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Author: Subject: Cost of rewire?

posted on 9/6/16 at 08:31 PM Reply With Quote
Cost of rewire?

I am plagued with an electrical gremlin, that I simply cannot solve. I keep melting (not just blowing) the fuse that feeds my ECU and fuel pump. I thought I had traced a short, and I have replaced the (melted) fuse box, but today, having driven 1.5 miles on my way to MOT the car, it has done it again. I have an auto electrician coming out tomorrow to offer his pearls of wisdom, but I really dont think he is going to be able to do a lot, given the non-standard wiring in our sort of cars (no real wiring diagram to go by for example).

So that has left me thinking of options:

1. Rewire the car myself.
2. Pay to have it rewired by a specialist, such as AB Performance
3. Find a local auto electrician who will take on the job, but I would be worried, as getting a bike engine running properly is not straightforward
4. Strip the car for parts (BEC engine setup) and maybe put in a simple car engine or bike engine setup, with a view to selling it as a running car next year
5. Sell it as is with the fault
6. Keep beavering away with trying to trace the fault.

Realistically, I have neither the time or inclination for option 1. My life has moved on a lot since I built the car, and I just don't have the energy or motivation to do this. Option 2 is my preference, but I suspect once I ask Andy for a quote I am going to be horrified at the cost, which might rule it out. Option 3 is likely to be cheaper than 2, but it is a gamble, as I could be left in a worse position than I am today. Option 4 would probably bring me back the most money, which would be nice. My car has a lot of trick parts, and carbon on it. Option 5 seems like a bad option to me - worst return on my time and money, and it is conceding defeat. Option 6 is what I am working on at the moment, but honestly, I cannot be bothered with it. I wanted to drive it this summer, and both times I have had it out, I have melted fuses!

So that brings me back to the subject - what would a full rewire cost for a BEC installation? Arguably, the sparky could use a lot of what is there if they wished (no issue with the majority of the loom, I think), but I want a turnkey price that says 'pay me x and in two weeks you have my guarantee of a working car'. Similarly, if anyone on here wants to entertain this, I would be up for paying a LCB member to do the work if it came with some sort of warranty/guarantee (i.e. I am not paying for something that melts after a couple of drives - I can do that myself!).

I have honestly never felt so despondent for my car - torching it is option 7! I built it, and have done an engine swap and it has been driving for 7 years quite happily, and now it seems to be kicking my backside!

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posted on 9/6/16 at 08:41 PM Reply With Quote
Is it just the fuel pump that's the issue? Do you know how it's powered? Is it switched off the ecu? Etc etc have you tried wiring straight to the fuel pump?
Had issues like this before with a rally car, feel your pain but usually it's somthing simple to sort, or bodge :-)
Where abouts are you in Derbyshire?

You can live in a car but can't rally a house

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Smoking Frog

posted on 9/6/16 at 08:48 PM Reply With Quote
Add a in-line fuse to the fuel pump. If this blows at least you know where to look.
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posted on 9/6/16 at 08:50 PM Reply With Quote
Have you checked the regulator/rectifier, it could be over charging, i had similar problems with the ZX9,went through a couple of reg/rec units, eventually i took the charge wire direct to the battery positive, rather than to the fuse box as. never had any problems after that.
If they go faulty it can be shoving 30-40v DC into the system. put a meter on the battery and rev the engine, you should not get more than around 14v

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posted on 9/6/16 at 10:34 PM Reply With Quote
No, not just the fuel pump. The fuse does both the ECU and the fuel pump. On both occasions it has blown another fuse as well. The first time, it blew the fuse for the ignition switch (which also powered other switched circuits such as my dash). This time it has blown a different fuse, which is labelled as 'Ignition control', but the wiring diagram I have is such bad quality that I cannot tell what it is powering. I am fairly sure it goes to the kill switch and starter button. The fuel pump is powered via a relay (and the ECU relay) and it is switched by the ECU via the relay.

