What's the 3 wires below the dizzy, from the block

[Steve1970]

Hello all!

Been troubleshooting a starting issue, trying to eliminate spark as being the problem.

Can anyone tell me what the 3 wires are coming from the engine block just under the fuel pump and distributor? They are connected to a three spade circular insulated 'plug' thing. I see nothing in Haynes about it.

I think I accidentally crossed these wire last week when i swapped in a new fuel pump. I touched the ratchet handle to this three spade circular thing while tightening the fuel pump. Nothing happened except some clicking noise coming from the front. But I'm wondering if I might have shorted out something very important.

When I get home I'll try to take a pic, but I'm not sure I can get the camera in at that angle.

Many thanks, -Steve

 

[Andrew Mace]

Sounds to me like the oil pressure warning light sender, and the extra wires on that control an anti-run-on valve of sorts.

 

[Steve1970]

Andy, I just googled "tr6 oil pressure sender" and it looks like the thing i was describing! Question is, could frying this sensor cause a starting problem? I don't see how. And I actually do get a weak current coming from the spades, so I think I can eliminate this for now.

Many thanks for your quick response!!

 

[Andrew Mace]

Offhand, I'm not sure, unless something actually DID short out.

FYI, here's a wiring diagram (see page 6) showing the switch wiring and that of the anti-run-on valve.

 

[mrv8q]

Re: What's the 3 wires below the dizzy, from the b

Here's a post on <span style="font-style: italic">everything</span> you'd ever want to know about the OPS switch:

https://www.britishcarforum.com/bcforum/u...e_sw#Post443039

 

[poolboy]

The clicking noise you heard was the Anti Run-on Valve opening and closing as you intermittently grounded the White/ Purple wire that is normally grounded within the Oil Pressure switch. The hot wire for the ARV is hot only when the ignition key is in the "OFF" position.
If there was no oil pressure it would not have been grounded, but you changed that by establishing a ground with your ratchet and thus the clicking.
The black wire in the OP switch goes directly to a ground
The White/ Brown wire is grounded when there is no oil pressure causing the low oil pressure lamp in the tach to glow.
Internal to the Oil Pressure switch the ground switches from the black wire to one or the other wires depending on the presence or absence of oil pressure.


Refer to the diagram that Brosky posted in the link provided (above) for the correct connections to the OP switch

 

[M_Pied_Lourd]

Re: What's the 3 wires below the dizzy, from the b

The clicking noise from the front would have most likely been the Anti Run on valve opening and closing.

Cheers,
M. Pied Lourd

 

[Steve1970]

Poolboy, your description of how this switch works matches what I have seen.

When i grounded the switch with my ratchet, the car ignition was "off" and i got the clicking.

When i hooked up a test light to one of the 3 spades, i could only get a current when i tried starting the car, and only then it was a very weak current (the light was barely glowing); when i ceased trying to start the car, then glow faded away completely. This must have represented the fading oil pressure.

Since the switch seems to be functioning, I don't think i can necessarily attribute it to my starting problem. I'm leaning towards a bad coil as being the cause, but i've still got some tests to get through.

Many thanks to all for the links and great info. It's funny how NOT knowing what that thing was bothered me.. until a yr or two ago i didn't know what 70% of the stuff was under the hood. just trying to keep the car running with the assistance of you guys and mr. haynes has taught me much.

 

[TR3driver]

Just to be sure, I might be inclined to disconnect the ARV until I got the engine running. I don't think that's your problem (as per discussion above), but there is something to be said for getting back to basics while troubleshooting.

 

[poolboy]

Steve, if you want to follow up on Randalls suggestion, just remove the hose on the intake manifold's banjo fitting that goes to the ARV and put a cap on the banjo's nipple. The banjo fitting has 2 hoses connected to it. One goes to the brake booster (servo) and the other is the one going to the ARV that's under the Carbon Canister.
By removing the hose and capping the nipple you've disabled the ARV's effect (whether it's open or closed) on the carbs or the engine's starting or running.
Here's a picture of my 74 with most of the emission stuff removed, including the Carbon Canister and ARV. .

 

[Steve1970]

The starting problem was due to the new fuel pump and/or fuel lines. Replacing the system apparently had the effect of substantially increasing the fuel pressure to the point that it was flooding the engine. This dramatically came to light after too many turnover attempts resulted in fuel spraying out of the air filter; 'twas a sight, let me tell ya.

The carb floats were not correctly shutting off the jets, so fuel just continued to be forced in to the bowl until it started shooting out all over the place. Apparently the fuel pump I had in there prior was only capable of much less pressure, and therefore hid the problem.

So I'm pretty much back to normal, and unfortunately that means I'm still dealing with an anemic MPG problem.. not convinced it's totally due to richness..but thats for another post.

Many thanks for all of your help.

Oh, and a special shout out to Dan Shaw.. a TR3 owner who spotted me broken down last fri about a mile from my house (due to mal-adjusted floats). He was able to drive me back home so I could get my tools.

-Steve