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MGB 1974 MGB- New main wiring harness, but no start

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wkilleffer

wkilleffer

Jedi Knight
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Good evening,

I finally got my dash back in place, harness hooked up, new battery, and was really looking forward to starting the car tonight.

Sadly, no joy...

The headlamps, tail lamps, turn signals, and hazard flashers all work. When I turn the key, the ignition light turns on and the fuel pump does its thing. But no cranking.

I've also noticed no courtesy lamp illumination.

I swapped the harnesses by leaving a portion of the end of each wire in place so I could color match and plug in the appropriate wire. To the best of my knowledge, I did this correctly.

Down at the starter, I'm getting 12+ volts, which isn't surprising considering that the lights work. Also not surprising that the appropriate terminals on the fuse box also get 12+ volts.

Seems like 1974 was a year where the driver's seat belt was required to be fastened before the car would start. Mine would start without it being fastened. Is it possible that in replacing the whole main harness that I inadvertently re-activated that feature?

Where are some other places to check for voltage?

Any assistance would be appreciated.

Thank you,
-William
 
Is your engine grounded? That would be my first place too look. I also once had a similar issue where it was as simple as two reversed wres on the solenoid
 
wkilleffer said:
How do I check if the engine's grounded?
Click to expand...

There should be a braided or battery cable attached to the engine mount or somewhere along the bell housing or engine block, and then attached to the body. Something like this:

BH_MG_engine mount.jpg
 
William,
On a 74 there should be a starter relay on the firewall. Brown wire comes from the fusebox. Check for hot all the time on the brown at the relay. The seat belt interlock is behind the radio console and has a big white plug with lots of wires. If the interlock unit goes bad it will not let "start" power go to the relay. I have had to disconnect and jump the wires here to make 2 of my rubber bumper 74 GTs starters work all the time. They were hit and miss when starting. I can give more details after I get back from a breakfast appointment if needed.
Bob
 
The brown wire has 12 volts at the starter relay.

I remember seeing the seatbelt interlock when I was doing the harness replacement. What I don't remember is whether or not there were any jumped wires or other obvious modifications. I still have the remnants of the original harness and can have a look at it.

I wanted to test the relay itself, but wasn't sure how without an assistant in the driver's seat. Live by myself, so someone's not always available.

Thank you,
-William

bob67bgt said:
William,
On a 74 there should be a starter relay on the firewall. Brown wire comes from the fusebox. Check for hot all the time on the brown at the relay. The seat belt interlock is behind the radio console and has a big white plug with lots of wires. If the interlock unit goes bad it will not let "start" power go to the relay. I have had to disconnect and jump the wires here to make 2 of my rubber bumper 74 GTs starters work all the time. They were hit and miss when starting. I can give more details after I get back from a breakfast appointment if needed.
Bob
Click to expand...
 
So do we have a vroom vroom moment?
 
We have vroom-vroom... There are still a few things I need to finish, but I couldn't resist a quick spin around the block.
 
Woohoo! :cheers:

So hard to resist that drive once it's running, even if all else is still not well. If nothing else it's a great motivator to keep going through those last projects.
 
Hi I have a 1974 mg midget . I put a new wireing harness in it new key switch new starter selonid and had the starter rebuilt and I have jumped the wires on the seat belt interlock and still nothing from the key switch .I can jump the starter relay and it will turn over . Can someone please help me out on this . my wife is wanting to drive her little car
 
George Allen said:
Hi I have a 1974 mg midget . I put a new wireing harness in it new key switch new starter selonid and had the starter rebuilt and I have jumped the wires on the seat belt interlock and still nothing from the key switch .I can jump the starter relay and it will turn over . Can someone please help me out on this . my wife is wanting to drive her little car
Click to expand...
Does anything happen when you turn the key?
 
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