Long run up hill, starvation

[Tahoe]

Before I begin, my car starts, idles, and runs good. Smooth, no hesitations, couldn't be happier, except! Except on a drive yesterday I drove around for several miles and decided to head up the mountain, over a pass just to do a nice run to make sure all is okay. As I started up the mountain starting at about 6300 ft all was great, just cruising at 60 in a 55. It is a steady climb as I approached the summit, which is close to 8000 ft. At about 1/4 mile from the summit it started to stumble. It was definitely starvation, not ignition or anything else. Pulled off the side, it never stopped running but stumbled. Eventually came back to smooth, and I headed back home.

So questions everyone asks:
Were you low on gas? No just filled it up the other day.
Is the filter clogged? No it's a see through and it's clear as can be.
Fuel pressure? Checked and it was 2.5 psi leaving the pressure regulator.
Crap (technical term) in the carbs? No, pulled covers, checked and all seemed clean.

Today I raised the fuel pressure to 3.5 psi and the exact same thing happened. The car runs just fine on long straight runs, around town, idling, etc.

I haven't checked 2 things yet. One is float levels, and the second being a possible flow restriction before the pump. Long story, but my Aluminum tank had (has) a problem with the pickup not working. Not working because of possible bad weld inside or ? Anyway to get the fuel pick up to work I inserted plastic (nylon) fuel line (the same as goes from the back to the carbs), inside the other original pick up and it did the trick. My concern is that it is possibly kinked slightly and could be restrictive. Not so much while driving normally, but maybe when under load going up a mountain. Still fuel pressure is good and if I let the pump dump fuel in a can it flows very well, so I tend to think it's not pressure or flow.

So, what am I missing?

[S2Jay]

Russ,

Missing is Air. It may be running rich due to lack of air, not starved for fuel.

Just a guess, but I had something similar happen years ago at Yosemite at about the same altitude. Based on experienced local advice at the time, I removed the air filter, and presto, it ran better, and smoothly. Not as strong as at sea level, of course, but good enough to complete the trip comfortably. (This was not in an Elan, but a Datsun 1600 Roadster with twin SUs. This had a stock air filter, not a K & N.)

Jay

[AHM]

If it does it whenever you accelerate after a good run ie pulling on to a motorway check the float levels.

If it only does it at 8000 ft go for mixture - That height is reserved for aircraft here, so I have nothing to add!

[69S4]

So, what am I missing?

Probably a set of Stromberg carbs No problem with altitude compensation with them!

[Tahoe]

Mystery continues. It's not the float levels. It's not running too rich either, it is definitely starvation for some reason. I'll figure it out in time, at least it runs great where I drive 99% of the time.

[S2Jay]

Random thoughts.

Fuel Pump: Mechanical, Electrical, or both?

Where did you check the fuel pressure? When you returned home, or at 8000 ft?

In tank pick up. Why did the original tank pick up not work? Because it was / is too large in diameter? Is that why the nylon hose was inserted?

Also perhaps check fuel tank cap vent.

Have you checked plugs yet to see if they look lean or rich? Perhaps duplicate starvation, then check plugs.

Is it possible to duplicate a similar scenario of a long uphill run at a lower altitude location?

[Tahoe]

Random thoughts.

Fuel Pump: Mechanical, Electrical, or both?

Where did you check the fuel pressure? When you returned home, or at 8000 ft?

In tank pick up. Why did the original tank pick up not work? Because it was / is too large in diameter? Is that why the nylon hose was inserted?

Also perhaps check fuel tank cap vent.

Have you checked plugs yet to see if they look lean or rich? Perhaps duplicate starvation, then check plugs.

Is it possible to duplicate a similar scenario of a long uphill run at a lower altitude location?

Fuel Pump: Mechanical, Electrical, or both? It was both, but removed the mechanical pump this Fall.

Where did you check the fuel pressure? When you returned home, or at 8000 ft? I checked after the regulator located at the pump, and just before the carbs. I checked pressure at home (6500 ft) because I needed to disconnect hoses to do it. My gauge is not in the fuel line.


