MoTeC Global Forum

Everything has been going well until yesterday .

I am using 2 pressure sensors on my engine.

The OEM is linked to the M800.
I have a honeywell to monitor pressure and to display to a MDD.

Normally on idle its around 250 ( dont know what this figure is )
When i rev it goes to 550 around.

While i was driving yesterday it went to zero. Then all of a sudden rose to 550 again only to drop to zero.

Its located in the top half of the sump in the oil gallery after the oil pump.

BTW the engine oil pressure light is operating as per normal , as it starts the light goes off.

I have another pressure sensensor on my fuel rail and thats constant 330

Im sure the fuel pressure one is 100 psi unit and the oil one is 250 psi unit.

btw checked wiring and there is no broken disconnected lines that i can see.Engine temps as per normal no overheating

Am i experiencing a sensor failure ?

Any comments/help is greatly appreciated.

Im going to change the oil soon , should i just replace it for the 500 psi unit ?

Run another wire some other path for awhile to see if that is the problem, or replace the sensor.
The other option is to start massaging the wires to see if the problem comes around.
(Massage with a bit of stretch)

I would bet it is a wire.

Is the Honewell sensor an MLH series sensor, MLH being the first 3 letters of the line directly under "Honeywell" if it is so and do you know if the reading is volts etc?

Had a chance to check this problem.
Disconnected the plug to the sensor.
Its a Honeywell MLH 58042. Unpluged the connector. Checked continuiety of the wire to the M800 all ok.
Then i ran another cable out of the car to the M800 and pluged it in the M800 same problem.
Start engine cold revs are 1300 pressure shows 550 on the MDD then goes down to idle and sits on 235 for a while then goes to zero.
Drive 1st gear accelerate and it goes to 550 as per normale but when the load is off goes back to zero.
Tuner said never seen a faulty sendor ?
Motec has asked to check the sender but i have to drain my engine oil.

Could a sender be at fault or could it be something else ?

Had a chance to check this problem.
Disconnected the plug to the sensor.
Its a Honeywell MLH 58042. Unpluged the connector. Checked continuiety of the wire to the M800 all ok.
Then i ran another cable out of the car to the M800 and pluged it in the M800 same problem.
Start engine cold revs are 1300 pressure shows 550 on the MDD then goes down to idle and sits on 235 for a while then goes to zero.
Drive 1st gear accelerate and it goes to 550 as per normale but when the load is off goes back to zero.
Tuner said never seen a faulty sendor ?
Motec has asked to check the sender but i have to drain my engine oil.

Could a sender be at fault or could it be something else ?

btw As pointed out before originally all was ok. This developed after about 800 kms

MANDALAY wrote:Had a chance to check this problem.
...
Could a sender be at fault or could it be something else ?

btw As pointed out before originally all was ok. This developed after about 800 kms

It is probably not an issue with the m800 set up if was fine before.
You checked the sensor to M800 wire, so that is fine.
Is there a power wire running to the sensor? or just one wire?
If it is not either wire to the sensor, and the M800 did not change, then the sensor seems like the only remaining piece or the puzzle.

<edit>
You should list all the possible causes and check them off... e.g.
Sensor wire #1
...
Sensor wire #N
Sensor bad
M800 change
M800 bad
Oil low in the car (Data is real).
<more>
<other unthought of>

Pilots often do not believe their instruments when they should have.

If the values are changing fast it sounds like a wire.
If they are changing slow it could be possible to be some leak in the sensor (maybe).

FWIW the Honeywell units have been the most unreliable, failure prone amplified pressure transducers I've ever used.

Between Honeywell, MSI, SSI, Kavlico, and Freescale/Motorola, Honeywell are the only multiple failure units, and the only failed units not related to user/installer error.

Well that doesnt sound promising, well in a way yes change it thats ok but if the one used for fuel pressure goes im in the shit because its locked up under the manifold.

BTW i was told that these senders are prone to failure due to vibration and heat. Any truth to that ?

Max operating temp is only 125 Deg and they are most commonly a 3 wire sender with output as a regulated voltage between 0.5V and 4.5V. A high supply voltage will kill them quickly due to their IC construction, but they are usually fairly resistant to vibration. The supply is +/- 10% and noise spikes wreak havoc. On the other side, to get a good Honeywell sensor, expect to pay $300 to $1000 depending on the build quality.

Ok guys just to follow up.
Disconnected the plug to the sensor. Pins and wiring ok.
Checked continuity of the wiring to the ecu board ok.
Check from the board to the M800 pins all ok .
Pluged connector to the sensor an started the car no pressure
Put a new pressure sender and presto came alive.
Ran all afternoon and no issues so far

Cold oil on idle around 350 kpa
90 degree oil 250 pka
Revining to 7,000 rpm and its about 620 kpa.

Hope this was the problem.
Ill send the suspect sender to MoTec on Monday and they can check it.
If its faulty hopefully i can get a refund on the 2nd unit i bought.

BTW on a separate note a track guy said to me not to connect the pressure sender to the engine due to vibration.
Instead to connect it to a pressure hose and mount the sendor to the car and have the hose connect to the engine.
Any thoughts ?
All their cars are done this way.