Fuel pump problem, runs ~5 secs then blows fuse

[Welcome to Hell A]

1997 D1. The fuel pump fuse is blowing after ~5 seconds of running normally.

New Master pump installed ~4-6 months ago, and has run great since. I can hear the pump when I first put the key in but do not start it. Only after starting the car does the fuel pump fuse blow.

One additional piece of info that might be handy is the disco has been throwing a code for a while: P1191 'Oxygen Sensor Heater Circuit Open Downstream'. The code has been largely ignored by me due to people claiming the downstream sensors don't do much toward engine performance since they're post-catalytic convertor.

I have looked at the connector on the top of the fuel pump, and as far as I can tell it looks fine...nothing looks shorted there. I also looked at the connector near the right rear tire that the fuel pump leads too. No signs of shorting seen there, from what I could tell. Just a bunch of dust inside. The front O2 sensors do not have any chafing on the wires. The right rear O2 sensor visually is fine as well. I haven't checked the left rear.

There was a thread by vray where he had a similar problem, but the resolution was not posted. http://www.discoweb.org/forums/showthread.php?t=43306&highlight=fuel+pump+fuse+blowing

Fuel pump relay? Kinda doubtful, since it doesn't blow until the truck is started.

Fuel filter? Possible, it needs to be changed.

O2 sensors need to be changed? Yes, but...Whiskey Tango Foxtrot if that could cause the fuel pump fuse to blow.

Little help here? Please, and thanks.

Jeff

 

[ptschram]

It could well be the oxygen sensor. On the earlier trucks, power for the oxygen sensors was run through the fuel pump relay. I'm waiting for my Rave to boot up so I can't see the schematic yet...

 

[Welcome to Hell A]

Sweet, I didn't even have to page you using the white security phone.

I looked at the Rave CD as well...but I'm at a loss when it comes to electrics. Thanks.

 

[ptschram]

LOL, the Rover Bat-phone is down today and we have the Rover Bat-signal turned off for the weekend.

When looking at the diagrams, just consider the lines to be pipes with little electrons moving down them. If the wire to the fuel pump is also tied to the oxygen sensors (my acrobat got corrupted somehow and I can't look at the pics right now), you at least have something to go on.

Stick by me kid, I'll have you reading schematics and using a meter in no time!

 

[Welcome to Hell A]

Alrighty then. Looking at Page 23 of 591 in the Rave cd... aka multi-port fuel injection V-8 circuit diagram page 3... the O2 sensors do go through the fuel pump relay, then on to the engine compartment and satellite fuse box.

I'll go ahead and order two of those AMR6244 thingy's for $119 each through British Pacific (close to home) and see what happens.

Thanks again. I'll try to remember to post here when I get them installed probably next week, so anybody searching knows the resolution. Going out of town until the end of next weekend.

 

[MUSKYMAN]

first unplug the 02's and make sure thats the issue.

you can also have a short at the pump from the clamp that holds the hose on.

the two exposed studs on top of the pump are live if they short to say the clamp on the little hose it will blow the fuse as well.

 

[ptschram]

first unplug the 02's and make sure thats the issue.

Thanx Thom. We can also supply power to the fuel pump independent of the same fuse to see if it is the pump (see, I told you I'd have you doing electrical work!).

When using the RAVE, always go through the entire file to make sure you're looking at the correct file. If you have a GEMS engine, make sure the file doesn't show a distributor or just two ignition coils!

 

[Welcome to Hell A]

I will unplug the O2 sensors as soon as I can and see what happens when it starts.

The top of the fuel pump is not showing anything making contact with anything else...and I don't see the two exposed studs you mentioned, Thom. I'll take a picture of the top of mine and post it up later.

I will attempt the impossible--jumping the fuel pump off another fuse--after unplugging the O2 sensors. I'm afraid of causing more problems if I do it wrong.

Thanks for the suggestions, I should have but did not think of them.

 

[MUSKYMAN]

I will unplug the O2 sensors as soon as I can and see what happens when it starts.

The top of the fuel pump is not showing anything making contact with anything else...and I don't see the two exposed studs you mentioned, Thom. I'll take a picture of the top of mine and post it up later.

I will attempt the impossible--jumping the fuel pump off another fuse--after unplugging the O2 sensors. I'm afraid of causing more problems if I do it wrong.

Thanks for the suggestions, I should have but did not think of them.

here is a pic of a pump similar to many that people have swaped into the rover after theirs went bad.

I have circled the studs that are live...see where the hose goes on the top...if the clamp used contacts those two studs it will short and blow the fuse.

 

[antichrist]

Thanx Thom. We can also supply power to the fuel pump independent of the same fuse to see if it is the pump (see, I told you I'd have you doing electrical work!).

That's what I did to confirm my pump was bad. Made a jumper wire from the pump to the battery with a 15amp fuse in line. I think it was 15amp, but use whatever the fuse is supposed to be.

 

[MUSKYMAN]

think its a 10 amp fuse

 

[Welcome to Hell A]

I'm back, after a week out of town, and week of being sick, and a week of rain. The supercross in SF is always fun.

Okay, the downstream O2 sensors have been unplugged and the fuel pump fuse promptly blew, this time even before the engine was started.

Next, I was going to make a jumper to the fuel pump and see if it is the fuel pump after all. I am guessing the problem is actually a short somewhere, because the battery is going dead. Correct me if that line of thinking is wrong. For the jumper, I don't know exactly where to contact the positive wire...or the ground. Any suggestions, from my picture of the top of the fuel pump?



Silly question: Was the suggestion to jump the pump while the pump is in the car, or out of the car...on the lawn or something? I assumed in the car. Thanks!

 

[Welcome to Hell A]

Can I get an amen?

 

[peter sherman]

White purple is the posi imho

 

[Welcome to Hell A]

first unplug the 02's and make sure thats the issue.

you can also have a short at the pump from the clamp that holds the hose on.

the two exposed studs on top of the pump are live if they short to say the clamp on the little hose it will blow the fuse as well.

Thanx Thom. We can also supply power to the fuel pump independent of the same fuse to see if it is the pump (see, I told you I'd have you doing electrical work!).

I finally got to work on the problem today since it was relatively nice out...shorts and t-shirt weather.

I jumped the pump directly off the battery and it was still blowing the fuse. The problem was the clamp shorting the two studs on the pump itself. To keep the clamp from contacting the studs, a teflon disc was inserted between the clamp and the studs after drilling a hole in the disc itself to pass the fuel line through. Forgot to check if teflon degrades in water... googling now. Google says it's inert in most things, gasoline included. Good to go. Pure teflon is great stuff.

Thanks for the help. Problem solved, hope this helps someone else.

 

[MUSKYMAN]

glad you found it:applause:

also glad you were not dealing with a almost empty tank :jumpfire:

You did the correct thing by using a fused power supply when testing the pump, I would also say people shouls always remove the pump from the tank when testing the pump in this way.

I am going to link the pump replacement thread to this one so people can avoid this very clear hazard when replacing their pump.

Thom

 

[Welcome to Hell A]

I should clarify something. It was a clamp that was shorting the fuel pump, but not the fuel line clamp. The clamp that holds the fuel pump in place at the bottom of the fuel pump housing is the clamp that was causing the short. It is conductive, but it took a few months for the strange corrosion on the clamp to wear off on the two live studs on the top of the fuel pump. The teflon disc is separating the live studs from both the fuel pump clamp and the fuel line clamp.

I don't recall what the original fuel pump looked like--whether or not it had the exposed live posts on the top--but at the very least they weren't as prominent thereby not shorting the pump.

Thanks again for the help.