RF Interference with EFI System

[speedster]

Has anyone had problems with electric water pump interference with the crank trigger and/or EFI computer on their car ?

Anyone know of a solution ?

Any help or people to contact is greatly appreciated.
-Bruce

[Jim Nilsen]

Hey Bruce, The only way to stop interference is with sheilding. You may be able to just sheild the wires but you may have to put a sheild between the 2 parts with a piece of aluminum or stainless.

Corvettes have had to put sheilding on the ignition parts of the early cars to stop RF for the same reasons. Those polished covers over the distributors and wiring were for a reason other than looks.

Line of sight is how RF is transmitted so a barrier in between will work.

Hope this helps.

Jim Nilsen

[Charley Lillard]

Also make sure their are no splices in the crank trigger wires.

[Fuelie Fan]

How do you know that this is your problem? Do you know that it is RF (through the air) or EMI (through the wires)?

As a note, as mentioned above crack pickup should always be wired using shielded cable.

[speedster]

Hey Guys, I really appreciate the info.

This was brought to my attention by the engine builder, Tom Nelson.
He said that they were having all kinds of intermittent problems and when they figured out what it was (electric water pump to EFI interference) they ran the water pump from a separate battery, i.e. a separate hardwired electrical circuit and the problem disappeared.

So in answer to your question, it must really be EMI, not RF.
I guess that means when I go out for the dyno test, I will need to bring gobs of sheilding material to see what works.


-Bruce

[Fuelie Fan]

I don't think shielding will protect against that problem, you probably need better power and ground distribution, and you need to examine your wiring design for ground loops as well. Shielding usually is only effective against airborne noise.

I know a few times when we went to the dyno, power systems were often wired very "hastily". Don't shortcut.

[speedster]

Thanks Fuelie...

I will probably put in a diode(s) and maybe a cap on a dedicated water pump circuit [Looks like this circuit will have to have both power and ground isolated]. Want to avoid feedback to the master system as much as possible. If you have another suggestions, feel free. I am open to whatever works.

Thanks,
-Bruce

[Sparky]

An Electric Water Pump will through off EMI (Electro Magnetic Interference). Any time you have an Electric motor with an Armature and Magnets and this device is powered up, it will produce EMI. The same can be said for an Electric Fan, and Electric fuel pump.

Even relays can through off a small amount of noise, due to the relay being charged with voltage to create a magnetic field, to pull the mechanical arm inside the relay form an open state to a closed state.

A Crank Trigger will throw off voltage as well. But the voltage a Crank Trigger will generate is AC Voltage and can generate up to 70 volts AC or more at 4000 to 5000 RPM. MSD does offer a Shielded Cable for Crank Trigger Applications. I use this cable specifically with every car I have wired, without any EMI issues. This helps reduce the cross talk (noise from other components), to interfere with the Crank Trigger Signal by isolating the Signal within the shield.

I have seen more times then not, poor and improper grounding methods that are practiced, literally add insult to injury to an electrical system.
Grounds are the #1 part of an electrical system which people abuse or overlook.
Depending how your electrical system is laid out, using various different grounding points can lead to ground loop problems, the same can be said for power, if you pull power from different areas, it will cause power strains, which will make components react differently then if they receive a proper power source. I would recommend one central power and grounding point, this will help eliminate ground loops and power strains.

I hope this helps
Sparky

[speedster]

Thanks for the info Sparky.
Sounds like one central ground point would be better than an isolated circuit for the water pump. I have always run a ground wire from the trunk mount battery to the front of the car instead of just relying on frame only ground. I will definately shield the crank trigger pick up.
The water pump is a Meziere 55 gpm 300 series.
The crank trigger is Electromotive Direct Ignition.
I guess I will bring a spectrum analyzer home from the office and check for interference once everything is set up.
My biggest fear on any of this is to have a signal that would cause a dangerous lean out or plug misfire under full power/full boost. Then I would have a very pretty, "blown" engine.

Thanks again.

[Sparky]

I understand that the Electromotive deal is all self contained (Injection and Ignition).



One of the leading causes of a miss fire condition in a fuel injected application, especially when you have a stand alone EFI and stand alone Ignition, is when the ignition and EFI are on different playing fields as far as ground is concerned.

For example: The point’s driver on the EFI unit sends a ground signal to the Ignition. Points wire, this signals the Ignition to fire the coil. The point’s driver signal is typically 300Mv or (.3 of a volt). The problem occurs when you have Ignition grounded in one place and the EFI unit grounded in another. If the difference between these two points is let’s say 150Mv, then your ignition is only going to receive a 150Mv signal, which is not enough to satisfy the Ignition, which results in misfire. This is just one example of how important the Ground side of any vehicle can be adversely affected if not done properly.





Is your Electromotive Crank and Cam Signals Hall Effect or IPU? The reason I ask is, the MSD Shielded Cable will not support a Hall Effect Set-up only IPU. But I have shielded Cable here that will support Hall Effect.



I hope this helps,

Sparky

[speedster]

Hey Sparky -

At this time I do not know if the ignition is hall effect of IPU. (Don't mean to be ignorant, but is IPU = Inductive Pick Up?) I read through the Electromotive stuff and it just says a magnetic pickup with 3 wire shielded cable. As the engine gets closer to completion and dyno testing I will have more info. I will definately keep your name on my contact list for questions if you don't mind. You really seem to know you stuff.

Thanks Again,

[Sparky]

IPU is Inductive Pick Up.
The easiest way to tell the difference between Hall Effect and IPU is, Hall Effect usually has 3 wires (Power, Signal and Ground), as IPU has 2 Wires ( Reference Hi, which is Signal and Reference Low which is a Ground)
A Hall Effect creates a Square Wave Pattern due to the on/off nature of the sensor and the IPU creates a Sine Wave.

Let me know if you need any further help
Sparky

[speedster]

Sparky -

Thanks again for all of your info. I will take you up on your offer as we get close to dyno time.

Very much appreciated...people like yourself our what makes boards like this so great.

[Fuelie Fan]

One comment, you can't necessarily tell from number of wires since a lot inductive sensors will have a 3rd pin tied to the shield, which in turn is routed to ground. I've seen a lot of 3 pin inductive sensors.