Fuel Pressure

[Mike_Pollock]

Ok then, my 2.7 runs rich so I've been looking into the FPR. According to Clarks 2.7s can have 2 different FPRs depending on the engine number, however both are rated at 3.8 Bar. Now Clarks also say in another (linked ) page that all 16 valve cars should run 3.8 Bar and all 8 valve ones (inc. Turbos) run at 2.5Bar.

Which means that an FPR with the same no would have to run at 2.5B in my car but 3.8b in an S2, which clearly (to me at least!) means that something is wrong somewhere.

Can anyone confirm the correct fuel pressure for a 2.7, and if there is any difference in the performance of the 2 different FPRs.

Thanks

 

[repsol]

more likely an air flow meter fault than pressure problem

 

[Mike_Pollock]

Beside wearing the track, what else can be wrong with the AFM?

 

[robwright]

It could have moved out of calibration for whatever reason. If that is the case Mike then you are looking at a 2nd hand AFM or new if you can afford one. Trying to realign would be futile. They are set in the factory by expensive and sensitive machines. I agree with repsol about it more likely being AFM than FPR. Or it could be the DME coolant sensor fooling the DME into thinking you have a cold engine and hence a rich mixture. Incidentally Mike how do you know you are running rich? By smell of the exhaust?

 

[Mike_Pollock]

Smell of exhaust and black plugs, not oily so pretty sure its too much fuel.

Top of the AFM had been removed and the screw holding the spring catch on the gear wheel was loose when I got the car so I have been regularly been tightening up the spring, which has an effect crisping up the throttle response and making the plugs a better colour, but it is only a temporary effect!

It almost as if the barn door is sliding back on the spindle or the spring is not properly attached at one end - but it is as far as I can tell!

It goes well enough (ask McNulty[8|]) after I've tensioned the spring.

I may well end up with another AFM, but I'm really curious!

Could be temp sensor - good thought thanks - it did come with a replacement but it doesn't fit!

 

[Paul 290T]

Mike,

My AFM (on BMW E34, same design as your 944 meter) had a worn track. I pulled the sweeper arm further up its axle to make the sweepers twin contact points touch a slightly tighter radius arc than previously set. The result was that the AFM worked fine for the next 5 years until I scrapped the car.

The procedure is well described in this website:
http://www.the944.com/afm.htm

This repair does therefore work effectively. It does not change the AF ratio, as I was not re-indexing the sweeper contact point's position on the track.

However your symptoms don't match those of an AFM with bad track section. A bad track section results in the car pulling roughly through a narrow rpm band, feels like the more familiar fault of an ignition short on a spark plug lead. Opening the throttle whilst the car is spluttering along moves the AFM sweeper past the bad point and all is smooth again. It won't affect your AF ratio.

Regards

 

[Mike_Pollock]

Thanks Paul, I have already moved the wiper to a different arc. its just the fact it seems to run rich all the time.

I checked the readings for the AFM earlier with the meter and it seems to be well within spec.

I also checked the temp sensor bot cant find any numbers to put mine against!

Since I disturbed these bits, its died a couple of times, fiddling with the temp sensor seemed to get it going again, so I'm going to order a replacement.

 

[Eldavo]

My 2.7 seems to run a bit rich too, I sometimes get a pop from the exhaust during full bore up shifts.

Will be interested to hear how you get along.

 

[JamesO]

ORIGINAL: A9XXC

Thanks Paul, I have already moved the wiper to a different arc. its just the fact it seems to run rich all the time.

I checked the readings for the AFM earlier with the meter and it seems to be well within spec.

I also checked the temp sensor bot cant find any numbers to put mine against!

Since I disturbed these bits, its died a couple of times, fiddling with the temp sensor seemed to get it going again, so I'm going to order a replacement.

I have pretty much all the original fuel / ignition stuff from my old 2.7. (apart from temp sensor). The AF ratios were fine as checked by wideband before removal. If you cant solve your issue I could send you the lot for testing if you want, might save a lot of time.

 

[Mike_Pollock]

Thanks for the offer James, I may take you up on that.

Hopefully getting a temp sensor tomorrow so will try that first - my car came with a new temp sensor but a wrong version, brown topped and wrong thread diameter, so I think somebody else had thoughts along the same lines.

 

[repsol]

beware of a meter that has been opened it usually means is duff the track can sometimes be moved over to get a better contact could be cooling sensor but sounds like previous owner changed it for the wrong one put the correct one in and see how u go with that

 

[Mike_Pollock]

Top marks to Rob!
Changed the temp sensor, plugs are so much cleaner!
Still need to adjust things - so many things have been changed it may take a while!
The PO gave me a new, brown topped sensor with the car, but I found this was the wrong thread when I tried to change it. Correct one is blue topped.
Thanks to all and especially Rob!

 

[Eldavo]

Got a part number for the temp sensor and general location?

Will give it a go and see if it sorts mine out too.

 

[Mike_Pollock]

944 606 125 00 or Bosch 0 280130 026 2 pin with blue head, mounted on the block underneath the J boot, the forward one of the 2 temp sensors (other is for the gauge). Not too easy to get at but just undoing the J boot and holding out of the way makes a big difference.

If you leave the coolant cap on, and are quick, you only lose a drop of water!