We have a 1990 volvo 740 gl. Noone I know can help me and I work for a GM dealership as a service advisor. My car continues to have stuttering problems, we have replaced spark plugs, fuel filters, fuel pump. It starts up fine, will run ok and then all of a sudden will die, then the next day it will not start, run a little while and die, doesn’t make sense, it definitely seems fuel related. What are signs of contamination, does anyone have any ideas?
So why does it “definitely seem fuel related”?
To verify this, try putting a fuel pressure gauge on the fuel rail and check the pressure when the car is failing. If the pressure is ok, check to make sure the injectors are getting a trigger.
If you haven’t done any of this yet, you’re guessing at the “fuel related” diagnosis.
It could be fuel or spark related. The latter can also mimic a fuel problem if it has a failing coil or module.
As suggested, check for fuel pressure when it acts up.
When it will not start try spraying a healthy shot of aerosol carb cleaner into the intake manifold through a vacuum hose.
If it starts for a few seconds you know the problem is probably related to the fuel pump controls (relay, ECM, and ignition module, etc.)
If it does not start then I would check for power at the positive side of the ignition coil and for a spark from the coil. If there is no power there then you may have a bad ignition switch (electrical part).