Vapour lock is back

[bigjones]

At least I think it is vapour lock.
Drove to local store - car running great with the new HS4. 15 min later left the store but now the car was almost cutting out - limped along for about 2 miles and it cleared up.
Its almost 90F here in NC today.

Anyways, I got 2 ideas:
1. Make a little heat blanket (ha!) for the float bowl.
2. Make another heat shield to bridge that gap between fender and existing heat shield.

Cheers

 

[dklawson]

Adrian, you've rearranged the fuel hoses since I last saw pictures. However it looks like the fuel line now goes across the front of the engine. Is that correct? That's what I was going to suggest since that's the common path on Spitfires (including the 1500).

 

[Cottontop]

5-6 of THESE

on the fuel line are guaranteed to eliminate vapor lock.

Tim

 

[bigjones]

Doug,
Thanks for the reply!
Here's the gas line at present - as MG intended. The mechanical fuel pump points the outlet to the rear. I can't see any advantage routing the fuel line to the front - especially seeing the fan is in the way. Prolly different in a Spitfire.
I've installed the 2nd heat shield and a little blanket for the fuel bowl. Can anyone guess what the second one is made from?
Tomorrow I'll go for for another identical test drive and see what happens.

Tim,
I'm not quite sure what you mean. Could you elabotate some?

Cheers!

 

[Billm]

Is it possible to unbolt the top of the float bowl and turn it 120 degrees clockwise? That way the fuel line isn't directly over the exhaust manifold.
BillM

 

[dklawson]

You can rotate the float bowl lid in 120 degree steps but when you do, keep in mind the direction the float swings. If it's left or right, and you plan on tossing the car into long sweeping corners, you may find places and times where you starve the float bowl. It's a common problem on Minis with HS2s... until you rotate the lids so the float wants to swing front to back.

I would have thought the MG and Spit used the same fuel pump? Curious. Not that this helps, but on the Spit (all the way back to the 1147 days (perhaps the 948 on Heralds too... but I don't know) the fuel exits the pump, runs through a steel line parallel to the block towards the front of the engine. The line turns up and goes behind the generator/alternator then at the top of the block turns across the front just below the t-stat housing. The line then goes wide to the right and turns back to point towards the carbs. I think their intention was to keep the slightly cooler air form the fan flowing over it.

What I don't understand with any vapor lock problem is that the pump on these engines is pretty low. I would have thought the intake to the pump was gravity fed. Apparently this must not be the case.

 

[jlaird]

Manual pump is not gravity feed. Its a sucker and a pusher.

Solution, an elec pump back by the tank.

 

[JPSmit]

How is the venting on your gas tank? 2 miles seems a long way to have the problem if the fuel is flowing.

 

[jlaird]

I'm sorry, it in my mind can not be vapor lock. Not hot enough nor was engine running long enough.

Fuel starvation I expect.

I would start with blowing the line and changing the fuel filter.

Tank vent is as commented an excellent thing to check.

 

[Sarastro]

in may experience, at least, there is more to vapor lock than just getting bubbles in the line. If you replaced the fuel lines with transparent tubing (as I did once, just for the experiment) you'd see that it is bubbling like ginger ale. That really doesn't hurt, even if a large bubble forms in the line. However, if you get a bubble lodged in the fuel filter or in the fuel pump valves or maybe in the float valve, the fuel won't move past it easily and then you have a problem.

Part of my solution to this problem was to use an electronic fuel pump, located back at the tank where everything is cool, or at least as cool as it gets. This, plus eliminating the fuel filter in the engine compartment, and finally arranging the fuel lines so bubbles could move upward and out through the foat-bowl vents, cured it for me.

 

[toysrrus]

Howdy,

I was just driving thru and thought I`d pass on my exp. with my `59 Bugeye 948 with a Stock Feul Pump.

I had "Exactly" the same symptoms your having. I bought a "New" manual pump (No Help); Blew out all the lines (No Help); Did "Everything" possible to include the "Clothes Pin" trick (No Help).

When the car stalled; Pulled off the Float Bowl covers and "No Gas" in one of the bowls.

This is called: "Feul Starvation".

The Bottom Line is this: Get Yourself an "Electric Feul Pump" and Your problems will be solved.

Russ

 

[Hap Waldrop]

That fuel line from what I see sneak behind the heatshield then comes back thru the heatshield to the fuel supply tube on the float bowl lid, I would suspect that is the problem. SU made about a kazillion different float lids with different orientations to them as for fuel supply and venting. OK with that said the orientation of your fuel supply lid is wrong for your application , it's too close the exhuast you need the fuel supply lid facing towards the fender not the engine for your application, now you could find another float lid, or you can use the one you have and do a old racer's trick as for orientating the way you need it. Racers want their float lids orientated front to rear , so in high g corners they don't try to close the float, a old trick used by racers to get the orientation you want is use some flat washers with float lid screw, and orientate the the float lid however you need it to be, then forget the screw ears on the float lid use the flat washer under the three screws to secure the float lid to the float bowl in whatever orientation you need, years ago Dave Tabor at Comptune used to remove the screw ears on the float lids so his customer would not be tempted to use them and orientate the float lid the way he wanted them to go.

 

[dklawson]

Manual pump is not gravity feed. Its a sucker and a pusher.
Solution, an elec pump back by the tank.

Thanks Jack. It sounds like the tank on a 1500 Midget is "lower" than the tank on a Spit.

 

[bigjones]

Thanks for all the advice!
OK, as Doug points out, the float bowl lid can be rotated 120 deg but in the 2 alternate positions the float swings side to side rather than fore and aft. So, I tried Haps idea. The lid is tight - don't worry - also used threadlock gel on the screws.
Blew through the vent line - no blockage.

Went for an identical drive - no problems! Not so hot today though.

Stay tuned!

 

[Guest]

Mine was heater core hose was too close, yours looks to be. Gotta cover my plastic filter too. Hasn't happened again.

 

[dklawson]

At least you got to drive yours today... and boy would it have been nice to go for a drive with today's weather. The Facet pump on the Mini died (fortunately at the bottom of my driveway) so I was in the Civic today.

Clever idea with the screws and washers. I'll have to take Hap's advice also when I get the Spit engine installed.

 

[Cottontop]

Tim, I'm not quite sure what you mean. Could you elabotate some?

I don't mean to be elusive, but the best way to find out what I mean is to ask your grandfather or even your father. If that is not possible, Google for "clothspins on fuel lines" and read some of the responses.

OR Follow THIS link and read some of the posts.

Tim