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Hit by cavitation last Sunday


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Last Sunday I went on the Tour of the Thames Valley run by the local Mini Cooper Club. I have owned my car for 48 years and never have had this problem before. My car stopped in the middle of Henley, after about 3 hours of driving and we had to push it into a side road. Open the bonnet and boot which we unloaded, I felt the pre filter and it was very hot and so was the Bosch pump and the base of the fuel tank which had at least 6 gals of petrol in it . We had to wait 3/4 of an hour to let it cool down before it would restart. I drove to the local Esso garage and filled it to the brim. No more problems and got home OK. I am now hearing that the present formula of petrol is very susceptible to this problem after speaking to one of the major TR restorer in the S.E. Have others had this problem during this hot spell?

Bruce.

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Went on 250 mls trip on Sunday, no problem with pump mounted outside in wheel arch. Tank

filled with Shell V-power ran tank down to 1/3 full.

                                         Harvey

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Is your tank venting OK? Any chance you had high vapour pressure fuel from a winter blend? I get by in Australia on days of  over 40 deg C by using a booster pump in the wheel well to feed the Bosch pump. But I don't use ethanol fuels.

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7 hours ago, astontr6 said:

Last Sunday I went on the Tour of the Thames Valley run by the local Mini Cooper Club. I have owned my car for 48 years and never have had this problem before. My car stopped in the middle of Henley, after about 3 hours of driving and we had to push it into a side road. Open the bonnet and boot which we unloaded, I felt the pre filter and it was very hot and so was the Bosch pump and the base of the fuel tank which had at least 6 gals of petrol in it . We had to wait 3/4 of an hour to let it cool down before it would restart. I drove to the local Esso garage and filled it to the brim. No more problems and got home OK. I am now hearing that the present formula of petrol is very susceptible to this problem after speaking to one of the major TR restorer in the S.E. Have others had this problem during this hot spell?

Bruce.

Petrol today is very volatile - its worth watching the Paul Ireland lecture on the TRR website.

https://www.tr-register.co.uk/past-issue/2021/07/0133/TR-Register-Summer-Lectures-Modern-Fuel-Classic-Engines-13

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A good chunk of our 150 mile run last weekend was on slow, scenic roads with plenty of 2nd, 2+o/d and 3rd gear driving. A friend in a modern car had the temp at 31c. The TR started on a full tank of Tesco 99 and although it drove okay, by the end of the run the Bosch pump was making some very strange noises at tickover. I'm guessing the high ambient temp, lack of a decent cooling flow and high under bonnet temp (plus fuel overflow back to the tank so it could start the cycle all over again) played their part here. Have had my TR6 over 12 years and only the second time this has happened. Went fine the next day on a full tank of much cooler Shell V Power. 

Ray in Pembrokeshire.

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Just a thought the old Lucas used a coil around the motor in an effort to cool the motor and hence the fuel. Has anyone tried running a small Spal or similar fan ducted to push  cool air over the pump Bosch or Lucas type?

I've yet to decide which way to jump with the pump (I have a reconditioned Lucas or buy Bosch type) and PRV but I can't help feeling that taking a leaf out of modern EFI systems is the way to go with an in tank pump and external PRV set to 105psi close to the metering unit as it would solve the cooling issue and other reported woes as long as the pump has an adequate 12v supply. 

I have my hard hat ready!

Andy

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Hi Bruce,

you are focused on what is likely - but was without problems before.

What about other reasons? Did you have sparks on the spark plugs?

Ciao, Marco

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2 hours ago, PodOne said:

Just a thought the old Lucas used a coil around the motor in an effort to cool the motor and hence the fuel. Has anyone tried running a small Spal or similar fan ducted to push  cool air over the pump Bosch or Lucas type?

I've yet to decide which way to jump with the pump (I have a reconditioned Lucas or buy Bosch type) and PRV but I can't help feeling that taking a leaf out of modern EFI systems is the way to go with an in tank pump and external PRV set to 105psi close to the metering unit as it would solve the cooling issue and other reported woes as long as the pump has an adequate 12v supply. 

