Casper’s Hotwire Kit Issues

Perhaps one of our computer ECM gurus might work on this! To my knowlege, the oem modulator systems are built into the ECM, and not capable of stand alone operation, nor capable of modulation of the current requirements of our large pumps.
ECUGN and Holly can do this with the newer pumps (Walbro "Hellcat Pump", DW300/DW400, etc). You need a good quality SSR (Solid State Relay) and you can set up a PWM output and table in the ECU to control it.
I have never in over 50 years of running high HP street/strip cars and high HP boats had a mechanical fuel pump failure that left me stranded. But I have had several electric pumps leave me walking, or swimming!
Why? Mechanical pumps are driven at engine rpm, so at low speeds/rpms, the pumps aren't doing much work. The electrics on the other hand, don't know what the engine speed or load is, so they are running wide open, full bore ALL OF THE TIME! They are puking their guts out making max pressure and flow all of the time! Even at idle!
Replace them, often! Once a year anyway, sell the old one to a race car guy that doesn't drive the car except once a week, or less at the track. It will last him for years!
The OEMs have solved these wear and fuel heating issues by pulse width modulation of the pumps supply amperge to drop pressure and volume in low load situations.
Until someone, MSD? Comes up with one of these modulation units for us, pump replacement is our only option.
Someone, perhaps MSD, had a resistor based unit that dropped pump voltage and current to carburated electric pumps, about 15/20 years ago. I had one on my blown BBC, 9 second Nova back in the 90s. Those worked in a carburated situation because carbs have float bowls to keep the flow constant pretty much regardless of fuel pressure. A full throttle switch bypassed the resistor stack at WOT. This won't work with FI. A Hobbs switch in the manifold could be used to shut off one of the double pumper pumps, but the main pump would still wear quickly. AND, if the system croaked, so would your engine!
Perhaps one of our computer ECM gurus might work on this! To my knowlege, the oem modulator systems are built into the ECM, and not capable of stand alone operation, nor capable of modulation of the current requirements of our large pumps.
Food for thought from the
The brushless spur this and can be run off the ecm
It's a varispeed pump

The brushless spur gear pump has the option of controlling pump speed with a 0-5V signal off of the TPS or outputs from aftermarket ECU's . Mine is controlled off of the TPS , you can hear it speed up with key on and pressing the gas pedal .
But I can't do it with the stock ecm?
Greg, the 255 that's never been used more than a few street miles in 5 years or so, cause the engines been out of my Turbo Coupe, do I need to replace it?
I will check pressure on it and replace the inline filter too. If so, with what?
The engine is done!!!!!
I'm dressing it now, headers, turbo, etc!
It's going in with the ported stock TB and upper, and stock, (was working fine 3 years ago,) MAF. I'll run it easy at low, (7lbs) boost and get a feel for everything, and install the rest of the gauges before doing anything cool. I have the Axis/maf kit too, that will go on later with the TB and upper. I'll fab my own crossover and cold air deal too. Besides, I need tires! Better than the new 255/ 55 BFG G force radials that I got in a trade, that are on it. Gonna do the rear suspension, and figure my clearances, then, I just may do a frame notch kit...
If y'all think I need to replace the pump, I'll order it now, and which one?
TIMINATOR and getting closer.....
But I can't do it with the stock ecm?
Yes , mine was installed with the stock ECM . It used the 0-5v signal from the TPS . I'm now switching to a Holley ECU and may control the pump trough it .
Care to elaborate how and with whose products you used please? Does this only work with some pumps, or all? Ya got me hooked! I need this!!!
The pumps are listed if they are variable speed , they have internal controllers and you supply the 0-5v signal . It will vary the speed accordingly . My car is with Mr Spool & chassis guy right now . This is the pump I'm using . A picture of it is in post #8
I made a mistake . The pump I listed is supposed to be AEI-11185 . The difference is the 11195 pump is rated @ 60psi and the 11185 is rated @ 90psi
AEI-11185 is the right pump . Maybe I can get the link removed .
Last edited:
The Caspers hotwire kit was designed for a single in-tank pump.

If you have two pumps in parallel, you need to separate them and run two separate relays, one for each. Your fuse and associated wiring is being pushed beyond its design limit, which causes excessive heat. When the fuse holder heats up, it triggers a "derating" on the terminals - for example, if a connector is rated at 40 amps at 80degC, its maximum rating drops to 20 amps at 120degC which is very likely the cause of your meltdown.

You will continue to see melted connectors if you keep your system as it is.

Add another 12 gage feeder, 30 amp fuse and 40 amp relay, and your issue will go away. A second hotwire kit with its end connections modified will do the trick.