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Paul Hill

Bosch Pump woe's & Noise

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Hi Guys

I had new Bosch Pump, PRV to suit MU and injectors it was all set up and as been running fine during the last 8 weeks and around 250 miles. Monday morning I started the car up and noticed the pump was more noisy then normal, like it was racing. I pulled out on to the road running fine  got to about a mile from home and the car just started jumping,  missing etc. I manged  to get to  the garage where the work was done and as I pulled on to the forecourt it cut out. They had it yesterday and checked a few thinks out 

Filters all clear 

Fuel Tank clear

Pressure to the pump ok

Fuel tank showing between I/2 & full

When I got there this morning it started but the pump was still making the same noise, and after starting and running  the engine cut out. We put some more fuel in just to make sure and started it up pump noise still there I decided to take it home which is about three miles, all the way back it was faultless but the pump noise is still there.

Before this started the pump was a tad noisy but that's to be expected and I could live with it, but how it is at this moment no way could I live with and I think its not running as it should. The garage are going to have it in early March and check it top to bottom, I have also told TR Shop about the problems with the pump and went through their trouble shooting list

 

Any ideas chaps

Paul 

Edited by Paul Hill

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Did your Bosch pump kit include a large diameter outlet pipe from tank to pre-filter? An increase from 1/4 to 5/16" outlet is included with many kits and works well.

If you're still using a 1/4" fuel tank outlet then the restriction noted in the previous post is very likely to be the cause of the trouble.

Nigel

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But why would it run perfect back to home.

 

 

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It’s run for Two months perfect and changed nothing. The pump noise is beyond how loud a pump could be 

 

has anybody had had a faulty new Bosch pump

Edited by Paul Hill

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Hi Paul,

Sounds like cavitation. Any tight bends in the inlet hoses that restrict flow?

I had a flake of rust that was sucked in the tank outlet, restricting flow, noticed this only when I removed the tank. Hard to inspect with fuel in the tank.

What is the type of Bosch pump you have installed? 

If you measure the current draw and have a pump curve ( from Bosch you can find these on the www) you can check if it is running where it should be, this is an indirect way of checking, but easy to do and provides additional info, especially if you know the current draw when it was running ok.

You can also “push in” the suction hose, just a bit, does it make things worse?

Are all the jubilee clups in the suction part tight?

Waldi

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Might have been a blocked fuel tank vent. If the pump is just on the limit of cavitation a long run on a warm day will tip it over. The weather in the UK's colder now so the fuel will be less inclined to boil in the pump suction line .

Have you tried the engine out at high speed? A low PRV setting will cause cavitation and high speed fuel starvation.  

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14 hours ago, Nigel Triumph said:

Did your Bosch pump kit include a large diameter outlet pipe from tank to pre-filter? An increase from 1/4 to 5/16" outlet is included with many kits and works well.

If you're still using a 1/4" fuel tank outlet then the restriction noted in the previous post is very likely to be the cause of the trouble.

Nigel

Nigel could be right could be right, flow rate to a Bosch must be 2.6 lt/min minimum, but preferably 5 lt/min, as per Bosch engineering UK in 1983. If you are still using the CAV filter/pipework system you will struggle to meet even the minimum figure. My system which was installed in 1983 uses 10mm bore feed hose, modified tank take off and I have had no cavitation problems in 30 +years of use. The pump I use is the 952 type, as used by Merc ,Ford , Volvo of that era, they are still made. What is the pressure at the M/U and is the needle steady when engine is running? I am assuming that you do not have the dreaded harmonic knocking?

Bruce.

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I'm using the Bosch kit from Malcolm at Prestige. It includes a large diameter tank outlet and a suitable low resistance pre-filter.

 

Never had any problems with cavitation, though if the fuel level is very low the pump can suck air when cornering. No surprise, as mine is an early car without any baffles/swirl pot built into the tank.

 

Nigel

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I have the same kit as Nigel, bought from Prestige around 10yrs ago. I have an Andy Wiltshire fuel tank with baffles, swirl pot etc. I find my pump very very loud, but......I've never heard another to make a comparison. So it could be quite normal???

Richard.

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1 hour ago, Nigel Triumph said:

I'm using the Bosch kit from Malcolm at Prestige. It includes a large diameter tank outlet and a suitable low resistance pre-filter.

 

Never had any problems with cavitation, though if the fuel level is very low the pump can suck air when cornering. No surprise, as mine is an early car without any baffles/swirl pot built into the tank.

 

Nigel

 

1 hour ago, Nigel Triumph said:

I'm using the Bosch kit from Malcolm at Prestige. It includes a large diameter tank outlet and a suitable low resistance pre-filter.

 

Never had any problems with cavitation, though if the fuel level is very low the pump can suck air when cornering. No surprise, as mine is an early car without any baffles/swirl pot built into the tank.

 

Nigel

 

1 hour ago, Nigel Triumph said:

I'm using the Bosch kit from Malcolm at Prestige. It includes a large diameter tank outlet and a suitable low resistance pre-filter.

