fiveliterlx1990

I don't know if any one has ever experienced this type of problem before. I have an unusual problem, when I turn my 1990 five liter off, I can still hear the fuel pump working. If it is a relay problem where is it located? If it is a fuel pump problem I can change that no problem, it will just take effort, but when I asked at the O'Reilly Auto Parts store if anyone had ever experienced something like this before, this guy said it was a purge valve solenoid problem, that it was gettin' stuck. I do know that normally the contacts are normally open, only becoming closed when the ignition is turned on and the circuit is complete. If it is purge valve solenoid problem, where is this located? At this point I don't know what to do, I'm having to kill the car completely by disconnecting the battery, and this is lame. Please, has anybody ever experienced this type of problem before on a Mustang?

5.0stanger

I remeber others having this problem and I think it was their relay. What year do you have? On my 87 it is under the driver seat.

mattdel

purge valve solenoid is for the evap system, nothing to do with the pump. it might be an ignition problem, but more likely the relay. relays for are $7, pick one up for the hell of it, bypass all that diag time.

shaners90lxhatch

Okay. #1 - it could be a stuck relay or the control side could be shorted to power via some sort of harness chaffing, or you could even have a bad ignition switch. That will take some testing to figure out but I have your wiring diagram and can give you all your possible causes in a few days when I get back home to Michigan.
#2 - The fuel pump relay is located underneath the driver's seat and you may need to remove the seat to gain the best access. Some of them are just so tough to get at under there, I just started pulling the seat. Its really easy and one needs only a crecent wrench.
#3 The guy at O'Reilly's is wrong. I don't know exactly where the VMV is on our mustangs but they don't make much noise at all. There will be a vacuum line going from the intake going to it and it would be somewhere under the hood. And you would have a nasty vacuum leak if that were the case... If the buzzing noise you hear is in the back - it is definately NOT the VMV. I am 99.9999% sure this guy is wrong about the purge valve (this valve is used for evaporative emissions testing that, if my memory serves correct, our vehilces are exempt from. We DO have charcoal canisters to collect the evaporative emissions but I don't think we have a purge or vent valve.)

Best thing to do at this point is remove the fuel pump relay and see if the noise goes away. If so, you are a voltmeter and 15 minutes away from knowing exactly what the problem is. Otherwise I can still help you out, it just may take a few more informative posts.

mattdel

look

[IMG]local://upfiles/53364/120E96678B334E5EB4082CB5D700FB1F.gif[/IMG]

[IMG]local://upfiles/53364/991CBE083FA24A61852CE1B63E78E2C9.gif[/IMG]

[IMG]local://upfiles/53364/909DFD9851FB47A5878C6BBC00E07C4C.gif[/IMG]

[IMG]local://upfiles/53364/BDA7E4BC6356458182394C4E03E07AF1.gif[/IMG]

Blckstng93

First thought was the ignition switch. The pumps ground may be shot to. As for the pump relay, yours may be under the drivers seat. If its not there, its under the MAF. Your relay should have 4 wires, the other is the EEC relay which has 5. They look like little black cubes, atleast on my 93 anyway.

Purge valve should be right next to the charcoal canister which its mounted under the airbox on the fram rail. The little round thing next to it is the purge. I dont see how that would keep the pump running tho as it just vents fuel vapor into the engine but it doesnt control the pump itself that i know of.

mattdel

shaners90lxhatch

Any chance I could ask where you got those EVTM pages? I don't know of anywhere online a lamen can find these. I am tired of trying to get stuff from my actual book or PTS to link onto the forum

mattdel

i have an account with AllData for my shop, so if anyone needs any diagrams or anything straight from a shop program, lemme know. all access.

5.0stanger

You can get pictures like that at http://autozone.com