CA20E running RICH... wonder what's wrong.

[TurboZ.Dude]

Howdy people!

I converted my brother's T12 Bluebird from the carby CA20S setup to CA20E. In practice it meant to replace the entire electrical system, the fuel tank (pump's in the tank now instead of in the engine bay) and the head and intake manifold + ECU installation. The car's completely assembled now and all the accessory stuff works perfectly. Wipers, lights, interior fan, rear defogger etc etc.

All parts are stock parts, there's no fancy custom aftermarket stuff under the bonnet of this T12. Except for a hose to a vacuum meter.

To get to the point; the engine starts up and runs on all 4 cylinders but it gets way too much fuel. The smoke cloud coming out of the exhaust looks like the soot coming out of a truck exhaust when it's -30 degrees centigrade outside and the truck engine is cold. A lot of black stuff, almost enough to cover up an entire unit of soldiers.

In normal "closed loop" running mode the ECU reports no errors (red led doesn't blink nor light up) except for a rich condition in the exhaust (green led is off). When I put on the ignition, before I crank the engine, both leds light up so the ECU is getting all the power it needs and seems to be working properly. But some nut has disabled the diagnostics screw so I can't change ECU mode to check for error codes.

Giving the engine some revs (for example up to about 2500) makes it give the engine even more fuel when the pedal is pushed so apparently the afm is operational, as is the throttle sensor. After a while the engine starts to splutter because of the constant rich condition. I've tried changing the exhaust gas sensor but that had no effect. Also, the intake vacuum is very low at idle (10-15 inHg) and of course a bit unstable too.

I'm thinking fuel pressure regulator failure, since everything else seems to check out. I took it out and tried to operate it... but the valve did not move at all. It seems to be stuck. Putting some pressure (below 0.2 bar, didn't want to blow up the diaphragm) on the vacuum side made it close, so I thought maybe it's OK to put it back... only to realize the valve must have opened completely, stuck open, and let through way too much fuel pressure because the engine was still running rich after exercising the regulator.

There is another thing I have been thinking about: we didn't change the crank and rods and pistons, just the head. So the compression is a whopping 9.6:1 (which is standard on the CA20S) instead of 8.5:1 which the CA20E should have. Plus the engine displacement is 1960cc instead of 1974cc which the CA20E should have. Can this cause rich running conditions too?

I haven't ever had an EFI car before, so I really don't know if I'm at it or completely lost. The guys at ZXOC couldn't help me because the CA20E is rather unusual in the UK. Well, it's unusual over here too so I don't know any people in my country that can help me out. So I thought maybe some of you petrolheads at this forum might be able to help me out, even though this is not a N12 but a T12.

I'm open for comments and suggestions. I need to get the engine running properly ASAP. I don't think it'll be long until this problem is solved, since the engine is running on all 4 and always starting up without problems. But where to look for the troublemaker; that's the big question.

I've got a workshop manual for the CA20E engine, but unfortunately it does not tell me where to start with this kind of a problem. And the manual is for a S12 Silvia so it differs on some points.

Cheers,
Jan

[15exa]

water temp sensor can some times cause rich mixtures

injectors could be stuffed, did you have them cleaned up before doing the efi conversion?

double check the fpr with a pressure guage just to make sure its working properly.

might be a worth while investment to find another ecu, one that will display diagnostic codes, would help with any future dramas too should there be any.

good luck with it

[TurboZ.Dude]

Thanks for the quick reply!

I'll check the stuff you suggested.

injectors could be stuffed, did you have them cleaned up before doing the efi conversion?

No, I didn't clean the injectors up before doing the conversion because I didn't come to think of the possibility that they might be stuffed. On the other hand, why would all four injectors be stuffed equally? It sounds pretty unlikely to me.

double check the fpr with a pressure guage just to make sure its working properly.

You mean with an in-line pressure gauge? I can try, but I don't know the proper fuel pressure for this specific engine. Some things are really hard to find out even though I have a workshop manual. The manual doesn't include all the specs I need, I'm afraid.

water temp sensor can some times cause rich mixtures

Interesting... but I wouldn't think it can cause the mixture to be quite as rich as it is... I'll still check it out.

might be a worth while investment to find another ecu, one that will display diagnostic codes, would help with any future dramas too should there be any.

That's true. However, many ECUs in my country were (and still are being) crippled so only certified Nissan dealership can perform diagnostics and maintenance on the units. (The same goes for all other brands as well.) It may be that I can't find one ECU with the diagnostic selector intact. (well, then I will have to get another one and butcher it, but without the proper electrical expertise I don't think it would be wise)

good luck with it

Thanks M8!