In tank pick up. Why did the original tank pick up not work? Because it was / is too large in diameter? Is that why the nylon hose was inserted? Long story, but I'm not happy with the tank, Yes the pick up tube is way too large and there may be a flaw with it. I bought the tank from someone on this forum and it was so frustrating. Anyway, the nylon hose works, but I'm concerned that it may have a slight kink in it, although flow seems to be okay.

Also perhaps check fuel tank cap vent. I have but will check again.

Have you checked plugs yet to see if they look lean or rich? Perhaps duplicate starvation, then check plugs. I did pull the plugs after my 3rd run at elevation, and they seemed fine. No indication of anything weird. Maybe slightly lean, which is to be expected, but definitely not rich.


Is it possible to duplicate a similar scenario of a long uphill run at a lower altitude location? My thoughts exactly. I'm trying to think of another location.

The starvation does not happen after I head down the mountain or at anytime while driving on level roads or around town. I would say it is a gradual lean condition that takes several minutes to worsen and only going up a long steady climb. I need to investigate the tank again. I may need to bite the bullet and pull the tank to fix it properly. (more money I don't need/want to spend).

[Tahoe]

I may have found the problem. I decided to start all over and check the obvious. Even though I had checked the fuel filter and so did my Austin Healy neighbor and RX7 neighbor I pulled it anyway. When I got it out I could see lots and lots of Aluminum shavings and fine particles. So I replaced the filter took another drive and same thing happened so I figure it can't be the filter. Get back to the garage, check the filter and a few more Aluminum particles. So I pull the nylon fuel line I'm using as a pick up and I try to put a rod thru it. Can't do it from either end. Something is big in there blocking it. I have a feeling my new electric fuel pump sucks so good it's getting all the crap that shouldn't have been there out. I can't replace the line until tomorrow, but tonight I'll cut the line to see what's blocking it. I don't understand how the flow looked so good when I tested it unless it isn't a full blockage. It is certainly very restrictive, like trying to suck ice through a straw. Hopefully that's it, but I won't know until tomorrow.

[Galwaylotus]

Is your fuel filter upstream or downstream from the pump? I had a problem with my car shortly after acquiring it and eventually found a blocked fuel filter. Fortunately it was upstream of the electric pump so the pump and everything after was protected. Replaced the filter and that particular problem went away.

[Tahoe]

My filter is before the pump to collect all the stuff. Last night I cut the pickup tube and found tons of Aluminum shavings, etc. So much I couldn't believe any gas could get through. That must be the entire problem. Today I replace the pick up tube and the gas line to the filter and go for another drive. I estimate at least one tablespoon of small Aluminum particles and several shavings like you would get from machining Aluminum. That's just in the pick up and doesn't account for the full filter. So much for quality control or cleaning your product before selling it. I have a feeling I'll be replacing the filter several more times before I collect all the crap in there. It's interesting because my old electric pump wasn't picking any of this stuff up so the new one must really suck (not in a bad way!).

[Tahoe]

Last post on this. 100% success! Took 1 hour drive over 3 summits, 1 at 80 mph, then took car into hope valley which is at 7000 ft plus hitting speeds up to 110 and elevations over 8000ft. Don't recommend those speeds, but needed to open it up to make sure everything was okay. Besides Bears aren't out of hibernation yet, and deer are still at lower elevations, and traffic is almost zero. I'm sure I'll replace the filter at least one more time but at least I'll know the warning signs.

[Quart Meg Miles]

Great resolution of your problem using proper engineering. But I'm surprised you didn't hear the tank rattling when you installed it!

I guess you'll be sending the bits back .....

[RotoFlexible]

Russ,

Glad you found your problem. I had the same symptoms some time ago with a reconditioned original tank. It turned out to be little blobs of silicone sealer from re-installation of the sender. I only figured it out when I sucked one of them out of the pickup line with a Mity Vac. I drained and flushed the tank - no problems since.

A long run up a hill puts a continuous heavy load on the engine that it doesn't ordinarily see. Fuel is used faster than the compromised system can supply it and eventually the carburetors run low. In my case, I experienced total blockage twice (both times with my granddaughter in the car, as it happened). After the second time, I applied the Mity Vac and discovered the blob.