Running Too Rich

[ALEX 98 1 Cars]

It's been running rich for a while now, I can smell petrol when driving with the window down and my mates said they could smell petrol really bad when following me too.

When the engine is idling it's smells fine, and it's even passed it's emissions test, so I'm reluctant to adjust the mixture on the AFM as

it's a brand new one (well a couple of years old now) with the plastic tamper proof cover still in it.

 

So where to start?

The inlet pipework looks fine, but I can check for an air leak after the AFM but the idle is smooth so I don't think that's it.

It could do with a service, and I can't remember when I last changed the plugs, so I can eliminate those when I service it this weekend.

I have a spare distributor to try as the Advance could be stuck?

 

Any other things I can check? seeing the ebay advert in Off topics made me think maybe It could be a bad earth symptom?

[kyepan 291]

firstly check your fuel hoses, rail and injectors for leaks, if it smells of unburned fuel in the cabin it may be evaporating from something in the engine bay. I had a slightly loose pipe recently, and a loose rail, and it did stink of fuel.

 

then take the temp sensor out and check the resistance in some cold / hot / boiling water, values can be found by searching on here, this controls when the ecu leans out the mixture for warm temp running.

 

Then back track to see if the value is the same at the sensor as it is at the ecu, to do this get the pin outs for the jetronic ecu, then back probe with your multimeter.

once you know your ecu is getting the right temp voltage signal when warm, and all your pipes are tight... now the afm... or afm wiring (more likely). the next step would be to back probe the afm (pull it's rubber boot back) and check it's sending the right voltages, then at the ecu backprobe the correct terminals to check all of the signal is getting there.

 

 

if the afm is ok, and the temp sender is ok, and you don't have an injector stuck open (which would make it run pants) then it might be worth looking at cam timing, spark plug gap / health.... to make sure all of the fuel going in is getting ignited.

 

A quick search should give you the reference voltages for the afm / ecu / temp sender..

 

J

[woodsy 0]

maybe worth checking the smell isnt coming from the fuel cap as the seal maybe worn if everthing else is ok.

[ALEX 98 1 Cars]

I can't see any leaks or anything damp, everything is bone dry.

If the Petrol filler cap seal was leaking wouldn't you be able to smell petrol all the time?

It only smells badly of fuel when I'm moving in it.

 

I didn't think of the blue temp sensor. I saw one of these fail on a mates 205 GTI and it just shorted out causing the car not to idle.

I might have a spare anyway which would be easier to try than test the original one.

Chances are it's the wiring, that's why I was thinking it's a bad earth, a while ago it failed to start on about 5 occasions not giving me a spark (tested on the one time I was at home so I could do some investigating). I thought it was a sticking relay or something as with out touching anything every time (other than when at home) and just trying after a short while it would fire up! strange.

It's not done that for over a month now though, but I think the petrol smell started around the same time I had that symptom.

 

First things first though I'll get the plugs and give it a service this weekend and go from there. I was hoping for it to be a common problem with a certain wire or relay or something but it looks like it's one of those things. Thanks anyway Kyepan I'll try testing the wiring to the AFM/Sensors before spending anything on it other than a service.

 

edit: the exhaust is quite sooty inside the tail pipe, so I'm sure the smell is from the exhaust.

 

 

EDIT EDIT: could a sticking SAD unit cause rich running?

Edited November 3, 2009 by ALEX

[aCe 0]

Might be wort having the igntion timing set up correctly and then geting a CO test at your local garage, from here you can adjust the mixture on the AFM and know its running corrctly.

[TT205 42]

OT - do I keep seeing you on Blackmoorfoot?

 

Dave

[CaptainK 11]

If the Petrol filler cap seal was leaking wouldn't you be able to smell petrol all the time?

Not necessarily, I had a minor problem where my fuel tank was being pressurised by a blockage or something to do with the charcoal canister. This meant that the fuel system couldn't vent the pressure out that way and was pressurising the fuel tank and the relief valve in the fuel cap was venting that pressure. With the engine running you could smell the vapours coming out the fuel cap. I believe it also leads to a little bit of overfueling.

 

For full details of this, talk to Sandy as he found and fixed it for me as it was discovered when it was down at his place earlier this year being checked over before a Nurburgring session.

[ALEX 98 1 Cars]

OT - do I keep seeing you on Blackmoorfoot?

 

Dave

 

 

Yeah, Probabaly. not seen any other 205's my way though?

 

 

Not necessarily, I had a minor problem where my fuel tank was being pressurised by a blockage or something to do with the charcoal canister. This meant that the fuel system couldn't vent the pressure out that way and was pressurising the fuel tank and the relief valve in the fuel cap was venting that pressure. With the engine running you could smell the vapours coming out the fuel cap. I believe it also leads to a little bit of overfueling.

 

For full details of this, talk to Sandy as he found and fixed it for me as it was discovered when it was down at his place earlier this year being checked over before a Nurburgring session.

 

I don't think Mine has a Charcoal canister!not too sure what that is?

Interesting theory though I'll check the tank vent pipe isn't clogged (assuming it's the pipe to the filler neck down to the inner arch) my phase 1.5 CTi has a white plastic cylinder connected to it. Is my gti (Phase2) missing it?

 

 

 

"With the engine running you could smell the vapours coming out the fuel cap"

I can't smell fuel when it's idling, only while driving.

Edited November 16, 2009 by ALEX

[TT205 42]

Yeah, Probabaly. not seen any other 205's my way though?

 

No, I'll have been in my exciting Saab

[CaptainK 11]

"With the engine running you could smell the vapours coming out the fuel cap"

I can't smell fuel when it's idling, only while driving.

On mine you had to be right at the fuel cap to smell anything at idle, but it was much more noticeable when on throttle as the pressure rises.

[ALEX 98 1 Cars]

I did some investigating at the weekend and thought to check the vacuum advance.

I removed it from the Dizzy to test it by sucking on the pipe connector to see if it was working.

It would move slightly but I couldn't keep the lever in, as air was leaking back in somewhere

I wasn't even sure if it was faulty until I did the same test on a spare I had from My CTi project.

Apparently you should be able to keep the lever sucked in until you release it.

 

It's stopped the fuel smell but now it pinks a little more than it did before, which makes sense as I would have been compensating the vacuum advance with the timing advance. The power is still there so I think I just need to retard the ignition only slightly.

[MerlinGTI 3]

New ECU temp sender (£17) - Ignition timing set up - CO setup at idle = sorted

 

Vacume advance makes bugger all difference really, mines been fubar for ages. I think most are!

Edited November 30, 2009 by MerlinGTI

[ALEX 98 1 Cars]

I adjusted the timing last night and retarded the ignition by a couple of degree's it goes like stink now!

Either that or it was the cold icy weather this morning!

[Galifrey 1]

I adjusted the timing last night and retarded the ignition by a couple of degree's it goes like stink now!

Either that or it was the cold icy weather this morning!

 

If you still smell the fuel, check the pipe that connects the fuel filler to the tank. It has a joiner between them (bottom of offside rear wheelarch).

 

Mine was rotten and leaking.

 

Explains why I was getting 20mpg