cant go fast for long....help!?, drives around town all day, but not on highway! Options

[rbmorrisiii]

Ok, so i got this car ('73 1.7L) about 2 months ago. single carb - yes i know this isnt the best fuel intake, but i am going to try to make it work. I tried to drive it home - about 90 miles, but it only went about 15 miles before it slowly crapped out. losing speed unitl i had to pull over. it would start again and drive, but couldnt go fast for long.

so, I: changed fuel filter, spark plugs, oil, cleaned oil screen, pulled gas tank and ran all new fuel hoses and clamps (found a kinked line which i thought was the problem - also found the vent in the gas tank to be smashed, so i re-opened that and ran a new hose to underneath the car) the lines looked fine running through the car - and when i blew them out they seemed to be free of any clogs etc.

I reconnected everything, and started her up today. same problem. she ran a little better and could run all day around town, but took her on the highway and she would only stay in 5th gear for like 20 seconds then started tanking in speed - down-shifted to 4th.....3rd...then pulled off the highway...noticed some smoke in the back so i pulled over to let her rest. the smoke was coming from the HE's - both sides on the "opening" closer to the muffler. the PO had screwed in wood screws into the gap i'm assuming to keep them from rattling, and that gap is where the smoke was flying out of. after a 15 minute rest i started up and drove for another 15 minutes with no major problems.

Why wont she go on the highway!

I'm stumped!

I'm new to the mechanical arena so overexplain things if you think you need to.

whats my next step? someone told me the timing may be messed up, 'cause when you switch to carbs you to need to adjust?!?!

help!

Thanks for all the help in advance, so glad to finally join the 914 world!

ill have pics of my bag of bolts soon!

-R.B.

[GeorgeRud]

What are you running for a fuel pump? The carbs need a low pressure (~3.5 psi pump), but if there is not enough flow, you will not be able to run at speed.

I've had the same thing happen when a fuel pump was going south. Just a thought.

Welcome to the jungle!

[rbmorrisiii]

Ive had a hunch that its the fuel pump this whole time, but everyone tells me that the little bugger i got is fine....i guess its worth replacing - anyway to test it?

i have the fuel pressure regulator set to 4 - i cant get it to turn over for anything less than 4 (2.5/3 psi IS recommended for my carb).

i forgot to mention also i rebuilt the carb too!

any other thoughts?

[ericread]

You've only got three areas to look: fuel, spark and mechanical.

I think we can rule out mechanical as it runs well at lower speeds.

As for spark, could be, but no indications yet.

Fuel. OK, you're running a single carb, which you recently rebuilt. We see fuel pump issues pretty apparent in the Fuel Injected engines, as there's either fuel pressure or there isn't fuel pressure. With the carb, you have two main areas; 1. The fuel pump must provide enough fuel to the carb so that your engine doesn't become starved for fuel. 2. Your carb float must be properly adjusted. If the carb float is not properly adjusted, then no matter what fuel pressure you're running, the float may not be allowing fuel into the carb itself.

As fuel pump failures are pretty rare (not that they never ocurr) I would take a look at your carb float adjustment.

Keep in mind, the only difference between running around in town using high rpms adn driving on the highway is merely your transmission gear. Therefore, you should be able to recreate your problem by driving at higher rpms around town.

Eric Read

[Rand]

Keep in mind, the only difference between running around in town using high rpms adn driving on the highway is merely your transmission gear. Therefore, you should be able to recreate your problem by driving at higher rpms around town.

Not really. The motor has to work a hell of a lot harder to pull your car down the freeway at 70 than it does around town at the same rpms.

How are your temperature readings? Do you have a head temp gauge?

[ericread]

Keep in mind, the only difference between running around in town using high rpms adn driving on the highway is merely your transmission gear. Therefore, you should be able to recreate your problem by driving at higher rpms around town.

Not really. The motor has to work a hell of a lot harder to pull your car down the freeway at 70 than it does around town at the same rpms.

