Vapor Lock 330GT

Moderators: 330GT, abrent

330GT_London
Posts: 17
Joined: Mon Nov 02, 2020 12:39 pm

Vapor Lock 330GT

Post by 330GT_London »

Hi everyone, hope you have some good advice regarding Vapor Lock in 330GT.

My car drives fine normally, but I get fuel supply problems once it is hot. It typically happens if I get stuck in traffic or have to stop for a bit after a long drive. The fuel bowl at the front goes empty or runs very low. If I then turn on the electric pump it solves the problem and I can continue driving. I want to know if anyone has a solution to this problem apart from turning on the electric pump. I would like to be able to drive it only on the mechanical pump if that is possible. I have already:
- Cleaned and refurbished the fuel bowl / regulator at front
- Cleaned and refurbished mechanical pump
- Cleaned and refurbished rear filter
- Flushed fuel line with air compressor
- Tried some heat wrap ( which maybe helped a bit, but didn't solve it)
- Tested with heat shield ( which maybe helped a bit, but didn't solve it)
- The original yellow fuel lines are all fresh
- The long main metal fuel pipe under the car is probably a bit old, but did flush it.
- By the rear filter there are some non original short lines and fitting. But these are in good condition and checked.

I have attached some pictures to illustrate. Believe the problem area is where the fuel line is crossing over the exhaust pipe, but I could be wrong.

I already talked to Tom about it and he said it is a common problem and is best solved with using the electric pump.
Appreciate advice from you experienced 330GT drivers. Must be a fix without using the electric pump.

Many thanks, Kristian ( London, UK )
Attachments
330GT_VAPORLOCK_web.jpg
DWR46
Posts: 621
Joined: Tue Sep 22, 2009 8:23 pm

Re: Vapor Lock 330GT

Post by DWR46 »

Kristian:

1. Have you measured the pressure produced by the mechanical pump? You should have 4-5 psi.

2. The original purpose of the electric pump was to fill the carbs on cold starts, and to ASSIST FUEL SUPPLY UNDER HARD RUNNING AND HOT CONDITIONS. The factory expected this to happen and provided the electric pump to address this issue. Also, today's fuels boil at MUCH lower temps than the fuels of the 1960s, so the problem is more common today.
Jumprun
Posts: 276
Joined: Wed Aug 01, 2012 6:28 pm
Contact:

Re: Vapor Lock 330GT

Post by Jumprun »

Hello Kristian,
You mention that you refurbished the mechanical pump, but I thought I would mention that some of the valves supplied with the so-called rebuilt kits are not very good.
I am assuming you addressed the many wear points in the mechanism to remove all the play because the amount of stroke produced by the drive pin is not much, and check that your pin is not overly worn.

The thickness of the phenolic spacer and gaskets are also very critical, too thick and you won't get enough stroke, and too thin may bend the lever arm. .75mm makes a difference!

All that said, I understand your frustrations, I went through all this and I got my pump to work as well as anyone could, but guess what? I still run my electric pump 100% of the time due to starvation in the conditions Dyke mentions, in fact I have two electric pumps in-line, the original click-click-click Fispa and a modern buzzer. I have them separately switched for redundancy.

Oops, forgot to mention, I run a GTC, but the pump and issues are the same.
John Vardanian
Posts: 1906
Joined: Wed Sep 04, 2002 12:13 am
Location: San Francisco Area

Re: Vapor Lock 330GT

Post by John Vardanian »

In my dealings with this issue, I learned that to get adequate supply with only the mechanical pump, the glass bowl needs to stay full to the top. Remember, the outlet is at the top of the bowl, so if you have air at the top instead of fuel, your carburetors will starve.

john
PF Coupe
User avatar
tyang
Posts: 4060
Joined: Wed Nov 27, 2002 10:28 pm
Location: New York
Contact:

Re: Vapor Lock 330GT

Post by tyang »

Hi Kristian,

The stroke of the push rod that powers the mechanical fuel pump is very short, only a few millimeters of movement. The back lash of the pump then becomes critical, for full efficiency, but be careful not to get it too tight, or the stress on the the pump will break things. You can check the length of travel of the pushrod by removing the mechanical pump and turning the engine over to see how much the pushrod moves in and out. I transfer that measurement to the fuel pump on a test rig I can mount a mechanical fuel pump to a vise to confirm there is enough travel to pump fuel. The Bakelite spacer is what adjusts the backlash. This is a lot of work to insure full efficiency that did not take into account the lower boiling point of modern fuel.

Good luck!

