No power to fuel pump - stumped

RCodePaul

RCodePaul

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Car died and had a crank no fire condition. Zero pressure at schrader on the fuel rail. Checked fuel pump fuse, clean connections, fuse was good both visually and had continuity. Did a search found this thread, useful, got me close.
http://www.lincolnvscadillac.com/showthread.php?t=85184&highlight=test+fuel+pump
Tested whether there was power to the fuel pump by connecting the green/red lead to the positive side of the multi-meter with the negative side of the meter jumpered to a tested ground. No voltage. Rechecked the connections and jumpers and turned on the ignition, no voltage.
Just to be certain the pump works, I used a 9v battery to jumper power to green/red + and to black/red - on the pump connector and I can hear the pump run. Clearly the issue is no power to the pump.
Checked the relay and it's good. When I apply power to the 1-2 coil connectors the open between 3-5 closes. Checked that there was power to the fuse (yes) and power to the 1-2 relay connectors when the ignition is turned on and there is.
The fuel pump diode has no continuity in one direction and 20 ohms of resistance the other way. I guess I will head to the wiring diagrams (which I hate) but was hoping for JoeGR to the rescue???
 
silly question, but you did check the fuel pump cut off switch right?
 
stihlboy said:
check the inertia switch in the kick panel?
Click to expand...

Yes, good point. I did by seeing if it was "popped up" and it wasn't. I tried to depress it by reaching through the little window in the kick panel and pushing down but it wouldn't depress. IMO it was not tripped. Tried to pull the kick panel to check for continuity but was unsure how it came off n didn't want to break the thing for no reason.
 
So, keep in mind that the REM will only turn fuel pump power on for a second or two without the engine running. All of your tests need to be done within a second or two of turning the key on. Trace the wiring to the REM.
 
I know this is way out there.....but like above said, fuel pump runs for a few seconds to pressurize the system......what is the fuel filter like? When you run the pump with the 9V does the system pressurize then? How much gas is in the tank?

The system could be plugged.

Also you said the car died...did it sputter or just shut off?

How old is the Battery?
 
On it...

joegr said:
So, keep in mind that the REM will only turn fuel pump power on for a second or two without the engine running. All of your tests need to be done within a second or two of turning the key on. Trace the wiring to the REM.
Click to expand...

Yes, I assumed that so I did all the tests with the meter connected and visible from the driver's seat before I inserted and turned the key so even momentary voltage would be read.

Car has 1/2 tank and was running traveling at 45mph and it quit. Would crank and die (residual fuel pressure) then later would just crank. Battery is less than a year old and I've not checked FP with the 9v battery test. Was just doing that momentarily to determine if the FP was live or dead.

I'm convinced it's a lack of power to FP issue. Stared at the wiring diagrams to no avail (a bit confusing) and I'm unsure how to trace wiring to the REM.
 
Still a little unclear...

Have you checked to see if you have power at the relay contacts? (Remove the relay. Measure the voltage between each of the two relay sockets for the relay power contacts and ground. There should be power on one, and not on the other. If there is power on one, then put a jumper wire between the two contact sockets. Will the fuel pump run now?
 
Well, sorta

joegr said:
Still a little unclear...

Have you checked to see if you have power at the relay contacts? (Remove the relay. Measure the voltage between each of the two relay sockets for the relay power contacts and ground. There should be power on one, and not on the other. If there is power on one, then put a jumper wire between the two contact sockets. Will the fuel pump run now?
Click to expand...

I will do the jumper test later tonight, but I tested both ends of that. I tested the relay, when power is applied to the coil (1-2 connectors) the open closes between the big pair (3-5). I tested the socket in the trunk and when my wife stuck the key in the ignition and turned it to run, there was power to to the 1-2 connectors.
 
Thanks for the ideas.
Well, that was weird, as the phone techs say, "cleared while testing!"
Big thanks to JoeGR, much obliged.
Went to test the relay contacts in the power box in the trunk and neither leg of the 3-5 had power. Just on a hunch I re-checked the fuse. It was blown even though I know for a fact the original was good at the time of the car dying.
I even changed it for another fuse bc the original seemed a little bent. So the new one I had changed to, a 20a which was good visually and had continuity when I installed it Sunday was blown. So I went back to the bent 15A original one that was in there at the time of the car dying.
With the original fuse back in, one leg of the 3-5 had power. So i reinstalled the relay put the key in and turned it to run, could hear the pump running, waited a few seconds, turned the key to start and the car fired right up.
So, here's my theory. One of the contacts somewhere along the line had lost continuity, the car stalls. I replace the fuse with another fuse. No go. fiddle with the connections, while testing I touch something wrong and blow the replacement fuse. While testing I get the bad connection to re establish continuity. Discover the blown 20A replacement fuse, reconnect everything, put the original 15A fuse back in and it runs.
Or, the pump really is dying, it's on its last gasp and it's going to strand me again.
It definitely has the exact same known good fuse in there now as it had when it died and wouldn't fire. How many times do I drive around the block before i trust it?
(Braces for impact)
 
RCodePaul said:
Thanks for the ideas.
Well, that was weird, as the phone techs say, "cleared while testing!"
Click to expand...

We phone techs also say that anything that comes clear while testing will be back soon, although we don't tell the customers because it's our job to clear trouble tickets, not actually fix anything. I used to fix stuff, now my whole job is to keep a ticketing system happy. :mad:

I would go ahead and replace the fuel pump if it's been in there for a while, especially since you don't seem to trust the pump anymore. Even if it's not the actual cause of the problem, it will be a problem soon if it's an older pump. Stay away from Airtex pumps unless you like replacing fuel pumps for fun. I suggest either a Motorcraft or a Carter fuel pump. Rock Auto is most likely going to be the best price for it.
 
I'd also replace the fuel pump relay and put a new 15A fuse in.
I think that most likely there is/was a loose or corroded connection somewhere, either the fuse box, the relay and socket, or the fuel pump connector. You disconnected and reconnected all of those, so it could have been any one of them. Putting a bad fuse in at the start just confused everything.
 
Cwt

Telco said:
We phone techs also say that anything that comes clear while testing will be back soon, although we don't tell the customers because it's our job to clear trouble tickets, not actually fix anything. I used to fix stuff, now my whole job is to keep a ticketing system happy. :mad:
Click to expand...

My bro worked for AT&T as a field tech then as a line splicer. He was really good, very focused on fixing things once and correctly. On one job he was the 3rd guy to be called on the same thing, the customer was pissed and said, "you are the THIRD tech on this same problem!" and he said, "That's right, that's whey they sent me." Kinda funny. Retired on a Friday from AT&T :mad: and started for the school district on Monday. Much happier away from AT&T.

My office is only 1.2 miles from the house and the kids' school 3.4 miles, so I'm going to stubbornly wait this thing out. Parts are notoriously expensive for BMWs but when the FP went in the BMW, it wasn't $230 like this one, or $600 like the Motorcraft.

Might have to search the forum on pumps in case this one is dying to see if there is a more reasonable solution.
 
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