22n 5G8 injected to rich

Hello all,

My second post here and it's a good one!

Been having some fun with my XJ750D (22n) 5G8. I got a new motor for the old girl was cheaper than doing the primary chain and gearbox, it is a good runner a 24L (off a police bike?). Came all assembled with carbs starter etc and a oil cooler bracket, no hoses or radiator though.

I installed it in the Yamaha and changed the timing plate and rotor with the 22n one. Got it running and ride able but it is running too rich. The trip computer says 10K/l (normally 22K/l) and the plugs are black (it does not smoke). I have tested as much as I can with a multimeter and all seems to be fine. The reason I had to test all circuits was when I took the old engine out the wires on the plug to the TCI with 4 wires, orange, grey, black and white/black came out of the plug. I transposed the black-white/black in the plug, opps. The white/black melted a bit but I noticed straight away and changed them. I have tested the circuit for the white/black and all is ok, through to the computer and throttle switch.

Would you have an Idea of what might be wrong?

Could I have damaged the TCI and would you know if a standard XJ one is the same if I have?

How does the choke work and might it be jammed? (does not seem to do anything)

I cleaned the outside and body of the throttle housing but tried not to disturb the injectors. Is there any mixture adjustment for them?

The bike revs out fine, the idle is rough (I did have it smooth as but still too rich at speed). With a timing light on no. 1 it does not flash untill revs are increased above 1500, though it did not do that at first. The plugs fire ok.

I have the XJCD, well worth it. I also have the Haynes '80-'84 Yamaha Fours manual. Very little info on the net re this model, I have seen Dave's page and met him (46Km away from where I live).

Spent 4 days on it now, oh well!

Thanks for any help you might be able to give, great site!

 

Quick update:

I have taken the injector unit out and there is alot of gasoline in the intake tracts, very wet looking. So for some reason the system is delivering way too much gasoline. Cannot see any way of adjusting any settings on the injectors themselves.

Any ideas?

 

No, there aren't any tweaks for the injectors. The mixture is set by the computer with input from its sensors.

I'm not familiar with your particular bike, but I can suggest some things to look at. There will be some sort of an engine temperature sensor for the computer. Most often this is a coolant temp sensor, and many vehicles have two (one for the computer and one for the gauge). Check the sensor for crack or leaks. If you find any corrosion, replace it. Check the reading from the sensor; is it accurate? If not, replace it.

If the temp sensor checks out, check the cooling system to make sure that the engine is reaching proper operating temperature. If the thermostat is opening too soon, the engine won't warm up and you'll have a rich condition.

There are some other possibilities but these are the most common. Hope this helps.

 

Hi Weavalo.
The bike is a air cooled XJ750D '83 4 cylinder DOHC YCIS.

Thanks, there are two sensors.

One is a temperature sensor on the head that works by increasing resistance with increase in temperature. This tests ok.

The other is a airflow sensor inside the airbox. This has a main and a bypass function. Both circuits give different readings with my multimeter, one higher than the other, but I am not sure if they are correct.

The bike was running ok before I did the engine swap, all electrics from the old engine have been swapped to the new engine. All wires are connected and I have gone through circuits with a multimeter checking for disconnects and high resistance joints.

I am at a loss, but thank you for your help I went outside and checked as per your suggestions.

 

Kiwi, there are a few contributors here that are injector nuts. Hopefully your post will tweak their ears and you'll get a response. I don't know squat about your model but there are some things that are univeral for most all 80s injector systems so I would invite you to check around. Best of luck to you on this problem, I've a feeling your going to need it.

 

The bypass circuit on your airflow meter is for idle. I have no idea why an injection system would have a choke. This IS an electronic FI system, right? It's not a mechanical system like the old Bosch K-Jetronic?

A couple more thoughts: Is there an oxygen sensor fitted to the exhaust? That's a potential source of problems and can create a rich condition. Is the airflow meter mechanical or electronic? If mechanical, make sure the damper door moves smoothly. Also, the fact that your timing light got no signal from the #1 plug wire concerns me. You might want to check the wire(s) for resistence and make sure that you're getting proper voltage to the coils.

One last idea: there should be some sort of throttle position sensor. Make sure that it's working and positioned properly. It should come off its enrichment circuit just off idle.

That's all I got. Good luck, Kiwi!

 

Hi Weavalo,

Thank you for your help.
Yes EFI, the choke does not seem to be connected to anything or do anything so I am puzzled on that one too.

There is no oxygen sensor, there is a boost sensor on the inlet side though.
I think the airflow sensor is electronic it is in the airbox and I cant get it (airbox) out with the engine in place.
The light did give a signal at first but now only when the RPM is above 1500 even though the plug is firing. I have checked with multi meter as per the XJCD seems ok though I am about to have another look. Going through everything again step by step.

There is a throttle position sensor on the injector rack, it is a on/off micro switch like old telephones used to use and tests ok.

Thanks for your efforts, given me alot more to think about, never had any EFI vehicles or worked on them before, all been carb. I have worked on many cars but few bikes.

Cheers.

 

Hi all,

Thank you all for your efforts in trying to help. I have narrowed the problem down to that white/black wire that goes back to the main computer and seems to be part of the control circuit for the EFI. I think I killed it!

For the 4 pin plug from the pickups:
Closest to the bike White/Black on your left looking at the bike Orange on the right.
Closest to the viewer Black on the left Grey on the right.

I will be taking th EFI gear out (not the computer all other functions work) and replacing it with the carbs. A costly lesson, but there is alot of good info about EFI on this thread for anyone in the future. I will take all the readings again and post them here for future reference. Might help others track down problems on this rarest of XJs.

 

OK, I managed to try an exchange computer (thanks Dave, Top bloke) and the problem is still there, just leaves the airflow sensor in the airbox. The components look ok, no fried parts.

Problem solved I am now running carbs!

Thanks again guys