Aeromotive Fuel Pump Speed Controller (P/N 16306)
 

I have no way to condense what I'm asking....it s a problem I'm well aware of. Apologies up front. I'm working on it. ;)

Posting this in the Street section because I feel its something geared more to making a "race" car street friendly than something one might see on non street driven car. I might post this in the Electrical section too.

Anyone running Aeromotive's Fuel Pump Speed Controller (P/N 16306)? I've got one on my Stealth A1000 pump and its driving me nuts. Here's whats happening -

The intent of this piece is to keep fuel pump RPM commensurate with engine RPM until a user defined RPM is set, whereas the pump then goes into Full mode pushing 100% of the fuel. Whats happening at idle (1000 rpm) is the controller is seeing random false spikes in RPM telling the pump to go to Full mode for a flash, then not, then Full mode, then not, then Full etc, at a rate of about 20x a min. I've even confirmed the voltage spikes at the pump with a meter. To protect the system, the controller senses the fault and initially was shutting off the pump.

On the recommendations of Aeromotive, I've gotten to the point where the pump no longer shuts off. That's good - but the problem is I'm still seeing the Full light flash intermittently as I'm idling the car. Perhaps 10x/min.

I've read all of the Aeromotive Tech Bulletins. I've even spoken to Brett in Tech Support and he seems to be stumped as to whats happening. (and is a tad slow in responding) The consensus is electromagnetic interference is the cause. I'm not convinced.

I used braided metal sheathing over the tach signal wire from the MSD to the FPSC. Just in case, I also ran a brand new wire here because the old one had a butt connector in it. This wire is completely isolated from others and is run outside of the glove box (MSD is there) to the controller for testing. The full light still flashes erratically, which means I still have a dirty signal on this input wire to the controller.

Here is what I also observed. As mentioned, idle in the car is about 1000rpm. If I lower it, it cleans up the signal and the Full light flashes less, it at all. If I stab the throttle, consistently what happens is the full light then starts blinking erratically. Not consistent with rpm, but consistent with the tip in of the throttle. Each time I tip in, the Full light will start blinking erratically. Could the MSD be causing this? Seems like it. It an older 6AL box...23 years running.

If so, and even though the Aeromotive Bulletins say that an EMI filter is only needed on the wire from the controller to the tachometer, does anyone see a problem with building the same EMI filter on the MSD input wire into the controller? The resistors and capacitors come tomorrow, so wanted to see if anyone though this was a bad idea before I went ahead and just did it.

How is your shielding grounded? Or is it? Shielded cable should do what you need, but it needs to be grounded on one end (only).
And... are the grounds for everything else good, and to the battery or engine block/head?

Can u take the tack signal from the ground side of the coil ? Or at least watch it with a test light to see if it is stable there. I have never seen a good MSD box they all eventually do weird **** send them in. No problem found but the problem goes away for a while.

No kiddin? Hmm, learn something new every day. Thanks! Shielding is definitely NOT grounded. I'll make that happen and report back. Rest is good - The ground circuit for the pump AND controller has 1.6 Ω resistance, connections are tight and all the crimps are good. Battery is new, ground cable is 1ga and is also new. Just to eliminate any question, I ran 10ga power and ground feeds direct to the battery for testing. What I've descried above happens with those wires in place, and slightly worse without.

Tried to get a good signal from the distributor but couldn't find a good one. Agree, the little red box is a mystery! Hate to throw parts at it, but if its done doing what it needs to do, I'm OK with getting another, although I doubt they are made as good today.

The square wave tach signal from the MSD is gonna be a much cleaner signal than trying to take it from the coil.

Basically you just had a good EMF antenna unless you ground it to one end of the block or ground strap to the battery.

Tom V.

You should make the wires direct from the battery to the controller permanent. Not just for testing. If I had to guess the instructions probably recommended hooking the main power and ground direct to the battery, probably to take alternator noise/spikes out of the equation.

Will do. They certainly helped me achieve the cleanest signal yet.

Many do not realize that a automotive vehicle battery is like a giant lake where varying flow to and from the engine demand has minor effect on the voltage (and amperage) leaving the battery to do specific jobs.

That is one reason why you need good grounds and proper sized cables to the engine and the automobile fuse box.

The suggestion to use dedicated wiring from the controller makes perfect sense.

Tom V.

I did that with the fuel pump circuit years ago when I ran the rear mounted fuel pumps. I used a separate fuse from the fuse block.

Just to close the loop on this. This is semi resolved. At least good enough for me, anyway.

Scott65 / Tom Vaught - I took your advice and grounded the shielded wire using a shield bond connector.

https://lh3.googleusercontent.com/jm...9v4=w1220-h380

Also, per Aeromotive Tech Bulletin #302, I created an EMI filter using the specified 2200pf 1KV ceramic disc capacitor and 1/8-Watt 2.2K Ohm resistor soldered inline with the MSD tach signal. While it cleaned up the signal, its not 100%. Check the vid.

FPSC video
https://youtu.be/w2nMspJQ9_8

Oddly enough, and I cant explain it, but subsequent idling of the engine a few hours later produced a much cleaner signal than the video shows. Still not 100%, but much less concerning. Not sure why but for those instances, the Full light only flashed about once every 15 seconds. We'll see how it goes when I actually get some miles on the car. There is a controller override wired in, so it wont leave me stranded.

I'm still wondering if its my ancient MSD, or if MSD ever had a box that produced a signal this controller isn't expecting. (something less "square" I guess)

Not to be one who looks a gift horse in the mouth, I'm moving on. Appreciate the assist here.

Glad to help.
Tom V.

If you decide to take it a step further... There are tach signal generators available. I think most of the aftermarket that deals with fuel only efi have a model they recommend. All probably close to the same. That would take your MSD out of the picture except maybe to operate your tach.

Good point. The Bulletin from Aeromotive talks about using those, but I ignored it because it was under their EFI section, talking about LS type, COP ignitions. But you're right, it would give me what I need. That too requires some fancy rigging of a capacitor to bring up voltage signal, but I could make it work. Will keep it in mind if I have any issues.