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John L

PI Fuel Pressure

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I have just rechecked my fuel pressure out of interest after my adventure, and the change of the battery, with just the key on engine not running I see 125psi.

I know the pressure should only be 110psi max.

I haven't had any problems, car runs fine, no extra fuel consumption, I think it even starts better.

Suppose I should put it back to 110psi max or leave?

This is just with my new battery, I must say I'm impressed with the Russian item so far, its showing 13V with nothing connected,  I didn't think the old Bosch battery was that bad, as I had set the pressure a few weeks before my departure.

John

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125 is a bit high and potentially shortens the life of your pump, damaging to the metering unit and greater potential for leaks.

The recommended is 105-110 psi.

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I agree with Andy 125 (assuming your pressure gauge is correct) requires the pump to work much harder drawing more current and thus running hotter. As heat in the pump is a problem and needs to use the fuel in the tank as a cooling reservoir more heat cannot be good.

As the system is designed to run at 10% lower pressure than you are using it will not bring any benefit, only the potential for grief and expense.

Strange though if a pressure relief valve "moves" its adjustment and is probably more likely to be stuck closed and the pump will be running at its maximum.

Alan 

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Hi Both 

Given all the problems with the pumps Lucas or Bosch has anyone run a modern in tank pump where it will be cool along with adjustable external pressure regulator/gauge similar to a modern EFI set up?

Andy 

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Having the pump submerged in the  petrol won't result in cooler fuel- which is the cause of most pump problems. My PRV has been set at 680 kPa (gauge) with air and the PI system has worked perfectly since I had the MU and injectors rebuilt and recalibrated a few years ago. The PRV setting has been unchanged since I bought the car in 1998- it works with my PI system so I see no point in changing it.

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2 hours ago, PodOne said:

Hi Both 

Given all the problems with the pumps Lucas or Bosch has anyone run a modern in tank pump where it will be cool along with adjustable external pressure regulator/gauge similar to a modern EFI set up?

Andy 

With a proper Bosch pump set up, a clean fuel tank and the metering unit/prv/injectors/throttle bodies  reconditioned by someone like Raven Smith there really are not a lot of problems to be honest...and I speak from experience...and we are talking a 50 year old vehicle here too

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I agree, my Bosch set up works fine. However  I guess a pump in the tank would remove any inlet piping restriction problems.

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Is there such a thing as a high pressure in-tank pump? I have only seen low pressure pumps for carbs, but I have never researched other pumps as my Bosch works well (chassis mounted).

Alan

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44 minutes ago, barkerwilliams said:

Is there such a thing as a high pressure in-tank pump?

Bosch 044 can be submerged. 

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The part no of the Bosch submersible pump is 0 580 254 040 ( runs at 100 psi )

 

                                               Harvey S. Maitland

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WElcome John!

First, do a search here (top right of page) for "Fuel pump noise" (the quotes are needed) to find all the previous posts about this problem.

And, tell us what sort of noise you have.  

JOhn

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John,

As per John above there is lots on here regarding fuel pump noise. However possibly the most common noise is resonance in the hoses connected to the pump and the pressure relief valve. Some TR6's have the pump in the boot, others under the boot you need to feel the hoses / pump whilst they are noisy and you will soon tell where the noise is coming from.

Hoses with a stainless outer braid are reputed to be the most common cause of resonating noise.

Alan

 

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Welcome John

it does seem that the modern ‘bosch conversion’ type pumps with braided hoses are more prone to ‘screaming’ , usually when the fuel gets low/hot

i converted a tr6 from a 1990’s bosch setup with rubber hoses to a kit from a reputable supplier and had terrible noise problems.

suggest you visit your local group or post photos of the pump setup and we can ‘advise’

mind you, you’ll probably get a dozen different opinions !

steve

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There seem to be so many different systems that we try to add together with the issue of Bosch pumps.  I will try and add my thoughts,

My system which I think could be common to many, but I'm sure is not a good system, which I would like to change, my pump can be heard bussing but has run much better having fitted a genuine CAV filter.  Restrictions with the will fit filters.