I was speaking from a fuel management issue. Granted, the engine will work harder from a stress standpoint getting up to highway speeds, but once the speed has been reached, maintaining the speed is not that stressful on the engine.

Eric

[Zundfolge]

One time I sucked a plastic bag into the fan...covered about half of the inside of the fan.

Could drive around town all I wanted, but the first time I hit the freeway it made it a few miles then I had to pull over and let it cool down.

[Spoke]

Check the fuel pump by getting a bottle like a 2L Coke bottle, disconnect the carb, put hose into it, turn on ignition, you should see significant fuel flow. If not, there is a problem in the fuel delivery system (clog in line, clogged filter, fuel pump issue, or fuel pressure regulator issue).

Before doing this, I would get a fire extinguisher handy and remove power from the coil (to save the points/coil or Pertronix as the engine will not be running).

[blitZ]

Keep in mind, the only difference between running around in town using high rpms adn driving on the highway is merely your transmission gear. Therefore, you should be able to recreate your problem by driving at higher rpms around town.

Not really. The motor has to work a hell of a lot harder to pull your car down the freeway at 70 than it does around town at the same rpms.

I was speaking from a fuel management issue. Granted, the engine will work harder from a stress standpoint getting up to highway speeds, but once the speed has been reached, maintaining the speed is not that stressful on the engine.

Eric

I disagree. I have a CHT and the only time my heads go above 400 degrees is when cruising on the highway in 5th at 70 or so. It's the amount of work the engine has to do with the wind resistance at highway speeds, produces heat in the heads. At 80 or above is fine in my car, which is not stock. Trying to reproduce this scenario in 4th around town is comparing apples to oranges. I think your heads are heating up and the engine is under huge stress. I would guess the carb and cam combination you are using is causing the problem. The stock cam is bad enough, plus the poor mixture from your carb is not helping.

Consider going to some FI, stock or after market or dual carbs to begin with.

[VaccaRabite]

While I don't disagree with Blitz about looking into FI or dual carbs, people run single carbs all the time and are able to maintain highway speeds.

You have checked everything up to the carb with fuel delivery. Now you need to check the carb. Make sure the float is set right, and that the carb is in good condition.

Do you have a CHT gauge? What are head temps at failure?

Could you describe your exhaust leak more? What color is the smoke?

And just because, have you done the basic engine diagnostic stuff? Compression test and valve adjustments? Probably not a central issue, but it may be a contributing factor. An out of tune engine could be more likely to overheat.

Zach

[Rand]

Granted, the engine will work harder from a stress standpoint getting up to highway speeds, but once the speed has been reached, maintaining the speed is not that stressful on the engine.

Clearly you don't have a head temp gauge!!! Or a feel for the workout factor of an aircooled engine at sustained freeway speeds. I'll spare the rest of what I was going to say. But, cheers to ya Eric - I've enjoyed your posts! (IMG:style_emoticons/default/beerchug.gif)

[ericread]

Granted, the engine will work harder from a stress standpoint getting up to highway speeds, but once the speed has been reached, maintaining the speed is not that stressful on the engine.

Clearly you don't have a head temp gauge or a feel for the workout factor of an aircooled engine in a car at freeway speeds. I'll spare the rest of what I was going to say.

But I love ya Eric, from what I see of your posts! (IMG:style_emoticons/default/beerchug.gif)

(IMG:style_emoticons/default/beerchug.gif) Thanks for the sentiments!

Aggain, I am speaking only of fuel management issues. The carb doesn't really care about the stress of the engine, but of the quantity of fuel needed to be delivered. Assuming it is a fuel problem (which is possibly incorrect, but just for shits and giggles), it would seem to be the fuel pump not delivering the fuel to the carb, or the carb floats being mis-adjusted, and the carb running dry. This would be independant of the stress or heat of the engine.

