Hi all,

I know its not a kit car but I am having problems with one of my other cars.

Its a 1989 XR3I with MFI but the previous owners has changed the induction unit for a ford motor sport item.

The problems is it is only doing 20mpg on the motorway and 12mpg on country lanes. I have put the strobe light on it today and set the timing right and adjusted the idle screw as it was running at 1250rpm but this has made no difference.

Should I adjust the mixture screw (if so which way should I turn it) or leave it alone and take it to a ford garage to get it set up right?

I would like to adjust it myself either way just as its costing me a fortune in fuel and I might not get it to a garage until next week.

Thanks,

Po79.

It could have been running fast on tick over because the mixture is wrong. Alter the tick over back to what it was, then alter the mixture, if it slows down then your going the right way. or take it to an MOT station and ask then to check the emissions.

Check the valve clearances and do a compression test

[Edited on 4/1/10 by britishtrident]

Mine wouldnt do much more than 25mpg

There was an artical in the ppc mag about the mfi metering head a good while back ?

I'd say your best bet is to get rid of the "ford motorsport otem" & fit some bog standard s/h bits - My XR3i used to do around 40 mpg on a run & well over 30 round town - I find it highly unlikely that changing the one item would significantly affect performance but can make as massive impact on consumption.
If it's still the same get the emissions checked & see whether it's rich all the way thro' the range or just at idle.

You could have a read of this and see if it helps.

quote:

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Originally posted by britishtrident
Check the valve clearances and do a compression test

[Edited on 4/1/10 by britishtrident]

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Six replies in under an hour!

The standard induction came in a box of bits with the car so if I can't get good mpg after I get it into a garage I'll be sticking that back on.

I'll have another look at it tommorrow and see if i can put some of the advise given to good use.

I put a new thermostate in it a few weeks ago as the gasket was leaking so thats all good.

If I can just get it to run without needing a fuel tanker following me everywhere that will do then I'll get it into a Ford garage and get everything checked over as I'm starting to think it could be one of the sensors as this problem came on quickly.

Thanks again, (I'll report back if I make any progress),

Po79.

www.xrstyle.co.uk

That's the owners club forum..

TT

Have you checked for fuel leaks in tank or pipes or rail?

First thing to do is figure out if it's running rich.....PUll the plugs, or better still ask a friendly MOT station to measure emissions.

As mentioned, it could be a leak!....

If it's not a leak then I would suspect the ECU thinks it is at either higher rpm or a higher throttle setting, and thus is throwing more fuel into the engine...Or, one of the sensors could be broken, and the car thinks it on warm up...Check coolant sensor, air temp sensor.....

PJ.

Hi guys,

Bit of an update for you all.

Drove the car to work the other day and went to start it to go home and it wouldn't start at all. I figured that as its over fueling it was most likely flooded, I left it half an hour and retried but no luck.

Went back to it the next day and it started on the button so I took off the cold start valve wires and drove it home but it was still using a stupid amount of fuel, by this time it was dark I so left it over night.

When I tried to start it the next day it would not start again so I reconnected the cold start valve and it still didn't start so then I tried disconnecting the warm up regulator plug, this made no difference.

Then I checked if I had a spark at the spark plugs and I did but when I took out the spark plug there was no fuel on the spark plug, in fact it was bone dry (even after all the turning of the engine).

I have checked the purple pump relay and there is power coming out (12volts ish) and it seems to be switching on and off with the key.

So then I checked the fuel pump itself and with someone turning over the engine i could not feel or here the pump running I took the wires off the pump and only have a few volts there.

What voltage should I have at the pump connections and how can I test the pump itself?

Electrics has never been my stong point but after spending a day outside in the cold checking and double checking everything and lying in the snow I am determined not to give in and pay someone else to fix it

Yours still warming up,

Po79.

Humm......faulty fuel pump would normally give you a lean mixture.......

To answer you question....Most pumps simply require a 12v feed, and this is normally via a relay controled by the ECU.

A simple test is to 'carefully' apply 12v acriss the pump terminals (consider 12v can give sparks, and you are screwing with a fuel related item!)......

If it spins, then you need to trace back to the control relay, and if thats ok, then the ECU signal...

Did the plugs look coaked up?...

Remember, a lot of ECU's will cut the power to the fuel pump if the engine hasn't been cranked after 2-3 seconds, so just turning on the ignition and then wandering around to the fuel pump to see if it's running isn't necessarily going to work. You need to be feeling or listening to the pump when someone turns on the ignition.