Still chasing a problem with my newly purchased 73 choking & dying after driving around town. Changed the plugs and ignition wires. It has an add-on fuel filter just before the carb that I also changed.
Here is what I (novice) have noticed:
When it quit on me yesterday after a 20 minute drive, I noticed the fuel filter looked empty. When I turn on the key, without cranking, I hear a pump running in the rear on the passenger side but I saw no fuel filling up the filter. Luckily I was across from a NAPA so I bought a new one and installed it. When I turned the key this time, it completely filled up. I thought I was now a mechanic. Not so. About 10 minutes later, chokes and dies again.
The temp gauge has never read much above 100 (maybe 110) so it was something I wanted to verify. So after driving around yesterday it was sitting right at 100. I know that can't be correct.
When I turn my key off it drops way below any reading, almost straight down. When the engine is completely cold and the key on, it sits just under 100 and never goes much above. The oil temp & battery sit a zero with key on & off.

Where should the gauge be with the key off?
What is the normal operating temp?
More likely the sending unit or the gauge causing a misreading?
Scared my engine may be overheating & causing it to choke & die (yes, it has antifreeze).

Thanks

 

your gauge is defective should not go below the scale to that extent.
your car did not come from the factory with an electric fuel pump. Thus you should not hear any sound from a pump unless someone for some reason added one.
Do you still have the original distributor with points? If you do have you adjusted the dwell angle and set the timing?
If you have checked the dwell and timing have you attempted to set the idle speed and mixture screws once the engine was at operating temperature.

 

I had new belts put on yesterday & I just noticed the wire to the sending unit was disconnected. That explains the 100* reading yesterday. I knew it read higher before even though it was only around 110*. So still sounds like I have a bad gauge then. I have something pumping fuel. It's mounted right above the muffler, passenger side. Must have been added for a reason.

I checked my timing & it already matched what Lars recommended. 18* at idle (750RPM) and 36* (3,000RPM). Have not checked the dwell. I do have points.

Lars also recommended I have a B26 vacuum advance control unit on my distributor since I measured only 14in of vacuum at the manifold. Looked online to find where the part # is stamped but see nothing stamped on mine.

 

I just removed the wire from the sensor & grounded it. It pegged the gauge to the right. Hoping that means my gauge is still good.

 

the gauge on this link shows the same position for the needle as yours but i have had my car since 73 and it never goes down to that position, puzzling. You may want to see what temperature thermostat is installed in your car. http://www.ecklerscorvette.com/corve...1968-1971.html

Have you tried adjusting the idle speed and mixture screws on the carburetor?

 

I'll check the thermostat once it cools down a bit more. Glad to see a new gauge is only $60. Would have expected to have to pay more.

I haven't made any adjustments to the carb yet. Do you think that may be my problem with it dying after 20-30 minutes on the road???

Going to swing by the car show this evening. There a few guys there with C3's. Maybe I'll learn something

 

Carb adjustment or vacuum leak which shows up when hot. Make sure the carburetor hold down bolts/nuts are tight but dont get too carried away when checking.

 

I have NUMEROUS BELLS going off in my head on this one....like 12 noon in front of a cathedral.

First off....I am CONCERNED on the location of the electric fuel pump. Right above your muffler??? Not a good area. I know you did not do it...but the 'brainiac' that put it there...has no brain. FUEL above a heat source = POSSIBLE FIRE If it is getting hot....it can fail...or cause a vapor lock in the fuel due to the fuel is getting too hot. Kinda funny how you put a fresh pump on that was cold and it worked and then failed again...what is the constant factor....LOCATION comes to mind.

Also concerned on how it is wired in and what gauge of wires were used and if they are using a relay (which is should be using a relay) or a straight wire approach

I am also wondering if you have a fuel return still in effect. Also. I am wondering on where you installed this added fuel filter you mentioned. A photo of your engine compartment would be nice and and just a close of of the filter. If you have headers and the fuel line has been butchered and modified..it can also be a cause of it.

The other 'bells' will come up later.

