Fuel starvation Healey 100

[jmepmn]

Any thoughts on the following issue would be most appreciated.
Have been having fuel starvation problems on my 100 for about a year. I've: 1) replaced a suspected gummed-up steel tank with an aluminum one, 2) installed a double ended SU pump wired as two separate pumps, checked the carbs and pulled out most of my hair. The gas line(s)are open, lots of fuel to the carbs, but from time to time, usually when I'm max distance from home, one or the other float bowel dries up. I know it sound like the float level adjustment, but I've got the "fingers" up so high I'm surprised there isn't gas puring out. I also run grosse ball-jets, that are working fine (as tested by blowing into them and moving the "fingers" up and down. Sometimes it's the front float bowl that goes dry and sometimes the rear. Ususally at speed. Tonight it started to pop and bang on me on the interstate at about 65. Rear float bowl almost dry when I got home and took it apart. "adjusted" the "fingers" all the way up, reassembled and it ran like a striped-ass ape up till about 75mph, and then putt-putt, bang-pop. After slowing down, it ran ok, but under any amount of acceleration, it was fuel starved.
Any ideas?
Also, Michael Oritz...if I can make it run, I'll be at BOG on Sunday. Hope to see you there.
Jeff Maynard (red 100 at Hunt Club last year)

 

[Dave Russell]

Is the gas cap vent open? Try running with the cap not fully tightened.
D

 

[Michael Oritt]

[ QUOTE ]
Have been having fuel starvation problems on my 100 for about a year....

Also, Michael Oritz...if I can make it run, I'll be at BOG on Sunday. Hope to see you there.
Jeff Maynard (red 100 at Hunt Club last year)

[/ QUOTE ]

Jeff--

I'd check out the electrical circuit to the fuel pump, perhaps even pull a new wire temporarily from a switched hot to the pump--maybe there is an intermittant loss of current, etc. Also, is there a screen filter on the fuel pickup in the tank--if so possibly it might be clogging under high fuel load, then when the engine is about to quit and the suction is nil, releasing the debris back into the tank.

I plan to be at BOG and hope you can make it--it should be a nice day.

 

[jmepmn]

Michael and Dave,
thanks for the quick reply,
Michael, sorry I misspelled your last name.
The **** tank is brand new. That's what I thought was happening to the old one. Can't have any junk in th enew one.
I'll look at runnning a new line to the pump, but can't understand why it would alternate between the front and back carb. If it was lack of fuel pressure, I'd think it would always be the back carb first.
Thoughts?
btw, we're caravaning up (if the **** thing will run) with a bunch from the Richmond Triumph club.
Hope to see you there.

 

[jmepmn]

Dave,
Good thought on the cap. That's acutally the only aspect of the new tank that is questionable. When I had the old tank in, I took off one day with the cap off, and it went about a mile and started it's "thing".
New cap is a bit suspect. I'll go back to the old one, but the fit is not great. Other than that, the new tank is great.

 

[Keoke]

--Jmepnn, Keoke says Fuel pump!

 

[jmepmn]

Update:
Became convinced sometime this afternoon that the rear float chamber was getting so hot that there was massive vapor lock going on. (Hey, you've got to believe something!)
It'll run fine all day long as long as the road speed stays below about 60. Ten minutes at 65 plus (ie: strong load at 3000 rpm in 3rd OD)_and she starts sputtering and popping.
So we wrapped the rear float bowl in aluminized-rubber heat-shield.
Didn't work, but I have a cool looking rear float bowl.
Tonight made a banzai run to radio shack and bought some butt connecters and a switch. Hot wired one side of my double pumper SU to the battery. They are a whopping 18 inches apart.
Going to Brits On The Green tomorrow up around Mount Vernon, about 100 miles. This will either be the solution or I'll have one of the best looking broken-down cars along US 1.
Thanks to Dave and Michael for all the advice.

Jeff

 

[Louie]

After you stop and find the dry bowl, is the fuel pump not pumping? BTW, there have been complaints about grosse jets in the past--look very closely at them, perhaps switch temporarily back to the stock style.
Readjust the levers to the correct position.
/ubbthreads/images/graemlins/wink.gif

 

[jmepmn]

Yes, the pumps (double-ended SU) are working.
However, I think you may be right on the levers. I suspected the Gross-jet in the back carb, and at a show today (Brits on the Green in Alexandria, VA)I used some down time to replace it. Had an extra with me. When I got it back together, I had a first class gas leak from the float bowl. Turns out the levers were WAY to high, never closing the Gross-jet.
So if that one was so far off, the front one may be too. I may be running way too low a level in the front bowl.
Thanks for your input.
Special note to Michael Orett and Tim Flaherty.
Thanks so much for your help today.
Got home fine, but MAN. there are a lot of traffic lights between Mount Vernon and Fredricksburg on US 1!!!
Thanks again, had a great time.

