Fuel Problems

[digitech]

Well, now I have an issue. After 700 miles of around town driving, now that summer is here, I seem to have fuel problem on my '79 spider. Twice now, I have encountered a no-start condition. Both times, I troubleshot the condition to no fuel in the float bowl. Also both times, I had just driven the car at least 30 miles without issue, turned it off, let it sit for 20 min and then the no-start condition. The first time, it seemed I was able to get fuel flowing again by taking the filler cap off. The second time, that seemed to work long enough for the car to start, run for 5min and that was that - it stop running and wouldn't restart. Due to approaching darkness, I swapped out the mechanical fuel pump with the spare I carry and after a bit of cranking, of course, it started and I was able to drive it home.

So, fuel pump? Or, a type of vapor lock? I have a new fuel tank but it did not have all of the vapor ports like the original so I had to re-rig those lines. Think that might be the problem?

[vandor]

If you are getting significant vacuum in the tank, that could prevent the fuel pump from drawing fuel. The solution could be as simple as the installation of a vented cap.

[digitech]

I'll certainly give it a try - know of a source for a cap that fits?

[dmwhiteoak]

Do you always carry spare a spare fuel pump with you ?

[digitech]

I always do.

[ga.spyder]

I led 18 Fiats across 'Tail of the Dragon',a couple years ago at FFO. We had one car that did the same thing when we stopped for pictures,and again for lunch.It was very hot,and everyone thought vapor lock.We took the cap off and he drove form Deals Gap back to lunch in Robbinsville.Then,after sitting,we couldnt get it going at all.We didnt have a spare pump.or we would have put it on.Had to tow it back to Asheville.I would think that with tank vents being altered,that would be the place to start.Csabas fix with a vented cap sounds like a great idea. Get that thing fixed ,so we can do a mountain ride soon!!

[124JOE]

drill a hole 1/8 inch in your cap
i think it was the fuel pump if not the filter

[Kent124]

I always do.

+1, only because mine is so old.

[vandor]

I'll certainly give it a try - know of a source for a cap that fits?

We carry them. They come with a plate with a tiiiinny hole. If you put in the plate, the gas cap is vented.
If you leave it out, then it's not.

[digitech]

Thanks, I'll check your site and order one - I have a couple of things to order and am waiting to hear if I need a lower control arm bushing or not. It doesn't look good to me but my front end man will make the call.

[digitech]

I may have had two issues at the same time - what are the chances? Went to the grocery store yesterday, 5 miles away, was inside 15 min. and when I came out, no start. So, pulled fuel line to carb - it was full of gas. Tried removing gas cap - no luck.
Removed top of carb and found the float bowl had plenty of fuel. After messing around for another 10 min, tried the car and it started up; drove it home and let it idle in the driveway, cooling fan came on and ran for a minute - then the car shut off and wouldn't restart. I let it sit for 30 min. without touching a thing and then it started right up. I let it idle until the cooling fan came on again and it shut off again.

At this point, I suspected the ignition control module and checked the output of the coil with my HV probe - no HV. I removed and replaced the coil (it was leaking oil) and the control module with my spares and so far, it's been starting and idling fine. We'll see. So it looks like I had a weak fuel pump AND a bad module/coil.

I plan on picking up a MSD Blaster 2 coil Monday and installing it - put my spare back into spares. Already ordered a replacement module from Csaba.

[digitech]

Been out in Vegas for the last month and finally got back to this issue. It has been a perplexing one to say the least, first seeming to be one thing and then something else. I may finally have a handle on what's going on and I'll have to aplogize to Keith and a few others on here - I was so sure the fuel level in my filter was a key indicator to my issue, I closed my ears (and mind) to any other possible causes. But, once I replaced my two fuel filters with the metal versions, replaced my carb with a brand new one, replaced the mechanical pump with a new one, pulled and cleaned some debris out of my new fuel tank, blew thru my fuel supply/return lines and replaced all of my rubber lines with fuel injection hose/clamps and resolved the tank venting, then I could safely say my issue is NOT fuel related. I have the most pristine fuel supply this side of the factory.

But, still had the issue. And since I'm no longer distracted my the fuel level in my filter, I was able to listen to Keith and look at my ignition system. What I found was voltage on the B+ side of my coil was all over the place - and the longer the car ran and the hotter it got then the more the volage began to drop until the engine finally quit running when the rad fan came on.

Pulled my alternator and took it to a shop for checkout/repair -all okay but he did polish the slip ring and gave me some advice concerning the alt. belt - namely get a Gates and tighten it "banjo" tight.

Re-installed, still the same issue so I began looking at my ign. system -which is all new as well-and found my coil heatsink was not getting a good ground. Pulled all of that apart, ran a separate gnd wire to the heatsink for good measure and replaced the ign. module (in case it had been damaged by not having the proper ground) and installed a new Accel 8145 coil to boot.

Voltage is steady now and everything appears to be much better, all around. Idled car for an hour today, supplied additional heat via a heat gun and no issues.

have noticed though, voltage starts out at 13.7v at the coil (cold), drops a couple of tenths to 13.5 as the engine heats up (fan on several cycles) and also drops .3v when the engine is revved. So, my question is, is that normal??? After getting off course once already chasing the fuel level issue, I don't want to do it again. So I promise to listen this time. If someone could put a DVM on their coil B+ and tell me their readings from cold to hot, engine idle and engine revved, I would greatly appreciate it.

[digitech]

Guys, I'm begging for someone to hook a DVM to their coil and grab those measurments for me -please!!!!

[aj81spider]

Not sure I'm doing what you want - and I'm alone tonight so I can only measure at idle.

However on my 1981 with the meter grounded to either the chassis or the heat sink I get a voltage at idle (car not warmed up - idles fairly low RPM) that moves around from roughly 11.8 to 12.5. Given that the coil is charging and discharging the moving voltage doesn't surprise me.

Based on that you seem a little high (or else my car has an issue I don't know about!).

My battery was 12.6 with the car turned off.