My Alfa Romeo 33 rebuild - FIRST TIMER

[WhizzMan]

For sure I'd like to know the accuracy of the old one.

I don't have a DMM that beeps but I could set it to a low resistance and see when it reads infinity.

It will read infinity when cold, then heat it up slowly while reading the thermometer, making a note when it switches on and off.

The beeping is just to make it easier to notice immediately when the contact opens or closes. Watching a kettle boil takes forever and you might get distracted glaring at the display. You could just as well put a light bulb circuit on it. The bright light will also make you notice and you won't even need a DMM at all.

I hope you and others understand that there is a hysteresis between opening an closing of the contact, to prevent jitter on the contact and fan. Therefor, both the opening and closing temperatures are relevant and you should measure both.

[Brit01]

I have a VDO oil temp gauge and not sure about the connections.

It has 3 x 6.3mm spade connections.

Labelled:

Upside down 'T' (ground?)
G
144 +

Now which is the 12v connection and which is the connection for the sender?

Thanks

Chris

[Brit01]

Been told 'G' is for the sender.

Regards

Chris

[Brit01]

Here's the nice VDO gauge that arrived today.

[Brit01]

I'll be fitting a new mechanical fuel pump this Saturday morning and wondering whether it's best to fit 1 filter before the pump inlet and one after.

Or just one filter before the pump, or one after (before the carbs).

If there is no fiter before the pump can't bits of metal/debris enter the pump and damage/block it?

This has never been clear to me.

thank you

[timinator]

There should be a screen or sock on the fuel pickup in the tank to protect the fuel pump. The fuel filter is to keep out material large enough to effect the needle and seat when using carbs. If you install the filter before the pump it won't cause any problems although most filters are fitted on or near the carb. I find the filter placement is a matter of convenience. If you mount the filter under the car be sure to add a shield to protect it.

Hope you are feeling better.

Tim

[Brit01]

Thanks Tim.

Yes just beginning to feel better now. Managed to gain 1 kilo finally which is a good sign as when you have gastritis this is virtually impossible.

Yes the tank has the fuel puck up filter.

I was told by fellow Alfa friends that the mechanical pump has a conical shaped filter inside the pump and 2 1 way valves. I will fit the new pump with the fine filter after just before the carbs as the pump apparently has a built in filter.
I might try and confirm that with the manufacturer though.

I will dismantle the old one and see what's going on inside.

Regards

Chris

[Guy Croft]

as it's a mech pump I assume the carbs have a fuel return line?

G

[Brit01]

Yes Guy they have a return to the tank.

Got a reply from QH the manufacturer:

I can confirm that the QFP15 Fuel Pump is fitted with a gauze filter in the inlet port.

Both inlet and outlet ports contain one-way valves.


Although the pump is fitted with a filter, it is advisable to fit an in-line filter before the pump as an extra precaution, to prevent rust deposits/contaminants from the fuel tank reaching the pump on older vehicles.


Best regards,

Quinton Hazell Automotive Ltd.

Taking this into consideration I might just put the easy replaceable fine filter before the pump as once the pump's filter/gauze gets clogged it is much harder to clean.

I hope there is'nt any pressure loss from the pump if the filter is before the pump.

[Brit01]

Spent 4 hours trying to get the new pump working!!
Put the old one back on - no issues.
New one - not pumping!!

Took a look inside the new one and everything looks fine. 1 way valves appear quite strong though. less flexible than the original ones.

Parts seem interchangeable. I may try fitting the bottom half with the new diagphragm with the original upper part with the 1 way valves.

Bit puzzling though.

[timinator]

Some fuel pumps need to be spaced very precisely to achieve the proper fuel pressure. On some engines the fuel pressure can be raised or lowered by using different thickness gaskets. Look through your service manual to see if this is the case. You can check the new pump fitness by covering the inlet port and cycling the pump. I would advise against swapping parts between the two pumps.

