Seca Turbo: Really Need Help Solving This...

I'm losin' my mind, guys....
The Seca Turbo runs great when started. Some days it goes 1mi., some days 9 or 10mi. before it craps out on me. It doesn't die suddenly, but like it's running out of fuel. Wait a while and I can get home with some dignity, but often with full choke.
One day I replaced the coils and caps and it went about 20mi. before it regressed. I thought for sure I had solved it....
Pickup coils test ok, cold. With a heat gun they both climb to about 150 mega ohms.
I replaced one exhaust shim that was out of spec. last month.
The fairings are off and I noticed today when I start it fuel is flowing through my filter. I took off from a stop on a main drag and ran at full(ish) throttle til the next stoplight (1/4mi). I looked at the filter. No movement. I expected it to die, but it got me home with no problem.
At home, in neutral idle, no flow. I turned it off and back on. No flow. I turned off the key. Started again and now fuel flows again.
I have been battling this for about two months, on and off. When it runs well, I truly love riding it - the only reason I haven't sold it. Like a husband of an alcoholic I keep holding on to this biyatch hoping she'll recover...
What am I missing?
Please, I don't want to give up on her...

 

Fuel cap vent??

 

Thanks Dan. I'm on my 3rd cap now. The one I had was clearly bad, visually. I replaced it with a new one, same model. Now I'm trying a simple vented cap.
I failed to mention I also have a 2nd Seca Turbo that is waiting to be brought back to life. I swapped the ECU from it, with no effect.

 

I had a Turbo for about a year that initially would run great up to about 55 mph. At 65 it was good for about 2 miles then dwindle for lack of fuel. It was the fuel pump unable to keep up. It had only 2500 miles from new but was still 40 years old. Aftermarket fuel pump fixed it, you sound like similar issues. Good luck.

 

Remove the fuel filter
I almost guarantee that is your issue

 

Thanks Fuller anc Simmy.
I have an aftermarket fuel pump on it currently. My tin can went bad and so, with the help of other posts here, I found one at O'Reilly's that fit the bill.
I had not thought of the filter. It had one on it when I bought it, so I assumed it was supposed to. The man who sold it to me mentioned it sat after his father experienced what he believed to be an electrical issue. Maybe he was going through the same thing.
Could the fuel pump relay go bad, or falter?

 

Oh, and I took her for a spin early this morning, nice crisp air. I put her through a few speed bursts to get the boost going, anc thereafter is usually when shr conks out in me. But not this morning! I put 12mi on her without an issue. It's supposed to get up to about 80 today, so I plan on a run when it's hotter. Maybe she's a cold weather gal?

 

Good for you! I had not thought about the filter, too obvious I guess. I would think the relay would be good or bad, not so much iffy. Not saying it can't, just less likely.

 

Well, as promised I took a tour at about 80 degrees. It went ok until the 8th mile when it started its crap. I pulled into a side street and coasted after it died. I let it sit for a few minutes. It started back up and made it home with some minimal burbling. It idled fine in the driveway, then I put it away.
Either it's cold blooded or senses when I have to get the kids somewhere soon...

 

Next time just pop the fuel cap open. I know you have thought of that, but it’s a really easy test to see if it burps and allows fuel to flow again.

 

Yes, I did just that. I do it everytime, so I cannot tell if it helps or not.
I will try deleting the filter next, to see if that helps.
I still don't know if it's fuel or electrical. I'd be happy if it's fuel, not so if it's one of one hundred electrical possibilities...
Thanks again

 

Sounds fair. Eliminating a possibility is a good step.

I think it’s important to be confident about eliminating fuel supply before going down too many rat holes.

I’m admittedly not familiar with the turbos, but how about the fuel petcock and the filter in the tank?

 

So, the Turbo has a fuel pump, obviously. The petcock is ON/RES/OFF. One stem on the petcock feeds fuel from the tank to the fuel pump, through the check valve and regulator. Leftover fuel goes back into the tank via the second stem on the petcock.
When I started this project I rebuilt the petcock. Since then I have changed fuel filters twice. Once because I tried a bigger one, the second time because it broke. Both times there was sediment, despite cleaning the tank.
It might be a good idea to tear into the petcock again to inspect.

 

Long time no post...
I dug up a discussion about the fuel pump and regulator. I followed their lead and bout a Carter fuel pump (Carter Electric Fuel Pump P74017) and a Holley regulator (Holley Performance 12-887 Carbureted By-Pass Regulator)
. That was the ticket. It runs fine now, for as long as I want. BUT, at wide open throttle it sputters when the turbo spins up. That didn't happen before. With the old (also aftermarket) pump and original regulator it would spin up flawlessly. I did not change any carb components, so it has to be actual delivery. Should I monkey with the regulator?

 

your fuel pump P74017 puts out 14psi max. you need 2-4psi over max boost to keep carbs full. My 83 is making 16psi at 9000rpm. I would verify your fuel pressure.

 

Indeed, carry on and you will get aloominium balls in the sump...