My system is fitted with a Bosch pump in the wheel arch at the rear, it takes its inlet feed from the CAV filter and the return from the PRV is sent back into the CAV filter at a port in the front of the CAV filter housing, with a return line that comes out of the top of the filter housing, and goes to the top of tank, into that is connected the return from the MU. This I understand is the original CP setup used by the Lucas pump.

Later models (I think CR) have the return from the PRV direct to the top of the tank, and a separate return from the MU to a separate connection to the top of the tank, this must allow much better flow from the PRV, but the Bosch pump may be struggling to get flow thru the CAV filter being too restrictive for the Bosch pump, and this may be where some of the noise/cavitation is coming from as the pump cannot get enough flow thru the CAV filter.  Bearing in mind that with relatively slow engine speeds, (not flat out) there is a large amount of fuel being returned from the PRV which in turn will be heating the fuel.

I want to change my system to the later system with the return from the PRV to the tank, and do away with the CAV filter and add a good free flow filter before the pump, and make a new return to the tank from the MU, which will need an adaptor adding to the tank.  Also the PRV needs to be a much larger hose to cope with the flow from the PRV, as the Bosch pump is producing much more flow than the Lucas pump.

I would think that the later conversions with the Bosch pump and pressure filter which do away with the CAV must run much quieter, then it seems to be the hoses that cause the noise/chatter.

It would be very helpful when people complain about noise, to add which system and layout they are using, as there seem to be so many options and are all lumped together in a general heading of Bosch pump noise. 

John

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My system is pretty much as you propose , the return from the PRV is located halfway down the tank on the opposite side from the pump suction  to maximize fuel cooling before it's returned to the pump and minimize return fuel splashing .

I have a separate return from the MU but its small as I don't believe significant quantities of fuel are returned from the MU.

I've kept the  filter to the original spec, as the PI system was  designed by Lucas Aerospace and I've assumed they wanted a higher filtration efficiency than provided by the carburettor system filters available at the time.

Gates Barricade rubber hoses with an anti resonance loop solved a lot of the noise problems, but a TR6 PI will never be as quiet as a modern car-that's part of its charm.

 

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Actually John i do think the bosch 996 pump in the wheel arch is the best system.

maybe not fed by the cav filter though, i prefer using sytec disposables mounted vertically under the fuel tank, like this one:

 

post-9473-0-23400500-1535489352_thumb.png
the prv return to the tank is probably better too.

steve

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Hi Steve

That Sytec is designed as a post filter near a modern injector rail.  It has filter Micron of 20 which is far to small for  a pre filter.  I would go for  a  Sytec Bullit filter( as fitted by Malcolm at Prestige) with a metal filter that has a micron filter of 55. For the post filter you could then have a Bosch filter at around 10 micron. I agree the best place for the pump and filter is in the wheel arch where it will  get cool air.

Roger

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Thanks Roger, that’s interesting

i’ve been running those filter for a number of years, but you make a valid point!

i shall investigate the bullet option.

steve

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2 hours ago, Steves_TR6 said:

Thanks Roger, that’s interesting

i’ve been running those filter for a number of years, but you make a valid point!

i shall investigate the bullet option.

steve

Those Sytec filters are fine, thats what we fit always, the small bullet filters arent as good.

Stuart.

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On ‎10‎/‎2‎/‎2019 at 9:26 AM, John L said:

I have just rechecked my fuel pressure out of interest after my adventure, and the change of the battery, with just the key on engine not running I see 125psi.

I know the pressure should only be 110psi max.

Hello John,

I assume the pressure will go down as soon as the engine is running and the fuel starts flowing. I would check this before changing the setting at the PRV.

Kind regards, Peter.

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Don't know if the pressure will drop much. As the engine uses fuel the PRV closes slightly to compensate. From memory the flow to the MU was minor compared to the flow through the PRV even at full load.

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1 hour ago, michaeldavis39 said:

So should we have a poll now of which filters work best as I'm totally confused and would like to get the best most reliable setup irrespective of cost. 

Michael

Haha, good idea, but generally speaking Stuart is always right !

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Ok, here we go:)

I have a large Sytec SSF2012 (suction) filter between tank and pump.

It has M14x1,5 female connections so large bore hoses can be used, improving flow to pump.

Waldi

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