97 Villager blowing Fuel Pump Fuse

[GTGT_bangbang]

NOTE - see final posting in thread for resolution

symptoms;
1997 started blowing fuel pump fuses any time the key is turned as far as 'start', ie , wont blow the fuse on 'run' ( started 40 miles into the desert but oh well).

So far apparently everything checks out OK;
good voltage from battery to fuse, no shorts.
good voltage to pump relay power-in, no shorts
good voltage on pump relay control legs, proper 5-second signal

Given all the upstream checks, its also true that disconnecting pump harness at rear of tank (disconnecting pump and level sender) prevents fuse blow.

Powering pump up directly with battery charger through a fused jumper runs pump but does not blow fuse, whether using the wire to ground or creating a chassis ground.

No shorts on wire from pump relay to pump.
Good connectivity through pump to impact switch to ground.

Good resistance through pump ( .5 to 5 ohm range, measure 2 ohm).

No shorts on power wire from rear connector at tank to pump.

The only thing that seems strange is the power wire into pump has connectivity to fuel gauge pins.

Anyone ever metered the pump & sender to find that?

wow just made me think to open impact switch ( breaking ground to pump), plug the at-tank harness, and look for grounds through the power wire. Should be none unless the sender is grounding the pump power.

any one have a similar stroke of luck ?

[jdl]

In your testing, did you use 15 amp fuse? I might have to replace wiring from fuse to fuel pump relay, the from relay to pump.

Diagram below.

[jdl]

You may need to check fuel pump amp draw? What is fuel pressure spec? How long since a tune-up?

[GTGT_bangbang]

appreciate your reply! Thanks

15A being the spec fuse ( blows immediately upon key@START, blowing so fast, I never hear the pump run), so during the 2:30AM-in-the-desert test, it pump blew a 20A fuse soon as key@START. I wasn't ready to smell a 25A fuse test, although the wires to pump are pretty hefty gauge, so maybe soon ...

I powered the pump up using just a battery charger (ie disconnected pump, thus car wires mostly not involved) with a 15A fuse in line the jumpers, and the pump worked continuous without problem & motor ran fine. So although I have a pump coming from rockauto, I don't believe that will be the problem.

The fuse is blowing so quickly after key@START, before any pressure builds, so while I have not checked P, it's rather early in the sequence to be that. It's also kinda obvious that the pump is pulling too much current (after all fuse blows) but I didn't rig up a Current check and I don't have a good clamp-on pick-up. Meanwhile resistance across the pump is OK at =2ohms (spec range is 0.2 - 5 ohm). Seems sounds like a good pump, ya know?

~~~~~~~
The interesting check as mentioned late in first post; after tripping the impact switch (near driver foot, which should disconnect pump's intended path to ground), but everything else hooked up, the fuse STILL blew with key@START. (recall that disconnecting pump back at tank connector does NOT cause blown fuse, thus power wires from under-hood & back to pump check out OK.

Probing the pump side of the disconnected pump+gauge harness ( two wires power the pump, two wires for the the gas gauge signal), there is continuity between the pump power-in wire and the fuel level sender wires ... between pump hot wire and one side of the gauge, there is ~3ohm (much like the pump) and 80 ohms between the pump hot and the other gauge wire (80ohm just like the half full / half empty ('pends on your optimism) tank gauge, which it actually is)...

But to make things confusing, there is no connection to chassis ground through the pump>gauge path. At least not during a key@ON, (I didn't have a helper to toggle key to START while I metered.)

I do have access to an earlier Villager tomorrow, and I am going to check that ones connector at the tank to see if path between pump and gauge circuit is normal.

I think the pump is shorting through the sender & gauge circuit and somehow only during key@ START, but damned if I know where or how without dropping the tank, waiting for pump to arrive as insurance before I do that next.

~~~~~
Kind of complicated, hope this makes sense + hope this helps somebody else NOT replace a pump for no reason , I have read a lot of "new pump didnt fix blowing fuses" posts.

