Carburetor and Gas pump overheating

[RIQUE]

My 72 CSA runs fine until it starts to get warm. The Temp gauge stays pretty much in the middle
but engine feels pretty hot. What happens if I park is the gas in the carbs evaporates and I get
stranded until things cool down. Cooling system works fine but I may have a 80C thermostat I will
swap to 71. Other than that how can I keep carbs from boiling my gas?

 

[deQuincey]

according to ...

then:

if needle is in the middle, your coolant temp is 85 assuming a linear scale, nothing severely wrong

 

[deQuincey]

hard to believe that your fuel evaporates in the carbs, not saying it can not happen, but...


engine feels hot, well 80cels is very hot, so nothing odd there

post pics of your setup

do you have an antireturn fuel valve ? do you have a filter ?

does your mech pump work properly ? i mean do you have fuel coming from the pump ?

i mean if your gauge shows 80cels and if the sensor and gauge are ok, if we can assume it is 80 cels; it is hard to believe that a 70cels will solve the problem

can you check pressure in your coolant hoses when engine is hot ? both big hoses up and down the radiator

how is ignition set ? have you checked it recently ?

if you do not stop for 40 km does the problem happen ?
only when you stop and iddle you find the problem ?


I would say that you might be having problems in the fuel feed, and then you open the hood and realize how hot is a normal engine, and you make that guess ?

but why does that change when engine cools down ?

 

[RIQUE]

hard to believe that your fuel evaporates in the carbs, not saying it can not happen, but...


engine feels hot, well 80cels is very hot, so nothing odd there

post pics of your setup

do you have an antireturn fuel valve ? do you have a filter ? I HAVE A FUEL FILTER YES. GLASS ONE. I BELEIVE NO ANTI RETURN.

does your mech pump work properly ? i mean do you have fuel coming from the pump ? YES WORKS FINE. NEW ONE

i mean if your gauge shows 80cels and if the sensor and gauge are ok, if we can assume it is 80 cels; it is hard to believe that a 70cels will solve the problem

can you check pressure in your coolant hoses when engine is hot ? both big hoses up and down the radiator I CAN CHECK PRESSURE BUT COLD NOT SURE YOU CAN DO HOT

how is ignition set ? have you checked it recently ? TIMING IS BY THE BOOK BUT WILL CHECK AGAIN.

if you do not stop for 40 km does the problem happen ? NO. PROBLEM HAPPENS WHEN I STOP
only when you stop and iddle you find the problem ?


I would say that you might be having problems in the fuel feed, and then you open the hood and realize how hot is a normal engine, and you make that guess ?

but why does that change when engine cools down ? WHEN ENGINE IS COOL OR WARM CAR RUNS PERFECT NO ISSUES. THE HOTTER IT GETS THE WORSE.

 

[Stevehose]

Are your chokes opening properly?
How old is your ignition coil?

As DeQ is getting at, it sounds like a vapor lock, are they Zenith or Weber carbs?

 

[RIQUE]

Are your chokes opening properly?
How old is your ignition coil?

As DeQ is getting at, it sounds like a vapor lock, are they Zenith or Weber carbs?

Yes chokes work fine. Coil is pretty new Bosch Blue. Carbs are Zenith. Yes it is Vapor Lock. How to solve. ?

 

[Stevehose]

Do you have a ballast resistor in your coil circuit? If so you are doubling the voltage drop with a blue coil which is internally resisted.

Otherwise I would check condition/tightness of fuel lines and that you have the spacer between the sender unit output pipe and the hose.

Confirm all connections at ignition coil are fresh and tight.

 

[Dan Wood]

I have been fighting vapor lock after a 10 to 15 minute heat soak since owning the E9. I just finished insulating the suction side of the mechanical fuel pump and the filter. It doesn't look great or original but might solve the issue. However, now the weather is cooling off so might not know until next summer. Turning on the electric pump solves it. I could go with electric only but want to solve the issue first.

 

[tochi]

Many things might account for your reported symptoms. You state that the problem occurs “if I park.” For how long do you park before the problem presents itself? Is it immediate, or after waiting 20+ minutes? DQ's information regarding your temperature gauge readings is quite good; however, perhaps you might try using a point and shoot thermometer to "guestimate" the relative temperatures of various components, including the temperature of your fuel pump, carburetors and intake manifolds.

While what you describe sounds like a classic heat sink/vapor lock issue - maybe it is something related. How long has this problem occurred? Have you considered checking the health of your fuel pump by using a simple vacuum gauge? Might the floats in one or both carb fuel bowls be adjusted - so that the fuel level in one or both carbs is very low? A few photos might be helpful. For example, the routing of your underhood fuel lines and their proximity to heat sources. Speaking of rubber fuel lines, they do not last forever. They might appear to look A-OK - but might be cracked permitting fuel to leak/weep/seep, especially when heated or under pressure. Conversely, a fuel line feeding your fuel pump is likely under vacuum pressure and, if cracked, might draw air into the line.

