O'k, it is possible my pump relay has an intermittent prooblem. I was using it to switch on two relays, one for my surge tank pump, and one for my main pump.

1- first symptom, turn car off pumps keep running, turn it off a second time, and pumps turn off.
2- Next, I turn on the car, and the pumps prime, switch the car off, and then on to prime a second time, Nothing... (used to prime twice no problem, prior to setting up two pumps)
3- Some times pumps will continue to run after shutting the car down, ie car is off pumps are running, I have to diconnect the battery.

4- Now, we remove the ECU cover, and find the the +12V wire for the pumps had been grounded intermittently due to crushing it w/ the ECU cover panel. We decide that perhaps we have fried the pump relay circuit in the ECU. Solution, Use a PWM to fire the pumps. (so we used the engine accessory selection), but pump is now on whenever acc. is on, and still have the problem that sometimes the pumps run when the key is in the off position......

5- Problem, Aux Pump PWM out requires at least 500 rpm ( Can I change this?)

6- I need a PWM selection that will turn on with the key and work at cranking speed(starter), and turn off at zero RPM for safety. I tried the Engine accesory PWM setting, but it too seems to be malfunctioning, ie as soon as the car is connected to the battery the pumps are on(key in "off" position)

7- I am sure I must be just doing something wrong with the wiring, but I cannot figure out what.

8- So, I suppose I should have tested the pump relay circuit before re-wiring, how do I test this( ie what voltage should I see, and I assume I should see it for ~20 seconds.

9- These are all brand new bosch relays, how do I test a relay?

10- crap
11- This is less fun than I thought....

11.5- Seems like I must have some other intermittent power being sent to round somewhere in the car, Yes?

12- If anyone wants to use their night time minutes, and call me, my number is 707-696-2705, and I'll be home after 6pm PDT. Thanks, Carl

 

I would first check all the wires that are a source of power to your relays, and verify that you know which conditions give them power. The FSM will show you which wires get power from the battery, when the key is in the accessory position, the cranking position, and the run position.

Next, I wouldn't use a relay to operate two more relays. I would use the orange fuel pump wire on the Haltech wire harness to give power to the low voltage side of each of the two relays. Then the relays can close the circuits that allow each of the pumps to run.

 

I figured out the problem. in essence, each relay was wired differently. You can wire a relay to operate either by giving it a ground, or by giving it power. One was wired each way in parralel, thus the lift pump operated correctly, and the main pump stayed on. I suspect the pump relay wire (BLK/YELLOW) is fine. I am not using a relay to run two other relays, hjust using the name for the wire in the Haltech manual. thanks, Carl

 

since I cannot start a new thread, I will continue on this one... I just noticed in my manual that it says not to run more than one relay off the pump circuit... anyone know why? I am currently running one for my lift pump, and one for the main pump. I am going to need a pretty hefty relay, as it seems the A1000 is draing more than 30 amps. My 10 gauge wires are getting warm after 10 minutes or so. Anyone shed some light on the two relay thing?

 

the way the ECU switchs the load it can only take a small amp draw. basicly the ECU can safely handle the load of one Bosch type relay safely. With some creative wiring you can use the load side of the original Haltech fuel relay to switch several other small bosch type relays, or better yet use the ignition switch lead to trigger the extra relays. just be sure to make the wire size appropriate to the load, and if the wire is warm it needs to be alot larger.

 

Carl,

PM me a contact number and time to call. I'll set you up: I run a Cosmo intank and a A1000 off of the surge tank. Spent 7 hours taking harnesses apart harnesses and monster wiring to get 13.6v at both. The Haltech wiring recommendations are less than optimal.

 

Yeah, like he said.

The smaller a wire, the more resistance it gives to the flow of electrons. (Amps is the measure of electrons per second). Resistance causes heat. The power source in the car is the battery and/or alternator, which is capable of putting out amps in the hundreds. But it only puts out as much as the circuit requires. This is called draw, or load. A fuel pump needing a max of 30 amps has to have wiring that will support more than 30 amps, or 30 electrons per second. The weakest link in the circuit shouldn't be the wire, it should be the fuse; in this case, say a 30 amp fuse.

A smaller wire will be able to handle less amps. If you were to use something like an 18 gauge wire which has a lower amp rating on the fuel pump circuit, it would burn through the shielding on the wire, exposing the copper wires on the inside, which would then most likely burn the carpeting around it, or other wires, or contact the body of the car which is metal.

Since electrons follow the path of least resistance, they will all flow toward the body of the car if the wires contact it. The draw, or load will then become extremely high since the body can draw a lot more electrons or amps then the pump could. This is called a short circuit, short, or short to ground. The extremely high amp flow will finally overcome the fuse rating of 30 electrons per second, and cause it to break which disrupts the circuit.

If you have a thicker gauge wire, like a 10 guage wire, it can handle more amps and be safely used in a fuel pump circuit. BUT, if you add so many devices to that fuel pump circuit that the total draw of all the devices added together is greater then the 30amps that the fuse or wiring in that circuit can support, then you start to run into the same problem as the example above.

This is why the book says not to use multiple relays in that circuit. The ciruit wiring and devices are designed to function pretty close to their rated limit, which leaves little room to add other devices since those devices will overload the circuit and cause damage. So your alternative is to use another source of power and find another way to switch it on and off as suggested by Tims.