It takes ten pumps of the pedal to start

[Moto Carlo]

This thread is getting a tad confusing. Sometimes these things simply do not make sense. You need to chart out what you have done and what remains to try.
When did it start happening? Has it done this since you have owned the car? Carb start spray make any difference? Temperature make any difference. Auto choke or cold start on the carb? 
Old fuel? Fuel filter? Fuel pressure? ... Why not look at the plugs? Dist cap...  Rain / humidity make any difference? Go over all the surface stuff . Often the thing that seems least connected is actually the problem. All we can do is take pot-shots at it. Especially an odd problem like this.

Step away and take a breath, then attach systematically.  You'll beat it.
(Wish I had more actual info  on it and could be more helpful. Every time I have had a similar problem it has been something different. Last time it was my fuel pump.)

[Healey3000]

Hi,

Good idea – time for an information reset.

When I bought the car, it ran okay but there were clearly a couple of issues.  One was that when warmed up, it would often diesel upon shutoff (carb does not have a cutoff solenoid).  The second issue was the hard starting, overnight.  In addition, the seat of the pants assessment suggested that the carb was not correctly jetted.

I started with the basics:

• Checked the condition of all fuel components (except the fuel pump, for which I had no metrics to go by) – okay

• Zinz noticed that my accelerator pump diaphragm seems to be leaking, which spurred me to do a full carb rebuild, which was on the list anyway.  Found that the jetting was indeed strange so adopted CD’s prescription – dieseling went away

• Added a check valve near the fuel pump – no improvement

• Moved the check valve to just after the tank – no improvement

• Changed all fuel hoses – no improvement

• Replaced sleeve on tank output tube – no improvement

• Replaced most ignition components (plugs, wires, cap, rotor).  Removed coil ballast wire as part of smog harness deletion (coil is high impedance) – no improvement

• Valves adjusted

• Timing set by ball as per manual

Observations:

• Fuel filter is always full, suggesting check valve is doing its job.

• Starting after a few hours is no problem, winter or summer

• Overnight or longer starts are a problem.  Engine fires, catches and dies.  This suggests all ignition systems are okay.  I *think* the problem is worse when ambient temps are lower

• Engine runs well once up and running.  Idle is not too good, never has been.  Suspect uneven mixture since the misfire(ish) behavior is random, so probably not a case of low compression in one cylinder (fingers crossed, need to run a compression test)

What I didn’t do:

Set the choke optimally.  I thought I had matched the setting as it was prior to the rebuild but I don’t think I did it well.  I am currently suspicious of the choke as it’s the one thing that could explain the symptoms.

Found this informative link http://www2.izook.com/?s=weber

This paragraph is particularly interesting in that it describes a behavior just like the one I’m experiencing – “This initial richness setting should allow the engine to start easily and quickly and continue to run regardless of idle speed. If the engine starts but dies immediately, the choke is not rich enough, if starts but "chugs" then the choke is set too rich.”

My engine does start but dies immediately.  Seems a likely candidate but it may be something else as well.  I’m feeling hopeful…

[Moto Carlo]

Next time it happens take a can of carburetor cleaner or starter fluid, and spray it in the throttle body. If it cranks, then you can throw your energy into the fuel side of things...

That way you can eliminate 50% of the options - one way or the other.

 

If fuel - Choke or cold start (the Weber idf has this blasted 'cold start' that most people simply delete) could be a problem at the carb.

And back to the fuel pump. My take on this is, why not upgrade to an electric fuel pump. If it fixes the problem - yahoo. If not , at least you have a better fuel pump.
IMHO

(In my case I added a Revolution relay which is an automatic off, in case  there is an accident - but that is an entirely different topic. Lets first simply get this thing to crank reliably for you.)
 

[ray_]

IMO an electric fuel pump is not an upgrade, even if safeguards are put in place.

 

BMW used the stock mechanical pump on ti's; they're certainly stout enough when functioning properly.

 

Cheers,

Edited March 5, 2018 by ray_

[M3M3]

11 hours ago, Moto Carlo said:

With the electric pump you turn the key and wait 15 seconds while the pump runs before cranking... Again not sure this is the path to take, but it fixed my problem with dual webers. (after rebuilding and rejetting a few times...this was what fixed it.)

 

 

Um...no.  If you have to wait 15sec after turning the key you have a bad pump.   Electric pump is instant on.  Internal check valve keeps the fuel in the line.    Turn key and go.

 

And an electric fuel pump is most definitely an upgrade!

Edited March 6, 2018 by mlytle

[Moto Carlo]

When you turn the key, you can hear the pump running for  about 10 seconds, then it stops (the entire process takes about 15 seconds). At that point you turn they key. At least that is what the pump directions said to do, and what I have done for the past 3 years without problem.  Although this was for a Porsche 356; I am new to the 2002.
(But I must say it was the same routine when I changed the pump in a Porsche 912, Volvo p1800 and a MGB. The fuel line pressure has to build a bit first.)
 

