Starting problem on 1999 S70

Robbie · Post by **Robbie** » 16 Jul 2012, 08:45

My 2 litre petrol engine S70 has developed a starting problem if I stop the car after a short trip when the engine is only just warmed up. It shows up as being difficult to start if the car is stopped for about 10 mins. Sometimes it will start but stalls if you rev the engine or try to move off. Then it will not start unless you let the engine stand for 10-15 minutes before trying again. No codes are showing up on the diagnostic port.

I have changed the plugs but this has not had much effect. Any suggestions on what to do next will be very welcome

Post by **jblackburn** » 16 Jul 2012, 08:49

I believe this may be a coolant temp sensor issue.

The temp sensor is located under the thermostat housing at the end of the upper radiator hose. Grab a voltmeter, put it on the resistance setting, and check resistance at both cold and hot engine temps.

ENGINE COOLANT TEMPERATURE SENSOR RESISTANCE TABLE
Temperature F ( C) Ohms
32 (0) .............................................. 7300
68 (20) ............................................. 2800
176 (80) ............................................. 300
212 (100) ............................................ 150

If those values are wonky (or you notice the temperature gauge showing the wrong readings), replace the sensor and clean up the plug.

Robbie · Post by **Robbie** » 16 Jul 2012, 11:40

Thanks for your reply. The temperature gauge appears to be working correctly but I will test the sensor asap.

Post by **igel513** » 16 Jul 2012, 15:46

JB, does the coolant temp. sensor issue also affect S60s?

Post by **jblackburn** » 16 Jul 2012, 16:01

It could if you're experiencing similar symptoms. The S60 in early years uses almost the exact same engine management system as the 1999-2000 models.

Post by **jimmy57** » 16 Jul 2012, 18:36

Fuel pump check valve or fuel pressure regulator not sealing are also possibilities.
Check fuel pressure for dropping too quickly after shutdown. Fuel pressure should not fall below 2 Bar in 20 minutes. On the cars with no return line from injector fuel rail to tank, and I think Euro models got that when North America did , if it vapor locks it is far tougher to get fuel back up to the injectors until the engine heat dissipates. The bit of fuel in rail burns and then it is a while before it gets the fuel back up there due to the fuel reaching a hot metal fuel line and vaporizing.

Post by **igel513** » 16 Jul 2012, 19:48

Jimmy, where is the FP regulator on an 03 S60? Is the check valve built into the FP assy.?

Robbie · Post by **Robbie** » 17 Jul 2012, 13:26

Update. Checked the resistance as suggested and the sensor was giving values close to those given at 20 and 80 degrees. My local mechanic now thinks problem is with ECU. Do you agree

Post by **jblackburn** » 17 Jul 2012, 13:42

No. The ECU's are hardly ever a problem.

Replicate the situation where it is hard to start. Remove the plastic cover around the fuses near the windshield (3 screws around the edges). Remove relay 103 and replace it with a jumper wire between pins 15 and 87. See if the car starts and runs without stumbling.

Post by **jimmy57** » 17 Jul 2012, 13:54

igel513 wrote:Jimmy, where is the FP regulator on an 03 S60? Is the check valve built into the FP assy.?

It is on the fuel pump assembly cap on the underside, the internal fuel tank side.