Testing MFRU multi function relay unit

[Thomasio]

A strange starting problem has appeared... '07 Exige S...

I've done all of the usual checks: battery is good, connections are good, grounds between engine and chassis are good, etc.

Here is what happens: I turn the key to the on position, press the keyfob button to disable the alarm... fuel pump primes for a few seconds... when I press the start button, I hear a solid "click" from the engine bay (seems to be the starter solenoid)... then nothing. No starter groan, nothing but one solid click.

Since the fuel pump is working, doesn't appear to be the immobilizer or the inertia switch. Since the solenoid is working, doesn't appear to be the immobilizer.

Pulled the multi function relay unit... is there any way to test it for obvious faults?

Any other thoughts? I have researched this thoroughly here on LT for the usual suspects.

The battery voltage only drops to about 12.4 volts when I push the start button. I've tried two different batteries, even jumped the battery with another car.

[charliex]

since you didn't list it, i'll say check the fuses, theough i'm guesing you did that.

i'll look up the mrfu circuit see what the pins are if no else gets to it before i do, i've got 3 people ahead

[Thomasio]

Originally Posted by charliex

since you didn't list it, i'll say check the fuses, theough i'm guesing you did that.

i'll look up the mrfu circuit see what the pins are if no else gets to it before i do, i've got 3 people ahead

You are correct sir, checked each fuse in the forward fuse bank and the engine bay fuse banks (2).

Also didn't mention that I turned over the engine by hand, it is turning over normally.

I appreciate your help Charlie.

[TheViper]

If it's the starter solenoid that you are hearing then that infers the starter relay is working. I would check the connections at the starter motor, especially the ground. A high resistance battery connection could also be responsible.
Michael

[charliex]

Here are the diagrams, first page has the starter via the immobiliser

RMC1/7 is VE+ Rear stud

RMC1/5 is the starter energise.

So 7 is VE+ ____/ ______ starter

RMC2/6 is the immobiliser
RMC2/4 is the ecu control

IIMOB 6, 6 ----[] --- 4 ECU LG2 control

[Thomasio]

Thank you Charlie.

Michael: the only connections that I can see at the starter are: 1) two large red cables, one is perhaps 6 gauge and the other is perhaps 4 gauge, both mounted to the same copper post... and 2) a very small black wire (with white stripe as I recall) that goes into a connector at the starter, in close proximity to the copper post but electrically isolated of course.

Wouldn't the starter ground through its body into the transmission? If there is a separate ground, I cannot see it from beneath the car.

[TheViper]

You are right, 3 cables:
Red 20mm from battery
Red 20mm looped to alternator
Black 2mm to start relay.
Seems to me that if all fuses are OK.....
Battery is OK.....
Starter Solinoid is operating (check the click you hear is not the Start Relay....
Makes me think its the starter or if the Start Relay is clicking then the Solinoid is suspect too)
Michael

[Thomasio]

Originally Posted by TheViper

You are right, 3 cables:
Red 20mm from battery
Red 20mm looped to alternator
Black 2mm to start relay.
Seems to me that if all fuses are OK.....
Battery is OK.....
Starter Solinoid is operating (check the click you hear is not the Start Relay....
Makes me think its the starter or if the Start Relay is clicking then the Solinoid is suspect too)
Michael

It's a pretty loud "click", sounds more like a solenoid click/clunk than a relay (although anything is possible).

The car has never hinted at a starter problem, and has been sitting in heated storage for a couple of months... this was a recent attempt to start the car that alerted me to the problem. Original battery (Exide) was low, charged it, same symptoms... replaced w/ a new Odyssey 680 same symptoms... charged 680 overnight, same symptoms... just one click.

P.S. Free Exide battery, pick up only...

[Thomasio]

P.P.S. Starter appears to be a true nightmare to replace... anyone done it? What's involved? (I haven't convinced myself it is the problem yet).

