27 replies to this topic

[ksin86]

Thanks guys, I'll check it out tomorrow in the morning.

 

 

Individual relays can be sourced. Open frame version of Omron G8P 12V is similar.
I would also be checking the circuit board of the MFU once open for cracks and re soldering the connections.

FS

 

 

Ok, it is looking like Guess-works.com was right from the beginning. The MFU is acting up. One of the fat brown wires feeds power to the main relay and the fuel pump relay. The fuel pump relay is activated by the white wire coming from the ignition switch that also activates the ECU pin 11.

The main relay is activated by a thin white/pink wire coming from the ECU pin 4.  The output from that relay, fat brown/pink wire, goes to several locations including the + side of the ignition coil. If any of those related functions are not operating properly, the car would no start. It seems that the only thing not working right is the fuel pump relay.

I think that you need to resolve this problem first before attacking the other. The pump relay might be intermittent causing the other issue.

You might want to open the relay box and inspect it using FlyingScot's info. The contacts could be dirty and cleaning them with a finger nail file might do the trick. 

[ksin86]

I've pulled the MFU out of the car but how would I go about opening it up? It seems to be in good condition (no cracks) and the contacts seem clean too. This car only has 77,000 kms on it and was garage kept.

  

Edited by ksin86, 15 July 2014 - 12:11 AM.

[xrocketengineer]

The thing is glued together. If you look at FlyingScot's picture of the opened up MFU, you can see where it separated.  You probably need a strong Knife to insert into the groove between the plastic housing and the piece that has the connectors and gently pry slowly all the way around the housing. I have not done it myself, maybe FlyingScot has some other trick.  

[FlyingScot]

No trick xrocketengineer sadly.
I used a strong knife and thin bladed screwdriver and a lot of care!

FS

[ksin86]

Here you go. I've only uploaded one picture for space reasons on this post.

 

Looks like it's dirty and some of it's been corroded? I'm not sure so if any of your expert eyes can tell, it would be much appreciated!

Please find all the pictures here at this link: Click here!

 

[xrocketengineer]

Using FlyingScot's reference picture, it looks like the fuel pump relay contacts might be burned. You could try cleaning them with a finger nail file but if the contacts are too rough, that will not work. Then you might need a replacement relay box or try replacing the relay per FlyingScot's suggestion. 

[xrocketengineer]

If you have some soldering tools and skill, the relay replacement would be very inexpensive.

 

As far as the relay replacement goes, I believe that the Omron one is this:

 

http://www.mouser.co...8lxuSlnRFbWuQ==

 

Page 3 of the data sheet shows the pin outs and dimension to compare with the original one:

 

http://components.om...e/G8PT_0812.pdf

[Guess-Works.com]

Burnt connections may also suggest a higher than anticipated current draw on the pump, maybe worth looking into that as well...

 

If the pump is starting to struggle or fail it may be drawing more than the system is designed to take.

[xrocketengineer]

Burnt connections may also suggest a higher than anticipated current draw on the pump, maybe worth looking into that as well...

 

If the pump is starting to struggle or fail it may be drawing more than the system is designed to take.

Good point! That goes back to my previous entry #4.

Edited by xrocketengineer, 19 July 2014 - 04:55 PM.

[FlyingScot]

The plastic looks a bit "cooked" on the power side (top socket in your picture).

Have a clean up of al of the connection and very fine emery on the contacts on the open frame relays.

If you have a multimeter test what readings you are getting in ohms for the coils.

 

FS

[ksin86]

I'll be going over your suggestions with the unit tomorrow.

Tanks for all the tips. I'll post up the results.

[ksin86]

Car still hasn't died or failed to start for a couple weeks now.

 

Today I got my friend, the ticketed avionic's technician, to check out the MFU and everything checks out with the multimeter.

 

Only thing extra that we did is clean it up with isopropyl alcohol and cleaned up some of the surface corrosion with some Scotchbrite.

 

Anything else to check out?

 

Thanks.

[xrocketengineer]

If the fuse does not blow again, declare victory and you are done.