Starving Under Load? Options

[kenshapiro2002]

Just brought the green machine back from CT this afternoon. After filling her up, she started to starve under load (trying to accelerate above 3,500 RPM...getting up a hill, etc.) so badly at one point I had to pull off the highway...she was dying. After sitting for 10-15 minutes, she fired up and was alright for another half hour. Then it all repeated. After the second rest she made it all the way back to Baltimore and ran beautifully for 90% of the time. I could sense a little starvation once in awhile.

I'm a shade tree mechanic at best, but my guess is that even though the seller (A Porsche tech) said the fuel tank was amazingly clean and needed nothing after being stored for 20 years, the fuel filter was getting clogged, and perhaps sitting for a while let things "settle". The seller suspects points. Any opinions?
Thanks in advance,
Ken

[ArtechnikA]

The seller suspects points. Any opinions?

Ignition points wouldn't be my guess for those symptoms but a good dwell (point gap) and timing check is always a good idea.

I had a car that needed trigger points do that, tho. As long as you're in the neighborhood of the dizzy anyway...

Could just be cloggy injectors - a can or two of good Techron couldn't hurt - and make sure your filter isn't loading up.

[orange914]

from what you said, sounds like your staring for fuel or vapor locking once warmed up. i'd run a fuel pressure check.

[McMark]

Take a flashlight and have a look into the gas tank through the filler. At the correct angle you can see the pickup tube. Look for garbage.

Check the filter, and I'd replace it just so I know exactly how old it is.

A standard tune up is a good way to set a 'baseline'. Adjust the valves, set the timing, check the dwell, etc.

Does this car have fuel injection, or a carburetor? What year is it?

[r_towle]

Take a flashlight and have a look into the gas tank through the filler. At the correct angle you can see the pickup tube. Look for garbage.

Check the filter, and I'd replace it just so I know exactly how old it is.

A standard tune up is a good way to set a 'baseline'. Adjust the valves, set the timing, check the dwell, etc.

Does this car have fuel injection, or a carburetor? What year is it?

(IMG:style_emoticons/default/agree.gif)

If you just bought it, tune it up, change the oil, set your valves.
Do all of this right away...then you will know how, and you will know its right.
I would not even look at the fuel filter until you know its tuned up correctly with new wires, points, plugs, cap and rotor...and the valves are right.

rich

[kenshapiro2002]

1970, big bore kit to 2.0, twin webers.
Ken

Take a flashlight and have a look into the gas tank through the filler. At the correct angle you can see the pickup tube. Look for garbage.

Check the filter, and I'd replace it just so I know exactly how old it is.

A standard tune up is a good way to set a 'baseline'. Adjust the valves, set the timing, check the dwell, etc.

Does this car have fuel injection, or a carburetor? What year is it?

[Rand]

my guess is that even though the seller (A Porsche tech) said the fuel tank was amazingly clean and needed nothing after being stored for 20 years, the fuel filter was getting clogged, and perhaps sitting for a while let things "settle"

I guess the beer is taking affect, because I'm not quite sure how to interpret that exactly... between what he said vs what you did.
Anything fuel related that sits for 20 years needs some attention. Whatever settled needs cleaning. You replaced the filter, right?

[McMark]

Vapor lock is a good possibility. While your doing your tuneup, find out where the fuel pump is located.

[r_towle]

Carbs dont do well with old fuel in them.
At the minumum clean the idle jets.

RIch

[kenshapiro2002]

Good point, but being a "shade tree mechanic" at best. how do I know what parameters to use on a tune up? The engine has been modified and I'm not 100% sure of the mods. Aren't the numbers for a tune up (even plugs) going to change since it was a 1.7 but now has a big bore kit? Since it was FI and now has twin Webers? I;m also guessing (hoping) the cam was changed when that car went to carbs. Is it a good idea to find a local type 4 "guru" to tune it the first time and eductae me?
Ken

Take a flashlight and have a look into the gas tank through the filler. At the correct angle you can see the pickup tube. Look for garbage.

Check the filter, and I'd replace it just so I know exactly how old it is.

A standard tune up is a good way to set a 'baseline'. Adjust the valves, set the timing, check the dwell, etc.

Does this car have fuel injection, or a carburetor? What year is it?

