Df40 and error code 3-2

[Allan Strachan]

Good morning from a wet and miserable Scotland!

I am primarily an auto enthusiast, but have a few friend with RHIB's which I occasionally help with servicing, so as far As outboards go my experience is limited, but as far as the 4 stroke engine goes i'de say I was pretty competent.

I currently have in my possession a df40 which is showing the error code 3-2. Engine seems to running pretty well, with maybe only a slight misfire at all rpm's, but this is maybe the nature of a 3cyl engine rather than a fault.

So far I've done the following:

Replace fuel with fresh
Replace both hp/lp fuel filters
Soak injectors in carb cleaner overnight, re-install. Add injector cleaner to fuel and run for 20 mins.
Remove map sensor and check passage to intake manifold - ok
Check voltage of map sensor. Haven't used a vacuum gauge, but voltage responds to vacuum throughout it's range.
Removed IAC valve and throttle body. Fully clean,test, replace and set up bypass air as per manual.
Test Crank position sensor and adjust as per manual.
Remove all temp sensors and check resistance in Hot water - all good.
Check resistance of all ignition coils and replace spark plugs.
Disconnected all other electrical equipment leaving only engine wiring connected to battery.
Battery charging ok, battery voltage ok.

One thing that I find odd, is that I can't seem to get the ecu to reset. Last night I disconnected the ecu and battery and left overnight to try and reset. This morning I connected everything back up and straight away it started the 3-2 code again before the engine was started. I also can't get this to clear by cycling the kill switch 3 times within a minute.

Any assistance would be appreciated. Due to the ecu not resetting I'm fearing that it's at fault, but I'm very hesitant to order such an expensive item in the fear that it's not the problem.

Regards, Allan

[Allan Strachan]

Further to the above, the engine has done just over 400hrs. The old spark plugs looked slightly black, but not what I would consider in bad condition, and they were all identical.

Cheers.

[redlowrey]

Back probe the signal line on the map sensor with a digital multimeter, use a thin needle to get to the conector on the plug. Turn the ignition on and if your on the right wire you should see around four volts, start the engine and it should be around one to two volts up to four volts when you snap the throttle. The engine has to be running for the ecu to erase the map sensor code. Do this simple test take the cowling off and run the engine, on them early engines the exhaust gas burns through the engine holder and lets exhaust gas into the throttle plate, manifold vacum drops and the signal line voltage drops and the ECU brings up a map sensor code.

[Allan Strachan]

Hi, thanks for the tips.

I probed the signal wire and all seems to be as you state.

3.9v with the ignition on, cold idle 2.2v and I can see up to around 3.7-3.9v with a quick blip of the throttle. Bearing in mind I'm on muffs and the engine is in neutral, so I only blip to 3000rpm.

The engine cowling has been off for some time, and most of my Internet trawling has come up with the corrosion problem, but from what I can see there's no corrosion, and the fault remains with all the cowling off.

Any other thoughts?

Allan.

[Allan Strachan]

hi, would the 2.2v at cold idle be far enough out of spec to cause this issue, or do i possibly have a fault ECM?

[redlowrey]

I would have thought it would have been under two volts, are you high in the mountains or at sea level. What is the manifold vacum at idle how many inches of mercury, if you have a hand held vacum pump trick the ecu and bring the signal line voltage under two volts when it is idling and see if the light goes out. The black plugs tell me it is runing rich. also that 3.2 code is for presure detect meaning the ecu is not seing a changing voltage so some thing might be wrong in the wiring to the ecu check the signal line votage at the ecu. I use a variable pot to change signal line voltages if you have not got one take the map sensor off plug the hole and use the vacum pump on the map sensor.

[Ads seajay]

3-2 refers in the service manual to "MAP Sensor 2 (Sensor hose) code 3-2 fail safe activating no"

Check the hose of running into the map sensor is not blocked and or the map sensor hose conncection is not also blocked.
If not replace the map sensor.

[Allan Strachan]

cheers for the replies.

I have taken redlowrey's advice and tried to fox the map sensor into outputting the correct voltage.

very crued, but i managed to put a hose over the map sensor, suck the hose and simultaneously clamp the hose. After a few attempts i managed to get 1.6v, so started the engine and hey presto. the alarm instantly cleared and the engine seemed to idle much better.

What i did seem to notice is that at low vacuum (suck!) its very easy to alter the voltage, but trying to get from 2.2v down to under two almost turns your lungs inside out.

I guess with the correct vacuum gauge etc it would have been much easier to fault find. Anyways, there doesnt seem to be any inlet manifold leaks and from i can gather the MAP sensor has deteriorated enough for the voltage to stray out with tolerance, and more than likely stay at 2.2v even if the vacuum increased a good way. Hence the 3-2 fault rather than the actual map fault.

Many thanks for the help, it is very much appreciated.

I'll let you know how i get on with a new map sensor.

Allan

[redlowrey]

Before you spend 250 bucks, check manifold vacum because low manifold vacum means high signal line voltage.

[Allan Strachan]

well, as it happens, a new sensor has made no difference!

i've ordered a vacuum gauge to test the manifold vacuum, but in the meantime, does anyone have any idea what could be causing this?

there are definatley no leaks on the manifold, since i've sprayed carb cleaner all round it, and no noticeable difference.

valve timing, worn rings?

again, if i fox the map sensor into outputting 1.6/1.7 volts the fault clears and the engine runs much smoother.

no wiring faults to be found anywhere?

Allan

[redlowrey]

I told you to check manifold vacum before you buy a sensor.

[Allan Strachan]

i bought the sensor after you advised to check vacuum. Never mind though, i'm sure Ebay will recoup the majority of the loss.

Moving on, i've ordered a vacuum gauge and compression tester. In the meantime is there anything else i could be looking at?

[Allan Strachan]

ok, so i fanally managed to get some testing done.

Manifold pressure- erratic readings, but average of 11" HG on idle and can be made to peak at about 17 after a throttle blip

Fuel pressure checked at a steady 35psi

next the bad news:

Comp test cold engine WOT:

#1 167psi
#2 170psi
#3 80psi

double checked a good few times and results are repeatable.

Would worn rings be common accross all cylinders? does it look like a sticky or burnt valve?

Regards, Allan

[Allan Strachan]

i bought the sensor after you advised to check vacuum. Never mind though, i'm sure Ebay will recoup the majority of the loss.

Moving on, i've ordered a vacuum gauge and compression tester. In the meantime is there anything else i could be looking at?

by the way, the above could be missinterpreted! i took a punt and bought the sensor due to not having the correct equipment to check the vacuum. all my fault and have learnt the hard way!

Al

[redlowrey]

Pull the cam cover off and check the clearance on all the buckets you will probably find a tight valve on the cyl with low comp.