Alfa Romeo Forums banner

1 - 11 of 11 Posts

·
Premium Member
Joined
·
254 Posts
Discussion Starter #1
Not your usual question I know but these 40 DCOE 2 carbs just won't start with out starting fluid help, cold or hot. Once started it seems to run and idle fine. Switch it off, try to restart, no go

Recently rebuilt

Any ideas?
 

·
Premium Member
Joined
·
14,028 Posts
Float levels too low?
 

·
Registered
Joined
·
3,940 Posts
Hi Tad,
I have had nothing but trouble with the old cars carbs ever since they started selling ethanol fuel (crap). There are several post about how to clean out the Weber jets and using Stabil or Marvel Mystery oil which I would use with non ethanol, Rec 90 fuel.

I wish that I could be more help but I suspect a stuck fuel cut off valve (steel ball acted on by float like JP suggested) that loosens up when the engine runs on starter fluid or a plugged jet. If you remove the big brass nut on the top of the Weber, I believe you can press down on the ball or float arm so fuel can fill the float chamber if it is not full.

Mark
 

·
Premium Member
Joined
·
254 Posts
Discussion Starter #4
A little history about what I have done to this point.

A had the carbs rebuilt by a respected Alfa Weber restorer.

I put them on the car.

I have not checked float level but I took the covers off last night and the fuel level looks good.
I took all the jets out and made sure everything matched up and there was no clogged jets.

I drained all old fuel from tank, replaced all filters, replaced old fuel pump with correct Facet fuel pump and all fuel lines. Good fuel pressure to carbs.

Like I said, will not start without Starter Fluid help. Runs pretty well once started.

Thanks!
 

·
Super Moderator
Joined
·
10,623 Posts
will not start without Starter Fluid help. Runs pretty well once started.
That is the classic symptom of acceleration pumps not pumping. Upon starting, the squirt of gas from the acceleration pumps is the only fuel that the engine gets, as it is turning too slowly to build enough vacuum to draw fuel off the idle or main jets.

When the carbs are removed from the manifold, have some gas in them, and the throttle is opened, you should see a jet of gas squirt out of each barrel, sort of like a water pistol shot. You could try doing that, and see if all four are squirting. Before removing the carbs, you could remove the pump jets, and verify that they are not plugged. Also, remove the carbs' top covers, and observe if the pump mechanism moves down as you open the throttle.

I can't explain why the acceleration pumps would fail on newly-rebuilt carbs. Did the carbs sit on the shelf for some time after the rebuild? If so, the pump mechanism may have stuck due to corrosion.

Runs pretty well once started.
Meaning it idles OK in the garage, or it runs fine on the road? If the problem is the acceleration pumps, it won't rev up smoothly.
 

·
Premium Member
Joined
·
254 Posts
Discussion Starter #7
Update- Removed everything associated with the accelerator pumps, blew out passages, cleaned jets, etc. Reassembled and the car started up! Did not have time to check actual fuel level but floats seem adjusted OK.

Ran pretty well, will road test this morning to see how well.
 

·
Premium Member
Joined
·
254 Posts
Discussion Starter #8
I just road tested my car and it bogs down / stumbles at low speed but does fine once "it clears its throats"

So something is causing it to stumble at lower rpm's.

Maybe I just need to drive it some, it has been a while since it was driven any.

Any idea's?


Thanks
 

·
Premium Member
Joined
·
14,028 Posts
I just road tested my car and it bogs down / stumbles at low speed but does fine once "it clears its throats"
It is helpful to know if the stumble is rich or lean. Do you have a bung for an oxygen sensor in your exhaust? I have a couple of narrow band AFR indicators that I no longer use. I will give you one of them if you can use it. I can include a good sensor as well. This is not for precise tuning - you need a wideband for that, but it will tell you if you are too rich or too lean.
 

·
Super Moderator
Joined
·
10,623 Posts
.... it has been a while since it was driven any.
Failure to make a smooth transition from the idle to the main circuit is a classic Weber problem, and that seems to be what you are describing.

You mentioned that the carbs have been rebuilt. When it was on the road previously, was it with the same carbs and the same jets? I.e., are you sure the jetting is correct? Did the car run well previously?

Since the pump jets were apparently clogged, is it possible that other jets are also clogged?

Maybe I just need to drive it some
That can help when the issue is fouled plugs. How is your ignition system? Clogged jets may clear with exposure to fuel. But just driving a car with incorrect jetting isn't likely to resolve anything.
 

·
Premium Member
Joined
·
254 Posts
Discussion Starter #11
Got side tracked with X-Mas stuff so I've not done much else other than pull the fuel tank, what a mess. When that gets back to 100% I'll continue with the carbs.
 
1 - 11 of 11 Posts
Top