Rear Fuel Pump Noise Suppressor

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Ah so it's a 4 wire, be interresting to see if it's just a shunt cap, or has series chokes... that would be nice and bad for the performance boys, don't want all those nasty volt drops... probably why yours is fobar John, with zee pankake battery state... much increased current draw with the motor still trying to do the same duty...

Thanks for all your help with this- much appreciated!


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[phildini]

Was there ever a replacement/alternative found?
the one on my GTA, the casing as corroded and it's got a hole in it now.

P.S. I do like listening to my radio.

Was there ever a replacement/alternative found?
the one on my GTA, the casing as corroded and it's got a hole in it now.

P.S. I do like listening to my radio.

a suppressor is just a capacitor...... JohnC will know how many farads you require and you
should be able to find a reasonably priced alternative readily available.....

Everyone should bin these, every car I measured was dropping voltage to the pump because of this, some down to 8v. Also bin the connector to the pump and hard wire it, voltage drop there too. If you need a suppressor, do it properly and fit one to the alternator or behind the radio.

Hi David,

Ironic that you should post today. I think the replacement one just failed too leaving my car with no fuel pump and unable to start!

I will hard wire it from now on and add a better suppressor to the radio. Any ideas as to the best one?

Thanks

Jon

Everyone should bin these, every car I measured was dropping voltage to the pump because of this, some down to 8v. Also bin the connector to the pump and hard wire it, voltage drop there too. If you need a suppressor, do it properly and fit one to the alternator or behind the radio.

David, as to fit it at the alternator or the radio is technically incorrect - need to suppress the noise at source, not at the convenient points. Yes adding suppression at the radio will shunt the RF noise at that point in the circuit (so you don't hear it on the radio, but the commutation noise from the brushed fuel pump motor will be conducted throughout the electrical system), and ultimately return it to the source, but you have included an extremely large loop that includes the low signal circuits of the ecu that would then be subject substantially increases levels of EM noise - given we are talking the low tech Renix ecu, not a great idea.... there is no noise suppression in the Renix 1 worth any salt to ensure the signal integrity.. Renault placed the suppression on the motor for a reason, and a good one too, the actual practical application is a bit lousy as I said at the bottom of this page before...

viewtopic.php?f=8&t=4899&start=30

Smiles,
Martin

Presumably as a short term fix then not too much of a problem but perhaps someone could let me know where to start in terms of spec and finding something to replace it with.

I suspect that age and an upgrade to 044 Bosch is killing them off...

Everyone should bin these, every car I measured was dropping voltage to the pump because of this, some down to 8v. Also bin the connector to the pump and hard wire it, voltage drop there too. If you need a suppressor, do it properly and fit one to the alternator or behind the radio.

David, as to fit it at the alternator or the radio is technically incorrect - need to suppress the noise at source, not at the convenient points. Yes adding suppression at the radio will shunt the RF noise at that point in the circuit (so you don't hear it on the radio, but the commutation noise from the brushed fuel pump motor will be conducted throughout the electrical system), and ultimately return it to the source, but you have included an extremely large loop that includes the low signal circuits of the ecu that would then be subject substantially increases levels of EM noise - given we are talking the low tech Renix ecu, not a great idea.... there is no noise suppression in the Renix 1 worth any salt to ensure the signal integrity.. Renault placed the suppression on the motor for a reason, and a good one too, the actual practical application is a bit lousy as I said at the bottom of this page before...


viewtopic.php?f=8&t=4899&start=30

Smiles,
Martin

I don't think anyone has ever reported getting radio noise from removing this 'noise suppressor', I know I haven't on several cars. Lots of things in the GTA have filters on because its a plastic car, pump, radio, wiper motor, doesn't mean it was absolutely necessary, so testing is better than hypothesizing.

Most of these filters are needed because some of the higher current drawing electrical items are grounded through looms, and not direct to the chassis, hence could cause ground loops. I always used to direct ground the rear subframe with a decent earth cable from the battery, then ground my new fuel pumps to the subframe, binning the filter and plugs.

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David, best you go back and read, then talk to a professional EMC engineer , cite their name as l work with all the EMC test houses in the UK as part of my daily job, and I'm not spinning discs or hypothersising as you suggest - I didn't mention the radio, as I personally I don't give a stuff about it, I spoke about the implications to the ecu - period. In fact you want to keep the noise off the chassis, go read Def Stan 59-411, can down load it off the nett; conducted emissions in my applications are typically greater than 80dB below commercial limits - I know my shite from Eurofighter, Lynx helicopters, Apache, A380s, A400s, AS90, the odd tank here and there, and few other bits that if I get it wrong, won't be pretty. On the subject of chassis return, miltary radios are about as sensitive as you can get, and Def Stan 61-5 rev 6 part 6 now specifically excludes the use of chassis return, two wire systems only... if you would like I could set up a practical demonsration for you, actually very interesting- you need to know how your noise sources are coupling into your ground planes, and these are only fully effective when there is no rf current flowing in them.

Martin, you could have a good chat with Jon Kenny.
He worked in a test lab on Emc stuff for Sony Ericsson phones.
Haha technical I know most manufacturers of army kit used to have real headache trying to get the limit down to army regs.

One said the limit was lower than background which made me laugh.

[phildini]

Interesting "Tech Chat" but still nobody can point out a suitable replacement...... I am a great believer in if the manufacturer put it there, it must be there for a reason, as we all know they love to save ££££££ if they can.

Interesting "Tech Chat" but still nobody can point out a suitable replacement...... I am a great believer in if the manufacturer put it there, it must be there for a reason, as we all know they love to save ££££££ if they can.

The chances are that you will hear no interference from the fuel pumps on tape or FM, however, if you are getting it on MW and LW, then it might be worth trying a One microfarad (1mf) suppressor of the type that are fitted to the alternator .... ie:- "P clip" type. Any Auto Electrical business's should have them, but they will be much smaller than the old type, but that is not a problem.
The biggest problem is fitting and finding a good earth connection for the body of the suppressor. I don't know if the clip holding the pump is bolted a chassis member, if so, problem solved as long as you make sure the contact area of the suppressor and the chassis are both clean metal, once fitted paint, to stop any rust from forming.
The wire that comes out of the suppressor is then fitted together with the 12v supply to the pump. (Yellow lead with Red dash tracer)
You need to give it a try, but I think you will find 1mf will be sufficient to kill any interference from the pump on M/LW. If it is reduced but not completely disappeared, you can get that type of suppressor up to 3mf, but they are 3 times the size. I certainly would start with the 1mf.
Let me know how you get on.
John

aiii seen seen ,de is some big mofos ,I don't think a three would fit in the wheelarch .
I have just got this ,should do the job . will be well fierce when me banging me tunes

I don't think a three would fit in the wheelarch ...... I have just got this ,should do the job .

Nice one Lee ... .... Where did you get the pic from ?
Just one small detail though .... 1 "MICRO FARADS" is a millionth of 1 "FARAD", so please don't try to fit that one ..... it will most probably drain the battery just trying to charge it up. ..... and take a long time too.
I have never seen a 1 or, in this case, a 1.5 Farad Capicator before ..... I knew they would be big, but .......................... I like it.