fuel pump is not priming!

[tla280]

Ok so undoubtedly I'll probably catch some flak for this cause there are some really good write up's on this subject:

http://www.stangnet.com/mustang-forums/792048-blue-orange-fuse-link-fuel-pump.html

http://www.stangnet.com/mustang-forums/790924-same-intermittent-fuel-pump-problem-sos.html

http://*******.com/index.php/topic,588.0.html

http://mustangforums.com/forum/5-0l-1979-1995-mustang/579035-93-eec-relay.html

The latter of which really parallels my situation...except for the part where I KNOW whats working lol.

So here goes. Last Thursday go to jump in the stang and head out and boom, wouldn't start..well it did at first, looow rpm, trying to stay running, and unresponsive to throttle. Eventually died out and wouldn't start. Dicked with it for a bit, gave up came back to see if I could hear my fuel pump and low and behold I did and it started right up. Skip to a few days later and the same thing happens..unfortunately in a wal-mart parking lot. Once again no fuel pump prime.

So I start with what seems the easiest thing, fuel pump relay, grabbed the one off my other fox - same year, same trim - put it on and still notta, bought a new one from o-reilly and still notta. Towed back home and heres where I'm at.

Turn key, eec relay clicks, fuel pump relay clicks...twice, is it supposed to? I know its only supposed to stay on for 2-5 seconds (the pump at prime) but it open and closes? in less than a second. Jumped the VIP/Diagnostic connector to bypass and I get ~11.8 vdc on both sides of the inertia switch. I get ~11.8 vdc at pink/black going to fuel pump? From relay, as well as yellow and ? wire when the relay is open and JUST the key in the "on" position, no jump on the vip/diagnostics connector. I'll check again cause that doesn't make sense to me, should be the pink/black that gets voltage when the relay opens right?

Two things I haven't check are the eec relay and if the pump is getting any power *waits for "wtf?!?" response* yeah I know, but the connector that I perceive as supplying power as the foam to water-proof it on the back side of both. So I can't get a prob in to check it, and to be honest I'm not exactly sure what I'd be looking for.

I'll upload any pics requested and answer questions to the best of my abilities, I guess I'm just tryin to avoid dropping the tank and replacing the fuel pump, so if you got any input I'd greatly appreciate it cause I can't seem to get my head around all this crap at one time.

 

[stang9150]

Had the same thing happen to me twice.First time was a bad ecu and the next time was the fuel pump itself.Its worth it to see if you have power even to the pump that should rule out everything else other than a bad pump.Good Luck

 

[tla280]

thanks man. Actually stopped by and got the eec relay from my other stang just to see. So I'm gonna pop that on and see if I can figure out how to test for power at the pump while its just me!

 

[mister5150]

same exact thing happened to me.. if u notice were Your coil is and the starter solenoid is located there is a short ground cable with a connector on it this i believe is the eec ground mine had come undone and will give a no start condition i learned this after i replaced the fuel pump and the relay wiggle that connection and see what happens ....good luck

 

[tla280]

eec relay out of my other car didn't work (no big surprise). And my grounds look solid, old - but solid.

I took some paper with me this time so I could actually remember what I was getting on the volt meter and here goes:

koeo-
(fuel pump relay)
pink/black - NO relay - I get 0 vdc. Relay and ign cycle I get 11.8 vdc
orange/lt blue(looks grey to me) - NO relay - I get 11.8 vdc. Relay and ign cycle I get 11.8vdc
red/black - NO relay - I get 11.8 vdc. Relay and ign cycle I get 11.8
yellow/ lt blue(I have no idea, not this color on diagrams) and this one is a bit weird...
with no relay attached I get .89 vdc. When attached and ign cycled when the FIRST clicks I get about .8 (from 0) second click and I get 11.8 till I turn the key off.

Next is koeo BUT with the diagnostic connector jumped to ground to give the fuel pump constant power (bypasses relay yes?)

So at the connector from the relay, to the pump heres what I get:
pink/black ~11.5 vdc
yellow/and what looks white to me..~8.5 vdc
and the grounds are within reasonable levels
(this is all on the relay side of the connector btw)

When I try to cross the connectors with my voltmeter I still get about 8.5 vdc on the yellow and whatever wire, but the pink/black wire (that is pink/blk on one lead of voltmeter and pink/black on other lead from other side of the connector) I get .26 vdc! WTF? It should still get power right? Or am I missing something? Or do I have to complete the ground circuit or will I still get a reading if I don't? It'll still draw power right, just not complete the circuit?

 

[liljoe07]

so you have 12v at the pink black wire at the relay. But .26v on the same wire on the fuel pumps connector?

The yellow wire should be for the fuel level sender. You leave that alone. Pink/ black is what you are concerned with.

 

[mister5150]

have you checked the inertia switch? it is located below the driver side taillight it is there to kill the fuel pump in case of a rear collision however they are known to fail

 

[tla280]

@mister5150
Inertia switch is good, 12 vdc on both sides.

@liljoe07
let me clear up my admittedly hazy description. At the relay and the relay side of the connector to the fuel pump (the one on the backside of the fuel tank) I was getting correct voltage. When I tried to go pin to pin with the volt meter with the connector unplugged I was getting .26 vdc as where when I did the same with the wire for the sending unit I got proper voltage. I have since just jammed the probe in through the foam when the connector is plugged in and DID get proper voltage on both sides. So essentially I am almost positive my pump has kicked the bucket...unless somebody has a better idea

 

[liljoe07]

Yes, drop the tank and bench test the pump.

 

[wv109323]

Fuel Pump

I had essentially the same problem about three years ago. The skematic was confusing to my way of thinking the system ought to work.
My problem turned out to be an extra kick in the teeth. The problem was a failed pump. When I got the tank dropped and pulled the pump out the tank was full of rust. The tank had rusted from the outside. There is a seam/lip that runs around four sides of the tank. On the front that seam acts like a shelf to collect mud and debris. That in turn allowed the tank to rust through. I had to replace pump, tank, and sending unit.
The pump usually quits as you describe it quits, works a while then quits then repeats. I have had that experience with other vehicles.

 

[seedeezy]

Grab the battery out of the the car or use another good battery close to 12v and put the positive on the pink black and the ground the adjacent black wire on that 4 pin going into the tank. If nothing happens the pump is lame.