In terms of the debate whether mechanical vs electric. We are all victims of our experience. If the mechanical was working fine, I probably would not bother with it. But at any hint of a problem , I am changing it. I have been stuck by the road a few times over the years - at night, flashlight in mouth, semis blowing past my ankles ... while I am working on the blasted mechanical pump. As far as I am concerned , electric is better.
 

Good luck Healey, I hope you get your problem sorted. 

[ray_]

What happens if you don't wait 15 seconds?

[Arizona02]

Healey , sounds like a little more choke closure is needed,. When turning the choke housing making the flap touch the barrel keep turning another 1/8 inch or so.There might be a vacuum leak which adds to the problem of cold start up then dies within seconds plus the warm idle being uneven.

[M3M3]

1 hour ago, Moto Carlo said:

(But I must say it was the same routine when I changed the pump in a Porsche 912, Volvo p1800 and a MGB. The fuel line pressure has to build a bit first.)

carbs require zero fuel pressure to operate.  the venturi sucks the fuel from the bowl into the intake through the jets.  it is all about the vacuum created by the engine turning over.  carbs are pretty cool devices.

 

carbs only need some fuel flow to keep the bowls full.  too much pressure and the float valve spring is overpowered and the carbs flood.  there is plenty of fuel in bowls to start the car and keep it running until the fuel flow from the pump starts.  a good check valve in the pump (and the pump should be near the tank) keeps the fuel line full, so as soon as the pump starts it is filling the bowl.  turn key and go.

 

if the car has been sitting for a long time, the gas in the carb bowl may have evaporated.

if the check valve isn't working, the fuel lines may drain back into the tank.

in either of those cases, it may take a second or two for the pump to flow enough fuel to refill the bowl.

 

fuel pump function is very different between carbs and fuel injection.

carbs..all the pump does is keep the bowl full.  2-3psi

FI.. pump and pressure regulator are responsible for blowing the fuel into the intake. 35-50psi.   no vacuum or jets needed.

 

 

for carbs..mechanical or electrical..as long as it is flowing a little gas, either good.  i prefer electric, but mostly i like to mess with Ray cause he likes mechanical!

[ray_]

2 minutes ago, mlytle said:

 

FI.. pump and pressure regulator are responsible for blowing the fuel into the intake. 35-50psi.   no vacuum or jets needed.

 

 

for carbs..mechanical or electrical..as long as it is flowing a little gas, either good.  i prefer electric, but mostly i like to mess with Ray cause he likes mechanical!

 

 

Or 400psi.

 

;-)

 

Photo courtesy of jgerock courtesy of C.Diesel ;-)

 

[Healey3000]

3 hours ago, Arizona02 said:

Healey , sounds like a little more choke closure is needed,. When turning the choke housing making the flap touch the barrel keep turning another 1/8 inch or so.There might be a vacuum leak which adds to the problem of cold start up then dies within seconds plus the warm idle being uneven.

That's my guess too, reinforced by that article in the link.  Sounds like the choke butterfly needs to be fully closed once you arm the choke by pressing the throttle.  I'll have to check if mine is that way or not..

 

I've looked everywhere for a vacuum leak because that idle is driving me nuts.  I've tried to find it with carb cleaner spray but nothing shows up.

['76mintgrün'02]

 

I checked today and my choke flaps are not snapping shut as they should... in spite of having oiled the shaft and fast idle mechanism about a week ago.  (At that time, it seemed to be working well again). 

 

I suspect I need to lubricate the lever arm/shaft that the bi-metal spring rotates.

[Moto Carlo]

"the venturi sucks the fuel from the bowl into the intake through the jets.  it is all about the vacuum created by the engine turning over." 

But ... getting the engine to turn over is the question (and reason for this thread).

Pressure is really important. That is why they make a variety of pressure regulators - especially important with dual carbs.

The fuel has to travel a long way from the tank to the carb(s) that is why we have a pump, it creates pressure for a reason, and it must be regulated. The rotary fuel pumps I have used in the past come pressure preset for the particular carb set up. But there also is an inline regulator that could go after the pump if needed...
 

Choke approach is also a good idea. (surprised that has not already been attacked)

Starting to feel a bit like a "pissing match", sorry about that.  So I am gong to bow-out now and enjoy seeing how the problem finally gets solved.

 

Edited March 6, 2018 by Moto Carlo

[Healey3000]

I think Marshal's point was that fuel pressure with carbs is only important in that it not flood the float chamber by overpowering the needle valve.  In theory, one could gravity-feed a carb and it would run.  All you need is enough pressure to overcome the drops along the plumbing from tank to carb inlet.

 

I remember when I first fired up my AH3000 engine after rebuilding it, I didn't want to hook up the pump and fill the tank.  I took a pressure pot and pumped it up to 7 psi to feed the twin SU carbs, since that  was the spec for the stock pump.  I promptly flood the carbs.  Once I dropped it to around 3-4 psi. it fired right up.   Touchy things, those SU's.

[jimk]

1 hour ago, Healey3000 said:

In theory, one could gravity-feed a carb and it would run. 

More than just theory.  The bowl is vented to atmosphere,(except for the air filter retsriction) so it operates with zero gauge pressure!