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1998 Mpi Fuel Test?


Best Answer Alexxx , 04 May 2021 - 08:38 PM

Got the car running.

Removed the fuel tank which was half full of rancid brown fuel, pulled the pump and sender out.

Got the tank shining inside after some acid treatments I usually use, replaced the pump with a pattern unit.

Replaced the fuel filter.

As soon as everything was reconnected, turned on the ign and I could hear the fuel pump whirring, car started first turn. great after 4 years:)

So rancid fuel and a clogged fuel pump was the main issue.

Thanks for the advice

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18 replies to this topic

#1 Alexxx

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Posted 17 April 2021 - 08:17 PM

Hi,

Trying to get a project car (1998 cooper sportpack) started that has been laid up for years.

It now turns over and has a good spark, the starter seems sluggish even with the plugs out so not sure it will turn over the motor with the plugs in.

I wanted to push fresh fuel through the system, the tank was empty but reeks of old fuel.

I put in 5 ltrs of fresh fuel and would like to open it at the engine end and let the pump push the old crap through.

When I turn the ign i cant hear any pump running, normal? Is there an easy way to test the pump and open the fuel system to get fuel pumped through before a start attempt?

I'm used to old minis but no experience with the mpi models.

 

Regards

 



#2 bluedragon

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Posted 17 April 2021 - 10:59 PM

I wouldn't advise opening up the fuel circuit and letting the MPi pump push fuel through. It is a high-pressure pump, running 40-50 psi (3-4 bar) so with a open end, the fuel will blast out with velocity and large quantities. I'm not sure how you could safely contain a jet of that pressure.

 

The pump is immersed in the fuel tank, so you won't be able to hear it unless an assistant starts the car for you and you listen for it with the boot lid open. If I were trying to get rid of a tankful of bad fuel, I'd remove the tank and drain it.  An alternative would be the good old fashioned siphon tube method made popular in the Arab oil embargo 70's era.

 

You can then remove the fuel filter mounted underneath on the left side of the rear subframe and see if there's gunk and rust coming out. If so, hopefully the filter will have caught the majority of it, protecting the rest of the fuel system leading to the engine. If that's bone dry then the fuel pump probably isn't working.

 

Also, for the injected models there is an inertia switch for the fuel pump mounted near the center of the engine bay bulkhead. If this has been triggered, it cuts off energy to the pump, as might be the case in a collision. Try resetting this switch if you suspect no activity from the fuel pump.

 

 

Dave



#3 Alexxx

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Posted 17 April 2021 - 11:27 PM

Thanks Dave,

 

Very helpful information, much appreciated, Ta :)



#4 sonscar

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Posted 18 April 2021 - 06:55 AM

As I understand the pump runs for 2 seconds when you turn on before cranking.Listening carefully you should hear this.Steve..

#5 Alexxx

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Posted 20 April 2021 - 11:16 PM

Had the car fire briefly on easy start a few times, so looks like no fuel getting through.

Will listen for the tank motor and check that filter and inertia switch

 

Regards,


Edited by Alexxx, 20 April 2021 - 11:21 PM.


#6 Alexxx

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Posted 23 April 2021 - 02:14 PM

Fuel pump.

Could not hear anything from the fuel pump when ign first on.

Removed the connector to pump at top of the tank, bit corroded, white dust came out the connector when pulled.

Cleaned up both ends.

Checked the voltage at the connector, virtually nothing, ign off or on. I never tried voltage with cranking as no one to help.

Should there be 12v at the two pin connector with the ign on?

I checked and clicked down the inertia switch in the engine bay, no difference.

 

Regards



#7 Steve220

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Posted 23 April 2021 - 02:24 PM

Try measuring the voltage at the intertia plug. Find the positive pin from the relay in the plug, and earth the other lead onto the cylinder head. You should receive voltage on the prime.

#8 Alexxx

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Posted 23 April 2021 - 03:04 PM

thanks,

Checked the voltage athe the plug going into the inertia sw..nothing each wire. checked the relay beside it as you suggested.

I pulled the relay out got 12 v on the two connectors that had purple wires and 0.45 on the other two.

put the relay in (ign still on) but heard no clicking, should it click or all solid state no noise.

 

Regards,



#9 Steve220

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Posted 23 April 2021 - 08:04 PM

The fuel pump relay is in the MFU, is that what you checked? If so, remove the plug from it and see if there are any scorch marks. They've been known to burn out.

 

For reference, the Brown and Slate coloured wire from the MFU to the inertia switch is the live wire for the pump.



#10 Alexxx

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Posted 23 April 2021 - 09:04 PM

The relay I checked was the yellow unit stamped r6ke beside the inertia switch.

what is the mfu and where is it?

 

Regards



#11 Alexxx

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Posted 24 April 2021 - 08:05 PM

Found the fuse relay box attached to the top of the servo, nothing burnt, no dry joints.

Connections all clean, put it back and powered up the ign, I could see the main relay had switched on but the fuel pump relay did not close, I closed it manually, nothing, no pump activation (I referred to SPI relay pack functionality on this site )

The connections to the ecu are all good and clean, that looks like it is rubber insulated and the case does not earth.

I checked and cleaned the pins on the three relays top LH engine bay, checked the 15 amp fuse there too, all good.

All the fuses inside the car are good.

What do I need to check next?


Edited by Alexxx, 24 April 2021 - 11:56 PM.


#12 sonscar

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Posted 25 April 2021 - 07:26 AM

Myself I would pull the fuel pump relay and apply power to the terminal that feeds the pump and see if it runs.Ignore everything you have so far done and start afresh.
At its basic level the relay is a switch,the ECU earths the relay,turns it on and supplies power to the pump.Probe the relay sockets to find if the coil terminal has power.Google how a relay works to gain a better understanding.
I am not trying to teach you to suck eggs.Faulting can be frustrating but can also be rewarding.Man made this thing so man can repair it.Have fun,Steve..

#13 Alexxx

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Posted 25 April 2021 - 01:40 PM

Thanks all for advice, appreciated.

I found I have 12v going into the fuel pump relay but the relay grounds for the fuel pump (black/purple) and the manifold heater(black/green) register no earth. The are meant to be earthed via the ECU.

I checked both those wires where they come out one of the plugs into the ECU they have continuity to the relay.

So..how to get the ECU earth to work? I guess it is some internal earth or does it route out to somewhere?

I then put 12v into the fuel pump at the tank...nothing, it just sparks a bit as I touch a wire from pump positive to battery positive so it looks like the fuel pump is also not working...aaaargh.

So how to remove the fuel tank? are these MPI models held by more than the metal strap?

Is it possible to move the tank over to extract the pump without disconnecting everything underneath?

 

Cheers



#14 sonscar

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Posted 25 April 2021 - 08:23 PM

The ECU only applies the earth when it is powered on for a short while and while cranking.It is unlikely but not impossible to have multiple faults.Steve..

#15 Alexxx

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Posted 25 April 2021 - 08:53 PM

Got the tank out, it was full of fuel, I had thought it was empty as the gauge did rise but just a bit so I put in 5l fresh fuel.

It was full of rancid fuel, the sender rusted in place, the pump unit pipes had brown furry corrosion...lucky it the pump relay does not work!

Sonscar, if the ecu only gives an earth to the fuel pump and manifold heater for a moment, how does the relay stay activated, it must need some kind of earth?






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