24 replies to this topic

[VNOMUS]

Hi all,
I've got 96 1.3 Auto SPI that's sputtering when the motor hits around 3400 rpm. Otherwise it seems to run fine (although it doesn't get near the gas mileage that my 86 carb'd Mini does). So far I've replaced the ECU vac lines (broke and also had a hole in one of the fittings), dried out the fuel trap, replaced the O2 sensor, checked the throttle index, and reset the ECU. I'm in the US so I don't have access to a scanner and can't check for any codes. However, looking down the throttle bore I can see the injector spray pattern sputter and breakup when I rev it above 3400 rpm.
Any ideas on possible causes (bad injector, fuel pump, ECU?) or additional things I can check?

Thanks in advance for any help!...

[Retro_10s]

I'd check fuel pump and as you say, injectors could be full of C**p.

[the old git]

A mate had the same problem at lower revs, as soon as you tried to accel, the engine died. Checked it with the air filter off,(as no faults were showing on code reader) injector fine for a while, then 'splattered' the fuel rather than sprayed it, the engine faltered and died. As a test, we borrowed another injection tank, car ran perfectly. Bought a secondhand fuel pump--no problems since

[fikus01]

i would have said check both of the above or possibly the crank timing sensor getting covered in C**p or swarf confusing it a little once the speed gets up!!

i've heard injection engines suffer lower economy sometimes because of the cat!! i think it was jsut because the engine couldnt cope with a large amount of back pressure!!

[AlexM]

i would have said check both of the above or possibly the crank timing sensor getting covered in C**p or swarf confusing it a little once the speed gets up!!

i've heard injection engines suffer lower economy sometimes because of the cat!! i think it was jsut because the engine couldnt cope with a large amount of back pressure!!

Take the Cat off! Lets face it a mini needs every horsepower it can get! Gotta keep up with those modern cars! Maniflow sell de-cat pipes.

[Sprocket]

Fuel filter!

[VNOMUS]

Thanks for the replys!...


Sorry, I forgot to mention the cats been removed and the fuel filter was just changed as well. Is there anyway to test the crank sensor? (I hate to throw money and parts at it)...

[Sprocket]

Crank sensor doesnt realy serve the injector so much as it does the ignition. The injector is pulsed to privide fueling to the base map in the ECU memory. This is further adjusted with feed back from the Lambda sensor to achieve the correct air fuel ratio. The injection period is not tied into the crank position.

I would be looking at the fuel supply first. See if you can fit a FI test pressure gauge to the fuel supply line and watch what happens when the engine starts to splutter. There should be very little variation in pressure of aprox 15psi.

Oh, and LOL, there is fuel in the tank, not just whats in the bottom?

Edited by Mini Sprocket, 19 October 2006 - 01:06 AM.

[VNOMUS]

Crank sensor doesnt realy serve the injector so much as it does the ignition. The injector is pulsed to privide fueling to the base map in the ECU memory. This is further adjusted with feed back from the Lambda sensor to achieve the correct air fuel ratio. The injection period is not tied into the crank position.

I would be looking at the fuel supply first. See if you can fit a FI test pressure gauge to the fuel supply line and watch what happens when the engine starts to splutter. There should be very little variation in pressure of aprox 15psi.

Oh, and LOL, there is fuel in the tank, not just whats in the bottom?

Thanks for the info and suggestion, waiting on a t-fitting with a schrader valve to hook up my test gauge...and yep, there's plenty of fuel!....

[VNOMUS]

Ok, schrader valve finally came in and I hooked up the fuel pressure gage. The pressure's steady up to about 3000 rpm(was ok to about 3700 about a week ago so it;'s definately getting worse) then starts fluctuating (about 3-4#s). So maybe it's the pump?

[fikus01]

possibly tho i dint see why it would change at a certain revs!! sounds more like the injection throttle body could be gettin upset at certain revs or just returning too much fuel so that as the revs go up its ok til its using more than it can get!!!!!!

what is the pressure actually reading?? does it read worse at the 5000rpm mark??

just to note although u were getting a flat spot and i mentioned checking the flywheel pickup!! that assumption was going on that it could also be a timing problem!! now defunced because fuel press was confirmed!!

Edited by fikus01, 02 November 2006 - 12:17 AM.

[VNOMUS]

possibly tho i dint see why it would change at a certain revs!! sounds more like the injection throttle body could be gettin upset at certain revs or just returning too much fuel so that as the revs go up its ok til its using more than it can get!!!!!!

what is the pressure actually reading?? does it read worse at the 5000rpm mark??

just to note although u were getting a flat spot and i mentioned checking the flywheel pickup!! that assumption was going on that it could also be a timing problem!! now defunced because fuel press was confirmed!!

Fuel pressure's around 15-16#s....I tried going higher, up over 4000 and it started backfiring (which is really exciting when you're leaning over intently watching the injector! )

Can the injector be disassembled/cleaned and/or bench tested?

Edited by VNOMUS, 02 November 2006 - 12:35 AM.

[fikus01]

15 - 16psi im assuming your meaning!! that does seem a little low!! from memory the spi's run on 2.7 bar!! thats closeto 45psi i think!! stil could be pressure regulator in the manifold but other than that i cannot help you!! didnt play too much with an spi

[VNOMUS]

15 - 16psi im assuming your meaning!! that does seem a little low!! from memory the spi's run on 2.7 bar!! thats closeto 45psi i think!! stil could be pressure regulator in the manifold but other than that i cannot help you!! didnt play too much with an spi

Yes, it's around 15-16psi, which is what Mini Sprocket quoted as normal... Would the ECU provide any error codes for this, and if so, are code scanners for the SPI still for sale in the UK?

by the way, MiniMania.com is quoting about $549(290 GBP) for a new pump!

[the old git]

15 - 16psi im assuming your meaning!! that does seem a little low!! from memory the spi's run on 2.7 bar!! thats closeto 45psi i think!! stil could be pressure regulator in the manifold but other than that i cannot help you!! didnt play too much with an spi

Yes, it's around 15-16psi, which is what Mini Sprocket quoted as normal... Would the ECU provide any error codes for this, and if so, are code scanners for the SPI still for sale in the UK?

by the way, MiniMania.com is quoting about $549(290 GBP) for a new pump!

My code reader is a Sykes Pickavant, it reads the ECU for faults and shows them on a small screen. It gives you the option to clear them. If they fail to clear you can then go to another test and check that the failed item is within its parameters. Likewise you are able to check all the other items are within. Especially good for quick diagnosis of the Map sensor/pipes to ECU/Manifold the common problem. It will operate the injector to show it is working, however if the pump has an intermittent fault, it can still spray fuel out of the injector. Hence my comment re my mates Spi. Easy over here because soeone always has an Spi to swop tanks for a quick diagnosis. Yes pump pricesare frightening-I bought a new one which we take with us when we race. Worth looking on ebay for a spare, even if yours turns out to be OK