Thread: Lean running on petrol

Probably the only complaint in history of an RRC running lean!! LOL

I would be looking at the fuel pump or fuel filter first. Also have a look at whether the little hose at the back of the plenum chamber to the fpr is intact, and that the little plate that the stepper fits onto is tight to the plenum.

The temp sensor for the injection should read 300 Ohms across the terminals when warm. It is almost unheard of for it to be lower .The usual problem is high resistance which leads to the ECU thinking the engine is cold.

The resistor is most probably the tune resistor and is what tells the ECU which tune to use eg whether it has cats or not so don't touch it.
regards
Philip A

Thanks! Perfect, 300ohms. SOmething to aim for

I swapped the fuel pump out of the other car into it and it has a new filter in the last few months. I'd imagine the problem would be far worse when cold (when it needs more fueling) if the pressure to the rail is low I'll see if there is an easy way to get a pressure gauge into the fuel rail to check.

thanks!
Shane.

How have I never been to this site before ??

Rover 14CUX Hot Wire Mass Flow EFI: Service and Troubleshooting


bloody brilliant.

"Bottom Row" - pins 1 to 13 (they're numbered from left to right as shown in the photo)
1	Red/Green	Idle bypass valve - circuit 1
2	Brown/Orange	Power feed to the fuel injection main relay
3	Yellow	Throttle position sensor output/reference - see also 20 and 25
4	Black	Oxygen sensors (ground) and to the relay that powers their heater coils
5	Grey/Black	Tune resistor (through VIN LA451517 only)
6	Yellow	Road speed input
7	Green/Blue	Coolant temperature sensor (input) - see also 25
8	Purple/Yellow	Windshield defroster input, if fitted
9	White/Light Green	Diagnostic connector output
10	Black/Yellow	"Check Engine" lamp
11	Yellow/White	Right bank of injectors - cylinders 2, 4, 6 and 8
12	Blue/Red	Main relay "request"
13	Yellow/Blue	Left bank of injectors - cylinders 1, 3, 5 and 7
"Middle Row" - pins 14 to 27 (they're numbered from right to left as shown in the photo)
14	Black	Ground
15	Brown	"Battery" supply
16	Blue/Purple	Fuel pump relay "request"
17	Grey/Yellow	Purge control valve output
18	White/Pink	Diagnostic connector output
19	White/Grey	"Ignition" supply
20	Red	Throttle position sensor (input) - see also 3 and 25
21	Yellow/Black	Air conditioning thermostat input, if fitted
22	Blue/Red	Air flow sensor (input) - see also 25
23	Blue	Signal from the LH oxygen sensor
24	Blue	Signal from the RH oxygen sensor
25	Red/Black	Ground side of coolant, fuel, airflow & throttle-position sensors
26	Green/White	Idle bypass valve - circuit 1
27	Black/Grey	Ground
"Top Row" - pins 28 to 40 (they're numbered from left to right as shown in the photo)
28	Blue/Grey	Idle bypass valve - circuit 2
29	Orange	Idle bypass valve - circuit 2
30	Black	Fault display data
31	Black/Green	Diagnostic connector "request" input
32	Grey/White	Fuel temperature sensor (input) - see also 25
33	Black/Grey	Air conditioning compressor clutch relay, if fitted
34	Orange/Black	Transmission gear switch signal
35	Blue/Green	Air flow sensor (input) - see also 25
36	Black/Green	Air conditioning condenser fan output, if fitted
37	(Not Used)
38	Brown/Black	Fault display data
39	White/Black	Engine speed signal cable (harness includes 6.8k ohm resistor)
40	Black	Ground

So I whipped the plug off and measured the resistance between pin 25 and 7..... Bugger ... within spec ...

The Coolant Temperature Sensor should change resistance with heat, per the following specs.
10C	(14°F)	9100-9300 Ohms
0C	(32°F)	5700-5900 Ohms
20C	(68°F)	2400-2600 Ohms
40C	(104°F)	1100-1300 Ohms
60C	(140°F)	500-700 Ohms
80C	(176°F)	300-400 Ohms
100C	(212°F)	150-200 Ohms

So I let the car warm upto 70degrees (there is a proper temperature gauge in the radiator ... the fans were not yet running, so the entire cooling system should be at about 70degrees.... And I think it was 2300ohms I still had. So the coolant sensor is quite a bit out of range .. but it should be RICHER not leaner.... bugger.

The petrol tempe sensor ( pins 32 and 25 ) measured much the same as the coolant sensor when cool ( at about 20degrees)... I didn't check again when it had warmed up.

You know, with it about 15 degrees outside rather than 5degrees.... It's drivable on petrol. It's all but un-usable when cold though.

I also checked the fuel map resistor.



mine is almost like this... For a few seconds I was dumb enough to think "crap I can't make out the colours well enough to decode the resistance" ........... then my snail like brain thought .... Oh, you actually have a multi-meter in your hand right now... so I chucked the ohm-meter over the resister ... 178ohms. So bloody close to 180ohms it doesn't matter .... Aussie spec fuel map. so leave alone.

Onto the fuel rail I guess, I'll see if I can figure out how get a pressure gauge into it.

seeya,
Shane L.

OK ... so has anyone figured out an easy way of fitting up a fuel pressure gauge to a 3.9 litre serpentine belt V8. The rail is metal, the lines running forward are metal, there is two lengths of flexible line front and back where the tank and motor connect. I do NOT want cut into them!

seeya,
Shane L.

Oh gee's ... when will I ever learn to put 2 and 2 together and get four.... I was just looking at the prices of fuel pumps on ebay (yes all the cheaper ones don't have the wiring harness on them required for htis car. I wonder if you can just wire the old plug on). Anyway, I'm looking at the pumps and thought .............................. Crap, there is another issue that my problems match. I head out to the shed and unscrew the filler cap ... It was hard to unscrew. The Oring was half way down the threads. With this off the car is running perfectly.

I'll take it for a drive on petrol later tonight and get it nice and hot and verify it's ok (with the cap on loosely).... but it looks like my problem the entire time has been the tank isn't vented. So yes, I sure did get it sealed up well when I was trying to stop the petrol smells last year!

seeeya,
Shane L.

That IS funny!

Shouldn't the tank be vented to the charcoal canister so that it can't be sealed up anyway?

Yes it should be vented to the charcoal canister which has a valve that is supposed to open at part throttle to vent into the inlet manifold. check that the connector is actually connected. I cannot remember whether it is 5v or 12v so be careful if you want to test it.
regards Philip A

the 4L has a schrader valve, next to the firewall behind the right? bank,,

maybe?