 

[deQuincey]

i have never experienced a vapor lock

but now reading about it and its possible consequences i would consider using an antireturn valve in the fuel feed line before the pump,
i also use a manometer in the line after the pump so i can check fuel pressure (mech pump gives 0,21 to 0,25 Bar) i do not know how it would read a vapor lock though

considering that according to gauge your engine is not that hot i would say if the routing of the fuel hoses is ok, nothing to worry, but good point on renewal of those fuel hoses

it has been mentioned to adjust fuel bowls level, but that is not possible with zeniths; anyway the point is a good one as to check the internal ball valves and check floats for tightness

checking pressure on hot coolant hoses is possible, if you are thinskinned you can wear gloves for the occasion, there is not pressure on cold hoses unfortunately

as to ingintion timing, retard may lead to overheating, even severe overheating, but you should notice at the gauge, and you refer no problems there

final point on coils, there are two type of bosch blue coils, the normal blue one is internally resisted, the TDZ one is not; TDZ usually has this yellow decals saying hey i am a coil for transistorized ignition, but decals might fade or go away...

 

[deQuincey]

my setup

here you can see manometer: even with air filter installed

green anti-return, glass filter is just before it

orange is manometer

red is route

 

[deQuincey]

my bosch blue coil, has a resistor

see here

but @Stevehose is right, you have to check for not double resistor setup

 

[JFENG]

Unlike pre-cross flow engines, we do not have exhaust manifolds under the carbs. So heat is less of an issue than on many other cars.

There are some relatively simple checks you can to to narrow down the root cause.

after you park and wait the time you associate with the problem, you can check

(1) is there still fuel in the carburetors? - look down the carb throats and see if you get a squirt of gas from the accelerator pump circuit as the linkage is opened quickly (have someone depress and hold down the pedal). If no healthy squirt in means the fuel in the float bowls is low due to leaks, evap, wrong float setting, etc. Check for leaks and missing heat insulator at the carb base. IMHO leaking fuel lines will not siphon fuel out of a carb due to the design of float bowl and needle valve.

(2) is the pump and supply line ok? you can pull off the outlet hose on the fuel pump and with a short hose + container you can see if the mechanical pump is delivering a good fuel flow immediately at the start of cranking. This is dangerous so make sure you have disconnected the coil to distributor HT lead as you don’t want the engine to fire/start or a stray spark to start a fire. Ice to have a fire extinguisher handy. If you get good flow but only after a delay, you are losing fuel in the line between the pump and tank or you have a clogged fuel filter (leak or simple backflow). If you get a weak flow, your fuel pump may be partially failing. If there is no flow, I would replace your pump and check your fuel line filters for clogging.

And there is always the classic problem of having a build up of vacuum in your fuel tank…

 

[stphers]

I have had some success with adding a phenolic/Bakelite 8mm spacer between the carb and intake manifold. That helps to isolate the carb body from the heat of the engine.

Thanks, Rick

 

[HB Chris]

I have had some success with adding a phenolic/Bakelite 8mm spacer between the carb and intake manifold. That helps to isolate the carb body from the heat of the engine.

Thanks, Rick

Rick, I considered this but with Zeniths the studs are too short.

 

[stphers]

Yes, I just make up new longer ones I wonder if there would be demand for a kit put together with longer studs and spacers and gaskets ?

Thanks, Rick

 

[lip277]

I have had some success with adding a phenolic/Bakelite 8mm spacer between the carb and intake manifold. That helps to isolate the carb body from the heat of the engine.

Thanks, Rick

That is actually how some of the older carb equipped cars came that I have seen (US domestic 1960's and 1970's anyway).
Yeah - it would take a longer stud to do that. Might be worth considering though still (just get longer studs... if it is that simple).

 

[Stevehose]

I live in a very hot climate and never had a vapor lock on my stock Zenith setup so something is not right

 

[RIQUE]

And there is always the classic problem of having a build up of vacuum in your fuel tank…

I have noticed vacuum in my tank as removing the cap is difficult and then opens with a pop. Is there a vent I should check I also notice fumes inside the car....mild but noticeable.

 

[deQuincey]

I have noticed vacuum in my tank as removing the cap is difficult and then opens with a pop. Is there a vent I should check I also notice fumes inside the car....mild but noticeable.

Impossible, there is a tiny tube in the fuel mouth that vents to the floor
is it clogged ?