To go back the your hard starting after several days of non-use issue, I have a few thoughts. When you are running an engine the intake runner and port are completely soaked with gasoline. The runners/ports will stay wet for some time aiding in re-starting the engine. If the time period between re-start is long enough the gasoline will have evaporated making starting difficult until there is sufficient gasoline added to the intake tract. Poor choke adjustment will make starting difficult even if there is sufficient fuel. Check that the choke plate is fully closed when reset.

Inadequate accelerator pump discharge volume because of poor adjustment or under-sized orifice will add to the difficultly. On some carbs the accelerator pump movement can be phased in regard to throttle plate movement causing a later and lower than expected pump discharge. Any or all of these can also result in a stumble when shifting from 1st to 2nd gear because of the rapid change in throttle position and rpm, resulting in a lean condition even when using a stock cam.

Carbs really require no more effort than the type you have already displayed in getting to this point with your project. Write down what changes you make and how the engine reacts.

[Brit01]

Some fuel pumps need to be spaced very precisely to achieve the proper fuel pressure. On some engines the fuel pressure can be raised or lowered by using different thickness gaskets. Look through your service manual to see if this is the case. You can check the new pump fitness by covering the inlet port and cycling the pump. I would advise against swapping parts between the two pumps.

Not really the case here but maybe I'm wrong as I see the Fiat pumps come in a variety of thickness (0.3mm - 1.2 mm) and they are very similar in design (in fact the gaskets are the same shape). I used the paper gaskets that came with the pump for Alfa AR30550 and I've used various gaskets from different sources with the old original pump and it still worked.
I think maybe a thinner gasket might be worth trying.

To go back the your hard starting after several days of non-use issue, I have a few thoughts. When you are running an engine the intake runner and port are completely soaked with gasoline. The runners/ports will stay wet for some time aiding in re-starting the engine. If the time period between re-start is long enough the gasoline will have evaporated making starting difficult until there is sufficient gasoline added to the intake tract. Poor choke adjustment will make starting difficult even if there is sufficient fuel. Check that the choke plate is fully closed when reset


Inadequate accelerator pump discharge volume because of poor adjustment or under-sized orifice will add to the difficultly. On some carbs the accelerator pump movement can be phased in regard to throttle plate movement causing a later and lower than expected pump discharge. Any or all of these can also result in a stumble when shifting from 1st to 2nd gear because of the rapid change in throttle position and rpm, resulting in a lean condition even when using a stock cam..

Chokes are disconnected and aren't ever used.
I only use (like many other boxers users I know) the pump jets to start the engine.
2/3 pumps is always sufficient.
Here the engine will always start straight away but the pump doesn't appear to be priming properly after 5-6 days of non use.

Carbs really require no more effort than the type you have already displayed in getting to this point with your project. Write down what changes you make and how the engine reacts.

Thanks Tim.

I will try the pump again but this time using a syringe to completely fill the inside chamber before trying to start to see what happens.
If all else fails it could be a worn oil pump shaft lobe. (solution: electric fuel pump)
The time I spent yesterday on this I could have had an electric fuel pump fitted and wired up! Fustrating at times. Thought it would have been a 30 min job.

[timinator]

Chokes are disconnected and aren't ever used.
I only use (like many other boxers users I know) the pump jets to start the engine.
2/3 pumps is always sufficient.

I fail to see the efficacy of disconnecting the chokes on a street driven car.

[Brit01]

I fail to see the efficacy of disconnecting the chokes on a street driven car.

Because most parking in Montevideo is a type of valet parking. This is to avoid the Alfa ignorant employee using the cold start device.
They are not aware of the pump jet technique type of starting.

I do not need it and they do not know how to use it.

So cables disconnected.
Does that shed some light on it?

[Urbancamo]

Cold start mechanism in most common dual carbs is a very harsh device. It only adds raw fuel from separate channel. There is no choke flaps or nothing similar than single carbs have. It's very easy to flood the engine with this device.
It works as good if you were dumping raw fuel straight to the rampipes.

In cold start, couple pumps before start and after engine has turned on slight "nursing" with throttle will do the job. Then it will run it self. There is no use for choke mechanism here as everybody who owns a dual carbs knows.