petrol temperature on my TR4A with mechanical pump

[Z320]

Hi all,

some of you perhaps remember my experiments with coolant temperatures and coolant flow years ago?

This was very interesting for me but finished. But the 3 thermometers are still on the car with the display hidden behind the radio.

Before I remove all that stuff my idea is to measure the petrol temperatures. Much has been tolt about, but no temperatures.

The sensors are now on the petrol pipes,

wrapped with tape and insulation to get the real temperature with little efford as real as possible.

1st in front of the mechanical fuel pump

2nd as close as possible behind the fuel pump

3rd between carb 1 and 2, with the pipe the original route.

Now I hope for some hot days in 2023, I'm a bit exited what the thermometers show me because I have already an idea.

Apart from that I never had any fuel / heat problem or restart / hot start problem. This is just for my interest.

Ciao, Marco

[BlueTR3A-5EKT]

Looking forward to seeing the results 

[stuart]

Would it be a good idea to also have a sensor that showed under bonnet temperature too for comparison purposes?

Stuart.

[BlueTR3A-5EKT]

3 hours ago, stuart said:

Would it be a good idea to also have a sensor that showed under bonnet temperature too for comparison purposes?

Stuart.

And perhaps petrol tank temperature.

[Z320]

And outside too? 

For no problem this are much sensors

[Z320]

Hi, just a short explanation:

it is often told the original route of the 4 cylinder petrol pipe from the fuel pump to the carbs is "disadvantageous",

because guided along on the cylider head and crossing behind the radiator heats the petrol up.

But when I touched pipes and pump serveral times my impression always was different:

- the petrol pipes are slightly warm before the fuel pump because of the heat of the engine is coming down there

- the pump, because directly fitted on the hot engine and in contact with the oil, heats the petrol up!

- the fuel pipe on the carbs is not hotter than directly after the pump, more likely colder again

 

This is the result after a 10 miles moderate drive, the last 500 m with some rain (changed nothing):

pump heats the petrol up, the pipe to the carbs cools it down again.

This was the case about 10 min after I stopped the engine.

That fitts to me. I'm hoping for some hot days for some more tests.

As told above: I had never any heat related fuel problem.

Ciao, Marco

[Z320]

Great, 26°C today and sunny,

out to the classic car meeting at the MB Museum / Stuttgart.

Arriving there the petrol temperatures did not tell anything surprising new.

When I wanted to restarted about 1 h later, the car all the time in the full sun, bonnet all time closed, this was on the thermometers:

 

Very likely the temperature of about 53-54°C was the temperature under the bonnet.

Restart was no problem at all, after about 2 km town traffic this was the temperature, all as expected:

Home on the Bundesstraße and fast county roads at home again, still 26°C and full sun:

Well, why should I worry the original petrol pipe routing?

Ciao, Marco

[BlueTR3A-5EKT]

No wheels to re invent there then.

[Z320]

Last test today on a 180 km tour at 26 - 30°C.

This was at the end of about 3 km / 20 min traffic jam.

I‘m shure the petrol pipe routing rear the engine will not give a better result.

Shure some incredients of the petrol boild, but this was no problem at all,

the temperatures dropped down to "normal" rapidly after driving less than 500 meter.

This was the case when we arrived at home.

Test finished.

Ciao, Marco

 

Edited September 11, 2023 by Z320

[Z320]

Hi and sorry me,

a last test today after a 120 miles autumn tour with my local classic car club mates.

The day started 20°C cold, hottest was about 30°C, when we arrived home it was 29°C, petrol temperature all day "normal".

Back in the garage at once I covered the bonnet with 2 old blankets, one cross, one lengthwise to keep the heat of the engine and rad in.

This have been about the highest temperatures, already dropped 0.1°C.

Ignition on, starter engages, engine runs on first attempt without any issue.

As I know it from my TR4A with original pump / pipe / carb setup.

Ciao, Marco

 

 

Edited September 17, 2023 by Z320

[BlueTR3A-5EKT]

I appreciate the test.

I would be reluctant to stop my engine when parked in traffic with the hope (based on your experience) it would definitely restart    I would be lynched by the following drivers.  
 

I think I will suffer the Lumpy tickover a just blip the throttle as required.   

Edited September 17, 2023 by BlueTR3A-5EKT

[RobH]

That is a pretty conclusive test Marco.  Thanks for that information -  it pretty much refutes the 'fuel vapourisation' argument. 

 

[Z320]

I found no matching explanation how „problems because of fuel vapourisation“ works

on a such simple setup like diaphragm fuel pump and SU H6 / HS6 carbs.

Shure - some cars have problems to start hot, in my opinion this must have different reasons.

