Testing MFRU multi function relay unit

[charliex]

immo 5 and 6 are the starter switch to starter relay.

so its IMMO-6 would be the deadlock for the starter switch at IMMO-5, they're listed in that first sheet.

if you get an on/off reading off MFRC 7 when the starter is depressed that should mean its ok.


RMC1/5 is where the output to feed the starter is.

[TheViper]

Jumper out these two immobilizer plug pins on the female side of this plug for the fuel pump and starter, but am doubtful (hope i'm wrong).
Michael

[Casey]

Put a meter on the starter soleniod wire and have someone hit the starter button.....I know it's bitch to get in there

[Thomasio]

I think that the single click that others are referring to may have been the relay sound. When I say "single click", technically the relay is making a click at the same time that the solenoid is making the loud click.

A few minutes ago I tried jumping the immobilizer, and achieved the same results that I've been having all along...

At this point I'm 90% certain that it is the starter and/or solenoid. Looks like it is time to ship her off to FVMC for a warranty repair.

I'm just happy it is winter in the midwest, else I'd be less amused than I am.

[Thomasio]

P.S. Thanks to everyone for their help... Charlie, Michael, Casey... I really appreciate your time and suggestions.

[TheViper]

Sorry you didn't find or fix the problem but after you do, perhaps you can repost the exact cause.
Good luck,
Michael

Originally Posted by Thomasio

P.S. Thanks to everyone for their help... Charlie, Michael, Casey... I really appreciate your time and suggestions.

[charliex]

did you measure the voltage on the starter/out of of the mfrc ?

[Thomasio]

Originally Posted by charliex

did you measure the voltage on the starter/out of of the mfrc ?

Not yet, will do that.

[ZAMMY1]

to actually test the starter, disconnect the small wire on the starter solenoid.
when you jumper the terminal you disconnected the small wire from, to the big terminal on the starter, the starter should crank.
if it does not, then it IS the starter at fault.
make sure it's out of gear when you do this.
good luck, sam

[tesprit]

Originally Posted by ZAMMY1

to actually test the starter, disconnect the small wire on the starter solenoid.
when you jumper the terminal you disconnected the small wire from, to the big terminal on the starter, the starter should crank.
if it does not, then it IS the starter at fault.
make sure it's out of gear when you do this.
good luck, sam

+1

Good advice Sam!
(I must be getting old--totally forgot about trying that procedure )

[ads_green]

Fuel pump will still prime even when the car is immobilised

[TheViper]

How can that be, it's open circuit?

Originally Posted by ads_green

Fuel pump will still prime even when the car is immobilised

[Simba]

Originally Posted by ads_green

Fuel pump will still prime even when the car is immobilised

No, it won't. Power goes from the fuel pump relay, to the inertia switch, to the immobilizer, to the fuel pump. If the immobilizer is open, no fuel pump.

This is one of the reasons the current at the fuel pump sucks and most people elect to run another relay in the system.

[TheViper]

"Current sucks"..interesting..."most people"..who are they?

Originally Posted by Simba

This is one of the reasons the current at the fuel pump sucks and most people elect to run another relay in the system.

[Simba]

Originally Posted by TheViper

"Current sucks"..interesting..."most people"..who are they?

A bunch of people who have done forced induction of some type and run into pressure issues.

The pump wiring is of a very light gauge which does not conduct current particularly well, and goes through a lot of circuits before it gets to the pump.

[TheViper]

Not true, the wiring is sufficient for the pump and only goes though simple contacts, no resistive loads.

Originally Posted by Simba

A bunch of people who have done forced induction of some type and run into pressure issues.

The pump wiring is of a very light gauge which does not conduct current particularly well, and goes through a lot of circuits before it gets to the pump.

[Simba]

Originally Posted by TheViper

Not true, the wiring is sufficient for the pump and only goes though simple contacts, no resistive loads.

I saw a gain of several psi at higher revs/boost going to thicker wire and a secondary relay. That implies a significant increase in current at the pump.

It goes through several relays which are, to a degree, resistive.

[TheViper]

The wiring for an electrical device is sized according to it's current draw & voltage drop, are you saying that the pump wiring is undersized?

[charliex]

Are you sure you weren't seeing the effects of a poor ground vs better ground ?

[Simba]

Originally Posted by TheViper

are you saying that the pump wiring is undersized?

For applications that are moving a lot more fuel, yes.

Are you sure you weren't seeing the effects of a poor ground vs better ground ?

I tried a more robust ground as well, but didn't see any real improvement.

One of these days when I have time, I'll take some ammeter readings of the pump at a set pressure with the stock versus larger gauge wiring.