Uprating the fuel pump...?

[thenick]

Hi all,

My fuel pump has been making that sort of buzzing sound on and off for a while now. Not the same noise as when it primes but more of an 'I'm about to break' noise. It used to just do it for a second or two when the car had just been started as a lot do, but now it does it when sitting in traffic jams or ambling along (the exhaust is too loud to hear it in anything above 'ambling' so I'm not sure if it does it past here). I have read that it can be caused by a blocked fuel filter and so seeing as it hadn't been changed for around 12k miles I had a new one fitted just to be sure. It is still doing it however so I'm slowly coming around to the idea of possibly needing to replace the pump.

First off, is this the right thing to do? Could it be that the pump isn't on the way out and if so how do I check? Coming to a slow and embarrasing halt on the M40 isn't an exciting prospect though so I'd like to be at least reasonably sure of its condition. Secondly: if the pump is indeed about to die, should I replace it with an uprated one?

I ask this because the car is currently running various bits including an Emerald ECU and I intend to take this further with bigger heads and hopefully some sort of forced induction, probably the sc-power supercharger system. This I've noticed comes with an uprated fuel pump and bigger injectors as standard let alone with higher boost so I'm thinking I might as well uprate it now to save doing it later. In this case, does anyone know of which pump I should be looking at for a higher flow rate and what sort of rate should I be aiming for?

Also if I uprate the fuel pump, am I right in saying I don't need to change anything else just yet? I assume the fuel pressure will stay the same, but it will be capable of supplying more fuel when the ECU demands it (with bigger injectors)?

Thanks,

Nick

[2Munkys]

Before you change anything: the pump bracket is mounted on rubber isolators; have these failed? Has the body of the pump come into contact with the chassis which would amplify the sound of normal operation?

[steve-V8s]

Have you changed the Fuel Filter recently ? I understand that if this gets a bit clagged up the pump has to work harder and makes more noise. I changed the pump and filter on the Griff last year precisely because it had started making the “ I’m about to brake” type noise you describe. In this case fixing it before it brakes seemed the best option.

[GreenV8S]

Blocked filter problems are more likely to be caused by the pre-filter in the tank. These pumps are very good at blowing but won't suck, iyswim.

[chrispitman]

How do you check/change the pre filter then.

[350Matt]

The only way to test the pump is to measure pressure whilst its under load (ie flowing a reasonable amount of fuel at pressure)

So you need to have the engine running but you can tee into the line just after the pump, I think std Griffmera is 2.8-3.0Bar? Ready to be corrected on that.

I've also read that the std pump will suit up to about 300Bhp but after that you need something beefier, that said my old 270Bhp wedge needed a bigger pump to keep up with the 4.0Bar flow I was after and I doubt the std griffmera pump is much better than the wedge one.

Matt

[thenick]

Thanks for the replies guys,

I had a look at the mounting brackets last week and they seem to be in good order and its no louder than it used to be, it just happens more often...

Pete, how would one go about checking/changing this pre-filter - where abouts is it? I have replaced the main filter so this could cause it I guess...

I'll do some research into checking out the fuel pressure but I think it's ok as when mapped a couple of weeks ago, the car was running fine and the injector times seem perfectly reasonable.

If I were to look at replacing it with an uprated unit, is there a good unit to choose? Or should I just speak to V8D or similar?

[GreenV8S]

The standard pump is rated at 150 litres an hour at 2.5 bar. Fag packet calcs suggest that flow rate would be adequate for something in the region of 350 bhp assuming sensible AFR, combustion efficiency etc. That's quite a bit more flow than the standard injectors would be able to deliver though and you'd expect the pump flow rate to drop off if the fuel pressure was being raised in an attempt to get more fuel into the engine.

[The AJP Griff]

To be fair,my standard pump coped fine,even running the standard injectors up around 350bhp with high fuel pressure(3.0bar).I would never change it purely out of worry of capability,only if there was a reliability issue,then i would uprate.

[thenick]

Sure it does sound pretty capable up to 350bhp, but the supercharger and heads will push it past this up to 400 or possibly even more at a later date. The thing is, I don't want to stick a standard one on there, only to have to take it off in 6 months and put on a bigger one!

[Johno]

thenick said:

Sure it does sound pretty capable up to 350bhp, but the supercharger and heads will push it past this up to 400 or possibly even more at a later date. The thing is, I don't want to stick a standard one on there, only to have to take it off in 6 months and put on a bigger one!

Then I suggest you leave it alone, as it's probably fine . ..

Fitting a higher flow pump will not have much affect with standard regulator and injectors, so you could check with SC Power what one they prefer to put in and make sure you cn run with the standard set up until then if you feel you must change it.

[chrispitman]

Nick

Give these guys a call http://www.fuelsystem.co.uk/injection.htm they have a range of bosch pumps they may do one with the same fitting / dimensions but higher flow rate.

Remember when you supercharge it requires more fuel than an normaly aspirated engine of the same BHP.

So for 400BHP supercharged I think you would be looking at a pump capable of 192 ltrs/hr running at 3Bar (remember Standard setup is 2.5Bar)

[GreenV8S]

Remember when you supercharge you will need to raise the fuel pressure with boost to maintain a given fuel flow, in addition to any pressure increase you might want to increase the fuel flow.

[GreenV8S]

Remember when you supercharge you will need to raise the fuel pressure with boost to maintain a given fuel flow, in addition to any pressure increase you might want to increase the fuel flow.

[shpub]

thenick said:

Sure it does sound pretty capable up to 350bhp, but the supercharger and heads will push it past this up to 400 or possibly even more at a later date. The thing is, I don't want to stick a standard one on there, only to have to take it off in 6 months and put on a bigger one!

In my experience you need al least a 20% margin as a lot of pumps output are voltage dependent and the regulator works better when provided with a good pressure differential. So while a pump on paper may be OK... the reality is often different. I have a SPA fuel pressure gauge and this is linked into the data logging so I can see if there are any problems. It is interesting seeing what happens during certain conditions.

Also bear in mind that should the pump start to have problems, the output will fail and this can lead to the dreaded detonation. I run TWO pumps in parallel so that if a pump dies or starts to fail the other is still running. Both are Sytek motorsport versions and each one is capable of supporting the engine on its own (in theory). Both have seperate 30A supplies because I have known them to take out the normal fuses and the voltage drop was becoming an issue. This started being a problem when the supercharger went on as the fuel pressure is referenced off the inlet manifold. So when running 11 psi boost, the fuel pressure goes up another 11 psi. The pumps have to be able to meet this sudden increase in demand which is why I run twin pumps etc. If this cannot be supported, there is a huge risk of leaning out and detonation.

Both have their own Sytek filter between the tank and the pumps.

The £500-600 cost is peanuts to the other costs involved but if overlooked can easily shrapnel an engine. The more power... the greater the risk.

Edited by shpub on Wednesday 5th March 14:11

[rev-erend]

Nick

If you are going the big bhp route then a big bosch (044) pump will probably be the choice.

Mine cost about £145 and then you also need to buy 8 mm and 12mm fittings as they dont come with them - so around £170 all in.