Just a thought. (IMG:style_emoticons/default/idea.gif)

The possibility of the problem being heat related would, of course, make my argument irrelevant. (IMG:style_emoticons/default/sad.gif)

Eric (IMG:style_emoticons/default/wavey.gif)

[jmill]

My vote is a cooling issue. My type II did the same thing. I found I had blown off my heater hoses. It's real fun if you get it hot enough that you blow the plugs out of the heads. I'd check the fan, tins and thermostat.

[Rand]

This issue may not be fuel related. The verdict is out. I'm still waiting to hear about head temps.

[Eric_Shea]

Fuel filter?

[rbmorrisiii]

Yeah, sorry no head temp gauge (should i get one? what do they cost? easy to install?)

No compression test. No valve adjustment. My neighbor is supposed to run me through timing adjustment soon ( I am a serious novice with this type of stuff). I've read about how to do a valve adjustment, but seems like something i want somebody to show me the first time i do it - anyone in the bay area? And whats up with compression tests? - something i need to do at a shop?

Fuel filter was replaced first thing and double checked it before yesterday.

Exhaust leaks are pictured. Smoke was blue-ish and poured out for some 5-10 minutes after stopping.

So i guess my next step is to examine the fan and making sure that fuel is making it to the carb (eliminating fuel pump/fuel pressure regulator problems). What are you saying is "significant fuel flow"? like what rate would be good with the pressure regulator set to 3 psi?

I'll probably adjust the float level as well - I'm assuming there is some kind of "how to" on line.

Amazing support guys! Heres a question for you....Everyone I ask offers different and sometimes blatently contradictory advice - who the hell do I listen too?

Thanks again!

-R.B.

[ericread]

Amazing support guys! Heres a question for you....Everyone I ask offers different and sometimes blatently contradictory advice - who the hell do I listen too?
-R.B.

hahaha! (IMG:style_emoticons/default/lol3.gif)

You have been getting some really good advice. Unfortunately, some of this advice is based upon our perception of your problem. If it's truely a fuel problem, then follow my advice (IMG:style_emoticons/default/laugh.gif)

Unfortunately, it's probably not a fuel problem. Your blue smoke is not a good thing. The guys that are arguing with me pretty much have a lot more experience than me, so pay attention to them. VACCA has a long history of being right, but don't tell him because it will only swell his head...

Prioritize your troubleshooting process. If you get five ideas, try to put them in order of how they should be perfromed. And when you don't know, do what you did here and ask again.

Eric (IMG:style_emoticons/default/wavey.gif)

[VaccaRabite]

eep, I was just wrong!

Sort of. My premise was right I bet. You have oil leaking into the heat exchangers somewhere. the blue smoke is that oil burning off.

I bet if you turn on the heater in the cabin, it stinks of burned oil.

Zach

[VaccaRabite]

By the way. Is the bottom of that heat exchanger painted black, or is that accumulated oil scum?

A CHT gauge is a great thing to have on these cars. Otherwise, you have no clue what the head temps are. If you are out of tune and running hot, you'd never know it until you dropped a valve. If you want a stock look, you can get a VDO CHT gauge. Its not the best, but its better then nothing. A lot of guys here like the Dakota Digital gauges. They DO NOT look stock, it has a digital readout. But they are temperature compensated, accurate gauges. If your head is not pre-drilled for a VDO CHT sender, get the spark plug type sender and put it on the no3 spark plug. That is your hottest cylinder (usually).

Cost will be about $200 ish for the Dakota Digital. Dunno what for the VDO.


Zach

[rbmorrisiii]

My heater isnt connected to the cabin right now. Hoses just stop (torn) as they enter into the fuel tank bay.

And I guess this is a good time to mention that the heater air hose on the driverside (coming from the blower) is ripped - what does this affect?

AND what does this leak in the HE's mean in the grand scheme of things? Focus on this first? Any best way for determining where the leak comes from?

Thanks,
R.B.

And - NO thats not black paint...