Edited September 18, 2023 by Z320

[Ralph Whitaker]

I have been exclusively using Esso Super, which had no ethanol until recently. Last week I filled up for the first time with 5% ethanol. After a long run I pulled over for a 10 minute break. It was a hot day and when I re started the car it was hunting on tickover and I had to keep blipping the throttle to keep it running. Eventually it cleared and settled down to a steady idle speed. I am assuming that heat from the exhaust manifold had evapourated the fuel in the float bowls or the delivery pipes. Anyway maybe it was coincidental, but I had never had it happen before.

Ralph

[Z320]

Hi Ralph,

thank you for joining this thread.

Apart from hunting at tickover - did you have any problem to start the engine, please?

Ciao, Marco 

[Ralph Whitaker]

18 hours ago, Z320 said:

Hi Ralph,

thank you for joining this thread.

Apart from hunting at tickover - did you have any problem to start the engine, please?

Ciao, Marco 

No, it started up instantly, but then after a couple of seconds started hunting, needing me to keep "blipping" the throttle, then after about a minute of doing that it cleared up and normal service was resumed. A similar thing happened a little later when I pulled over to remove my jacket, this time I kept it running while I got out of the car and removed jacket, got back in and re fastened seat belt, went to pull away and it started to misfire, pressed the clutch and revved the engine a few times and it cleared. Was fine for the rest of the day and has been OK since, but the weather has not been as hot.

Ralph

[stuart]

4 hours ago, Ralph Whitaker said:

No, it started up instantly, but then after a couple of seconds started hunting, needing me to keep "blipping" the throttle, then after about a minute of doing that it cleared up and normal service was resumed. A similar thing happened a little later when I pulled over to remove my jacket, this time I kept it running while I got out of the car and removed jacket, got back in and re fastened seat belt, went to pull away and it started to misfire, pressed the clutch and revved the engine a few times and it cleared. Was fine for the rest of the day and has been OK since, but the weather has not been as hot.

Ralph

Check that your jets are returning fully as hunting can be rich mixture.

Stuart.

[Z320]

Hi,

last weekend my TR4A had a brake down because of "fuel problems".

It was a hot day, end of a 300 km tour to a club meeting, remaining 20 liter fuel in the tank, road really steep upwards to the hotel.

Suddently no petrol flow, also by prming the pump. No fuel at all.

We have been towed to the parking the last 4 km, went to the hotel and let the TR cool down.

A test 3 hours later without any repair: starting without problems, running well a short tour.

Club members wanted to convince me it is fuel vaporisation but did not convice me. In 17 years ownership I never had.

Next day a very sunny tour started with 20 liter pertol, 50 km later again fuel problems on a steep uphill road.

Drove "slowly" to the next petrol station, topped the tank up, no problems anymore, but I changed the pump 50 km later after the lunch brake.

No problems since, anyhow I drove the TR, up, down, fast, traffic jam, Autobahn. But club mates still wnated to convice me from fuel vaporation.

At home I opened the failed pump: one valve was missing!?

No, the inlet valve has been fallen out and stucked on the outlet valve.

WHAT A LOVELY PUMP IS THIS!

It worked this way for 100 km (and sure more) until the engine needed much more petrol for driving steep uphill!

I love this original diaphragm pumps! Tomorrow I will swap the pumps again, spare pump (new repro)n will be again spare pump.

Ciao, Marco 

Edited June 25, 2025 by Z320

[RogerH]

Hi Marco,

 I had exactly the same problem (twice) about 10 years ago. 

 On the first occasion I repaired the issue (at home) by using a centre punch to deform the edge of the valve counterbore.

However the constant valve action caused it to pop out again.

After this second failure I made a retaining plate to hold the valves in place. There is just enough room for an M3 screw to hold the plate.

 

Roger

[Z320]

1 hour ago, RogerH said:

Hi Marco,

 I had exactly the same problem (twice) about 10 years ago. 

 On the first occasion I repaired the issue (at home) by using a centre punch to deform the edge of the valve counterbore.

However the constant valve action caused it to pop out again.

After this second failure I made a retaining plate to hold the valves in place. There is just enough room for an M3 screw to hold the plate.

 

Roger

A good idea!

Thank you, I have a look.

[stuart]

It worked OK down to that level of fuel on a steep incline as the height of the tank above the pump was such that it happily syphons through till the level was too low. Thats why without a shutoff tap the only way to service the pump is with the front of the car jacked up as high as possible. Obviously you know that Marco and youve got a shutoff valve fitted.

Stuart.

[Z320]

 

[Z320]

This is what I did,

I fitted modified circlips 20 mm.

Pump is back in  the car, works well

Ciao, Marco