QuestionQUESTION: Gents: On a 1973 USA MGB with HIF Carbs, the float on the
front carb had filled with gas & was spilling gas.
Accordingly, I replaced the floats on both carbs, and set
the float level as instructed in Haynes Manual. As the kit
came with the jet assembly tube, I replaced it in each carb;
I also sprayed some carb cleaner in the orifices & blew them
out with compressed air. After reassembly, the car would not
fire unless spray starter used. Then it only ran on the
spray starter. No gas from carb. Crap. I pulled them
again & replaced the new jet tube (which did not
differentiate the front from the rear carb) with the
originals that I pulled. Again, although I could hear the
fuel pump filling the float chamber & then stopping
clicking, no gas getting through the carbs when engine was
cranked.
I did not remove or tinker with any part of the cold start
enrichment. Did I blow something out in the enrichment
device by blasting compressed air through various orifices?
Any other thoughts? Aargh. Your input will be appreciated.
Thx
ANSWER: Hi Moose. The fact that the pump fills the float chamber and then stops proves to me that you have correctly refitted the front float. However, the rear carb is filled by the overflow from the front one. Are you sure that the rear carb is filling up ok?
The jet is just an L-shaped tube with the bottom sitting in fuel. The level of the fuel should be about 1/8 of an inch down from the top of the tube, maybe a bit less than that.
I would remove the top of the rear carb complete with piston and needle, then look down the tube. If you blow on it (with your mouth, not an air line) you should be able to see the fuel brimming to the top of the tube as the level bounces up and down. If you cannot see any fuel, perhaps you have blocked the connecting pipe?
Check that the front carb does the same thing, but re-assemble the rear one first, so that you don't mix up any parts between the two carbs.
By the way, the jets are not identical, they are handed left and right. The front one has a white plastic base and the rear one is black. Have you gotten them mixed up? Did you fit two white ones by mistake?
---------- FOLLOW-UP ----------
QUESTION: Thanks for the wisdom. I pulled the fuel line between carbs
& found it to have gasoline under pressure. I then took off
the top of each carb & could not see any fuel down the jet
apperture. I also noted that the needles were not wet, so i
probed the jet apperture with a tookpick & came up dry.
Ref the Jets, the new ones that came with the kit had no "L"
shape on the bottom & seemed identical. When I replaced
them with the originals, the originals would only fit its
appropriate carb. One white & one black.
What have I possibly done??
Thanks,
Moose
AnswerHi Moose. I think you have rebuilt the carbs incorrectly, so you will have to take them apart again. It is not a long job on the HIF type. It sounds as though you have set the floats so high that the chambers are not filling correctly with fuel. This exploded diagram may help you:
http://www.mossmotors.com/Shop/ViewProducts.aspx?PlateIndexID=28997&SortOrder=19
The jet is part #15, and the L-shape is the plastic bit on the bottom.
It is essential that the float sits correcly when you invert the carb to check the clearance. In my Haynes manual this is shown in diagram 2:34 with a clearance of about 40 thou (1 mm).
