seen plenty of 30 year old o-rings that work perfectly well.

 

[mikidymac]

The problem is if the selector leaks air or restricts fuel the you ruin the engine from running lean. It happens a lot here and I have seen it too many times. I prefer to spend the $38 and not ruin an engine.
I will say I have seen the cheap knockoff ones ruin engines also so do what you are most comfortable with, if that is replacing o-rings that is fine too but test the selector before installing it.
Fuel Valve
275500098
$38.99

 

[BrianMoore]

I agree, $39 is a lot cheaper than an engine.