Ruston 2VTH Injection Pump

[billh]

The thread is stripped in the   iron pump casing  where the fuel supply banjo bolt screws in , the result being it won't tighten and fuel leaks out.

i'm looking at helicoil repair but haven't a clue what the original thread is. Its a CAV pump around 80 years old and  similar  size to 3/8ths BSP but  more coarse.

Anyone know what the thread will be?

Thanks in advance

[David Mack]

Can you measure the thread pitch on the banjo bolt?

[Iain_S]

According to my thread chart, 3/8" BSP is 19tpi with an outside diameter of 0.656".

5/8" Whitworth is 11 tpi with outside diameter 0.625" 5/8" UNC is the same, but a different thread form.

 

Would it be easier to drill and tap a larger diameter thread , and change the banjo?

 

 

[billh]

On 06/11/2024 at 14:45, David Mack said:

Can you measure the thread pitch on the banjo bolt?

I've had a measure of the banjo bolt|: Best fit seems to be metric 18mm diamx 1.5mm pitch. Sounds unlikely but the original  pump design would be Bosch?

So that might explain its metricity. Can anyone confirm please?

Just now, billh said:

I've had a measure of the banjo bolt|: Best fit seems to be metric 18mm diamx 1.5mm pitch. Sounds unlikely but the original  pump design would be Bosch?

So that might explain its metricity. Can anyone confirm please?

That size looks to be 18mm spark plug thread like Kelvin plugs!

[BEngo]

AFAIK all  'bought in'   injection equipment  has metric threads. Kelvin injectors have bought in nozzles (with metric threads)  but the body (made in Glasgae) is imperial threads. I think Gardner sprayers are similar, but not sure. 

 As you surmise, this is because the original design was by Robert Bosch but as a result of WW1 his patents were invalidated / taken as reparations.  Both CAV and Bryce found alternative ways to do the same thing as Bosch, as did others.

 

Is it a BPE pump?  If so I will have a measure at the one in the workshop.

 

N

 

 

[john.k]

Try a new banjo bolt ..the hollow bolts close down if over tightened ,and a new bolt may cure the problem ........ if its a individual CAV pumping unit ,then Id think a repacement body would be a better option than thread repair ........you will likely need your current plunger and barrel (or one the same dia) swapped over ..........I 'd have dozens of these units ,and so would any other diesel engineer that repaired older UK diesels 

[billh]

 

11 hours ago, john.k said:

Try a new banjo bolt ..the hollow bolts close down if over tightened ,and a new bolt may cure the problem ........ if its a individual CAV pumping unit ,then Id think a repacement body would be a better option than thread repair ........you will likely need your current plunger and barrel (or one the same dia) swapped over ..........I 'd have dozens of these units ,and so would any other diesel engineer that repaired older UK diesels 

Thanks for suggestions. I'm convinced  now that it's 18mmx1.5  and that  I can get  an expensive  helicoil  kit in that size. the next problem is the shallow depth of thread in the pump body, there is a reduced hole only about 12mm inside which will not allow the special helicoil tap  to fully cut the new thread.

11 hours ago, john.k said:

Try a new banjo bolt ..the hollow bolts close down if over tightened ,and a new bolt may cure the problem

Tried that , the thread in the body is almost non existant

 

14 hours ago, BEngo said:

Is it a BPE pump? 

No, I think it is BPF1B (?) mounts vertically with flanges at the back, not on a pedestal. The fuel in feed banjo is on the front not the side.

 

John K said:

I 'd have dozens of these units ,and so would any other diesel engineer that repaired older UK diesels 

 Perhaps you could send a few over? 😄

Thanks again all.

•  

[jonesthenuke]

FWIW I have a NOS CAV pump for our Gardner engine. I have measured the banjo bolt and compared it to a M18 1.5 pitch tap, so can confirm ours is M18 1.5

[john.k]

Interesting fact ...CAV and Bosch set up a joint venture in the 1920s to share designs and patents .......CAV-Bosch Ltd .........initially the heavy duty Bosch truck electrics ,but into the 1930s ,CAV were involved in making Whittles jet engine work........without CAV ,there would never have been a British jet engine ..........and as you might imagine ,Bosch were interested parties ...........CAV-Bosch Ltd was dissolved in 1938 with war clouds gathering .........Its fashionable for the young and ignorant to rubbish Joseph Lucas Ltd,....but CAV was a Lucas subsidiary from 1927..