[TurboZ.Dude]

Quick update:

The temperature sensor and the AFM both seem to check out fine. Plus the mixture is only slightly rich at 3600 rpm, which would indicate that something mechanical independent of the ECU is malfunctioning. I tried putting some "masinol" in the gasoline but it didn't have any effect so I think the injectors are clean. I'm still thinking about the fpr... I didn't have a pressure meter at hand so I couldn't test it in any way.

I have got hold if a couple of CA20E T12:s at a junkyard so I will buy a fpr and check if that solves the problem. A new one from Nissan would cost 175 EUR (~296 AUD), not going to waste that much money on a part that may or may not be malfunctioning.

[tassuperkart]

Fuel pressure does not vary much in the ordinary efi world.
Usually between 35 and 40psi @ atmospheric pressure

Compression would have NOTHING to do with it.

The temp sensor can really mess with things.

The FPR only works with vacuum and the movement is very slight to get the desired pressures.
The change will be kpa for kpa (1:1) so 0kpa would drop fuel pressure by 14.7psi
this is to maintain a constant head of pressure at the injector nozzles.

Did you use the EFI temp sensor?
The ecu uses water temp to enrich the mixture on cold running. Literally a "choke".
The efi temp sensors are a thermistor of a certain range and the correct one must be used.
They are different to dash guage temp sensors.
If you have connected to the stock single wire water sensor, then all sorts of dramas can happen.
The efi temp sensor MUST be above earth as well. The ECU circuitry for the temp sensing is very touchy and can be very prone to "noise" and earth loops.
Its why they are always a 2 wire sensor with what looks like an injector plug on them. One of the wires is signal and the other earths back to the ecu directly.

L8tr
E

[TurboZ.Dude]

Thanks for the reply! I'll forget about the fpr, I actually thought the fuel pressure was supposed to be varying according to rpm.

This CA20E doesn't have an air temperature sensor at the afm. Neither does the AFM wire have those wires that belong to an AFM temperature sensor. I've checked that with the S12 workshop manual.

I know approximately where to look for the temperature sensor you are talking about, I must have seen that particular sensor now that you mention it!

I have not connected any two-wire connector to a single-wire sensor (it would go against my better judgment), that's for sure. But the intake manifold was already completely assembled so all cables are connected and I didn't see anything incorrectly connected prior to installing it on the head.

In effect, I have constructed something I (almost) don't understand a jack about. I installed a complete CA20E loom (with all the interior electronics etc.), put in all the plugs and expected it to work completely. It seems I overestimated myself once again.

But on the other hand this is a learny experience so I won't do the same mistakes when I convert my N12 from E15S to E15ET at some point in time.

I'll try to find the appropriate temperature sensor and disconnect the plug, clean it up and re-connect it. But I'm afraid it won't do any good... since that kind of plugs are so well sealed. But perhaps the sensor itself is broken...

[tassuperkart]

Jan
Dont diss urself M8. Youve successfully done a job not a lot of others would even try.
The fact that its running (ok rich) but running is a big positive M8.
Id be giving urself a pat on the are, not kicking it!!!

Now, that temp sensor should live somewhere up near the thermostat housing. Somewhere up where it gets hot water. Possible even in the inlet manifold somewhere where hot water goes by.
As I mentioned, it will have a square plug, exactly the same as an injector plug and it would usually require a 19mm spanner to undo it.

They are a very common type of thermal sensor (thermistor) used in a million cars.
Its identical to your E15 item.
Universally know as a "Delco" type of temp sensor. From memory, they should read 2.2K to 2.7K Ohms @ 20 Deg.C

Can be found in legions of Jap cars except Mazda Rotors. They are different and cant be used.
Sometimes have different thread sizes but the ones of Jap cars are mostly universal.
They are also cheap if you need to buy a new one.

Id be looking long and hard at this temp sensor and/or its wiring right back to the ecu.

L8tr
E

[TurboZ.Dude]

Jan
Dont diss urself M8. Youve successfully done a job not a lot of others would even try.
The fact that its running (ok rich) but running is a big positive M8.
Id be giving urself a pat on the are, not kicking it!!!

Maybe you're right. Currently it feels like I've destroyed my brother's car. But I know that's not true.

For example; 100% of the interior stuff works and so do exterior lights, horn, rear window defogger, seat heaters, etc. etc. , everything except for the oil pressure warning lamp which did work the day before yesterday... probably a bit of oxidation on the connector and the engine shakes quite a bit when it starts spluttering so I guess it can cause a contact failure. I mean, the oil pressure lamp should of course not light up when the engine runs and it hasn't done that either. But up until yesterday it did light up prior to starting up the engine. Well, I'll concentrate on the engine. The warning lamp is a very minor matter compared to the engine.