Enjoy

[GTGT_bangbang]

opps duplicate post

[GTGT_bangbang]

if this were my piece of crap, it would probably run fine if I just cut both gauge wires, isolating pump, and keep it above 1/4 tank for time immemorial, but I KNOW if I applied that "appalachian american engineering" fix, my daft brother in law would be calling me to "bring some gas to the desert, I'm stuck in the 'zact same gawdforsaken place"

[GTGT_bangbang]

to sum up;

'97 Villager started blowing Fuel Pump power fuse (the 15A in fuse box near battery).

Traced all pump wires and components, found no short circuits to ground on power side wires, found correct connectivity on ground side of pump, resistance across pump was correct, 'bang head here' label correct, ie everything checked OK.

HOWEVER, measuring at the rear connector (connector behind tank, wire half going ~into tank...) and checking resistance between pump power / ground wires AND either fuel level sender (or 'gas gauge') wires, I was able to find connection to the fuel level sender THROUGH the power wires. In other words, between one power>gauge wire pairing, you could again measure just the pump resistance, while with the other power>gauge wire pairing, you could measure the resistance for the existing fuel level (+ a couple ohms from the pump). In short (hehe) the pump got connected to the float level thingy and started puking fuses. Whats more, the pump did not actually GROUND (to frame) through the gauge while metering with car off (I didnt or wouldnt try under other conditions), so the root issue is a conditional short through the gauge circuit ( 'conditional' or temporary, as it probably only shows up during START or possibly after engine already running). Sort of amazed the Eng Control Module isn't smoking A Big One due to the fuel pump sending power through it.

Measured another (earlier) Villager and found, as expected, the pump should NOT be connected to the sender.
To my best info, the dash gas gauge read correct up to the moment of boof. Don't really know ...

I have seen more than a few posts around web laying out 'fuel pump fuse blowing, replaced pump, fuse still blowing'.

I think you could verify this condition without getting under the car simply by installing a good fuse, tripping the impact switch (breaks normal / expected ground for pump) and trying a START. If fuse still blows, you might have the same problem.

I cut the two small wires on the rear connector ( those going to/from the fuel gauge sender, which isolates the gauge from the rest of the vehicle) and vehicle runs fine, only thing is gas gauge of course inaccurate, reading full.

This tidbit could save your bacon miles from home, or even get your big big brain possibly laid for being a Hero (ymmv), as your secret info source will be safe with me.

I don't know exactly where the short between pump and sender circuit is, going to drive the tank dry & then drop the tank to inspect pump & sender, but should be easy to isolate after the pump & sender removed from car.

One final note, on earlier Villagers, the fuel pump power circuit ALSO powered the Idle Air Control, so a shorted / failed IAC could also blow the fuel fuse, but net symptoms would probably be a little different. If you have this situation, disconnecting the IAC should keep a new fuse from blowing although I dont know how well the thing would run. Maybe balls out to the nearest comfort zone ...
Later year Villager / Quest removed the IAC from that pump circuit.

Luck to all you Villager townspeople. Bye ! GTGT

[kpooch]

Hey there GTGT what was the outcome of the blown fuse issue, I have the same problem on my 97......

[GTGT_bangbang]

low down birds eye view was


there was positively a short between the pump's power wire and the pump's metal cap (plate which bolts to the tank), or more exactly some breakdown in the power wire's feedthrough bushing on the cap.

Replacing the entire fuel pump (pump and metal bracket) was required.

Once I had the pump out, you could certainly measure the short (pump hot wire to cap) but breaking the old pump apart (if I recall, the wires are bonded together and you can't remove the wires without breaking it) then damned if I could see the actual short. I had expected to see an obvious wire short inside the tank but nope.

Make sure you put index marks on the old pump & tank before you pull it, as it is not 100% obvious installing the new pump which direction must face to let the float arm clear splash wall inside.

[GTGT_bangbang]

one other thing maybe noted I dont know;
I think I proved this this tidbit out later,
plus it has been awhile but easy to test;


because the power wire short went to the pump plate cap, and then shorted to ground but only THROUGH the fuel pump collision switch (under the driver's kick panel), opening the collision switch ( hard flick, pry the top up) cured the short and would have let the vehicle drive home (after replacing the original fuse.)

my lawyer told me to tell you - just don't leave it that way if you like to get rear ended and want to sue me for the lost gas spewed out on the road