Stumped Advisor


#1

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?


#2

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.


#3

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).