[TheViper]

Do a "Load" test on the battery:
If the battery's state-of-charge is at 75% or higher, then load test the battery by :

Turn the headlights on high beam for five minutes,

DURING the load test, the voltage on a good battery will NOT drop below 9.7 volts with the electrolyte at 80 degrees F (26.7 degrees C). [If the electrolyte is above 80 degrees F, add .1 volt for every 10 degrees above 80 until you reach 100 degrees. If below 80 degrees F, subtract .1 volt for every 10 degrees until 40 degrees.] After the load is removed, wait five minutes and the battery should "bounce back" to the 50% state-of-charge level or above. If the battery drops below minimum test voltage, does not bounce back, or will not start the engine, then you should replace it. If the battery passes this test, you should recharge it to restore it to peak performance.

[Simba]

If the battery is low or otherwise toast, you'll generally hear a series of clicks from the solenoid as you hold down the start button, not just one.

My guess is your starter is done. Whack it with a hammer and see if it comes to life, if so there's a dead spot on the armature.

[tesprit]

Originally Posted by TheViper

You are right, 3 cables:
Red 20mm from battery
Red 20mm looped to alternator
Black 2mm to start relay.
Seems to me that if all fuses are OK.....
Battery is OK.....
Starter Solinoid is operating (check the click you hear is not the Start Relay....
Makes me think its the starter or if the Start Relay is clicking then the Solinoid is suspect too)
Michael

Hey Thomas, I have to agree with Michael that it sure sounds like your starter has failed. The one solid click is the solenoid closing the contacts between the battery cable and the + lead into the motor. The contact bar or contacts in the solenoid may have failed or the motor itself may have a dead spot on the armature. Unfortunately the only decent way to test it is to remove the starter and bench test it. The starter is incredibly small and on my spare engine and trans., there were only two bolts holding the starter in place so it really wasn't hard to remove at all. Of course the engine and trans. were not in the car so I had a lot of room to work around the starter and I haven't taken a look at the starter in my car so it may not be that easy.

One other thought would be to check for a grounding strap between the chassis and the engine/trans. assembly and make sure it is clean and secure. Again, I haven't looked for one on my car, but just about every car I have seen has one. A bad connection at the grounding strap can cause the symptoms you are describing. If it is not making good contact to ground there will not be enough juice to spin the starter motor, yet there will be enough to make the solenoid click.

[Casey]

HaHa....Ive seen this problem similar to this on an ExigeS and it had me stumped for 2 weeks. I changed starter...a real pita on the supercharged car...removed the clam and pinned out the entire wiring harness. It ended up being an immobilizer problem. I can't remember which wire(they are all black) but there was supposed to be 12 volts key on but there wasn't....I jumped 12v to the wire and it blew a couple fuses up front...replaced them and the worked fine. This whole problem occurred after disconnecting the battery.

[TheViper]

The only thing, in this case is, that the fuel pump is priming & the starter relay or solenoid is active, therefore it does not seem to be the immobilizer.
Michael

Originally Posted by Casey@ForcedFed

HaHa....Ive seen this problem similar to this on an ExigeS and it had me stumped for 2 weeks. I changed starter...a real pita on the supercharged car...removed the clam and pinned out the entire wiring harness. It ended up being an immobilizer problem. I can't remember which wire(they are all black) but there was supposed to be 12 volts key on but there wasn't....I jumped 12v to the wire and it blew a couple fuses up front...replaced them and the worked fine. This whole problem occurred after disconnecting the battery.

[Casey]

The fuel pump worked on the car I was speaking of as well....It was displaying the same exact symptoms...fuel pump prime and single click on the starter.

[charliex]

from casey's description i'd hazard a guess at RMC2/6 on the first sheet i posted.

[Casey]

Charlie...do you have the immobilizer schematic.....mine are at work.

[Thomasio]

I had an accomplice press the starter button while I held my head perilously close to the starter... the single click is definitely the sound of the solenoid.

So I should be looking at the immobilizer? My understanding was that the fuel pump and the solenoid action ruled that out, but perhaps not?

[Thomasio]

Originally Posted by Casey@ForcedFed

Charlie...do you have the immobilizer schematic.....mine are at work.

Jeeze Casey, can't you just go back to work for it?

[charliex]

yeah i have it, i'm pretty sure its that one though, thats the engergise for the starter.