DUB

 

So now that I found out the fuel pump was aftermarket, I crawled under the car. I agree, it should not be mounted above the muffler. The wiring is bad as well.
Here is what I noticed:
When the car is cold, I can just turn the key on (not crank) and watch the add-on fuel filter that is just in front of the carb fill with fuel.
After driving the car, the fuel filter is about 1/8 of the way full and the car still runs ok. I see some fuel still pumping in the fuel filter.
After 30 minutes, it chokes and dies.
Turning the key on, I hear the fuel pump running but see no fuel pumping into the fuel filter.
Wait 15-30 minutes or so, turn on the key and the fuel filter fills up with fuel and the car cranks.

DUB...wait til you see this pic. The fuel pump is 6-8" directly above the muffler, passenger side.
Where should it be mounted?
Curious why it needed one if it didn't original have one.

 

With an electric fuel pump, you will also need a pressure regulator in the system. Pump is producing too much pressure for your carb. It should be set around 5-6 psi MAXIMUM. That's likely your engine problem.

Your temp gauge error is probably due to a 'mismatched' sending unit (for the gauge in your cluster). Only way to know is to borrow an infrared temp indicator to see what your engine temp really is. You can use an ohmmeter to measure the resistance of the temp sender (measure between signal pin, with wire removed, and the sender body/engine) when engine is 'cold' [ambient temperature] and when 'hot' [stable running temp]. With those temp vs.resistance measurements, you should be able to purchase the correct sender from Willcox.

P.S. The fact that you are getting ANY readings from your temp gauge means that the gauge [itself] and the wiring are NOT the problem.

From my perspective, having rubber fuel line and a plastic fuel filter housing in a "pressurized" fuel line is risky. If either fails (and with time, both will eventually fail), you will be spraying fuel around in the engine compartment. It's not "wrong" to plumb it that way; it's just dangerous, IMO.

 

Bottom line, ditch the electric pump and plastic filter, reinstall a mechanical pump with a proper hard metal line. You also may want to reinstall the correct engine cooling fan and clutch assembly.

 

After work I traced the fuel lines to see what I was working with.
Looks like the line from the bottom of the tank goes to the fuel pump then the add-on filter.
The side of the tank has a smaller (I think) line.
Both go along the chassis together and the smaller line is plugged.
Looks like this

 

It appears the problem may be heat generated by the pump itself and/or by the close proximity to the muffler. Based on the amount of dirt (age) on that pump it must have been installed and worked somewhat correctly for a while. I would guess the pump is wearing out. If that assumption is correct you probably have a 5-6psi pump with no regulator needed and that is why the return line is blocked off. I would seriously consider a new mechanical pump and at least SS braided lines from the pump to carb. I would also reattach the return line.

 

Does you engine have the mechanical fuel pump mounted on it??? Passenger side of the engine...on the side...at the front... down low. Right near where that capped line is.

I agree...I do not know why they did what they did...but I can write this.

If you can get a mechanical pump to work...that would be great.

The plastic fuel filter is a problem just waiting to happen.

The lack of fuel return can be a contributing factor. I have had to make a special 'T' fitting that allowed me to get the fuel return to come off the supply line...and the amount of fuel returned...allowed me to regulate the pressure. The bogus wiring to the electric pump does not surprise me. I am wondering what gauge of wire they are using...and also the quality of the pump can also be a factor in why it stops pumping when it gets hot or runs for a while. I doubt that the pump is drawing fuel so hard that it is collapsing the fuel hose in front of it...but I have seen stranger things.

I am not the person to be talking to on this because I am SUPER PICKY when it comes to fuel supply systems.... (high or low pressure)...so if you are looking for fast fix...maybe someone can chime in....but I will write this. I get Corvettes in my shop that some idiot got their hands into it and fudged it all up. I have had to make custom fuel lines that keep the connections to a minimum and NO HOSE clamps are used. I do it all in hard line. And the dual line that you have on your carb now...is something that I throw away and re-make myself. The reason being is that many of these dual line set-ups will run right into the heater hose on the intake manifold. And oddly enough ...when you look at them in catalogs...if they are mounted on the carb to 'show it off'... there is NO heater hose in the photo...and it appears to look fine...until you buy it and find out it does not work well at all. Now this is all depending on the carb and the intake...but I find that the fuel line and the heater hose touch if not almost touch...which to me...is also a BIG NO-NO.