I have my hard hat ready!

Andy

Andy, the old Lucas style cooling coil collected heat from the pump and dumped it into the fuel !  Not a real benefit if hot fuel then causes the problem. I think your in tank pump comment is a lot more interesting - ever heard of anyone doing it?

Bob

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I can't see how the Lucas coil in the boot worked from a thermo point of view- it just transferred heat from the pump back into the petrol.

I have an Isuzu ute which has a small radiator (like a transmission fluid cooler) under the chassis for the returned fuel- that will dump heat from the fuel to the outside air.

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4 minutes ago, OldBob said:

Andy, the old Lucas style cooling coil collected heat from the pump and dumped it into the fuel !  Not a real benefit if hot fuel then causes the problem. I think your in tank pump comment is a lot more interesting - ever heard of anyone doing it?

Bob

It's a better idea if the returned fuel from the PRV near the MU returns through a small radiator- that will keep the fuel temp close to the ambient- getting rid of excess heat from the pump.

Anyone measure the bulk fuel temp in the tank when their systems started cavitating?

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Hi Bruce 

I had the problem on Weds for the first time in 5 years of ownership & managed to limp home. The tank was down to about 1/4 full which was possibly a factor. Both pump & fuel tank were hot. I'm running with a Lucas pump (good power supply/earth) & always use Shell V power. I have purchased some heat sink material used in electronics & looking for a way to fit this to the pump as an improvement. I'm not sure how effective this will be as the fundamental problem seem to be warm fuel returning to an already warm tank (due to high ambient) & then picking up more heat from the pump.

Alan  

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6 minutes ago, Mike C said:

It's a better idea if the returned fuel from the PRV near the MU returns through a small radiator- that will keep the fuel temp close to the ambient- getting rid of excess heat from the pump.

Anyone measure the bulk fuel temp in the tank when their systems started cavitating?

Sadly not, however I have measured the pump temp in the past. At 23 deg ambient the pump runs around 50 deg. It was hotter than that on Weds. Ambient was around 25 deg but the car had sat in full sun for about 4 hours & the tank was hot to the touch - I would guess around 35-40 deg

Alan

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Just a thought; does heat from the exhaust running under the boot/fuel tank area contribute to this problem, especially if using a stainless exhaust? Would some form of insulation under the tank and boot floor help?

Although temperatures inside the car will be high if the car is parked in direct sunlight in this weather, given that the tank has an air gap between it and the car exterior a tank temperature of 35-40 degrees sounds excessive.

Ref the cooling coil, although it does add warm fuel to the tank the volume of relatively cool fuel in the tank should in theory be able to absorb  that heat without raising the temperature greatly.

Mike.

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31 minutes ago, michaelfinnis said:

Just a thought; does heat from the exhaust running under the boot/fuel tank area contribute to this problem, especially if using a stainless exhaust? Would some form of insulation under the tank and boot floor help?

Although temperatures inside the car will be high if the car is parked in direct sunlight in this weather, given that the tank has an air gap between it and the car exterior a tank temperature of 35-40 degrees sounds excessive.

Ref the cooling coil, although it does add warm fuel to the tank the volume of relatively cool fuel in the tank should in theory be able to absorb  that heat without raising the temperature greatly.

Mike.

I should add my piping connections to the tank are such that the return fuel from the PRV has to cross the tank before it can reenter the pump inlet- close return/supply connections to the pumping system will lead to short circuiting of the petrol flow  and rapid fuel heating.

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Regarding a small cooling fan blowing air over the pump. Back in the early seventies a number of us 

fitted various fans to cool the Lucas pump in the boot. From my own experience when the pump

overheated resulting in sudden loss of power switching the fan on instantaneously restored

full power again. I have also fitted a small oil cooler outside in the wheel arch connected to the

by-pass fuel from the P.R.V. back to the tank, this was when my pump was in the boot.

 

                                                                     Harvey

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It would seem that mounting the pump in the wheel arch has been for years & years the best cure, though none of the usual suppliers seem to offer a kit of mounting hardware.

