97 Gt Fuel Pump Issues
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wmburns
SN Certified Technician
I'm aware that some model years of Mustangs have an error in the owner's manual. The fuse listed as fuel pump is actually the PCM. The fuse listed as PCM is actually the fuel pump.
The other thing that I know about the 96-98 Mustang is that all (4) O2 sensor heaters are powered from the PCM. The thing about that is a fault in any one of the O2 heater circuits will blow the PCM fuse.
Given the fact that recent exhaust work was done, my $$ is on a wiring harness fault from touching hot exhaust somewhere in the system.
One quick test is the measure the resistance between the VPWR line at an O2 sensor and battery negative with the battery positive disconnected. Should be a very high value. If the Ohm reading is low, this puts you miles ahead in the trouble shooting.
Knowing now that the problem could be in any of the (4) O2 lines, suggesting a recheck with the "Mark I eyeball" as well.
The other thing that I know about the 96-98 Mustang is that all (4) O2 sensor heaters are powered from the PCM. The thing about that is a fault in any one of the O2 heater circuits will blow the PCM fuse.
Given the fact that recent exhaust work was done, my $$ is on a wiring harness fault from touching hot exhaust somewhere in the system.
One quick test is the measure the resistance between the VPWR line at an O2 sensor and battery negative with the battery positive disconnected. Should be a very high value. If the Ohm reading is low, this puts you miles ahead in the trouble shooting.
Knowing now that the problem could be in any of the (4) O2 lines, suggesting a recheck with the "Mark I eyeball" as well.
I replaced the down line I looked in the Haynes manual I don't have the factory manual. What is Mark I eyeball?
wmburns
SN Certified Technician
Visual inspection
https://en.wikipedia.org/wiki/Visual_inspection
If this were my car likely I would disconnect every sensor on the Red VPWR line and see if the fuse blows. If not, then plug the sensors back in one at a time until it does.
If the fuse still blows, then it just got real. As in real harder. Likely the next step is to pull the PCM and retest.
wmburns
SN Certified Technician
So how did you find it? How did an engine ground cause a fuse to blow?
There are others reading these thread that may have the same (or similar) problem that might benefit from your experience.
There are others reading these thread that may have the same (or similar) problem that might benefit from your experience.
wmburns
SN Certified Technician
Soooooooooo. The "Mark I eyeball" actually was the tool that saved the day. But your Wife's version is better than yours.
The "Mark I eyeball" was vital during the Battle of Briton. It was an important simple tool used to spot inbound aircraft to make reports to central command.
The "Mark I eyeball" was vital during the Battle of Briton. It was an important simple tool used to spot inbound aircraft to make reports to central command.
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