Also...it is possible that your Holley might be able to hold a fuel filter in each bowl fitting where the dual lines go into it.

DANGER!!!!!!

That Corbin clamp on the plastic fuel filer in your photo ( carb side of filter) is NOT designed for holding pressure. It is possible that that those can pop off. I can not tell if there is a Corbin clamp on the other side of the plastic fuel filter.

DUB

 

I did have a corbin clamp on both sides. My fuel lines are long enough where I could just remove the fuel filter and still reach the carb connection. For now, I replaced the corbin clamps with hose clamps as it may help me troubleshooting. Also found that the fuel line and the heater hose were loosely cable-tied together. Removed that.

I realized my vacuum gauge is also a fuel pressure gauge. With everything cold, I get 4 psi and it builds slowly up to 5.5 psi.
So I verified again today, after 20 minutes of runtime, the fuel filter was all but empty. I shut it off, turned on the key & no fuel was pumped in. Unfortunately I broke my fuel pressure gauge connector trying not to spill the gas so I couldn't re-check. After a while, turned the key and it began pumping fuel. So bad pump or the gas is so hot in the pipe it turns to vapor. Or maybe it's a vapor lock.

I could not find a mechanical fuel pump. Aircon blocks the view a bit but I felt around also.

So I need to get rid of the existing pump and wiring (probably about 20 gauge). Would this be the right part to connect the tank to the fuel line in the rear? Or should I get something better, maybe the SS braided line? I see it comes with more corbin clips.
http://www.zip-corvette.com/catalog/...line-hose-kit/

Could I add a new 4-6 psi fuel pump in the engine compartment rather than the mechanical? I am thinking if I have to go mechanical I need to take it to someone for the work. And that may not be a bad idea either way I go.

 

If you need to work in the area of the fuel pump, you're best move is to jack up the right-front and remove the tire. Good access after that....

 

The location for the factory mechanical fuel pump can be somewhat easily seen from the passenger side of the engine.

I did not watch the video so I can not endorse it entirely...but it shows where the mechanical fuel pump is located.


20 gauge wire is really small and may be part of the problem especially if you check and see if the wiring is getting hot and flexible. Possible adding a larger gauge wire could correct the problem of it cutting out.

I am still not liking where the fuel pump is located as you know....and I would NOT put it in the engine compartment. It gets hot there also.

I would do a test that I know how to do to see if and when the fuel pump begins to fail...but with you dealing with gasoline...I am having a hard time giving you this information...because I do not want to read that you had a fire and then I get the blame.

I do not know what you want to do....fill me in some if you can.

DUB

 

Tonight I removed the fuel filter and in it's place I added an inline pressure gauge. Going to double check it for leaks in the morning and see what the pump is does after driving a while.
If it drops to 0 psi could that also mean a vapor lock?

 

It all depends on how hot the pumps gets when running for a while...it could be internal issues with the pump. Which could be the volume of fuel it can actually pump or is designed to pump at the pressure it can produce.

Do you know know where the mechanical pump is located?????

DUB

 

The man is in FLORIDA, it's HOT as hell here now, and that pump is above the exhaust pipe, and so the tank sock is probably 1/2 bad or so, and enables the pump to go into vapor lock under suction....make sure the charcoal canister is ok and hooked up/functional, if the tank can not breathe air into it, the thing will further encourage vapor lock.....

number ONE, replace the plastic filter with a stainless Fuel Injection pressure rated filter and use good clamps,

second off, 16 ga wire is needed for the pump electricals.....

move the pump from above the muffler to the rear rail just aft of the tank near the center....

next if all that fails.....leave the tank cap off, for a test drive with maybe 1/2 a tank in there so it don't spill out so damn easy....keep the cornering down slo, just in case....see what happens.....the pump maybe not so good on the suck side, and so if there is any vacuum on the tank due to a NON VENTED/STOCK filler cap.....replace it with a lockable vented cap, and kiss your problems good BYE!!!!

BTDT with DPFI and a return line, finally got my '72 sorted out....your '73 if anything close to stock was very similar to mine, when starting out almost 20 years ago.....