Is there anyone on this forum with the fabrication skills willing to take advantage of this small gap in the market?

Richard.

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Dunno if relevant but will add it to the list.

Similar problem with Camry, packed it in twice when temperatures went over the ton, engine stopped, symptoms not enough fuel.  (This in NSW) After cooling down no problems. Toyota mob tested everything and couldn't find a cause.

Same thing started happening months later in the hot part of Western Australia, found keeping the tank full reduced the occurrence a bit. Limped in to nearby town where the local car fixer said they were used to it in the hot area. He said that a couple of windings in the (in tank) petrol pump had gone with age, and in the extreme temperatures the pump got too hot to work and seized, full tank kept it cooler and helped.

At great expense the in tank fuel pump was replaced and never had the problem again.

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I was considering fitting a Fuel cooler on my TR5 on the return pipe run from the Metering Unit, my car was fitted with an original Lucas pump and it go so hot on warm summer days you could hardly touch it!

I ended up fitting a Heat sink to it which helped but didn't cure the problem, I've seen people fit cooling fans to blow air onto the pump, but ideally you need a supply of cool air from outside, ducting to feed the air onto the pump then an outlet to feed the hot air back outside the boot?   

I believe most Diesel cars have Fuel coolers fitted to the Fuel system, which look like small oil coolers, that is probably the way to go to solve the problem?

Gary

 

 

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I good friend of mine used to run a TR250, fitted with Lucas PI and Lucas fuel pump. He had a small computer fan that was always switched on to keep the fuel pump cool. That was some 20 + years ago.

I run a Bosch pump in my TR6, and just driven back from Scotland, after covering 1600 miles in 30 degree + heat earlier this week, but never experienced any problems.  My fuel pump is mounted in the boot, next to the spare wheel.

 

Cheers.

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Had this problem in northern Spain 2 years ago. Left the UK with a full tank of fuel, car stopped with about a 1/4 tank of fuel on the first day, temp in the mid 30c. After waiting some time, managed to limp to a petrol station. Filled up with local fuel, no more problems over the following 2 weeks.

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Similar story...back in 1981 with my one year old stock 5 litre V8 Chevrolet Camaro conked out and embarrassingly refused to restart in the middle of Putney High Street in the Rush Hour! A Bolshy 'know-it-all' motorcycle cop, tried to start it and said..."congratulation you've got a flat battery!"...I hadn't it...was just fuel vapourisation on a red hot summers day! when it cooled down it burst into life again...It did it again in heavy Silverstone summer traffic, so I got rid of it!   

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18 hours ago, PodOne said:

Just a thought the old Lucas used a coil around the motor in an effort to cool the motor and hence the fuel. Has anyone tried running a small Spal or similar fan ducted to push  cool air over the pump Bosch or Lucas type?

I've yet to decide which way to jump with the pump (I have a reconditioned Lucas or buy Bosch type) and PRV but I can't help feeling that taking a leaf out of modern EFI systems is the way to go with an in tank pump and external PRV set to 105psi close to the metering unit as it would solve the cooling issue and other reported woes as long as the pump has an adequate 12v supply. 

I have my hard hat ready!

Andy

Yes, back in the days of the Lucas pump and heatwaves in SW France I tried a cooling fan.  Though now a Bosch setup, the fan is still fitted and works well. Keeps the boot space cool and free of any fumes.  It is a 1 inch computer fan mounted on a 1 inch plastic sink waste fitting.  This has a length of flexi tube, again from a sink waste which blows through the floor via the original 1 inch hole which was the Lucas drain I think.  Inward air supply comes via removal of the centre forward grommet in the spare wheeel well.  Strangely no water has ever come in via that missing grommet.  The setup is very simple, looks a bodge but is hidden behind the cardboard where the Lucas pump used to live.

Also have heavy duty cable from battery starter motor terminal into the boot.  This supplies pump and fan via a relay. The relay is switched by the original circuit.  Take care to get a heavy duty relay, the first one I got soon melted!

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