Xsta Z 28

iTrader: (2)

Mark has the Speartech LS1 harness that has the added on fuse block. The block has three 20 amp fuses in it. Two of them I know but one I cannot figure out. They are:

1. 20 amp Orange Lead = Constant power to PCM
2. 20 amp Pink Lead = Switched power to PCM
3. 20 amp Red Lead = ????? What it this for?

Reason why I ask, is the two leads, (Pink and Red) are jumped together, in the fuse block and we were provided with one 16 to 14 gauge wire to hook up to the ignition switch.

Well the one lead providing power to the separate fuse block gets pretty damned warm, and I do not like warm wire. ( I really do not want to see Mark's Vette go up in flames. )

So anyway I am running two new power feeds through relays to run the pink and red wires to the LS1 harness, any other feed back would be greatly appreciated.

Jones'n

Maybe power for the fuel pump?

Speartech

iTrader: (14)

Yep, that should be the fuel pump circuit.

Xsta Z 28

iTrader: (2)

Well I tried running the separate fuse block with a single dedicated 10 gauge wire through a 40 amp relay, and the wire still got pretty darned hot, so . . .

To hopefully prevent an electrical melt down I broke the PCM and fuel pump down to their own dedicated 10 gauge wire lead to the battery, with a switched relay, and all appears good in the world of wiring, no more blown fuses and no more hot wires . . .

Xsta Z 28

iTrader: (2)

If that is fuel pump circuit which requires a 20 amp fuse, and the PCM is a 20 amp fuse, why do you jump those together and feed it with one small wire? You expect a 40 amp load to run through the typical ignition circuit on a conversion fuse block?

I had to run two dedicated wires with relays to run both those items to get rid of the hot wire issue. . . .

Speartech

iTrader: (14)

The fuses that are used are to protect against circuits that may become shorted to ground, etc.

Do I expect a 40 amp load to run through the typical ignition circuit on a conversion fuse block? No. I don't expect a 40 amp load at all. The biggest problem I see in swaps are wires routed through drilled holes, etc. that rub through and short to ground.

The feed side of the fuse block is fed with a 12 gauge wire. This should be sufficient for a normal operating system.

If you need two 10 gauge wires with relays to control "wire heat", I'd say you have other issues in the system.

We have LOTS of vehicles running with this setup, as well as in-shop test engines, and I've seen no wire heating issues at all.

If you are testing in the garage, drop down to some lower amperage fuses and see where you start blowing, and which fuse blows. It may help indicate where the high current draw is.

Xsta Z 28

iTrader: (2)

I'm wondering if it is the fuel pump itself. It is an after market in tank unit, no idea which one since the chassis builder provided it. That may draw more power than the OEM F-Car pump.

When I had the fuse block wired through the ignition switch the wires got hot. And would blow the fuse to the circuit providing power (30amp) when revved into high RPM.

When I had the fuse block wired through one 10ga wire and relay, just that wire got hot.

It's wierd that the problem went away with running dedicated (relay switched) power to the PCM (pink) and Fuel (red). There are no other issues with the wiring.

Thanks for your feedback, gives me some more to research.

Mark IXZD 150

iTrader: (1)

The pump is a Walbro in-tank unit but I don't know which model...

jdperk-86elco

I am using a Walbro intank pump also but I haven't powered everything up yet. I might wire it up temporally and use my DC clamp on amp meter to measure the independant loads.

I will report my results after I get back on my project. I am in the middle of moving into a new house and I can't get back on the car yet.