I don't know it is the fuel pump - it could be a fault on the fuel pump wiring, or indeed the ECU, but given the fuel pump is the largest load (I assume compared to the ECU), it looked like a culprit. Someone at work suggested a tired or partially blocked fuel pump could cause this, as it draws more current to maintain pressure/flow, and hence pop goes the fuse (or melt goes the fuse in my case) - does this sound likely? Can the current it is pulling be tested some how? I could break into the fuel pump wiring, and power it directly from a fused feed - this would allow the engine to run, whilst isolating one major load - I will suggest this to the spark tomorrow.

I have not checked the reg/rec. The first time it went pop, I was really gunning it, this time, I was just tickling along. I assumed a failing reg/rec would be more likely to cause issues at higher revs (when it is creating higher voltage/current). The charge wire does worry me,. I traced it the other day, and it is not that thick. Plus my reg/rec connectors are all either lightly burned, or just dirty - it is hard to tell, and certainly hard to tell how old the marks are. I can check this with the sparky once we bypass the molten fuse panel!

Phil - I am based just to the north of Derby, in the Morley area.

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posted on 9/6/16 at 11:13 PM Reply With Quote
No need for the charge wire to be heavy duty, but regulators don't like corroded or dirty connections. By wiring it direct to the battery it takes out any uncertainty.
Check your charge voltage first off, and rule it out if nothing else. It's a common problem on bikes and bec's.

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posted on 10/6/16 at 08:11 AM Reply With Quote
I bought a ready made loom to that was designed to fit in my car. However I ended up making so many changes and adding circuits in here and there that it doesn't resemble anything like what it did or should. At some point in the future I'd like to remake the entire loom but I just don't know if I want to set about such a large task. If I were to remake the loom I'd take the old loom out and use it as a template. I would also have three self contained bus bars under the dash (Earth, Switch +ve, and Perm +ve) with two fuse boxes. I would leave plenty of space for new circuits to be added at a later date.

The problem I have come across on my ready made loom is the manufacturers made no allowance for adding new circuits later. There is no space in the existing fuse box so a inline fuse is the only option making circuits more and more complex.

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posted on 10/6/16 at 11:40 AM Reply With Quote
I hope you sort this - I'm interested in the results if you could post up if you work out what's causing the problems.


When all you have is a hammer, everything around you is a nail.

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posted on 10/6/16 at 02:11 PM Reply With Quote
I have an update. I had the auto sparky out this morning, and whilst he did not fix it (or find the root cause), he has made some findings that give me some direction. He spent some time with me looking for shorts/chaffed wiring on the circuit, but found nothing obvious (no current drain with the circuits off). He bridged the (melted) fuse with an old school ammeter, and we were able to assess the current load with the ignition on (6A dropping to 0.5A once fuel pump had primed), and with the engine running (4-6A with no other circuits powered).What was strange was that as we turned on other circuits, we were seeing a rise in current - despite this being supposedly just the circuit for the fuel pump/ECU. With the engine running, and the headlights, indicators and brakes on, we were peaking at 15-25A, which is of course above the 15A rating of the fuse.

So we disconnected the reg/rec and did it again, this time, it peaked well below 15A - more like 6-8A, and no change when we turned on other loads. So that got us thinking.... Is the charging circuit also attached into the ECU/fuel pump circuit, and effectively, when we apply other loads to the vehicle, the generator tries to match the load, and feeds it back through the 15A fuse that controls the ECU/fuel pump....? the sparky suggests charging the battery, and disconnecting the reg/rec and going for a drive, and see what happens. I am also going to track the wiring fully to see where this cable goes, and what circuits it powers. I will also check the wiring of the rec/rec, and see if I can set it so that it has a direct feed back to the battery (or at least to the permanent live feed in the fusebox) - this is similar the concern raised by Wadders. FYI, the battery was charging at 14.4-14.8V, so I think that is ok and indicates that the reg/rec is functioning correctly.

So progress, but no definitive fix yet!

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posted on 10/6/16 at 04:05 PM Reply With Quote
are you talking about the fuse that sits in / near the starter solenoid?
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posted on 10/6/16 at 04:27 PM Reply With Quote
Originally posted by BaileyPerformance
are you talking about the fuse that sits in / near the starter solenoid?

I don't know as i am not using the original bike fuse box - I wired it into my existing fuse box 4 years ago as a standalone loom, so the engine loom is separate to other functions.

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