Hello folks! I'm new to this forum and I really need you help. I have a 1998 S40 2.0 with manual transmission. Last week I removed the injector and the spark plugs to do a tune up. I had the injectors cleaned in an ultrasonic machine and bought the new plugs and the fuel filter at the dealer.

I removed the throttle body and the intake hoses to clean them as they were pretty dirty from the crankcase ventilation. I also cleaned the vacuum lines the go to the MAP sensor, to the fuel pressure regulator and to the booster. After putting everything together I checked all the parts were properly installed. When I tried to start the engine, it will start, idles fines for about 30-40 seconds and then the idle start getting lower and lower until it stalls... If I press the accelerator pedal, the engine chokes and stalls right away.

I really don't know what could went wrong... I'm baffled here. I must admit that when I connected the spark plugs, I made a mistake and connected cyl 3 and 4 wrong. I noticed this after the first starting attempt due to engine misfire. I corrected this and the engine started, but it will behave in the mentioned way.

Any idea or suggestion here? Could I have damaged the throttle position sensor when I cleaned the throttle body with carb cleaner? Any idea on how to measure the TPS resistance with a multimeter? I don't have a scanner...

BTW, I have VADIS installed in my laptop but I can't find the test parameters for the sensor and the fuel system. Any idea of where I can find this?

Thanks for all your help folks!!

 

Throttle position sensors normally don't have much effect. When you first start the car does the idle start high and come down? You may have a iac problem but it sounds like a fuel problem. Try unhooking a small vacuum line if you can then start the car and see if you have a high idle. If the car won't idle at all I would then unhook the injector rail (if you can) and look for a good spray pattern when cranking.

 

Thanks for the info escape-performance. You are right. In fact it was a fuel problem.

I borrowed a fuel pressure gauge to check fuel delivery and to my surprise the there was no fuel pressure. Therefore, I removed the fuel pump to check the failure since the fuses were ok, the relay was properly working and the pump was getting power. It turned out that the car was low on fuel. However, the fuel meter showed the car had around 20 liters of fuel in the tank, about a third of its capacity. I really don't know the amount of fuel that was in the tank when I checked, but I'm sure it was not even close of being empty. Anyway, after installing the fuel pump, I poured some gas in the tank and it fired right away. No sensor failures whatsoever.

Yesterday, I was driving the car and it was working properly. At some point the engine stalled, showing the same initial symptoms. Again, the fuel meter showed a bit less than 20 liters left in the tank. I managed to get the engine running and got to a gas station. After filling up the tank, the car ran fine.

I'm confused. The weird part is that the fuel meter was working properly before. I mean, when I parked the car to do the tune-up, the fuel meter worked fine, along with the fuel level warning light. I just don't know what could have happened that the fuel meter stopped working properly... Or could it be that the fuel pump is starting to fail? Could it be possible that a failing fuel pump is not capable of sucking the fuel if its bellow certain level?

Thanks for any help!

 

A failing pump will give the same symptoms regardless of how much fuel is in the tank. However it is best to keep the tank half full or better for two reasons. One being that fuel is the lubricant for the pump so any time you run out of fuel you can damage the pump. The return fuel systems found in most cars send more fuel to the engine than needed. The excess fuel passes through the rail and back to the tank. The less fuel in the tank the more often it gets sucked back into the pump. The pump heats the fuel when it pass through it, so the lower the fuel the hotter it gets. This can cause premature pump failure. Warm fuel increases the chance of knock and detonation especially in modified vehicles.
Ok back on track.....nothing that you mentioned doing should have any effect on the pump or fuel level sensor. Check the quick and easy first. Make sure you reattached the vacuum line to the fuel pressure regulator, and check there are no fuel leaks at the filter. Also double check you put the filter in facing the correct direction, some can go in backwards. Did you use any chemicals on the lines that could melt them ie carb cleaner? I don't have the schematic in front of me but the pump and level sensor should be separate circuits possibly sharing a ground. However if that was the problem I would expect the gauge to read full or empty not 1/3. It does sound like you have a pump going bad. If you can get at it easily pull the pump out and keep it connected. With the key on try lifting and lowering the float arm slowly. Watch to see if the fuel gauge goes up and down without any glitches. It is possible that these problems occurring at the same time as the work you did is just a coincidence. Good luck, Ethan