99 Mustang Gt Won't Stay Running...

[clayLong]

noob to stangs here. Bought a 99 GT auto today for super cheap. Guy tells me it drives good except sometimes at a light it'll idle down, pop the throttle, goes away. I drove it home from the notary with no issue at all, like waiting for it. Go to ride to the park, stop at the red light otw out of the neighborhood, and it idles down rough af for like ten seconds with me tapping then halfway hitting the throttle. Dies. No start. I tried not to kill the battery trying it and got it out of the intersection. Tried it a few more and with a jump when my buddy showed up; nothing. Seems like no fuel but I haven't taken a line off yet or anything. Oh and I tried it with the fuel cutoff switch both ways.

Just wondering if y'all think I may have some of the stuff in this thread going on, or like.. fuel pump/filter/relay/fuse...? Something completely different that's common to make them not even start after all of that idle dip?? Any help at all is greatly appreciated.

 

[soupnutz]

Can you hear the fuel pump priming? Should be able to hear it for a few seconds when turning power on? If not, I believe that the 99+'s use a FPDM. Not sure how they are on mustangs, but on f150's they are a common fail item. If the pump isn't kicking on, that gives you a direction to troubleshoot in at least. If it is, could be a few other things. Possibly a filter if it's severely clogged, might as well change it. Probably costs about $10 for a filter and the fuel line tool, and takes maybe 15 minutes. Has there been any check engine lights or anything?

 

[wmburns]

If you are just looking for a "guess" as for a common problem why your Mustang doesn't have fuel pressure then "bad fuel pump" has to be near the top of the list. If however you don't like replacing parts only to find out it didn't fix the issue, then recommend doing some testing first.

As mentioned above, do you HEAR the fuel pump run at initial key on? If not STOP and find out why.

For a verified no fuel pressure situation:
With the key on, test for key on +12 volts at the trunk mounted IFS switch. Use a known good ground.

IF no voltage the problem is upstream. Think fuse, CCRM, ignition switch, ground, wiring fault

IF there is voltage, the problem is down stream. Think bad fuel pump, bad FPDM, trunk ground, wiring fault.