Fuel issue - Stumped

[starliner]

Hello all. 78 Sport Regal Turbo.
Fuel starvation problem

After sitting for 20 years, this Regal came to me.
Runs great, but then it shuts down almost completely. I have to either back completely off the pedal, or feather in and limp it. Sometimes i put it in neutral, shut it off, then restart.

What I have done:
Dropped and inspected the tank.
Cleaned and inspected the sending unit.
Replaced the junk fuel hoses to the sending U.
Replaced the fuel pump and hoses.
Put a see through inline filter before the carb.
Rebuilt the carb completely.

A sude note, since installing the new mechanical pump, i see the inline filter emptying, indicating bleed-down.

I am stumped here. Still having the starvation.

Any ideas?

Thank you.

 

[Clone TIE Pilot]

Could be sticky needle valve, the engine will run ok at low speeds but starve at higher speeds or under high load.

 

[69hurstolds]

Are you sure it's only fuel issues? Don't rule out ignition problems. Something sitting around for that long gathers moisture/corrosion in places you can't see. If you've installed new ignition module with heat sink grease, cap and rotor, you may be fine. What about ignition timing? Vacuum advance can? Is all that junk working correctly?

How's fuel pump pressure? Although rare, I've seen new, aftermarket pumps fail right out of the gate, whether check valve issues or diaphragm issues.

Did you use the puny, shrouded type of needle valve and seat on the inlet? They tend to be more prone to sticking and restricting flow at higher speeds as Clone TIE Pilot mentioned. Also, if you didn't place that needle hanger just right on the float, that could also cause high-load flow problems.

 

[spidereyes455]

Kind of a dumb question but , did you remove or replace the paper fuel filter in the carb?
Also have you checked the spark plugs? I have seen bad plugs act like a fuel starvation issue under heavy load but run fine at idle or light throttle.
Have you checked the hard fuel lines for leaks? Even if fuel lines don't leak any liquid they can still have a small leak that sucks air, that will give you a starvation problem that will have you ripping your hair out to diagnose. Is the float set correctly? An improperly adjusted float will for sure cause a starvation issue by not letting enough fuel in the bowl and then it runs dry.

 

[86 Salon]

Are you sure it's only fuel issues? Don't rule out ignition problems. Something sitting around for that long gathers moisture/corrosion in places you can't see. If you've installed new ignition module with heat sink grease, cap and rotor, you may be fine. What about ignition timing? Vacuum advance can? Is all that junk working correctly?

How's fuel pump pressure? Although rare, I've seen new, aftermarket pumps fail right out of the gate, whether check valve issues or diaphragm issues.

Did you use the puny, shrouded type of needle valve and seat on the inlet? They tend to be more prone to sticking and restricting flow at higher speeds as Clone TIE Pilot mentioned. Also, if you didn't place that needle hanger just right on the float, that could also cause high-load flow problems.

I don't think it's that rare to have new pumps fail out of the box.😔

 

[69hurstolds]

I don't think it's that rare to have new pumps fail out of the box.😔

I can't speak from personal experience for my own engines with that. Law of averages says that it is likely at some point one will every so often.

I think I've maybe bought 2, maybe 3 fuel pumps that didn't come in an ACDelco box. Two were NAPA/Echlin, back in the day and they were good pumps. The other was a Carter if memory serves. I remember I bought one of those Echlins because I was about 17, and on my bicycle and I only had one car at the time with the old, bad pump already removed and no ride. There were 2 auto parts stores in town, a NAPA and another one that sold ACDelco and FoMoCo and MoPar genuine junk. The NAPA was about a mile closer, so I got it faster.

Helped a couple of friends out over the years with bad new pumps made in Packmyassitan and similar questionable automotive parts-supplier countries. One had an Olds Cutlass Supreme, another a Chevy MCSS. On the plus side, I've never, ever had a new ACDelco pump fail outta the box. (Now I probably will, just my luck.)

 

[Clone TIE Pilot]

I don't think it's that rare to have new pumps fail out of the box.😔

The most common issue with new replacement pumps is higher than stock or spec fuel pressure. Excess fuel pressure can lift the needle of its seat and cause rich running or flooding, especially with hipo large seats.

Qjets came with several different sizes of fuel inlet seats depending on the application. Qjet guru Cliff often suggests using a .135 seat for most setups. Some of the cheap rebuild kits come with restrictive seats, sometings even werid ones with caged needles.

 

[starliner]

I don't think it's that rare to have new pumps fail out of the box.😔

All great questions, yes. Yes, and yes.

Crawling under last night, it looks like I used a REALLY cheap POS fuel hose from the sending unit. I could pinch it between my fingers.
I blew out a brake line at the same time, so as soon as i am back on the road to test in a few days, i will update.
Thanks alot, guys.

 

[Built6spdMCSS]

I would definitely replace that hose if that's the case.

 

[starliner]

I would definitely replace that hose if that's the case.

Done!