Fuel pump fuse keeps blowing - why?

Fuel pump fuse keeps blowing - why?

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zed4

Original Poster:

7,248 posts

223 months

Sunday 8th December 2013
quotequote all
Hi,

So, got up in a great mood today, we were off to the Hampshire TVR club Christmas dinner! The car was clean and waxed and ready to go. It started up but did sound like it wasn't running on all cylinders for a couple of seconds. Then it ran fine, although the fuel pump pitch kept changing, suggesting the pump was running faster and slower.

Then, 4 miles down the road, sat at idle, it spluttered and stalled. It was completely dead and wouldn't turn over. I pressed the immobiliser button a few times, nothing, plugged in the fob a couple of times and eventually it did turn over, but wouldn't start. Then I couldn't get it to turn over again.

I checked the fuses and the fuel pump fuse had blown. I swapped it for another 20A fuse and it popped again, so left it by the side of the road and got a taxi home. Then drove to the dinner in our reliable Honda!

On the upside, I had a nice meal at the Milburys and enjoyed chatting to everyone.

Hope to hear of some solutions. I plan to have a look at it tomorrow night.

Dan

zed4

Original Poster:

7,248 posts

223 months

Sunday 8th December 2013
quotequote all
LongBaz383BHP said:
Check out my thread ' Its broken'
Thanks, I'll have a look at that wire tomorrow.

zed4

Original Poster:

7,248 posts

223 months

Sunday 8th December 2013
quotequote all
zed4 said:
LongBaz383BHP said:
Check out my thread ' Its broken'
Thanks, I'll have a look at that wire tomorrow.
Just checked all the wires, all seem fine. No signs of any having been worn at all.

Ps. Southways have made a very tidy job of routing and securing all the wires under there when they did the cam. Looks much better.

zed4

Original Poster:

7,248 posts

223 months

Sunday 8th December 2013
quotequote all
PRTVR said:
I don't know the design of the pump but would the load on the motor go up if the fuel filter was blocked perhaps leading to the fuse blowing.
Pretty sure the fuel filter was replaced during the major service recently.

zed4

Original Poster:

7,248 posts

223 months

Monday 9th December 2013
quotequote all
keith2.2 said:
That doesn't mean anything if your tank has anything spurious in it.

An early issue I had with mine was the engine trying to die on me intermittently. It already had new pump and filter so the tank was removed and drained - there was an "unknown substance" in the bottom of it that had blocked the filter. The tank was cleaned out, filter and pipes replaced and all was well (with fuelling at least!)
Fair point. I will bear that in mind.

zed4

Original Poster:

7,248 posts

223 months

Monday 9th December 2013
quotequote all
NZ fan said:
If the fuel pump fuse blows immediately the it shouldn't be too hard to diagnose. I would start by removing the power wire off the fuel pump. (If not sure which is power remove both) replace fuse again and see if it blows. If not the your pump has gone to earth ( bad). If it still blows then the wire between fuse and pump is going to earth. (not so easy o trace). Good luck. my money would be on a bad pump, seen it a few times.
Right , disconnected the fuel pump, switched on the ignition and the fuse pops straight away. So that rules out the pump, wiring problem somewhere then.

zed4

Original Poster:

7,248 posts

223 months

Monday 9th December 2013
quotequote all
Bit more fault finding.

Swapped the relay and it still pops the fuse. Took the relay out and it didn't pop the fuse. Really need a wiring diagram now. What's on the switched side of the relay, is it just the pump, nothing else?

zed4

Original Poster:

7,248 posts

223 months

Monday 9th December 2013
quotequote all
Can someone tell me which relay is for the fuel pump please? The blue connector or the brown one?

I've tested them both, one tests for continuity to earth on two connectors, the other tests one three.


zed4

Original Poster:

7,248 posts

223 months

Monday 9th December 2013
quotequote all

zed4

Original Poster:

7,248 posts

223 months

Monday 9th December 2013
quotequote all
I've tested the relay outputs, but each relay is giving me different results. I need to know what they should be really. Trying to get hold of a wiring diagram.

zed4

Original Poster:

7,248 posts

223 months

Monday 9th December 2013
quotequote all
Calling it a day now, too tired to try and get my head around the multimeter readings!

Also, I've traced the fuel pump yellow wire back from the fuel pump to the connector behind the carpet, by the passenger's seatbelt, and it's got continuity from the pump to the connector there. But it's not buzzing back to any of the pins on either of the two relays! Also, I've checked for any shorts on any of the other pins on the connector and there aren't any. I've also checked the live feed to the pump (at the pump connector) against the ground and there's no continuity, so I can't see where there's a short.

Still more investigation to do then.

Edited by zed4 on Tuesday 10th December 00:04

zed4

Original Poster:

7,248 posts

223 months

Monday 9th December 2013
quotequote all
Mark. said:
Did you get my mail Dan?
Yes thanks, just going through the diagram now.

zed4

Original Poster:

7,248 posts

223 months

Tuesday 10th December 2013
quotequote all
If anyone else has any more info or help for me, discussion has moved more towards this thread now: http://www.pistonheads.com/gassing/topic.asp?h=0&a...