Fuel pump being triggered by water pump

[lemans70sport]

I have an electrical glitch that has been kicking my butt for several days now. The water pump relay and ground is located in the front of the car, the fuel pump relay and ground in the trunk. When I run the water pump, MS triggers the fuel pump to run for a couple of seconds. I figure MS is resetting every time but I can't determine why. If I disconnect the water pump power wire then turn it on, I can hear the relay close but MS doesn't trigger the pump so it has to have something to do with the pump running. Also, it doesn't happen all the time but the pump will stay running and the fuel pump LED will flicker like it is seeing a short. MS ground is connected directly to the battery, the water pump to the frame. I had them sharing a ground at one time but it didn't make a difference. Any ideas?

Steve

[Mike_Robert]

Is their +12 feed shared in any way? A voltage sag of either polarity gives the same result. Your grounding scheme sounds good. As a test, I would run a jumper wire from the battery (+) to the MS +12 feed and see if this makes a difference. A log of the event would be helpful as well...

-Mike

[lemans70sport]

Mike thanks for the reply. MS and the water pump does share the same power connection as do both fans. I don't have this problem with the fans but I suppose the water pump draws a lot more amps. I've also been running off of battery power because I wanted to verify the water pump was working. It might not be an issue if the alternator was supplying added power. I'll do some more experimenting this weekend and post what I find.

Steve

[Mike_Robert]

Steve, were I you, I would source a dedicated clean +12 line for the MS if at all possible. If the capacity of the +12 for the MS and fans is so close to being saturated where the alternator's additional voltage makes this go away I wouldn't feel comfortable with that slim of a margin. Let us know how you progress, this info can possibly help others.

-Mike

[S.Bretz]

Sounds like you might need a larger gauge wire. When an electric motor first starts up, thats when it draws the most amperes.

I have alot of stuff running off of one 100amp relay. The relay has 8 gauge wire going to it and 8 gauge wire leading from the realy to the fuse distribution box; wich supplies 12+ to the two cooling fans, all m gauges, nitrous soleniods, eids, and MS. As a precation, I also installed a 1/2 farod audio capacitor to the power wire going up to the 100amp relay to help stabilze the the current to all of the devices.

[lemans70sport]

Back from being temporarily banished. I moved the ground and connected the water pump directly to the battery but it didn't help. I tried to shield the motor and the pick up with aluminum tape. That didn't work either. I also moved the water pump harness away from the pick up. No luck with that. Now I'm researching installing an inline filter similar to what is used on alternators to take noise out of the stereo system. I'm just unsure of how big the capacitor needs to be. I've emailed CSR as well to see if they have any solutions.

Steve

[Heribert]

Hi ,
It is likely that the backemf of the DC water pump motor sends out a lot of radiated and conducted noise.
This is how I solved it on a Ford 350 installed in a GT40 replica, and has an electric water pump.

Separately fused wire from the B+ to the pump relay and then onto the +feed of the pump.
-feed to pump earthed directly to the engine block.
Very close to the pump we cut the +wire and
Inserted a 500µH inductor in series. ( The type used in step up switching power supplies)
At the pump side of the inductor we installed the following components to ground:
A 2000µF-25 V electrolytic capacitor
A 100 nF-25 V polyester capacitor
A 30 A 100V silicon diode that has the anode in the casing. The casing has an 8mm bolt that was threaded into
an alu part on the engine. The cathode was connected to the joint caps/+feed to pump.

And to top that of we installed an RC snubber over the relay contact that runs the pump. 220nF in series with 680 Ohms.

And that was the ed of resets ( The car runs on an electromotive system that regularly had multiple resets when the pump started and stopped)


Quite a lot , but it certainly did the trick!

Heribert

[lemans70sport]

Wow! That made my head spin but great information. I had no clue what capacitor to buy but I knew that was part of the solution. I raided Radio Shack and came back with a 100uF capacitor and a couple of choke cores that snap onto the power lead and are supposed to reduce EMI and RFI (same thing?). I'll give those a try first then go with your set up.

Thanks again,
Steve

[lemans70sport]

I installed the 100uF capacitor to the water pump power wire and grounded the other side using the same ground as the water pump. Didn't fix the problem. I also installed all of the clip on filters..no help with those either. I decided to run Megatune to watch what was happening and I'm not getting a reset. The engine rpm jumps to around 1700 when I turn on the pump then bounces all around from there. This is a pain in the butt. I didn't expect this much hassle when I decided to go with an electric water pump. UGH!

Steve

[Heribert]

Yo!

If you do not get resets , keep smiling
For the rpm to bounce around when you switch on the pump and keep bouncing is a bit unusual.
It almost has to be magntic coupling from the pump or the pump wires ( magnetic stray fields)
that influences the wiring to the VR sensor or the sensor itself.

Would you get rpm in MT with the pump running and the engine not spinning?

Try using the best quality shielded VR wire you can get and separate the pump power leads and the VR sensor lead as much as you can.

If the VR sensor picks up the stray magnetic field, try slipping a mild steel > 2mm thick magnetic shield over the VR sensor.

Heribert

[lemans70sport]

I did a little more experimenting yesterday and found that when the engine is running it isn't a factor. My RPM's remain fairly steady. I may find an issue with a high rpm misfire but for now I think I'll let it go. I will install a metal shield though. I like that idea. Thank you for everyone's input.

Steve