Tom
'63 330 America #5053
User avatar
330GT
Posts: 1640
Joined: Wed Sep 04, 2002 9:30 am
Location: Seattle, WA
Contact:

Re: Vapor Lock 330GT

Post by 330GT »

In fighting vapor lock in my 330GT for quite a while, I've come to several conclusions.
1. In my case, the vapor lock is occurring in the fuel hose running from the fuel tank to the rear filter. I determined this by the fact that when the car is being starved, the electric pump (original FISPA) no longer is clicking, but thumping. So it is no longer pumping fuel, but fuel vapor. After sitting on the side of the road for several minutes (perhaps up to 20), eventually things cool down in the rear and the FISPA pump goes back to normal. Then the car will run as normal until it gets too hot again.
2. In trying to resolve this, I have added a second modern electric pump in parallel with the FISPA one, using TYs banjo bolts with nipples. I also added a heat shield over the exhaust pipes under the filter and pump area. Neither resolved the problem. See http://www.parrotbyte.com/kbc/ferrari/3 ... orLock.htm for details.
3. I also eventually figured out that the vapor lock occurred mainly when I was low on fuel, i.e. no head pressure was being generated by the fuel in the tank.
4. The vapor lock only occurred on hot days (>80F) and driving at highway speeds.
5. My 330 GT is a series 2, so there is a small return pipe from the fuel log to the tank that is designed to keep fuel flowing even when the car is stopped and idling. A series 1 without this revision, probably would have issues with vapor lock in the engine compartment.
6. This started occurring in recent years, never a problem in the first 20 years I owned the car. I attribute this to the modern fuel with alcohol, thus a lower boiling point.
7. I never tired insulating the fuel hose from the tank to the filter.

In hind sight, I think that keeping the tank 3/4 full would have prevented most of the vapor lock issues I've had. If non-alcohol fuels are available in your area, that will help. However, when traveling long distances, it becomes difficult to find when needed.
Regards, Kerry
http://www.330gt.com 330 GT Registry
http://www.parrotbyte.com/kbc/ferrari 250 PF Coupe 1643GT, 330 GT 2+2 8755GT, 308 GTS 23605
User avatar
peterp
Posts: 314
Joined: Sun Feb 12, 2006 9:42 am
Location: NJ

Re: Vapor Lock 330GT

Post by peterp »

I've never seen anybody mention this as a solution, but I saw a pretty large improvement by putting fuel insulation around the chrome fuel rail feeding the carbs. I used insulation that wraps around the rail with velcro as a temporary test. I haven't really put it through the paces on a very hot day, but it seems to help a lot.
Peter P
1966 330 2+2 series 2 #8169
330GT_London
Posts: 17
Joined: Mon Nov 02, 2020 12:39 pm

Re: Vapor Lock 330GT

Post by 330GT_London »

Appreciate all the expertise from everyone on the Vapor Lock problem. I did some more observations:
Fuel Pressure:
My fuel pressure is showing correct 4.5 - 5 psi.
Mechanical pump stroke:
I believe the stroke is good. First I attached it a bit too tight and it made a noise, I then loosened it to the point where the noise disappeared. So I think now the stroke is at the maximum, without pushing too far.
Mechanical Fuel Pump Rebuild:
The kit I got looked just like the original and I also replaced the lever arm.
Electric Fuel Pump:
If I get fuel starvation, I turn the electrical pump on and it runs perfectly straight away with the electric pump. So there is no problem there at that end. Member 330GT mention vapour lock at the rear before the rear filter, put I don't think that is the case here.
Fispa Glass Bowel:
When the engine is cold, the glass bowl stays full. After a 20min run around town with a bit of traffic, the fuel glass bowl is very low, but car is still running. If I now get stuck in traffic when it is very low, the Vapor Lock happens after some time ( not sufficient fuel ). I checked the pressure also when engine is hot and the glass bowl is low; the pressure still show correct 4.5 - 5 psi.
Fispa Glass Bowl top screw:
What function does the screw on the top of the Fispa Glass Bowl have. I turned it up and down all the way while checking pressure. It didn't change the pressure or the level of fuel in the bowl.
Fuel:
I am normally using the premium 99 Octane Fuel. Also tried with standard 95, but didn't make any difference.
High Speed Driving:
When I drive on the motorway I never have any problems with fuel supply, only when I get into traffic jam after a long drive ( hot engine ).

Just to clarify: the Vapour Lock problem was exactly the same before and after rebuilding all the filters and pump and flushing the lines. Which makes me conclude that none of them are the problem.

Does any of you have any further suggestions?
Would it help to relocate or replace the main long metal fuel line that crosses path with the exhaust?
Did I miss something?

Last resort I will install a second electrical pump to run the main fuel line. Hope there is a way to solve it keeping the system original.