 

[Michael Oritt]

The good news is that Jeff made it to the show today--and won first in 100 class with his beautiful car. The bad news is that when I last saw him he had a fuel leak.

After Jeff shared his symptoms and tales of woe the consensus of those present was that one or both jets might be stuck, so Jeff took off the float bowl covers and changed out the Grose Jets (which seemed fine). He then went to reassemble the carbs but there was a persistent leak from the rear one. After a new cover gasket and fibre washer did not stop the leak we noticed that the rear cover hole had two machined vertical slots where the bolt passes down (like keyways) which carried up to the top of the cover where they were notched like a crenellated nut and that gas was seeping out of the notches. When I last saw Jeff he was in Tim Flaherty's car heading to Tim's house to get some JB Weld or some kind of sealant to hopefully eliminate the leak. Some of us could not understand why the leak had not been there previously and Jeff surmised that he had perhaps adjusted the float arms a bit too high resulting in a higher fuel level and thus the leak.

In any case Jeff was travelling with some other folks from Richmond and I am looking forward to his enlightening about his trip home and what fix he employed.

 

[Michael Oritt]

Jeff--

Glad you made it--hope you didn't have to JB Weld the carb permanenty together.... Wonder what the deal is on that rear cover?

 

[jmepmn]

Michael,
Sorry, misspelled your name again. I'll get it right eventually.
Went to Tim's house and he was gracious enough to climb into his attic and retrieve his stock H4's.
Turns out the rear float bowl has that notch on all Healey 100's.
Actually his front one did too as opposed to mine with no notch.
Go figure.
So no goop or magic weld, only needed to push the lever fingers down so the float would close the Grosse-jet. Worked like a charm.
Tomorrow...I'll pull the front one off to see it it's too far in the other direction, causing the front float bowl to run low.
Car ran fine on the way home, but was still fuel starved above 65 mph.
Thanks again for your help and input today.
Can't believe you (or Tim) didn't take first.
Great seeing you. What a great show.
Jeff

 

[jmepmn]

How many posts do I need to post to get out of "Newbie" status?

 

[jmepmn]

Figured it out, need 25...that shouldn't be too tough

 

[kurts100]

I once had a problem with fuel starvation on my 100-4 and the problem was those machined groves on the top of the float bowl lid. Somewhere along the way someone had filed the top of one flat and when the copper washer was put on top it didn't vent properly. I got a different cap with the groove and it worked fine. Check both front and rear to make sure grooves are cleaned out and they should then vent properly as long as you have the proper washer on top. Shouldn't leak if floats are adjusted correctly.

Good Luck!

Kurt

 

[Dave Russell]

The older SU carbs have two different types of float bowl vents. On both types, the shank of the cap hold down nut is smaller in diameter than the hole in the lid.

On the H4's, a couple of slots in the lid below where the nut shoulder fits, provide a vent channel to the outside, no banjo.

On H6's, there is a similar but longer nut, again with a smaller shank. On this type, the cap is not slotted. A special fiber washer with scallops cut out of it's internal diameter, allows for passage of air around the nut shank & into the banjo vent above it. A non slotted gasket goes between the nut shoulder & the top of the banjo.

If the vent is inadvertently blocked by using the wrong gasket or the sealing washer is not correct, there will be fuel starvation because there is pressure in the bowl which opposes the inlet fuel pressure. For example, a soft washer on the first type could squeeze down enough to block the slots. On the second type, a non slotted gaket would block venting. Bowl pressure can also force fuel into the main jet & cause rich running. Rich at low fuel flows, lean at high flows.
D

 

[jmepmn]

Kurts,
Thanks for the reply. Now I'm totally confused. Not only aer there notches where the top bolt (brass) goes in to hold the top on the bowl, there are also notched on the top of the bowl itself where it "seals" against the top.
Hee's why I'm confused. Only my rear float bowl has these. We pulled a friend's original pair apart (he's now running HS-6's), and BOTH of his had the notches.
Any thoughts?
Anyone, anyone, Buehler?

 

[Keoke]

"And both of his had the notches"---WHERE were HIS notches located?---Keoke- /ubbthreads/images/graemlins/confused.gif

 

[Dave Russell]

The simplest solution would be to cut notches in the lid where the hold down bolt seats, on the lid that doesn't have notches. Use aluminum or copper washers between the lid & the hold down bolt heads. A soft washer will squeeze into the notches & restrict them. The original slotted vents had an inverted cup shaped washer between the hold down bolt heads & the bowl top which partially shielded the slots.

I don't know what the notches between the lid & the bowl itself are, but they won't hurt anything.
D