[ArtechnikA]

Good point, but being a "shade tree mechanic" at best. how do I know what parameters to use on a tune up? The engine has been modified and I'm not 100% sure of the mods. Aren't the numbers for a tune up (even plugs) going to change

Not as much as you might think. If the plugs need to be different, the different plugs should be in there now. Pull 'em and have a look. If they're Bosch, and 20 years old, you may have to find a cross-reference (Bosch changes their numbering scheme with the tides...)

Old plug wires are presumptively bad.

If it has the original ignition, get new Bosch (accept no substitutes) points, condenser, cap, and rotor. Set the point gap to 0.016" and static-time to some nominal value (maybe 6º BTDC). After you're sure all the basics are working properly you can go for the full timing-light full-advance method.

Clean ALL the jets - you'll be amazed what can crawl into the main jet stack over time. Weber idle jets are notorious for clogging under even the best of conditions.

Use only good, fresh gas - bad gas kills engines !

Unless you have hydraulic lifters (unlikely, but check, 'cause ya never know...) the valve lash numbers don't change much - there's a bunch of basic tune up threads with those numbers - I don't try to keep up with them since I don't have a T-IV...

[VaccaRabite]

The valve lash for a 1.7 was .006 intake and .006 exhaust. Since your car was a 1.7, its a good guess...

Zach

[orange914]

pertronix electronic ign. conversion is a very good cost effective upgrade, consider it at this piont.(for no pionts, get my piont (IMG:style_emoticons/default/biggrin.gif) ).

there has been some posts recently about murdered engines because of a bad tank of gas. do yourself a favor, please, flush your 20 year old fuel and fill with chevron or another good fuel.

mike

[kenshapiro2002]

Thanks folks!
Ken

[Rand]

Ken, reading your original post, it looks like you've already been through enough gas to have a fresh tank? Have you checked/replaced the fuel filter yet?

[charliew]

There is a chance the techron will thin and break down the varnish and crud and maybe clean the sock in the tank some, It's worth a try before you remove the tank and the sock.

I would bet the tank had some varnish in it from setting and now the new good gas has knocked it loose and the crud is floating around on the bottom of the tank and after awhile it gets clumped around the fuel pickup sock and starts to reduce flow so the carbs can't get full in their bowls while it's going through the gears. When you turn it off the crud falls back away from the sock and it all gets back up on the sock after it runs for awhile. If it runs good at times I would not go through the tune up till your sure the tank and sock are clean. There's always the possibility of putting more problems on it than it has now if you are not quite up to speed on it yet. Pulling the tank is easier to me than going through a complete tune up only to pull the tank anyway.

You might try if you want to mess around with it for awhile to disconnect the fuel line and put a small electric pump on it and pump the gas into a gas can and watch the output for awhile and see if it falls off while the pump is emptying the tank.

[Eddie914]

"After filling up" .... Bad gas? It will not be the first time. Drain/pump some of the gas out and put it in a clear container. Look for any separation. Perform a quick smell test.

A clogged fuel filter is not uncommon on a vehicle that has been sitting for a long time. Condensation can result in water in the fuel. I always put a can or two of can dryer in the fuel of my vehicles that have been sitting (like through the winter).

My motorhome (carbed Chevy 454) exhibited the same symptoms - clogged fuel filter.

My BMW M5 exhibited the same symptoms - worn plugs, cap & rotor.

My Chevy Suburban (TBI 350) exhibited the same symptoms - worn cap & rotor.

When my vehicles start running poorly the culprit is USUALLY ignition related ... but since your teener started running poorly after a fuel fill up ... check the fuel system.

Eddie

[kenshapiro2002]

Yeah...after sitting for 20 years, the Porsche tech who "awakened " the car, drove it for a few months, so the fuel is not old. I have not changed the filter yet...just been busy.

Ken, reading your original post, it looks like you've already been through enough gas to have a fresh tank? Have you checked/replaced the fuel filter yet?

[crash914]

hmmm carbs, I was going to go with trigger points after fuel filter...

Try the fuel filter first. That sounds like the most likely suspect.

next would be to disassemble the carbs and clean...look for the varnish. I just had to do this to my snowblower....

[kenshapiro2002]

Never heard of "trigger points". Are we talking regular points...the ones in the dist.?
Ken

hmmm carbs, I was going to go with trigger points after fuel filter...

Try the fuel filter first. That sounds like the most likely suspect.

next would be to disassemble the carbs and clean...look for the varnish. I just had to do this to my snowblower....