Thank you everyone for your input !
Kristian
Attachments
Fuel_pressure_web.jpg
DWR46
Posts: 621
Joined: Tue Sep 22, 2009 8:23 pm

Re: Vapor Lock 330GT

Post by DWR46 »

Kristian: The screw slot on the top of the glass bowl fuel filter is supposed to adjust the pressure, as the upper part of this component is a pressure regulator. I have seen many of them react as yours did. In all honestly, it sounds like your fuel system is functioning "normally" and as designed. In this form, you should have no trouble in using your car in all normal conditions. In hot weather, when you approach heavy traffic or stop and go traffic, just turn on the electric pump. The earlier you turn on the electric pump the better off you will be. In other conditions, the car will run fine on the mechanical pump only. I would not worry about the glass bowl filter not being "full" all the time. Most of the cars I see are not full all the time, yet run fine. If you can find non-ethanol fuel that might help the situation.
User avatar
peterp
Posts: 314
Joined: Sun Feb 12, 2006 9:42 am
Location: NJ

Re: Vapor Lock 330GT

Post by peterp »

330GT_London wrote: Wed Apr 28, 2021 6:26 am Does any of you have any further suggestions?
Would it help to relocate or replace the main long metal fuel line that crosses path with the exhaust?
Did I miss something?
Have you tried wrapping insulation around the chrome fuel rail that feeds the carburetors?

The fact that non-ethanol gas doesn't help the situation seems unusual.

The comments below are from vague memories from the past, so hopefully somebody will correct me if I'm wrong.

I think I recall Dyke posting in another thread (a long time ago) that Ferrari raced with the same Fispa mechanical pumps back in the day with the 250 GTO's and that the cars that run vintage racing today have the same, so if my memory is correct, it should be a workable combination.

Also, I think I recall that all of the "correct" yellow fuel line that is available today actually has a larger inside diameter than the original yellow fuel line. If that is correct, I wonder if that larger inside diameter causes the original design not to work as well (for example, maybe the surrounding hose is thinner and more prone to heat than the original, or the original pressure spec doesn't work as well with larger diameter hose, etc).
Peter P
1966 330 2+2 series 2 #8169
DWR46
Posts: 621
Joined: Tue Sep 22, 2009 8:23 pm

Re: Vapor Lock 330GT

Post by DWR46 »

Peter: You raised some good points, so let me try to clarify them:

1. 250 GTO's do not use the FISPA mechanical or electric pump. They have two of the Bendix electrics. I think Ferrari found the Bendix pumps were superior to the FISPA electric units. Primarily their "points" systems are much more reliable than the FISPA, and for a reason I do not fully understand, they are less susceptible to cavitation.

2. The modern production (for at least the last 30 years) "yellow" wrapped fuel line is the SAME id, but a different od, thus requiring different ferrules to be used when switching over to the new lines.

3. In my earlier post I forgot a significant item, and that is to use Marvel Mystery Oil in the fuel at the recommended rate of 4 oz/10 gallons. This adds "lubricity" to the fuel and helps the valves in both the mechanical and electric pumps seal better. Maserati learned this at Sebring in 1957 when they experienced fuel feed problems in practice and finally traced it to the Amoco unleaded (yes, unleaded) fuel provided by the organizers. As soon as the team started adding a quart of motor oil to each 40 gallon tank of fuel, all the problems went away. Today's fuels have the same problem as they are very "dry" and meant to be pumped at high pressures in modern cars. The Marvel Oil will make a difference.
John Vardanian
Posts: 1906
Joined: Wed Sep 04, 2002 12:13 am
Location: San Francisco Area

Re: Vapor Lock 330GT

Post by John Vardanian »

Dyke, I have been a dedicated customer for 20+ years, but I didn't realize that MMO had that kind of creds... Maserati.

john
PF Coupe
User avatar
peterp
Posts: 314
Joined: Sun Feb 12, 2006 9:42 am
Location: NJ

Re: Vapor Lock 330GT

Post by peterp »

DWR46 wrote: Wed Apr 28, 2021 7:51 pm Peter: You raised some good points, so let me try to clarify them ...
Well, so much for my memory, but at least I spelled "GTO" correctly :). Thanks very much for the clarification.

I can feel the difference when I run MMO in the 330. I'm not a fan of additives generally, but never heard a negative comment about MMO, tons of positive comments, and your endorsement sealed the deal. I think it also helps lubricate the Weber carb throttle shafts.

I don't use it on modern cars, but many do. There's seems to be a large following of people who run MMO simply because they claim they get better gas mileage with it (for modern cars).
Peter P
1966 330 2+2 series 2 #8169
DWR46
Posts: 621
Joined: Tue Sep 22, 2009 8:23 pm

Re: Vapor Lock 330GT

Post by DWR46 »

Peter: Sorry, but forgot to tell you it also adds 50 bhp and 25 mph to the top speed, as well as doubling the gas mileage!! Like others I have not seen any benefits to using MMO in modern cars. Very interesting comment about lubricating the throttle shafts. I tend to agree with your thoughts.
Jimmyr
Posts: 447
Joined: Thu Aug 19, 2004 11:20 pm
Location: Scottsdale, AZ

Re: Vapor Lock 330GT

Post by Jimmyr »

As usual Dyke brings these tips to us that always make sense and work well. Another application for MMO, is to help old engines that have been stored or not used for many years; a little squirt into each cyl. can help keep sticking rings and rust from freezing up engines. Makes a lot of sense that it could help the carb shafts and pump valves!
Post Reply