dt420sel

Hello All,
I have a 1086 420 sel with 100 000 km on it.
A couple of weeks ago my wife was driving it and the engine started cutting out. She could restart it but it would soon stall so she had it towed home. By the time I had a chance to look at it, it 'fixed' itself and drove beautifully for a couple of weeks. But it's happened again this time with me driving.
I thought it was the fuel pump relay as when the engine idles I can feel it 'click' off right when it stalls and it was cutting the power to the fuel pumps. So I replaced the fuel pump relay with a new one and also replaced the fuel filter but the exact same thing happens. I don't think its the fuel pumps as they are both running and the car will run/idle fine until the relay turns off.
I have noticed that the relay won't turn off untill the engine is warm. I live in Canada and if I start the engine and let it idle it will take about 15 minutes for the relay to turn off the first time. The car will restart but only idle for 15 to 120 seconds before turning off again. There are no malfunction lights lit on the dash.
Is there any other sensor that could make a fuel pump relay turn off? If no, do you have any suggestions of what else to look at?
Thanks, I hope somebody can help. Drew

sosh

Sounds more like a CPS to me. Why not have it correctly diagnosed by a dealer.

dt420sel

Money is tight (tis the season) and I only want to bring it to a dealer as a last resort. I guess it could be the crankshaft position sensor as it sends the rmp signal to the fuel pump relay and when there is no signal the pumps are shut off. Any idea how to test a CPS to see if it is working correctly? Is there a way to bypass it?

sosh

I do not think there is any test for it and sometimes they do not even throw a code. However the typical symtom of a bad one is that it will run when cold and shut down when it warms up. Then will not restart until it cools. They are inexpensive and there is no way to bypass them. Will not run without one.

dt420sel

Thanks for your help, it sounds extremely likely. I will get a replacement and hopefully that will do the trick.

dt420sel

Sosh, just to clarify by CPS do you mean the Camshaft Position Sensor P#002 153 46 28 ($60.89 in Canada) or the Crankshaft Position Sensor P#002 153 34 28 ($270.89)? Thanks, Drew

sosh

I was refering to the crankshaft position sensor. The cam sensor would cause a similar issue but most of these failures are due to a bad crankshaft position sensor.