 

Never had any problems with cavitation, though if the fuel level is very low the pump can suck air when cornering. No surprise, as mine is an early car without any baffles/swirl pot built into the tank.

 

Nigel

I am assuming that you do not have the dreaded harmonic knocking? Have you got his s/s braided hose which runs from pump to PRV, as this is well known to cause harmonic knocking that is why he has gone for the diaphragm PRV as he still insists on using 1000psi PTFE hose which has no give in it unlike Gates barricade hose which am using and no harmonic knocking.

Bruce..

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Yes, the kit I have includes the braided PTFE hose. I'm not aware of any harmonic knocking, just the expected muted buzzing when the pump is operating. I fitted one of Malcolm's PRVs when I fitted the pump kit over 10 years ago, so perhaps that's why there's been no knocking. It's been a 'fit and forget' installation, apart from cleaning the filter occasionally.

Nigel

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My Bosch 126 pump is now humming, although 10 A is a bit higher than I hoped (this is with engine not running, so relative low voltage, and amp meter in series with battery, so even less voltage at pump, so I guess the current draw will reduce with engine running.

5 liters in the tank only.

Like Bruce I have 10 mm hose in suction part, even 12 mm from suction filter to pump. Smallest ID in the suction is 8.5 mm, and this is my modified tank outlet ferrule. But too soon to jump to conlcusions for me, have nor driven or even run my car.

Hope this helps,

Waldi

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What Waldi said in an earlier post makes sense that there could be a restriction from the tank ie rust flake or old fuel, it could make the pump work harder to pull it in

Edited by Paul Hill

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The whole PI  pump-filter-hose-prv selection remains a bit of a special art, unfortunately. Some of us run with the “high flow” Bosch pumps with no issues for years, even with standard (small) outlet.

Others have issues, that are hard to resolve.

It looks as if there are several contributing factors, but most are related to cavitation. And cavitation is always related to flow restrictions in the suction section of the system (or more precisely: NPSH)

With increased fuel temperature (as a result of the higher current draw of the Bosch pumps that leads to energy dissipation which warms up the fuel) things get even worse, the available NPSH reduces quickly and cavitation starts.

A higher flow sooner leads to cavitation and the higher fuel temperature does the same, both conditions are related and magnify each other.

Some PI enthusiasts in Germany have experimented with a speed control on the pump that is set by the outlet pressure. Minimal fuel return to tank could be the result, so if this is made to work that would be a fundamental solution! Food for thought....

Waldi

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I've been thinking about that Waldi. Controlling the pump speed by either monitoring the pressure of the metering unit feed, or the flow back from the pressure regulator valve. One day I might get time to do more than think about it! I don't have problems with my Bosch pump, it just doesn't sound very nice!

Cheers, Richard

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Hi Richard,

my Bosch pump is “humming”, so sounds good, but it has not seen real driving conditions. First want to finish the restauration (another year or so), and then maybe do things like that.

Waldi

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Hi Mike,

thanks, that was my plan; I went to 3 petrol stations today for “diesel start”; they had 15 flavours of crisps, 4 flavours of body milk, but no diesel start:)

Modern times...I was my last resort today.

Time for a moment of reflection now.

Waldi

 

 

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Update 

I started the car this morning fired up first time, tootaled off down the road  for a couple of miles running normal Pump noisy as before. I came back around the island and put my foot down car pulled like a train through all gears then after a mile engine died and cut out, I came to a halt, turned the key fired up first time drove two miles back to home car ran faultless. Pulled on to the drive into neutral engine died and would not start. I then opened the boot and felt the pump,  the bottom  (intake) was hot, the top one (out) was cold, I left it 5 minutes and it started first time.. 

I am thinking it must be some rubbish from or in the tank outlet, its an original tank and when the car was finished it did stand over two years only doing 500 miles. Does that sound as it could be the problem.

I am more or less convinced that I will replace the fuel tank as I want baffles in to stop the fuel starvation when turning left. Now chaps what's the best tank to buy, I was thinking the steel one from the TR Shop

 

Paul 

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Paul

I had a similar problem on my TR5 which baffled me and a couple of other far more knowledgeable guys for a couple of months?

It was a Pea sized lump of congealed Fuel or something or other rolling around inside the tank and blocking the Outlet!

I suggest you drain and remove the tank and give it a thorough clean out.

Regards

Gary 

 

 

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47 minutes ago, Gary Flinn said:

Paul

I had a similar problem on my TR5 which baffled me and a couple of other far more knowledgeable guys for a couple of months?

It was a Pea sized lump of congealed Fuel or something or other rolling around inside the tank and blocking the Outlet!

I suggest you drain and remove the tank and give it a thorough clean out.

Regards

Gary 

 

 

That's my intention Gary but will install a new tank with baffels

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Hi Guys

Sounds like something floating about in the fuel tank and coming to rest now and then over exit for the fuel. One of our club members had a similar problem which turned out to be the small cardboard disc from a cap of fuel additive which fell in!!. Took a while and a lot of fishing about with a stick and pin thing to remove it.

Paul

 

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I had a rust flake stuck in the tank wich resulted in cavitation and a screaming Bosch pump.

Waldi

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