Now, that temp sensor should live somewhere up near the thermostat housing. Somewhere up where it gets hot water. Possible even in the inlet manifold somewhere where hot water goes by.
As I mentioned, it will have a square plug, exactly the same as an injector plug and it would usually require a 19mm spanner to undo it.

If it's somewhere there, I'll find it!

They are a very common type of thermal sensor (thermistor) used in a million cars.
Its identical to your E15 item.
Universally know as a "Delco" type of temp sensor. From memory, they should read 2.2K to 2.7K Ohms @ 20 Deg.C

I'll dig up my universal meter from somewhere and check the resistance. Too bad it's 50 km from here right now but I'll retrieve it ASAP. Thanks for the values, I think I haven't seen anything about those values in the 784-page workshop manual.

Can be found in legions of Jap cars except Mazda Rotors. They are different and cant be used.
Sometimes have different thread sizes but the ones of Jap cars are mostly universal.
They are also cheap if you need to buy a new one.

That's good to know. Parts that are specific to this particular rare fuel injected T12 bluebird setup are very expensive, glad this part isn't.

Id be looking long and hard at this temp sensor and/or its wiring right back to the ecu.

L8tr
E

Will do. Probably needs replacement. The wiring itself is intact, I've checked all the wires (visually) before installing, don't want anything to short out or blow up instantly.

Cheers,
Jan

[TurboZ.Dude]

Alright, so now the sensor's measured and deoxidized etc. etc.

Deoxidization had no effect. And the wires are intact. At least that checks out.

The measured value of the was 3.15K at 19 degrees Centigrade. Is this good or bad? I don't know whether the resistance should rise when the temperature goes up or when the temperature goes down.

Cheers,
Jan

[boosted]

Alright, so now the sensor's measured and deoxidized etc. etc.

Deoxidization had no effect. And the wires are intact. At least that checks out.

The measured value of the was 3.15K at 19 degrees Centigrade. Is this good or bad? I don't know whether the resistance should rise when the temperature goes up or when the temperature goes down.

Cheers,
Jan

hi jan,
this value seems ok.
the resistance is rising as the temp decreases.
for some reason, FAST doesnt list the coolant temp sensor for the n12 turbo, but it will be the same as the ca20e one.
you can see the °C vs. Ohm -diagram in the e15et-manual

did you also try to measure the sensors resistance at the ecu-plugs?

greets
martin

[TurboZ.Dude]

hi jan,
this value seems ok.

Hello Martin and thanks for the reply! This rules out the temperature sensor!

the resistance is rising as the temp decreases.
for some reason, FAST doesnt list the coolant temp sensor for the n12 turbo, but it will be the same as the ca20e one.
you can see the °C vs. Ohm -diagram in the e15et-manual

Ah, so it's that way. I almost expected it to be that way but I wasn't sure!

did you also try to measure the sensors resistance at the ecu-plugs?

greets
martin

I didn't measure it at the ECU, good idea! I'll do that tomorrow! I'll have to check the workshop manual for which pins I should be measuring.

I'll also check the fuel pressure regulator once and for all... because the guys at club-s12.org said usually it's either the fpr or water temp sensor that fails on these, which then causes the engine to run rich.

They said that the fpr is easy to check. I have to pull out the vacuum hose and plug it. If the car runs with the fpr vacuum unplugged and running as bad as before but not worse, the regulator is broken. If it runs worse or doesn't start at all when the vacuum is unplugged from the fpr, the fpr is working.

So this is what I will do tomorrow. Thank you once more, it's a good idea to check the wiring electrically now when I'm at it!

[TurboZ.Dude]

Success!

The fpr is genuinely broken! Disconnecting the fpr's vacuum hose did absolutely nothing to the mixture, which confirms that it is broken. It may not be the only cause to rich mixture but we need to replace it anyway since it is broken. If we're lucky, the engine will run properly after this swap.

[tassuperkart]

Use anything temporarily as a test.
Even your ET one will be fine.
See what happens.

You really need to set up a pressure guage M8.
Its the only way to tell for sure.

Then you can apply vacuum to the sense tube and see exactly what the regulator is actually doing.

L8tr
E

[TurboZ.Dude]

Installing a fuel pressure meter is a good idea. Do you mean a dashboard-mounted one?

I'm afraid I can't use my E15ET one for two reasons: on the E15ET it is not located directly on the fuel rail; and I seem to be lacking mine as it is right now. But we'll get a replacement part from the junkyard for a very cheap price so don't worry, we won't waste much money if it wasn't broken even though we believe it is.

[Callumgw]

just buy one of the dicky aftermarket adjustable FPRs, they come with a gauge in them.

C