KAMAZ, SPN 97: water in the filter - when to drive, what to drain

What the code says

In the SAE J1939 list SPN 97 is Water In Fuel Indicator. Water is heavier than diesel and collects at the bottom of the sump, where the sensor sits. The second part (FMI) says what happened. By the Cummins table, whose engines are fitted to some KAMAZ models:

FMI 15 and 16 are about water, FMI 3 and 4 about the sensor electrics. On KAMAZ, YaMZ and MAZ FMI 11 also occurs: the standard calls it "cause unknown", and its meaning comes from the vehicle table.

Can you keep driving

Cummins puts FMI 15 at the lightest level and FMI 16 at the middle: a warning, not an order to stop. A rule of thumb:

• even pull and no red lamp: reach the nearest stop and drain the water;
• power lost or a red STOP lamp: stop; per the Cummins card you must not drive with the red lamp on;
• do not wait for scheduled service: drain at the first opportunity.

How exactly a KAMAZ behaves (lamp, power reduction) is in the manual for your model.

How to drain the sump

1. Shut off the engine and set the parking brake.
2. Place a clear container under the drain tap of the primary fuel filter (separator).
3. Open the tap and drain the sediment; the clear jar is there so you can see the water.
4. Look at what came out: besides water, the Detroit Diesel instruction says to look for AdBlue, petrol, kerosene and coolant in the fuel.
5. Drain until clean fuel comes out, close the tap but do not overtighten it.
6. Prime the system with the hand pump per the manual, start the engine and see whether the signal returns.

If the water comes back in a day or two, there is a lot in the tank: drain the tank sump and think about where you refuelled.

No water but the code is there

Detroit Diesel describes a case where coolant got into the harness connectors, the contacts oxidised and the unit "saw" water. The principle is general: inspect the sensor connector for moisture and green deposits. FMI 3 and 4 mean a sensor circuit fault: break, short, poor contact. Replace the sensor only after draining the water and inspecting the connector.

What not to do and when to see a workshop

• do not clear the code and drive on without draining the sump;
• do not overtighten the drain tap: per Detroit Diesel it can damage the tap and the housing;
• do not buy a sensor until the water is drained and the connector checked.

See a workshop if water returns after draining and cleaning the tank, a red STOP lamp is on or power is lost, something besides water and diesel is in the drain (AdBlue, petrol, coolant), or the code stays after draining and connector inspection.

Questions and answers

What does SPN 97 mean on a KAMAZ?

The water-in-fuel sensor signals that water has collected in the sump of the primary fuel filter. Sometimes the sensor or its connector is the cause.

Can I drive with SPN 97?

With an even pull and no red lamp you can reach a stop and drain the water. If power is lost or a red STOP lamp is on, stop.

How is FMI 15 different from FMI 3?

FMI 15 is water above normal (the lightest level), FMI 3 is sensor electrics: voltage above normal or a short to positive. Replacing the sensor for FMI 15 is premature.

There is no water in the sump but the code is set. Why?

Moisture and oxidation in the sensor connector or a circuit fault (FMI 3 and 4) are possible. Inspect the connector first and only then replace the sensor.

Code pages on the site

• SPN 97 - water in fuel, all makes
• SPN 95 - fuel filter differential pressure
• SPN 94 - fuel pressure
• All KAMAZ codes